Popping carb
 

Hi all, I have a 1930 Tudor sedan that I am ready to put back on the road. It hasn't been driven since 1970. The motor, engine and drive train was supposedly all rebuilt in the 70's when the previous owner started the restoration. I have tried driving it a time or 2 but it wants to pop back through the carburetor when you give it gas. I have done the following and am at a loss on what to look at next. Rebuilt carb and distributor, replaced coil, checked and replaced cracked head, had 4 valves that did not have enough clearance so I fixed that. Went back in and replaced the valves, guides, and springs. Thought there may have been a weak point there. The popping is more prevalent the hotter the engine gets. It idles great, just won't run on the road. Any ideas are greatly appreciated!

Re: Popping carb
 

check the timing gear.

Re: Popping carb
 

Ayers 1. Welcome to the barn. The times I’ve had this problem I have found it to be a vacuum leak somewhere in the intake system. Make sure the connection between the carb and intake manifold is nice and tight. Also make sure there are no leaks in the manifold itself The engine will pop from getting to much air. Hope this helps. Good luck. Frank

Re: Popping carb
 

Yes, welcome to the Barn....

Re: Popping carb
 

Thanks for bringing that up. I have also replaced the intake and exhaust manifolds as the old ones were warped. New gaskets and all but I'll check it out.

Re: Popping carb
 

Thanks Jack, since it's been almost 50 years since the engine was apart you think the fiber timing gear could be soft and moving?

Re: Popping carb
 

You may open up the gas valve to the card. May be starved for gas.

Re: Popping carb
 

How is the valve lash ? One valve too tight could cause the condition.

Re: Popping carb
 

See post #1.

Re: Popping carb
 

Try a couple of squirts a Marval Mistery oil in to the carb. while she's running sounds like maybe a sticky valve

Re: Popping carb
 

Thanks for everyone's suggestions. As soon as it gets warm enough I'll go out in the garage and try again. Since I had put a new manifold set on I didn't think about a vacuum leak. I'll start there and see where it leads me. I'll post as soon as I try a couple of things.

Re: Popping carb
 

Did you check for flatness on the new manifold set? Put a straight edge across the 4 ports, you should have no gaps.

Re: Popping carb
 

I'm not sure if your 30 Tudor has a vacuum windshield wiper like my 29 Tudor does but if it does check the condition of the rubber tubing that runs on the outside of the windshield between the metal tubeing connection and the wiper body. If cracked it will change the air intake to the carb.

Re: Popping carb
 

I didn't think to check the flatness of the new set. I assumed they would be right. We know what assuming does for ya!

Mine does have the vacuum wiper. I had it professionally rebuilt before I put it on. Now that I have been pointed in the direction of a leak, I may have to go back and check it again.

Re: Popping carb
 

Ayers, welcome to the forum.

If you have about a full tank then put in about 4 oz of Mystery Marvell oil in the tank.

Check your vacuum line from the intake all the way to the wiper to make sure the hose does not have any holes or cracks.

On the road, try opening up the GAV 2-3 turns and see if that makes a difference. To me, it sounds more like a carb issue.

Re: Popping carb
 

My carb did the same- sticking float..........


MMO and all quieted down.

Re: Popping carb
 

Thanks for the additional suggestions! I'll try the Marvel Mystery oil and see how that goes. Hopefully I'll get a chance to work with it tomorrow and get something figured out!

Re: Popping carb
 

To check for manifold gasket leak, use a LP gas torch, unlit, and direct the gas around the gasket area while the engine is idling. RPM change will tell you about a leak. However, any gas getting sucked inyo the intake will also affect it so be careful to keep it away from there.

Re: Popping carb
 

Try opening AGV further. Works everytime for me. This is the under dash gas adjusting valve.

Re: Popping carb
 

I agree with the suggestions on this thread. However, a restricted gas flow will cause your engine to pop.
Things to check:
Disconnect the gas line at the carb and see if you have good flow from the gas tank.
If not a good flow, check to see that the ferrule on each end of the gas line is very close to the end of the gas line. You will have a restriction if the gas line is too far into the filter bowl or carb.