302 Power Loss When Accelerating Help

Sorry for the long response but here is an update.

Replaced the carb with another 600 cfm holley street warrior
Installed a custom exhaust with a y pipe (later will be replaced with duel exhaust due to clearance issues)

Now I am thinking its a tranny issue. Everything is now 100% new.
The same problem persists with power loss when in drive. The car seems to run perfectly in idle, but when you move it into drive and start pressing the gas it begins to hesitate significantly. If you push the pedal down too far too quickly the engine will shut off. When you go easy on it I can floor it, but there is almost no immediate acceleration and the car feels like it weighs 8 tons. Even when I floor it when I take off pedal too fast the engine will cut off. The reason I think it might be a transmission problem is that when we started to load the car up on the car trailer I could barely get it on. Even easing it up and flooring it the car would not climb the ramps which weren't even elevated that high. The way I had to get it on was to drop it down into first. When I did this and finally got the car on the trailer more than a quart of transmission fluid puked out where I assume was the vent (mushroom shaped metal piece on top and on passenger side of the transmission.

I am not sure if the problem is 100% the transmission.

My suspicions are maybe my shifting linkage could be messed up preventing the transmission to shift correctly or sit in between gears (not sure if that's even possible).

Otherwise I have no clue. I plan on adjusting the timing and tuning the carb as well as again checking for any vacuum leaks.

I am just baffled on what the problem is. Thank you everyone that has been helping me out.

 

Holley says that the carburetor is calibrated for performance "right out of the box." I would make sure your accelerator pump is delivering a good steady shot of fuel. With engine off, look down the primary side (front) and run the throttle to see if you have a good discharge. If not, you need a new accelerator pump. If you have a steady stream (not a dribble), you may need a larger discharge nozzle. Google this if you are not familiar with the part.

Also, if your mixture screws seem to not change anything, that is a sign that the throttle plate is opened too far and that will affect off idle performance too.

 

Forget the transmission. Built with a transbrake, a automatic transmission is essentially locked up, a properly tuned engine can be held at any throttle opening till brake is released for car to launch.

I still say fuel, need to check fuel pressure at various throttle openings with vehicle at speed.

 

That is interesting. Why don't you try this, remove the driveshaft and then perform the same procedure as you described above. What happens?

 

check and see if the E-brake is on...
sounds like you are power braking it.

 

I bought a "new" Holley that had about 10 things wrong with it as the previous owner tried many things to make it work and finally replaced it with something else. My point is new out of the box was not working for him either. I wonder if your C4 has a white dot drive valve body, and a sloppy shifter is engaging 2nd instead of drive, but If your carb is NOT enriching your fuel charge when the throttle is opened, you will stall under a load every time. Holleys are fairly fussy until they are set up right and it may not matter that you have tried 2 of them.

 

I understand your logic but having two carbs with same issue points to other issues. If fuel supply is sufficient, it's difficult to misadjust one so badly it won't pull at WOT(at least after getting past bog). Maybe if float level was low as could be adjusted or it had a dozen sizes too small jets.

 

Something crazy happened!

It started working perfectly.

There must have been an air trapped in the tranny. The only thing I adjusted when I ran it today was the timing. Either the timing totally fixed it or the pressure on the transmission blew all the air out of the tranny. Not really sure, but I am glad this headache is out of the way.

Now I need a new radiator, a 3 row, and a fan shroud.

If anyone has an extra I would love to buy them from you!


Thank you again for all the help and recommendations!

 

...

 

That makes sense too....and there could be 2 or more problems. I love trouble shooting stuff, but it is tough when the car is not hands on. Even when it is hands on, sometimes I can overlook simple things. When that car was trying to go up the trailer ramps, I wonder if the transmission was in 2nd gear until 1st was manually chosen. If it is starting in 2nd, might account for the 8 ton feel.

 

oops!!! the game is over!

 

I'm taking the wait & see stance.

Assuming proper fill, automatic transmissions don't have "air" issues. Even if it did, problem would be slipping and run away RPM on WOT shift. Not bogging or dying engine.

 

71gold, Frank perhaps your ghostly spirit went north to escape the heat. Seems like PerformanceMav's strange problems started about the time yours ended.

 

How many times I have watched racers that their motor is laying over at rpm and claim the fuel flow is good based on a new fuel pump and reading a pressure gauge. When they finally open the filter and disconnect the fuel tank to check a tampon falls out and the problem is fixed. You need to check the flow to the filter first.