i-h scout engine running problem

friend brought in a 65 scout with running problems. fresh engine rebuild,pistons, rings, bearings, cambearing, head rebuilt. carb was sent to national in florida, rebuilt and tested there on an engine. has a 1 barrel holley, 196 cu in 4 cylinder. main jets are # 52"s. truck will only run with the choke fully on. it has been to 2 other shops and no one has yet to find the problem. as soon as you try and push the choke in, even a little, the truck dies. it did this before the complete rebuild too,was purchased about a year ago with the same problem. timing is solid at idle, 5 deg btdc, compression is 125 psi across the board. cam timing is correct. no vacuum leaks that i could find. the engine is running very rich with the choke on, but it does backfire occassionally when trying to rev it. also, engine lags when you try to rev it. there is a 1/2 inch pcv hose coming from the intake below the throttle plate that connects to the valve cover pcv valve. valve is working. removing the hose from the valve,the engine rpm just about doubles and revs good with the choke closed, but dies as soon as you try and open the choke. the old fuel tanks were replaced with poly tanks, along with all new fuel lines. no difference. also ran fuel from a seperate tank with an electric fuel pump, running 4-6 psi fuel pressure. no difference. new spark plugs, new points and condenser, cap rotor wires, distributor has been rebuilt. about the only things that are original that havent been gone thru are the intake and exhaust manifold. engine has about 22 in of vacuum at idle too. fuel filter is clear. oil bath air cleaner on or off the motor makes no difference. any ideas???

Does it have a vacum advance distibutor? if so maybe the diaphram in it is tore

vaccuum advance is new, unit works good with no leakage. problem is still there whether it is coonnected or the line is removed and plugged.

heres a couple pics of the engine

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<a href="http://s121.photobucket.com/albums/o234/glennster_01/?action=view&amp;current=DSCF2767.jpg" target="_blank"></a>
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Is the float level set high enough? It has to be starving for gas. Have you blown some air through the jets? Could be plugged. Hal

With it choked the answer must be a vacuum leak. The intake manifold is a recasting of a V8 with 50% missing. The casting may have a rusted through or cracked exhaust heat riser passage, allowing dramatic EGR.
The issue would be internal. To check it the manifold must be removed. Block off the carb passage and turn it so the passages are upward. Then fill the intake with water and see if it comes out the riser passage. Jim

But if it was leaking there, would his vacuum readings be that high? Still sounds like a carb problem.

Sounds like it is still the carb to me. What happens if you whiff a little carb cleaner in the throat when it is idling? Does it pick up (meaning its lean) or stumble(meaning it is rich) ? What happens when you cover the carb with your hand while idling? If it sucks hard and dies that is normal. If it picks up or races, its a vacuum leak somewhere. Also,I know you said the plugs are new, but I would try 4 new ones anyhow again. They can get fouled or coated from running bad and tinkering around with stuff trying to correct the problem. Dont just clean em, and even if they look fine, try new ones. Easy and cheap. I have learned that leason the hard way. It is especially true of low output ignitions and seemingly simple engines. I assume your gas is good, cuz you tried running it of a can.

Remember he is running it with the choke fully closed, that could explain the high and seemingly "good" vacuum reading....

I'm thinking intake manifold also.

Are you timing off the #1 cylinder? They are happiest at about 7-8 degrees.

The 4-6 psi is way too much for the 1904 carb. I run 2.5-4.5 psi pumps on all my Scouts.

I think he posted this problem up on www.binderplanet.com too.

-Gary

You could test that by adding propane till it would run with the choke open. If the vacuum drops it would be a manifold leak.