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30u Engine running, but not quite as it should

Started by abradney, May 28, 2019, 10:26:37 AM

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abradney

So i've been working on the 30u a little more now that it's back from upholstery, a couple of notes/questions;
-Every time I wish to start the engine it needs just a little squirt of ether in the carb, then 9/10 it starts up, but always needs a little choke to run, just a hair, any thoughts on why this might be?  I've rebuilt the carb (drt08) and made sure all passageways are clear etc.
-Once the engine is warm, it will occasionally misfire
-I'm thinking I need to adjust the valves to try and get the engine to run smoother, I can't find what tappet clearance the valves need to be adjusted to, any leads?
-Is there a good alternative to the drt08 that bolts up and is slightly more adjustable?

chetbrz

Don't know, where to start.  There are inherent design issues with the timing of this old 1929 engine but for the most part if everything is close to perfect it should run OK even with the occasional cough.  Actually it's the charm of having an old engine.   At least it doesn't backfire. 

Check the basic stuff first.  Compression across all 4 cyls should be consistently the same.  Also what you described sounds like you might have a leak in the intake manifold.   You may also have problems with the timing gears in the distributor housing.  The housing converts the movement of the cam shaft at right angle to facilitate the vertical mounting of the distributor.  If this housing is original you probably have issues with it.

I downloaded a pdf file containing two pages from the 1929 Plymouth Instruction Book that talks about valve timing.  Yes the timing is important to help eliminate the cough.

See attached,  Chet...
http://www.1948Plymouth.info           Web Master - Forum Administrator - AACA member

abradney

Thanks Chet, i'll take another look at the intake for cracks and test it.  When I ran a compression test they were all equal, but I will test again.Then i'll pull the side cover off and check valve clearances.

Any thoughts on an alternative carb?

abradney

So checked all valves, that seems fine, no intake leaks.
I honestly think it's carb related, these carbs are so archaic!!

Took it for a drive down the road, pulls pretty good, but then in 2nd gear it seems to top out a little too low, then in 3rd I had some 'speed' wobble, so I had to slow down again, that's for another day though.

Here is a video of the engine running
https://www.youtube.com/watch?v=cS1Q0r5FWr8


Russ T. Fender

I run a Carter BB-1 carburetor on mt 30-U and all my other non Ford old cars.  It is a good universal carburetor easily adjusted to adopt to existing linkage and parts are available for them.  The earlier ones are brass and are more desirable but the later pot metal ones are OK too.

abradney

Quote from: Russ T. Fender on May 29, 2019, 01:28:05 PM
I run a Carter BB-1 carburetor on mt 30-U and all my other non Ford old cars.  It is a good universal carburetor easily adjusted to adopt to existing linkage and parts are available for them.  The earlier ones are brass and are more desirable but the later pot metal ones are OK too.

Does the bb1 bolt straight up or are there different bolt patterns to look out for?

abradney

I ended up ordering a BB-1 from www.vintagecarb.com

I figured i'm this deep in the project I may as well dive in fully.

He has them with a 2-3/8 flange so it should bolt right up without the need for an adapter.