1933 model 56

[Branded]

High evreyone my name is Dave and this is my first post. Hoping you fellas can answer a couple question. I buddy bought this restored 33 awhile back and it has a few issues. To begin with it was idling rough and back fireing through the carb. Cleaned the carb and everything is better but it seems that even when running at normal temperature the choke needs to be pulled not quite 1/4 way to keep from having a slight pop back through carb when giving it throttle. Is this normal for these cars. Owner also say heat riser has been blocked off. I havent driven the car but owner says it gets hot driving mainly when on hills. temp looks good after idleing for 2 hours. Used a temp gun and radiator is about 177 degrees at the top and 160 at the bottom. Any ideas or where to start.

[Guest outlaw car man]

he may have blocked the heat riser at the front , a common thing to do, BUT left the two heat riser tubes in place that maybe rusted & therefore feeding exhaust gas back into the intake manifold. Exhaust gas doesn't burn to well !!

That being said you really have to inspect the two tubes well, sometimes you can't see a rust holes and assume all is well- I've done that.

Suggest getting a Shop manual, reprints or whatever- Ebay.

Start there then head to the almighty Marvel if it still continues and the forum can pick it up again.

Keep us posted.

OCM

[Bob Engle]

Welcome to the wonderful world of early Buick Carb issues. First, the reat riser blocked off is not a problem, gas so much easier to get to vaporize today than what they had in the early 30's.

Second take the time to go back and read through all the threads on 31,32, 33 Marvel carb issues and solutions. Floats, cracked jet tubes, fuel pressure, dirt in jets, etc. You will be an expert at removing and assembling them in no time.

I'm a believer in using a vacuum gauge to monitor what's going on when they don't want to run right. If you are not familiar with their use, just google tuning and troubleshooting with a vaccum gauge.

The engine does not sound like it is running too hot, but the early straight 8's had a problem with crud buildup in the back portion of the waterjacket at # 8 cylinder. Is the oil/water cooler operational? Have you run a compression check and leakdown check on the cylinders?

This should get you started.

Bob

[Branded]

Thanks for the replies fella this gives me a starting point, I didn't realize the car had a water/oil cooler (wheres it located and what problems with it should I be looking for. Whats the best way ti determine if there is crud built up in the water jacket. The straight 8 is new new animal to me I,m 55 years old and been a motorhead all my life but mostly small block and big block Chevy. This straight 8 seem a little intimidating but hey it just a combustible engine RIGHT.

[Bob Engle]

There's nothing intimidating about the straight 8's. Just think Roller cam and tappets in 1931!!

The oil water cooler is just above the water pump. the cover has the Buick logo on it. Leaking water into the oil system, or oil into the water are the key problems. The cooler can restrict water flow or oil flow.

The easist way to check for water jacket blockage at #8 cylinder is to remove the passengerside rear head bolt and stick a long straight rod down in the bolt hole. If it hits metal you're in good shape. Don't forget to drain some coolant out so it doesn't run out the bolt hole before removing the bolt. You can guestimate the depth of the water jack by looking at the outside of the block..

Sandy's comments on the heat riser are spot on. The vacuum gauge would tell you if there are exhaust leaks into the intake.

With your heat gun, you can see what parts of the radiator are doing the cooling. Are the edges cooling as well as the center? These old open cooling systems collect a lot of crud and can plug portions of the water jacket and radiator.

Keep us informed of what you find.

Bob

[Pete Phillips]

Rough idling and back-firing through the carburetor could also be a stuck valve, which can happen if the car has been sitting in storage for a long time, unused.

Pete Phillips, BCA #7338

[Branded]

Thanks for the information, I'm going to to more checks on the issues Friday. Talked to the owner and he tells me if he drives the car at highway speed it will get hot within the 1st 10 miles. Says top speed is about 50 mph (is that all you can expect). Radiator temps have no hot and cold spots. using the gun temps are pretty much consistant at 177 near top and 160 at bottom. Engine seem to rev slow to me but thought maybe thats just the way they are. I attached a vac gauge to the tube coming off the center of the intact shows 12 inches of vac. I was thinking it should be near 20 inches. Will the heat riser cause over heating. Owner tells me flapper has been removed or blocked off. I'm not sure what has really been done to the riser. But if the riser can cause over heating I think I'll pull it also just to see whats been done. I think every shade tree machanic has had a hand in this. Now I get to try my hand at it and not sure where to start first. :)

[Guest outlaw car man]

By flapper (?) he might be saying the damper valve has been removed and plugged, then as I was saying the front was blocked off from the exhaust manifold so you would have direct imput from the Marvel to the intake manifold.

One of my 33s is that way, other is still original.

Bob talked me through this a couple years ago, made a little custom plate to block the front. , the damper valves had been welded over years ago,

The heat riser is a double walled twin " tubed" riser that is between your Marvel ( carb) and the intake. What they did is used this automatic " flapper" to control the flow of engine heat to the riser AND used the exhaust gas to circle around inside this double walled heat riser to preheat the gas/air mixture to the intake.

If you have the " flapper" blocked off and the connection from the exhaust, you basically have a direct connection from one to the other- carb to intake.

With the " vodka " gas we are burning these days, it's not a problem to get this mixture to vaporize at a milder temp. However, that's the ONLY positive thing I can say about the Vodka gas- nuff said on the subject-

IF you are leaking exhaust gas from the double wall, into the mixture, you will have a great loss in power. as if you were burning only have the gas allowed.

Cause overheating, I just don't know, maybe. i.e. you are running at 50 MPH but the engine is only getting say 50% of the gas, since the mixture is 50% exhaust fumes. ( Just an example ) Yes overheating could come into play.

Mark has a great explaination on Marvel problems and cures. As Bob says revisit the 31,21,33 posts from the past.

Sandy

OCM

[Bob Engle]

I'll quote 32 Buick specs, and I am sure the 33 specs are very close. The straight 8 is 230 CI with 2 15/16" bore and 4 1/4" stroke. A real stroker engine. 82.5 HP at 3200 RPM. Compression is 106.5 psi. 5:1 compression ratio. The charts show 3860 rpm at 70 mph.

You can see that these engines are built for low rpm. All the Buicks in the 30's are challenged for speed because of the low gear ratios and long stroke engines. With modern engine rebuilds many owners wish for better gear ratios for cruising. I say slow down and enjoy the ride.

It will be interesting to see a compression check on this engine. 12" of vacuum seems low. This could be the heat riser, valves leaking or sticking, or rings, Low vacuum will cause a lean condition and could contribute to the heat problem.

Bob

[Guest outlaw car man]

I'm running a 1933 90 series: 344.8 CI; 3 5/15" X 5" B&S.

113 ( high compression ) @ 3200. 99 psi; 4.8 to 1 CR.

Lot of torque, big car to get moving, 261 ft/lb

I need to do a new compression check on the green 90, as it has a rebuilt engine in it with about 2 hours on it, never check mileage, maybe 40.

Keep us posted- not a lot of 33s around these days.

Sandy

[Branded]

I'll quote 32 Buick specs, and I am sure the 33 It will be interesting to see a compression check on this engine. 12" of vacuum seems low. This could be the heat riser, valves leaking or sticking, or rings, Low vacuum will cause a lean condition and could contribute to the heat problem.

Bob

Bob.... Just run a compression check.

1. 90

2. 90

3. 95

4. 95

5. 90

6. 91

7. 90

8. 85

I've played with the carb large air mixture adjustment also. Ran it al the way in and all the way out to the stop and engine doesn't change much at all.

Edited June 7, 2012 by Branded (see edit history)

[Branded]

Hers a picture of the Buick I'm working on. 1933 Buick Series 50 Convertible

[Bob Engle]

Great looking car!!

The adjustment on the carb is not like a conventional needle valve. It is called an air valve and has only minor effect on running not much on idle. Your vacuum problem can not let this valve work properly.

From the compresssion #'s, it doesn't look like a valve problem. The lower compression on #8 probably means more ring/cylinder wear on this cylinder. Does it show any smoke out the crankcase breather tube? If not, the lower compression probably won't prevent proper running. In my limited experience on 4 engines, I've found more wear on #8 cylinder. My assumption has been that the poor coolant circulation to the back of the block increases heat and wear in #8.

Bob

[Branded]

There is no smoke from the exhaust or crankcase that would indicate worn rings. The engine is suppose to only have about a 1000 miles on it since being rebuilt. This is going by what the seller told the present owner. I did talk to the owner last night and he said another guy that worked on this car adjusted the valves cold to .008, what I gather is they are suppose to be set at .008 hot. I'm thinking this could be the reason for the low vacuum. I think this engine has more that one issue. Like I said before to many people have worked on it. I may pull the carb, heat riser, and see what was actually block and the reset the valve lash.

[Branded]

There's nothing intimidating about the straight 8's. Just think Roller cam and tappets in 1931!!

The easist way to check for water jacket blockage at #8 cylinder is to remove the passengerside rear head bolt and stick a long straight rod down in the bolt hole. If it hits metal you're in good shape. Don't forget to drain some coolant out so it doesn't run out the bolt hole before removing the bolt. You can guestimate the depth of the water jack by looking at the outside of the block..

Bob

Bob I pulled the rocker cover and the rear head bolt is a stud. Is there any other place to check for pluggage at #8 cylinder. The infered heat gun show this area of the block as being near the same temperature as the other areas of the block on the passenger side.

[Guest Mike Hanning]

Check for a vacuum leak at inlet manifold fittings and connections such as carb gasket leak or head to manifold gasket leaks. Check distributer points gap, condensor condition and ignition timing. I would also rest the valve clearances as that is a favourite cause of the low vacuum reading you noted.

Mike Hanning, New Zealand.