1957 Buick Roadmaster, hesitation problem

[vermontboy]

Looking at my "quick guide" for troubleshooting (Peterson's Basic Auto Repair Manual from the 60's) it would appear that there are only a couple of things not checked to date. First would be plugs and wires (no cross firing from rubbing or running together, or at plug insulators). Second would be any primary or secondary ignition wiring.

 

Fixing these things is strictly trial and error and can be a bit frustrating.. If it was mine the first step I would do would be jumping around the ignition switch.

 

Just my two cents.

[JohnD1956]

I tend to think it is not the ignition switch.  Other fellows on the Buick side of this Forum group have reported the same phenomena. My 56 Super with the Rochester 4 bbl is doing this right now.  Before my last rebuild ( 2 years ago) it did not do it, now it does.  The thing is, it's not an every time event.  Start it cold, and no hesitation. Warm it up and it hesitates off the line maybe 50% of the time.  No telling when, or under what circumstances it will do so. I've had my car out just about every other day for the last two months or so, and am constantly trying to analyze what's happening here.  Here is my best guess.

Since folks who are running the carter 4bbl,  and some the Edelbrock new carbs, with no such issue, I doubt this is ignition related, except for how the carb impacts vacuum, thus the vacuum advance.  I suspect one or more gaskets in todays Rochester Carb kits have a misaligned hole that impacts the operation.  During warm up when the choke is partially closed it masks this issue with a richer mixture.

 

I am no engineer, and this is just a guess.  I don't know how to go about analyzing this theory and I am not desperate enough to dig deeper. The hesitation is slight. It never stalls, and I am fortunate that I don't do a lot of stop and go driving.  I did purchase almost every part to rebuild a spare distributor.  Just haven't done the work yet cause other than this slight infraction, I am totally pleased with the vehicles performance.  If I was doing more stop & go driving I'd probably reconsider that.  But for now it's no big deal to me.

 

I do have a 56 Rochester from a vehicle that was junked decades ago.  I have not been able to get one screw to turn loose on it yet.  But if I get it apart and can save the gaskets, I may buy a new carb kit to see if my theory is correct. 

[carbking]

We are seemingly considering two DIFFERENT hesitation issues in this thread:

 

(1) The issue of Warren (nailhead) of an intermittant engine cutoff and recovery while driving at a constant speed.

(2) The issue of JohnD of an intermittant hesitation while accelerating.

 

I do not see Warren's issue being carburetor related - either ignition or possibly contaminated fuel.

 

JohnD's issue MAY be carburetor related, possibly a lean condition from the ethanol fuel. We have advocated increasing the diameter of the idle tubes by 0.002 inch to alleviate this condition when we talk to people about an idle/acceleration stumble. However, setting the idle for the highest vacuum reading will also give this stumble on a hot engine as it causes an incorrect balance between the idle fuel supplied by the lower idle port and the idle transistion circuits. Accelerator pumps get blamed for many things (and occasionally, they are actually the culprit), but a leather accelerator pump is generally good for the life of the owner! Cannot say the same about the chemically created accelerator pumps. JohnD - as to the gaskets today having a hole in the wrong spot - there is a lot of stuff coming from offshore suppliers, and I have not looked at most of it; however we have been using the same gasket dies for our gaskets for probably 40 years. And have used our gaskets successfully when we were still active restoring carbs.

 

As to the comments concerning the Rochester 4GC and the Carter AFB/WCFB carbs. We restored many 4GC carbs. The only issue I can remember was with a 1956 or 1957 Oldsmobile (don't remember which) 4GC that some previous rebuilder had installed the wrong choke spring. I tested the spring, and it tested good; but Oldsmobile had a much longer warm-up period (controlled by the spring), and the spring on the car allowed for hesitation from idle when the choke was off but the engine was not totally warmed up. I totally missed the fact that the spring had been changed on the initial restoration. Changing the spring solved the issue. The 4GC's are, in my opinion, great carbs; but the engineers did not forsee the stupidity of those in authority demanding E-10 (or worse). Thus these carbs, like any other carb, need to be slightly recalibrated for the different fuel.

 

Jon. 

Edited July 4, 2016 by carbking (see edit history)

[padgett]

Back in the day we had things like homebuilt flow benches, distributer machines, Sun Scopes, and exhaust sniffers. Today we have computers. That said, a minor hesitation on a street engine would just be something we lived with and a lumpy idle was not to be scorned.

 

Somebody good could probably just drive around the block and tell you what to do. Otherwise richening up the mixture a bit is not a bad thing unless you are competing in an economy run. Ethanol does not have as many btus/lb as pure gasoline and you need to compensate.

[JohnD1956]

You're right Jon, I forgot about the cut out while driving part of the original post.  I apologize for going off track, but I thank you for your thoughts on my situation.   

[Guest]

On ‎6‎/‎21‎/‎2016 at 4:39 AM, nailhead9 said:

 

I am presuming that it idles fine (yes it idles very well), If you stomp on it does it really go flat? Yes! while driving if I just floor it, it dies momentarily and then takes right off.

 

Thanks again to all who are helping solve this problem for me.

 

Warren

Well, it seems you do have a accelerator pump issue. you also have a steady state issue as well.

I read this thread and through the dialogue it seems like it was not a pump involved here until the quote above.

 

So you've covered the basic's:

Good engine compression.

No engine vacuum leaks

Ignition system-  distributor bushings ok, points clean and set, good breaker plate ground, good plug wires and boots. Good cap and rotor with no carbon tracks arching, spark plug in good order, engine running-   proper mechanical advance-how many degrees and at what rpm, vacuum advance and how many degrees, timing set to specification what is the total advance ? plus initial?

Fuel system- fuel condition, tank vented properly?  fuel pump pressure...how many pounds? Carburetor bench tested for accelerator pump ( some carbs have a pump stroke adjustment ) Carburetor is absolutely clean- you need to disassemble to look.. has proper gaskets? 

[nailhead9]

To everyone taking the time and helping with some very informative suggestions. For the first 9 years that I owned the Buick I never had this problem. The Rochester 4Jet has been professionally rebuilt. The problem happens while driving without changing speed and is starting to really show up when going up a grade. Hope these clues help with all your thought possess. Thank again I will keep you informed thru this post and let you know if and when I get the problem solved.   

 

being car guys you may enjoy see this short video I made yesterday while driving my 1926 Model T Coupe

 

[JohnD1956]

Imagine what those Model T's could tell you , if they could talk.

 

Great video... and thanks for the ride.

[JamesBulldogMiller55Buick]

perhaps it is a problem with ethanol 

Maybe the carburetor needs rebuilding  again

Edited July 9, 2016 by JamesBulldogMiller55Buick (see edit history)

[nailhead9]

Thank you John and James, it definitely is a problem with the gas (1957 Buick's called for premium gas, which in 1957 was leaded 104 octane (unless you got Amoco lead free gas which was called "white gas", back in the day), although I do not believe that's what I'm trying to fix as it has just started doing this the last coupe of years. 

 

Warren

[Guest]

38 minutes ago, nailhead9 said:

Thank you John and James, it definitely is a problem with the gas (1957 Buick's called for premium gas, which in 1957 was leaded 104 octane (unless you got Amoco lead free gas which was called "white gas", back in the day), although I do not believe that's what I'm trying to fix as it has just started doing this the last coupe of years. 

 

Warren

Remember the octane rating is different than when your Buick was new just like the horsepower ratings are different since they changed from gross HP to Net HP rating in the very early 70's. You must remember your car has been running on ethanol for a good long time now ever since they substituted it for MBTE. I must admit though it's some mean stuff though. It reminds me of people who have diabetes who don't actually die of diabetes, but rather what diabetes does to the other parts of the body and in most cases the circulatory system in particular.  

[JamesBulldogMiller55Buick]

I've sworn off ethanol

For my Roadmaster, I put five galoons of 112 octane leaded racing fuel. I fill up rhe rest of the way with 87 octane non-ethanol (9-12 gallons)

 

 

[Guest]

2 hours ago, JamesBulldogMiller55Buick said:

I've sworn off ethanol

For my Roadmaster, I put five galoons of 112 octane leaded racing fuel. I fill up rhe rest of the way with 87 octane non-ethanol (9-12 gallons)

 

 

I know you probably don't care at all so there is no need to comment, but it's illegal to use any fuel laced with lead on a American HWY these days.

[JamesBulldogMiller55Buick]

2 hours ago, helfen said:

I know you probably don't care at all so there is no need to comment, but it's illegal to use any fuel laced with lead on a American HWY these days.

you're right.

there is no need to comment.

But, you'll be glad to know that the tag is still on my matress

Edited July 11, 2016 by JamesBulldogMiller55Buick (see edit history)

[nailhead9]

James, I went to Haffner's in Hudson NH, got 12 gallons of 100 octane leaded gas and did not notice any difference in performance, I don't remember if it helped my hesitation problem. Has your mixture solved that problem. At the time I paid around $8.00 a gallon for the 100 octane.

 

Thanks, Warren

[JamesBulldogMiller55Buick]

On 7/11/2016 at 6:17 AM, nailhead9 said:

James, I went to Haffner's in Hudson NH, got 12 gallons of 100 octane leaded gas and did not notice any difference in performance, I don't remember if it helped my hesitation problem. Has your mixture solved that problem. At the time I paid around $8.00 a gallon for the 100 octane.

 

Thanks, Warren

I've not had problems with hesitation.There was a lot of knocking and pinging  

The higher octane made a BIG boost in performance. And no more knocking and pinging..

my mixture is about $4/gallon

Edited July 14, 2016 by JamesBulldogMiller55Buick (see edit history)

[padgett]

The higher the octane, the slower the burn and the more advance needed. So timing that pings a bit on pump gas may be retarded on 100 (research method ?) octane. In the bad old days the rule of thumb was to advance until revving with the vacuum advance disconnected produced a little rattle then back off two degrees and reconnect the VA. This would often give a little pop when stomping it as it takes a second or two for the cruise VA to back off.

 

AFAIR part of the GM engine test cycle was "Standard Test 7 - Maximum Power and Detonation". Title speaks for itself. Anyone else remember those big Toledo dials ?