Only runs with the choke on

Hello, First time on and I really could use some help.

I have a 53 with the 216 engine. We rebuilt the engine years ago and it ran great. Now it will only run with the choke on and then very poorly.
I have been told this means their is a vacuum leak.

I have had a warp in the manifold planed out so its flat on the head
new intake manifold rings
replaced gaskets
Carb kits and then a factory rebuilt carb
the exhaust is not plugged
there is not difference when I plug the vacuum advance or
wiper feed
Cleaned gas tank and line
was told to spray WD-40 around the gasket hold in the manifold
together and that showed no leaks
The timing is as accurate as I can get it with the way its running
Reset distributor with shop manual

Anyone have suggestion for me?

I would appreciate any help Thanks

 

I'd start from scratch, they say these old clunks only take three things; fuel, compression, and spark. Throw in valves and ignition working at the right time and one should run. Run a compression check and if all is well there then hook up a vacuum gauge. These things do a bunch of different things like showing sticky valves, loose guides, timing that's off, leakey rings, you name it. Try to get one with the little booklet or instruction sheet that shows how all these conditions display on the gauge. It also reads fuel pressure when hooked to the fuel line. Two or so psi is enough for these old carbs. Don't rebuild and buy anything else till you KNOW what the problem is.

 

The most likely spots for vacuum leaks on an engine you've worked on recently are :

The Bakelite spacer under the carby and those pesky (but all imporant) intake
alignment rings ~ they like to cock askew and hold the intake manifold loose a little bit even though you've tightened the bolts to 50 Lb. Ft. .

Easy to diagnose with a squirt bottle .

 

Thanks

we are still looking for the problem. thanks for the help

 

Vaccum Leak found

The vacuum leak causing the problem has been found.
The gasket in the manifold holding the intake and exhaust together. It was corroded on the engine side.

Thanks to Evan and Nate for giving me some new ideas to work with.

Mark

 

any way you can post a pic or two showing exactly where the leak was?

glad you got it fixed

 

Mark ;

Did you have to replace either half of the manifold ?

or just have it milled flat again ? .

Pix are always good , even if just a pic with an arrow pointing to the leak area .