Need help with 64 chevy truck 1 barrel carb problems

I just bought a 64 chevy truck with a 230 or 250 straight 6 and 3 on the tree. It has a 1 barrel rochester, model number 7004522. The truck starts up and will take the gas some with the choke on. When warm the truck will not take no gas with out stalling out and backfiring and poping. I have rebulit the carb with a kit from LMC truck and also bought a used carb from ebay, same model number and even rebulit that one. I have taken the carb apart like 10 times now. The float drop is dead on and the float height is dead on. The pump pluger seems to be working right. I have put new points and condensor in new from carquest and gapped and cleaned the plugs and checked and set and played with the timing. What else could it be before I buy a new 150$ carb?? Thanks in advance, Tony  
1964 chevy LB truck 1969 chevelle mailbu

Back fire sounds like timming problem. Bring # one up to top dead center like a screw driver in # one plug hole and see if the rotor lines up with # one wire. Hold the wire a short distance from the plug and see if you have good spark jump. you can do this on older engines.
Check your full pump preasure maybe a bad pump. Does the gas flow freely form the tank to the pump? I had a 51 Ford that had a piece of rubber in the tank that would block the flow.
They ran that same engine up in the 80'S so you might look in the junk yards for a HEI distributer. Thats all I can think of for now anybody else.  

Thanks for the reply. I have taken the #1 plug out and got it to the top of the stroke and the rotor lined up with the #1 Wire on the cap. I then marked the bottom pully with a paint marker on 0. Then I set the timing on 4 degrees BTDC. I even tried setting by ear. It had dead gas in the tank so I drained the tank at the pump and it flows great. Prevous owner put a new pump on it from autozone. Carb is always full of gas when I take it apart plus it smokes real bad when running and smells like strong gas. Any other thoughts? Thanks in advance. Tony  
1964 chevy LB truck 1969 chevelle mailbu

Don't realy know maybe do a engine flush. Buy just that Engine Flush. You might have a bunch of sticky lifters and rings. What we used to do was 1 qt. regular straight weight oil and fill the rest with fuel oil and run it until it gets operating temp and let it cool down and run it again. Thats about the only thing left.  

Thanks, I think I will check the compression on all the cylinders sometime this week and see what I get. I was told the motor was rebuilt in the last few years so I hope all that is ok. Thanks Tony  
1964 chevy LB truck 1969 chevelle mailbu

My 72' Chevy 250 w/3 on the tree had a similar problem this past year. Turns out I had a partially clogged fuel line in the gas tank at the the pick up. It would let just enough gas thru to feed the fuel pump and get the truck up on idle. But the lack of volume meant the engine would not carry any load, popping and backfiring all the while. I found the blockage by shooting air from an air tank back to the gas tank while troubleshooting what I thought was a bad fuel pump.

Just my .02 cents
88Ironduke  

. Maybe check for a vacuum leak either under the carby or around the manifold. If by leaving the choke on slightly makes it run at idle,you have a air fuel mixture problem.Spray some air-o-start around the areas, if it speeds up in revs, you have an air leak.  

Hey All, I went out a few minutes ago and started the truck. It will idle good with the choke off so I sprayed some carb cleaner around the whole intake manifold. No change in RPMs or anything. I did pull the PCV valve out of the valve cover and it raddles and you can hear the air being sucked through it. I put my thumb over the bottom of the PCV valve and it killed the motor instantly. I still cant give the motor any throttle with the choke off with out it stalling out. Im going to check the compression this week sometime. Any other thoughts??? Thanks Tony  
1964 chevy LB truck 1969 chevelle mailbu

I know you have built the carby many times,but it still sounds like you have too much air to fuel.Look down the carby and see if the accelerator pump is working when you operate the accelerator, does it squirt? It must have a good solid stream.Also check it when running. Advice #1 becarefull of the backfire otherwise you will be looking like OBAMA'S brother  

Hey All, I looked in the carb and goosed the throttle with the engine off and I saw a good stream of gas squit out the small hole. I took the carb back off and tore it down and cleaned it with carb cleaner and compressed air and put it back togather. I even used a differant bowl cover From a parts carb. I got the same thing, will not idle still will not take the gas, stalling, backfiring and so on. Im starting to beleive maybe the valves are to tight?? Anyways im going to do a compression check tomorrow and see what I find out. Its just hard for me to belive that carb is bad. Any other thoughts??? Thanks Tony  
1964 chevy LB truck 1969 chevelle mailbu

Well lets wait and see what the compression will be, obviously there is a valve opened for it to back fire. You'll probably have to go back to basics, maybe the valves may have to be backed off. If you have to do it, turn the motor over by hand completely 2 revolutions to check that the valves are slack at compression for exhaust and at fuel. I guess the Dissy is next.  

You could take the valve cover off and see if all the valves are opening and closing.  

Hey All, Ok I checked the compression today. I rented a comp tester from autozone and just my luck it doent work right, it want hold the presssure even using my air hose and putting air in it. I watched the gage as I turned the motor over and it jumped up to like 80 or 90 at on all cylinders. So at least it builds pressure in all the cylinders. I pulled the valve cover off and all the valves are opening and closing right. I even adjusted all of them. All of the spark plugs were solid black so I cleaned them and put them back in. Same thing motor will not take the gas unless the choke is all the way closed. I can rev the motor up and hold rpms with the choke on before it loads up. If I take the choke off I cant do nothing with it, stalls out and want even idle. So what do yall think now?? I leaning toward a bad carb I think. What else is left to try?? Thanks in advance, Tony  
1964 chevy LB truck 1969 chevelle mailbu

Hell, your going to send us all to an early grave. Still sounds like a air/fuel mix problem myself.Holding the choke on is restricting the air flow. Well we could go on and on and on. This is what I would do.You have to cancel out certain parts one at a time. When I am troubleshooting issues like that I have spare parts,such as dissy,carby,NEW leads, NEW plugs etc.Since I mainly do V8's, it is worth while me having the parts. I would cancel the carby out first and put one on from another motor somewhere that you know that works.If you are going to have that motor for a while,believe me you will need spares to troubleshoot issues in the future. Otherwise put a small block V8 in it.  

Hey, That is funny!! I have a whole bunch of spare V8 parts, even motors. This is the first 6 cylinder I have owned as far as a classic. Im on the verge of snatching it out and dropping in a V8. I have like 3 spare good 4 barrels. Well im going to mess with it and see if I can find another carb before I do the swap. Thanks guys  
1964 chevy LB truck 1969 chevelle mailbu