1938 Buick overheating

[West Peterson]

Normally, my friend's 1938 Buick Special runs at about 180 F. When pushed in the summer, it will run a bit hotter. This weekend, running between 45 and 50mph for about 5+ miles, it ran beautifully, and the temperature was stable at about 190 F. After climbing a long hill, we stopped at our destination. The temperature climbed to about 200 F, then when shut it down, it boiled over (just for a brief moment, lost no more than a quart).

Similar observation on the way home - we stopped to look at an antique. This time, I let it idle, for fear of vapor lock. Watching the temperature gauge, it slowly crept up to 200 F - so we hopped in and took off. Once moving, the temperature came back to about 185 F or 190 F.

Normal? The only concern I have is that it wasn't that hot outside (maybe 82 F ?). The engine was flushed about 2,000 miles ago (however, that was 8-10 years ago).

Any advice beyond trying another flushing? How about removing the thermostat (if there's one in there)? This doesn't seem normal for 85-degree temperatures, and easy driving.

[Guest sixpack2639]

West,

My 51 had pretty much the same symptoms when I got it. I did't know when it was last flushed if ever. At 55mph the temp would steadily climb to near overheating although it never actually overheated. If I turned the heater and defroster on wide open the temp would drop back down to an acceptable range. I did a thorough flush of the radiator and the heat, defrost system and engine all seperately in both directions (flushed one way then reversed and back flushed the other) and put in a new t-stat and now she'll cruise at 70mph all day long with the temp gage at mid range without fluxuation.

All that to say this, flush it and put in a new t-stat.

Carl

[Guest]

Flushing the engine does almost nothing. If you want to get it back to normal (and there are some people that say the straight eights were always hot runnung) you need to knock out the core plugs and physically remove the crud etc in the water passages. When I worked for GM many years ago it was not unheard of to remove eight or ten pounds of gunk out of the water passages. A scraper and various shaped pieces of heavy wire and some [a lot] of patience is required. However it is worth it. Removing the thermostat will not prevent overheating. In fact it often encourages it because the coolant circulates through the radiator too fast and therefore is not cooled down before it goes through again. When I had my Buicks; 1929, 1931 and 2 1953's I physically cleaned them out an then always ran with 50/50 ethylene glycol antifreeze and never had a problem.

[Guest ZondaC12]

well i dont know how much crud is lurking in my coolant passages, but mine will stay a little under 180 highway cruising or even around town after awhile, and then stopping, whether it is idling or shut off the temperature does come up, not quite all the way to the mark between 180 and 212. just letting you know i get the same thing, i think it's as someone mentioned "they just run hot".

[Guest De Soto Frank]

Tinindian has a good point about cleaning-out the "crud in the block"...

Us guys with flathead Chryslers often have issues with our cars running "hot"...

If flushing and new thermostat don't resolve the problem, then it usually turns-out to be water jackets full of scale and rust, and the water distributor tube that runs down the length of the block ( under the valves of the flathead MoPar) is disintegrated and/or plugged.

When the MoPar guys rebuild one of these flatheads, they all comment about the amount of crud they scrape out of the water jackets when they knock-out the core plugs...

Prior to 1950 or so, most of our cars were run with alcohol-based antifreezes, and the cooling systems probably tended to rust internally more than they do with modern "Prestone" ethylene glycol.

(And besides that, any iron vessel that holds a water-based solution for fifty or sixty years is going to do some rusting...)

While it is fairly normal for a car to run about 5-10 degrees hotter when stopped at a light or driving in slow urban traffic, remember that Buicks were premium cars, and GM would have made sure that they were equipped with capable cooling systems when new...

The only common post-Depression cars I know of with inherent "running hot" problems are flathead Ford V-8s, and that is supposedly due to the exhaust passages running through the block...

[West Peterson]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">well i dont know how much crud is lurking in my coolant passages, but mine will stay a little under 180 highway cruising or even around town after awhile, and then stopping, whether it is idling or shut off the temperature does come up, not quite all the way to the mark between 180 and 212. just letting you know i get the same thing, i think it's as someone mentioned "they just run hot". </div></div>

Does your car "burp" about a quart of coolant every time you stop after the car has been running above 200 degrees?

[mrpushbutton]

The first antique car engine rebuild I was ever involved with was a 1938 Buick special. It was very touchy as to temperature. It would do little trips around town OK, as long as it was under 85 degrees. But go freeway-to-surface streets and it would climb up and puke out. It would run very rough, we would pull the plugs and find that the electrodes were touching each other-no gap at all! Finally bit the bullet and rebuilt the engine. Upon dissasembly we found that the top ridge of the pistons (between the uppermost ring grove and top of piston) was breaking off in chunks that were dancing on the top of the pistons and mashing the plug gaps closed.

We sent the block, head, pans, brackets and manifolds to the chemical stripers. the cooling passenges had the usual build-up of shale-rust, so deep that you could sink the tip of a screwdriver well into it. Everything came back spotlessly clean. after all of the usual rebuild machining, the engine went back together, and ran beautifully, didn't care about temperature. I could run the car 65 mph on the freeway, get of and troll in a parade, and it stayed at temp. I have since done other antique engines this way, except now I have learned to paint the inside cooling passenges with epoxy primer, while I'm priming the block. Just tape off the freeze plug holes and pour some e-prminer in, turn the block on the engine stand, and raise end to end with your cherry picker/chain fall to slosh the primer around. These engines are getting old now, and some were not always run on antifreeze.

[Oxnard Montalvo]

Good idea, a flush.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> If I turned the heater and defroster on wide open the temp would drop back down to an acceptable range. </div></div>

I hope you rolled the windows all the way down.

<img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" />

[Guest sixpack2639]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Good idea, a flush.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> If I turned the heater and defroster on wide open the temp would drop back down to an acceptable range. </div></div>

I hope you rolled the windows all the way down.

<img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> </div></div>

ALL 4 windows down, both wing vents open and both fresh air ducts open and still roasted! LOL

[Guest ZondaC12]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">

Does your car "burp" about a quart of coolant every time you stop after the car has been running above 200 degrees? </div></div>

uhhhhh....no. lol <img src="http://forums.aaca.org/images/graemlins/laugh.gif" alt="" />

[West Peterson]

Thanks for all your replys.

My friend took his thermostat housing off last night. It appears that the water regulator/spring mechanism "thingy" at the bottom of the unit was installed upside down. There was a thermostat in there as well, so he's going to check to see if it's working properly. We're hoping that the "burping" of about a quart of coolant was caused by this incorrect installation.

I've forwarded all of your replys, and he's absolutely astounded every time he hears someone that says they take their car up to 65mph and can hold it at that speed for long periods of time. He says his car absolutely screams at 45-50mph and is afraid to take it any faster. I haven't ridden with him yet at those speeds, so I haven't been able to give an opinion as to whether the car is stressed at that speed or not. It seems a bit slow for a Buick, no matter what rear-end ratio he's got in it.

[The Old Guy]

Gearing is very important in the older Buicks. The ratios varied from 4.4 to 3.6, and they make a tremendous difference. The later (40 up) straight eights had the option of gears down to 3.4. I have a 3.4 in my 40 and drive it 70-75 on the interstates regularly.

[Guest ZondaC12]

to chime in on the noise/stability/etc at speed issue, at 55-60 mph, with the 4.4 rear end (its a special, series 40, im pretty sure that was the only rear end avail. in the 40 right?) it's singin', but its doesnt sound like its about to blow its top or anything. according to the chart in my shop manual its about 3200 rpms i think at that speed, and even in a modern car youd hear the engine pretty good. i took it from where i live (right near Albany NY, to Rhinebeck NY, was about an hour and 45 min of driving, 55-60 mph 95% of the time probably, was smooth, ran nice, cant find any ill effects. obviously the engine is wearing faster than cruising around town 30-40 mph at between 1600 and 2200 rpms, and its an original engine in my case with 84000 miles almost, compression in all cylinders is like 95 or 100 psi dead on every one, but still its not new, not rebuilt or anything. it should be alright, bottom line. i dont really like driving the thing at that speed a whole lot, but the car doesnt shake or anything it rides smooth even at that speed, and it seems the engine is up to the task and is tough enough, so i dont sweat it. i just keep an eye on the oil pressure gauge, which always is where its supposed to be, same with the temp gauge. im not an expert by any means, just an 18 year old whose put about 500 or so miles on his car since i started driving it this spring, just driving it and observing what happens.

[Guest De Soto Frank]

In general, I (personally) regard any engine with a stroke of 4 inches ( or longer) as "long-stroke", and like to keep the revs under 3,000 rpm for prolonged driving... especially any un-restored, high-mileage engine.

Now, if you're starting with a fresh, carefully rebuilt, balanced engine, it'll tolerate the higher REVs better...

In 1938, there just weren't that many places East of the Missippi where one could drive more than 50 MPH...

As a tender (read: "clueless") youth, I cooked my share of 216 & 235 Chevy sixes, trying to pound those vehicles down the road at 55-60 MPH with a 4.11 to 4.57 rear... they'd do it for a while... then the "man with the hammer" would start pecking away inside the crankcase...

Just my thoughts on the subject...

You can't just send away to Sears for reconditioned Buick rods for $10 a piece these days...

[Guest ZondaC12]

well in case thats the message you're getting from me, De Soto Frank, let me tell you that my feeling isnt that "oh itll be fine", just that it seemed ok. i dont feel totally comfortable because i think youre right and the engine's "max rpm" at least from what ive heard is like 4300 rpm and i think thats probably PUSHING it, as in if it were a modern engine that'd be above the redline rating, i would never drive the car that fast, though fellow member here Oxnard Montalvo said once in a thread that he drove his 38 special at 85 mph (top speed) when he first bought it just to see how it did <img src="http://forums.aaca.org/images/graemlins/shocked.gif" alt="" /> and it handled it but he stayed there for a short time. i mean to me it doesnt sound like, again, like its about to blow but its a bit loud and you know its going fast. the only time its been at that speed for a prolonged time was the trip to rhinebeck. i have no idea what my dad did with it when he was my age and had the car back in the sixties. he couldnt have abused it too much or it wouldnt be in the shape its in now, right? but when i was like 10 years old he told me "you know me and my friends would sometimes race around in the buick at like 80 miles an hour (and other friends in another car) throwing cherries and stuff at each other". <img src="http://forums.aaca.org/images/graemlins/laugh.gif" alt="" /> im sure thats what he said. "cherries and stuff". so i wonder... <img src="http://forums.aaca.org/images/graemlins/smirk.gif" alt="" />

i really enjoyed driving it the long distance to the show and i wanted to go to the show and it happened to be far away. if it were my choice wed have been going 45-50 mph, but we needed to make decent time and putting myself in the shoes of the memebers of the caravan driving 60's wildcats and skylarks id be annoyed too if i were them, having to crawl down I-90 at 45 mph.

[Guest De Soto Frank]

Zonda...

Sorry, I get "preachy" sometimes... <img src="http://forums.aaca.org/images/graemlins/blush.gif" alt="" />

It took me quite a while to understand what my old iron "was trying to tell me"...

I would imagine that rebuild parts for the Buick eight are more expensive and more scarce than stuff for the Stovebolt Chevy six, so if you 've got one in good shape, it would be nice to keep it that way...

According to my math, my '41 De Soto, with 228 cid six, 4.11 rear, and 6.50 x 16 tires is spinning about 2900 RPM @ 60 MPH. Now, since the mid Twenties, Chrysler Corp had an engineering dictum that all of its engines must be able to withstand a MINIMUM of 50 hours continous operation on the test bench at Full power output; for my car, that would be 105 HP @ 3,600 RPM ( We MoPar guys consider this to be the "official" redline).

Even though 2,900 RPM (60 mph) is 700 RPMS under Redline, it still sounds darn busy, especially on a motor that's showing 101,000 miles...

It sounds a lot "happier" at around 2,500 RPMS(or less), which as about 53-55 MPH ( Still "suicide-slow" on the Interstates, I'll admit !). I try to keep her under 55 for prolonged cruising.

I think it's a bit of a cruel joke that in the case of Buick and Chevy, with their superior valve-in-head design, "handicapped" their cars with stump-puller rears into the early '50s, and did NOT offer an Overdrive option... and with that torque-tube, it's darned difficult to retrofit an OD into the car ! In the case of Chevy, they didn't offer Overdrive until 1955, when they had both done away with the Torque-tube, and now had that small-block V-8, so they could put taller gears in the rear-end, and fairly eliminating the need for OD ! <img src="http://forums.aaca.org/images/graemlins/crazy.gif" alt="" />

I think one of the keys to happy motoring with the older (slower) cars is to stick to the US and WPA "highways" ( although I'm finding a lot of knuckle-heads that still want to race along at 70 MPH in their SUVs on these secondary roads ! <img src="http://forums.aaca.org/images/graemlins/mad.gif" alt="" /> ).

Glad to hear you're driving your '38 Special, and hope you have many miles of enjoyment with it !

A '37-'38 Roadmaster or Century is on my "wish-list" !

<img src="http://forums.aaca.org/images/graemlins/cool.gif" alt="" />

[Guest MNRoadMaster]

My '47 Buick Road Master cruises quite nicely at 80 or so and I'm sure it'll do quite a bit more. As I understand it this was the fastest car in it's day. (40's) (In the 50's the Hudson Hornet was the only car that could beat it.) The speedometer says it'll do 120 and I'd sure bet it will - not that I'll try it without some work on the original 48 engine first. It floats down the road. I have a "Buick Buddy" who knows these cars well. Here's a story about him checking out a 30's Road Master with the tall gears in it. The gentleman who was showing him the car asked if he wanted to take it for a little test drive. So off they went. The owner tells my buddy to leave it in second until he tells him to shift. "And don't be scared to push down on the foot feed there you know." I believe he said that they were doing better than 60? or so in 2nd before he told him to shift / accelerate and he told me "Holy crap - the thing pinned me back in the seat as it took off like a rocket ship! He also claims that there's nothing like it in the world - flooring an old Buick - what a feeling!' That's about as closely as I can quote him. Even with a Super - or Any Road Master especially there's lots of power there - especially if it's in reasonable condition. The 320 engine was used in greyhound buses, of course they had blowers of some sort on the engine. These cars were built for the highway as well as gravel roads. I'm quite certain a Special / Super should cruise in the 70's range in any kind of reasonable condition quite nicely. I have a friend that has a 50 Super that does so regularly - no sweat. According to the "What you'll want to know about your '47 Buick" Manual: on page 23 the 50 series will get 13 mpg @70 mph. I know of other folks that will guarentee a decent running Buick of this vintage has plenty of pep and speed. If you look around here on this list you'll see that in fact they are still hot rodding the Buick 320 inline eight...

Happy and safe motoring!

Oh and as for the overheating - I'm told be several sources that it MUST have a thermostat as well as the spring assembly in the housing - otherwise the water flows too fast to cool - even with the ample radiator these cars had. CAREFUL if you do a flush with an original metal gasket it it as the flush could harm the gasket - especially an "extended flush"...

"1937-44" makes a good point about the radiator cap and others have mentioned timing / fuel so there is more info to cover your bases.

On an additional note here - there is a product my family has been using for years - Zecol radiator conditioner and also Zecol radiator flush. My boys and I just did a flush / rinse (times 3) and dropped our temp at least 10 degrees. The conditioner will clean as you drive as well so it's good for maintenence. I'm fairly certain we will have to take the frost plugs out and do some cleaning, but I'm trying to stall it off until I get the head done and new rings in it... I'm still trying to figure out where to get the radiator hose filter "Grandpa" mentions here to check out the block's status...

Don

Edited July 13, 2010 by MNRoadMaster
additional info (see edit history)

[1937-44]

One more item to check would be the radiator cap. If it isn't sealing it could account for some of your problem.

I've driven my 1937 Special across the New York thruway without problem at speed (35 years ago) but don't really remember how fast I went. The engine is still untouched except for a recent valve job and it has always run under 180 degrees. I don't abuse it as much as I once did, but I still put it on the highway for short times and it doesn't seem to mind it at all.

Carl

[Guest Earl]

People just didn't drive all that fast in the 30's & 40's. My Dad used to tell me that all the time. That was one reason they didn't have speed limits, they really didn't need them out in the country. My Mom is 80 and she always drove fast, but even she admits she had to be careful because you'd come flying over some hill (she had an Olds 88) and there would be some Model A poking it's way down the road. And they respected property lines in those days and had all sorts of corners to turn. And remember how those old highways went down the main street of every town they passed through? And here in the midwest we had those stupid highways that were narrow with curbs on both sides. And then you'd need to figure out what to do when you saw a semi coming.... Out west it was different, but even then, most of those people didn't drive the miles we do today. There's a picture of my Dad plowing snow in the middle 30's and behind him you can see that gas was something like 12 cents a gallon. I said something to him about how cheap gas was then. He reminded me that he was making about 45 cents and hour and it didn't seem so cheap at the time! They knew that speed was hard on mileage.

For whatever reason my '41 Buick really likes to go 50-55. But it will go 75 easily as well, but I don't trust my tires for those speeds for a long time. It has the 3.6 rear end and is a Century. I put one of those LED brake lights in the back window and that seems to let the folks behind me know I'm slowing down a lot better than the factory brake lights. I see fewer suprised looks in the rear veiw mirror now.

[Guest 46BuickSuper]

I am soooo happy to hear that overheating isn't unique to my 46 Buick Super. I took the manifold off the engine and took the freeze plugs out and cleaned out the water reservoir. Had the radiator cleaned and flushed, new thermostat, radiator cap and still it pegs when driven in warm temps. I'm considering installing an electric fan to assist the radiator. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>

Also the under the seat heat is always on, maybe if i clean that system out it would improve the water flow from the radiator.<o:p></o:p>

And to comment on speed- I drove it on I-95 near DC (where I live) at 65 with no problem in engine noise or stability. I would prefer to not go above 55 but when I'm on the highway I have to drive at a decent clip or I will be road fodder.<o:p></o:p>

I love this forum- it really does take a "village" on this hobby.<o:p></o:p>

[Guest MNRoadMaster]

I put an electric fan off of a 90's buick that had 2 fans in it - one smaller one speed and one larger 2 speed - so you know it was a full sized car. Anyways the 2 speed fan fits really well and I wired it to the high speed with 6 volts - it cartainly helps in needed.

Time to hit the bone yard!

Did you deal with the water jackets accessable by removing the head?

I was talking to an older mechanic here and he was telling me about a plugged heater core - in desperation he said he put in muriatic acid and steam cleaner soap and it worked very well. I can tell you that he does know his old cars very well and has been a mechanic for many many years.

Don

[Rusty_OToole]

"I think it's a bit of a cruel joke that in the case of Buick and Chevy, with their superior valve-in-head design, "handicapped" their cars with stump-puller rears into the early '50s, and did NOT offer an Overdrive option."

Where did you get the idea valve-in-head was superior? It certainly was not. Quite the reverse.

When the Ricardo type head was introduced in 1921 or 22 it made the flathead king. After that no one built anything but a flathead for the next 25 years.

There were a few exceptions, cars that had nailed their colors to the mast so to speak, by promoting their OHV engines BEFORE the Ricardo head came out.

This camp included Chev, Buick and Nash who were more or less stuck with OHV engines unless they wanted to admit all their ads were bullshit.

The only other exceptions were a very few, exotic engines with overhead cams as well as overhead valves like Stutz, or the V12 or V16 Cadillac that was forced to use overhead valves because their narrow cylinder angle did not permit side valves.

Chrysler had the superior flathead design which laughs at high RPMs thanks to its light valve train. They also have full pressure lubrication and insert bearings, while Chev has neither and Buick has only the pressure lubrication but with the inferior poured babbit bearings.

Of the 3 designs, any Chrysler product in good shape will handle the high speeds best, while the Buick will do OK as long as the bearings last. The Chev is more or less hopeless at speeds over 50 or 55 and always was.

This was well known in the 40s and 50s. My father blew up a 51 Chev before he found this out, after that he knew to slow down or buy a different make of car. Any mechanic or savvy car guy could have told him.

[Guest MNRoadMaster]

From Wikipedia:

History and applications

Although flathead in-line 4 and 6 cylinder engines were frequently used for automobiles, tractors, and other products, the best known flathead automotive engine is the early 20th century Ford V-8, which has both sets of valves (intake and exhaust) located on the inside of the "Vee," and which are all operated by a single camshaft located above the crankshaft. Other common configurations included in-line ("straight") eights and a V 12 Lincoln version of the Ford V 8.

Due to cooling and efficiency problems, flathead engines fell out of favor in "high power" applications, such as aircraft engines, prior to World War I.[citation needed] However they lived on for some time in the automotive world and were used on the Jeep for instance. Flatheads are no longer in common use for automobiles (except in some rodding and customizing circles),[1][3] although they are still used for some small-engine applications like lawnmowers. Because of their design, the size of valves and the compression ratio are limited, which in turn reduces available power and economy."

Also from wikipedia:

"Advantages

Overhead valve (OHV) engines have specific advantages:

Smaller overall packaging — because of the camshaft's location inside the engine block, OHV engines are more compact than an overhead cam engine of comparable displacement. For example, Ford's 4.6 L OHC modular V8 is larger than the 5.0 L I-head Windsor V8 it replaced. GM's 4.6 L OHC Northstar V8 is slightly taller and wider than GM's larger displacement 5.7 to 7.0 L I-head LS V8. The Ford Ka uses the venerable Kent Crossflow OHV engine to fit under its low bonnet line.

Less complex drive system — OHV engines have a less complex drive system to time the camshaft when compared with OHC engines. Most OHC engines drive the camshaft or camshafts using a timing belt, a chain or multiple chains. These systems require the use of tensioners which add some complexity to the engine. In contrast a OHV engine has the camshaft positioned just above crankshaft and can be run with a much smaller chain or even direct gear connection.

[edit] Limitations

Some specific problems that remain with overhead valve (OHV) engines:

Limited engine speeds or RPM — OHV engines have more valvetrain moving parts, thus more valvetrain inertia and mass, as a result they suffer more easily from valve "float", and may exhibit a tendency for the pushrods, if improperly designed, to flex or snap at high engine speeds. Therefore, OHV engine designs cannot revolve ("rev") at engine speeds as high as OHC [3]

Modern OHV engines are usually limited to about 6,000 to 8,000 revolutions per minute (rpm) in production cars, and 9,000 rpm to 10,500 rpm in racing applications. In contrast, many modern DOHC engines may have rev limits from 6,000 rpm to 9,000 rpm in road car engines, and in excess of 20,000 rpm (though now limited to 18,000 rpm) in current Formula One race engines using pneumatic valve springs. High-revving pushrod engines are normally solid (mechanical) lifter designs, flat and roller. In 1969, Chevrolet offered a Corvette and a Camaro model with a solid lifter cam pushrod V8 (the ZL-1) that could rev to 8,000 rpm. The Volvo B18 and B20 engines can rev to more than 7,000 rpm with their solid lifter camshaft. However, the LS7 of the C6 Corvette Z06 is the first production hydraulic roller cam pushrod engine to have a redline of 7,100 rpm.

Limited cylinder head design flexibility — overhead camshaft (OHC) engines benefit substantially from the ability to use multiple valves per cylinder, as well as much greater freedom of component placement, and intake and exhaust port geometry. Most modern OHV engines have two valves per cylinder, while many OHC engines can have three, four or even five valves per cylinder to achieve greater power. Though multi-valve OHV engines exist, their use is somewhat limited due to their complexity and is mostly restricted to low and medium speed diesel engines. In OHV engines, the size and shape of the intake ports as well as the position of the valves are limited by the pushrods."

Most automobiles today have some sort of OHV arrangement (OHC or DOHC) and there are still Some pushrod style engines available as well. I'm personally more partial to the pushrod style because I find them easier to work on than the modern OHC DOHC engines.

I'm not "bashing" the flatheads here because they are good engines too, I'm simply passing on some information I have found. There's an interesting article at: The Pushrod Engine Finally Gets its Due - Column - Auto Reviews - Car and Driver

as well.

The Buick was well known for dependability as well as speed. My friend tells me that in the early 70's he street raced a 69 Charger 40 miles and beat him in his 48 stock Buick. There are other stories as well. As for the babbited bearings - that is also a matter that has been much debated. Like anything else - including this subject - there always seem to be trade offs. Your Mileage May Vary...

Modern lubricants make a huge difference in any of our older engines holding up.

The original engine is back in my car with a very much on the cheap - rebuild with much help from my friends! My heating issues went away and I have a 180 degree thermostat in it. When the engine went south it got plenty hot and it appears that this essentially "cooked" out the block. Also my friend did a radical center exhaust manifold repair that is working like a charm!

Edited November 29, 2010 by MNRoadMaster (see edit history)

[Rusty_OToole]

Whoever wrote the Wikipedia article did not know what he was talking about.

It is easier to explain if you have some illustrations. Can you find a picture of a flathead (any make) with the head off? Do you notice that the valve chamber is considerably wider than the cylinder bore and the valves are large?

In a typical OHV engine the valves must be small enough to fit within the cylinder bore, and small enough that the cylinder wall does not shroud the valve. In the long stroke, small bore engines of the twenties and thirties the OHV engine is at a considerable breathing disadvantage. But it did have the advantage of a smaller combustion chamber and higher compression.

It did, that is, until the Ricardo combustion chamber came along. Ricardo's inspiration was to bring the roof of the combustion chamber down until it practically touched the piston at top dead center. This meant higher compression and a small combustion chamber, negating the advantage of the OHV engine.

But the flathead still had the advantage of larger valves, more breathing room around the valves, light weight free revving valve train, and no chance of the valve hitting the piston in case of a broken valve spring.

It was also simpler, lighter, more compact, quieter and cheaper to make and cheaper and easier to service.

It's no wonder that all new engines designed after 1922 were flatheads.

The exceptions that prove the rule, were those makes who were already committed to OHV (Buick Chev and Nash) and Stutz and Duesenberg.

These last 2 were cost no object luxury cars with a performance reputation. At that, their overhead cam engines had a hard job outperforming a flathead. Look up the Stutz/Auburn stock car record contest of 1927. Both were straight eights of the same bore and stroke and the same displacement. Stutz had an OHC engine, Auburn had a conventional flathead. On Daytona Beach the Stutz managed to beat the Auburn by less than 2 MPH. The Stutz cost $5000, the Auburn under $2000.

There is a similar conparison between the flathead Pierce Arrow V12 and Duesenberg straight eight. In the early 30s Pierce set speed records on the Bonneville Salt Flats. I believe their best performance was to average 117 MPH for a full 24 hours. This was real rocket ship stuff for that time.

The next year Ab Jenkins broke the record with the Mormon Meteor, a special Duesenberg with supercharged OHC straight eight known to be the most powerful car of its time. It is significant that it took such a car to beat the unsupercharged flathead Pierce. It is also significant that the next time Jenkins brought the car to the flats it had a Curtis Conqueror aircraft engine under the hood. Evidently it strained the supercharged Duesy to the utmost to beat the Pierce and it had reached its limit of performance.

Since the Pierce Arrow displaced 429 Cu In and the Duesenberg 427 Cu In this is a fair comparison. The 2 cars were also similar in overall size and weight.

Edited November 30, 2010 by Rusty_OToole (see edit history)

[Rusty_OToole]

You could also look up the HP and torque figures for flathead vs OHV engines in the twenties and thirties. You might be surprised.

[Guest MNRoadMaster]

Thanks so much for your thoughtful and educational post regarding this topic Rusty! I love learning all about this stuff! I do have a 49 Plymouth Special Deluxe I'm hoping to get running in the future. I'm determined to get the original, but very stuck engine going rather than putting something diffferent in it.

[Rusty_OToole]

There is another interesting comparison of flathead vs overhead cam performance. The LeMans 24 hour race of 1929. The winner was a six cylinder Bentley with overhead cam engine. Second was a Stutz overhead cam straight eight. 3d and 4th place were taken by flathead six cylinder Chryslers.

The point is that an OHC performance car could beat a flathead, although not by much. The OHV pushrod engines weren't in it and had no performance advantage over a good flathead.

This was also proven many times by the Ford flathead V8. It was the hot rod king for many years. The OHV Chev had its fans but seldom beat the Fords.

[Guest De Soto Frank]

If L-head engines were "superior", how come no one has used them in American autos since Rambler finally abandoned them in 1964-'65 ?

Even Chrysler got away from them after 1959....

I will agree that most were dead reliable, but most had breathing issues when it came to performance.

Hudson probably exacted the most "performance" out of an L-head engine, with their 7-X "severe-usage" version of the 308 Hornet six.

Probably the best-breathing flat-heads were the old T-head racing engines before the Depression; but their better breathing came at the expensive of a much heavier and complicated engine.

In my opinion, the Achilles' Heel of both the Buick Eight and Chevy Six was their lack of pressurized oiling for the rods... splash lubrication is simply not very effective at high speeds.

[Rusty_OToole]

There is such a thing as progress. The long stroke flathead was state of the art from 1921 to the early fifties. Then the new short stroke OHV designs took over.

What made the difference was the new high octane gas plus the short stroke design.

A flathead is limited to about a 7.5:1 compression ratio. Squeeze the combustion chamber any tighter and you cut off the breathing. Plus the new big bore short stroke design made room for bigger valves.

Hudson and Packard used some clever design tricks to push the compression higher, even then they could not match the OHV head. Packard at 8.7:1 was the highest compression flathead ever. A few years later OHV high performance gas engines were built with 13:1 compression and diesel engines even higher.

Here is another interesting comparison. In 1949 2 American luxury car makers brought out brand new V8s. Everyone remembers the trend setting OHV Cadillac but who remembers the flathead Lincoln? It was obsolete the day it was born and was dropped in 1952 in favor of a new OHV V8.

Would it surprise you to learn the Cadillac made just 6 more horsepower than the Lincoln ? That's right the 331 Cu In Caddy made 160 HP the 337 Cu In Lincoln 154HP. This was accounted for by the Caddy's higher compression, 7.5:1 vs 7:1.

At that time the OHV had little or no advantage over the flathead but how things changed in the next few years. The Caddy was designed in anticipation of higher octane gas. Once it was on the market they upped the compression and got 235HP with the same displacement.

If high octane gas had not become available we would still be driving flatheads.

Edited December 1, 2010 by Rusty_OToole (see edit history)

[Rusty_OToole]

In the 30s and 40s it was the OHV engines that had breathing issues. Their valve sizes were restricted by the size of the cylinder. Flatheads suffered no such restriction. Look at any flathead with the head off. Compare the valve sizes to a pushrod engine with the same bore. The flathead Harley Vtwins were a particularly good example. Their valves are huge.

Some racing and performance OHV engines had hemi heads with valves set at an angle. This allowed larger valves less shrouded by the cylinder. Stutz, Duesenberg and Bentley featured the hemi head with overhead cams. They had the advantage over the typical flathead although not by much.

The typical pushrod OHV had parallel valves and they were considerably smaller. This design had a hard job keeping up with a good flathead.

[LAS VEGAS DAVE]

FLATHEADS ARE BETTER AND COWS ARE QUICKER THAN HORSES