A long while back, I posted about my buddies '75 302 that he wanted me to finish off for him. He has since got rid of it but don't worry, he worked out a deal with the guy for a F350 that has a 351 in it.

Anyhow, here is the problem. It is a stock rebuild except for the cam (512 lift, 283 duration) and currently has a Rochester (?sp) carb on it (possibly a quadra-jet, size unknown). The motor starts up fine and idles with no problems BUT and here is the kicker. When they shift it into gear the truck stalls. They even try to increase the rpm some and it still stalls, they just can't get it to run once in gear. The transmission is a re-built C6 with a factory torque converter and a shift kit set for towing. Now one thing for the carb is that when they try to turn the idle screw, it doesn't affect the motor at all. They can crank it right tight or back it off all the way and it doesn't affect the motor.

What is the problem here ???? The guy is working on re-building a 600 cfm Holley carb and they are going to try that. Anyone have any ideas on this. My buddy and I are kinda leaning towards the carb on it now but we are uncertain. Any help on this would be greatly appreciated.

Have Fun & Keep on Truckin'
Dean

 

Maybe the tranny pump is siezed or too tight. How is the vacuum line(s)? I'm gonna rifle thru my Rochester book, back in a few minutes.

*i knew there was a reason i kept that book *

 

Are you sure its a Rochester? Most were on GMs. There is no specific troubleshoot for your situation "idles well, then stalls when put in gear". But things point to ...
a. idle mixture incorrect
b. idle speed incorrect
c. manifold vac lines disconnected or improperly install
d. carb is loose
e. flooding carb/ float/valve
f. not enough fuel in carb/ float /valve
g. linkage for kickdown and throttle valve for trans.
h. I don't have a clue

Does it rev well in nuetral? Is the idle screw reaching anything? Can you bend anything to get it to work?

 

Change the trans fluid and filter. If its recently rebuilt it might have some metal shavings in there or maybe the PO bernt the fluid.

 

The stalling may be due to a transmission problem, but you definitely have a carb problem if you can't change the idle speed.

What does the engine idle at (rpms)?

Which screw is being turned for the idle?

Quadrajets (are never on Fords, but whatever) have there idle speed screw on the drivers side of the carb, running parallel with the throttle plate (horizontal). Make sure that the engine is warmed up first, and that the fast idle cam isn't holding the idle high. To verify, after the engine warms up, manually crack the throttle a couple times, and the idle speed should come down. Once that happens, the idle speed screw should control the idle speed.

Once the idle speed is set, you will need to adjust the mixture with the mixture screws in the front of the carb. Turn them to acheive the highest idle speed, and then turn them the opposite direction 1/8th of a turn, and reset the idle speed with the idle speed screw.

Take care,
~Chris

 

Inski21, a couple of my buddies friends said that samething, "A Rochester on a Ford" ??? That is why they are re-building the Holley up and going to try that.

I appreciate all the help so far and will pass this along to see if it helps at all. I will try to get answers of the few questions that have been asked.

Another question ... is a 650 cfm Holley too big for a 302 engine ???

Thanks again ...

Have Fun & Keep on Truckin'
Dean

 

A 650 is an excellent carb for a mild to warm 302, it's a bit bigger than a stock 302 actually needs but not big enough to cause problems.

 

Guys, I have some more questions for my buddy. The guys that bought the engine now has a Holley 600 cfm carburator (stock jets) on the truck. The problem is the engine only has 8 inches of vacuum, it should have higher. Now remember this is a fresh rebuilt with close to no mileage on it whatsoever and a high lift cam. Should a rebuild run a little crappy at first until everything gets seated or what ??? It blows black smoke which we know means it is running rich but when they lean it out to a normal position, the truck stalls when put into gear. The has had the intake manifold off and has completely sealed everything, no leaks anywhere.

Any ideas and what would be causing this ??????

Thanks guys ....

Have Fun & Keep on Truckin'
Dean

 

Run a compression check and see what the cylinders are at, and post the results. I'm not convinced the cam is in correctly.

 

Thanks Chris, I will get back to ya.

Have Fun & Keep on Truckin'
Dean