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Old 01-15-2017, 02:35 AM   #1
29Phaeton
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Question Russian Motor in a 31 Cabriolet

I bought a 31 Cabriolet 68-B and have been having a tough time curing a carb backfire problem. I discovered this engine looks slightly different from other As as the oil return line is missing and it has a fuel pump port with a cover plate on the block. Looking through some old hand written records that came with the car I see the note "Russian motor from Long Beach". The block has no engine number stamped on it, the plate completely is blank. The head says USA and has standard size 7/8 spark plug holes, not metric like the GAZ head.

How do I confirm my suspicion of having a GAZ B Motor? If someone later installed a standard "A" head on it would that work? It idles well but continues to backfire out the carb when trying to rev over about 2200rpm and acts like it's runnning lean unless I really open the GAV a few turns. I've verified free flowing fuel, timing is spot on and spark is good. It also has a Zenith 1 carb and I read the Zenith carb for a B engine is bigger so if I have a B block can it run with A parts (head/carb/Dist)? Here's a pic (ignore the large plug in the vacuum port). Is a GAZ B more valuable since it's so rare?

Thanks for your help!
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Old 01-15-2017, 03:38 AM   #2
jw hash
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Default Re: Russian Motor in a 31 Cabriolet

it looks like a B motor with a A manifold and head.
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Old 01-15-2017, 04:12 AM   #3
Cornishman
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Default Re: Russian Motor in a 31 Cabriolet

My car has a Model B block with a Model A head, Zenith carb, distributor and water pump. It runs perfectly. Like yours it has no engine number on the block.
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Old 01-15-2017, 05:15 AM   #4
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Default Re: Russian Motor in a 31 Cabriolet

B motors had no number on the block. It was on a boss on the flywheel cover just above the starter motor. The flywheel cover is discarded when coupling it to an A gearbox and replaced with a standard A flywheel housing, hence the original engine number is lost.
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Old 01-15-2017, 07:30 AM   #5
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Default Re: Russian Motor in a 31 Cabriolet

''''Spark is good'''''

Did you run it with a spark tester inline while its breaking up at 2200 rpm's to see if its erratic?
Try inducing a richer fuel mixture

One or the other should lead you in a certain direction

Could it be an exhaust leak and not actuallly breaking up

Last edited by Mitch//pa; 01-15-2017 at 07:48 AM.
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Old 01-15-2017, 08:52 AM   #6
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Default Re: Russian Motor in a 31 Cabriolet

Valves sticking?? Run some MMoil thru it. Nothing to lose. Is it an A or B distributor?? Front cover an A or B??
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Old 01-15-2017, 08:55 AM   #7
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Default Re: Russian Motor in a 31 Cabriolet

the note most likely was someone's past opinion and not valid.

if the engine doesnt run right, could it be communist?
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Old 01-15-2017, 10:31 AM   #8
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Default Re: Russian Motor in a 31 Cabriolet

Try carb on a good running A and see if it is good?
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Old 01-15-2017, 11:22 AM   #9
Bob C
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Default Re: Russian Motor in a 31 Cabriolet

In the mid 1960's Ford Obsolete in Long Beach CA imported a bunch of the GAZ
engines. Some were complete engines and they also assembled some short blocks
from parts. I have one assembled from parts.

Bob
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Old 01-15-2017, 12:08 PM   #10
Jim Brierley
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Default Re: Russian Motor in a 31 Cabriolet

GAZ blocks were quite crude (rough) castings. They also had big lettering on the left side, center, and the left front and rear corners were more square. This could have been ground off and smoothed.
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Old 01-15-2017, 12:32 PM   #11
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Default Re: Russian Motor in a 31 Cabriolet

Thanks to all who responded. I did hand crank the engine while inspecting the valves through the plug holes and they all seemed to move as they should, not sure about needing adjustment. I have replaced every ignition part from the coil to the spark plugs including an new style distributor so I'm not sure what more could be causing this. My gaps are at spec so how to I test for a breakdown at higher rpms?

If it's a B block is that a plus? Balanced crank?
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Old 01-15-2017, 12:35 PM   #12
Mitch//pa
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Default Re: Russian Motor in a 31 Cabriolet

Quote:
Originally Posted by 29Phaeton View Post
Thanks to all who responded. I did hand crank the engine while inspecting the valves through the plug holes and they all seemed to move as they should, not sure about needing adjustment. I have replaced every ignition part from the coil to the spark plugs including an new style distributor so I'm not sure what more could be causing this. My gaps are at spec so how to I test for a breakdown at higher rpms?

If it's a B block is that a plus? Balanced crank?
Read post #5.
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Old 01-15-2017, 12:38 PM   #13
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Default Re: Russian Motor in a 31 Cabriolet

Sorry, I don't know what a spark tester is. I'll do some searching here in the forum. As I posted, if I open the GAV a few turns to give it more gas it gets much better but you can smell it's running too rich.
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Old 01-15-2017, 01:04 PM   #14
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Default Re: Russian Motor in a 31 Cabriolet

GAZ engines I saw had distinctive markings on the side of the block.
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Old 01-15-2017, 01:31 PM   #15
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Default Re: Russian Motor in a 31 Cabriolet

G28T engines have welch plugs in block front & back , alloy sump, down draft intake, plus many other differences , some of which can be replaced with A-B parts , but not the block or sump .
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Old 01-15-2017, 01:37 PM   #16
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Default Re: Russian Motor in a 31 Cabriolet

I'm so frustrated with this car I'm thinking about setting her free on Craigslist. I've spent the last four weekends solid trying to fix it with no luck. Very frustrating to say the least. I'm going to go see if I can find a spark tester today at my local parts store.
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Old 01-15-2017, 01:43 PM   #17
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Default Re: Russian Motor in a 31 Cabriolet

Yup, my block has those markings on the left side "M-6015"
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Old 01-15-2017, 02:00 PM   #18
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Default Re: Russian Motor in a 31 Cabriolet

I'm AMAZED at how much info can be acquired, in a few minutes, when folks care enough to contribute what they know.
This is what we're ALL ABOUT, NOT just a "contest" about who's the SMARTEST--LOL
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Old 01-15-2017, 02:01 PM   #19
Art Newland
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Default Re: Russian Motor in a 31 Cabriolet

Just because the valves appear to open and close properly, at speed they may be sticking slightly and not closing all the way before combustion takes place thus producing the back-fire. The valve(s) may not be seating properly either and need lapped (or replacement). Did you try some MMO as mentioned earlier? A compression and leak-down test might be helpful in this instance. A bad distributor cap can cause a "cross-fire" situation, but since you mentioned trying a modern distributor you can rule that out. The Zenith has a filter screen inside that could be plugged, maybe just crud partially blocking something in the carb. Do you belong to an A club? Borrowing a known good carb would be nice to try. Looks loke a nice car, don't give up on her!
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Old 01-15-2017, 02:08 PM   #20
1931 flamingo
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Default Re: Russian Motor in a 31 Cabriolet

Give us the town you live in, maybe there's someone around the block that can help you??
Paul in CT
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