gotta_believe

My restored 454 with rebuilt Rochester Quadrajet has started to lose power under hard acceleration and stops RPM climbing at a certain point.
In beginning it started to lose power at 65-70 mph, then 50 mph , and now at almost any speed when I put the pedal down for full throttle. This is now happening even when parked.

Changed carbs with no improvement. Fuel filter, fuel lines and tank are new and spotless. Fuel pump works. So you might think it was an electrical problem, but there is no misfiring, no back firing, no apparent timing issues and idles OK.

We are going to have to take it apart and look at the distributor gear, maybe the timing chain (although no misfiring).

Has anyone had such a problem?

stumpshot

Sounds to me like you are srarving for fuel. Before you tear things apart, check your accellerator pump and make sure your float is set correctly and the needle valve and seat is clean.

derekderek

And the little porous rock filter under the fuel fitting on the front of your carb.

gotta_believe

I had the same problem even after installing my 2nd rebuilt Rochester Quad.
FUEL SUPPLY was the first suspicion and had some black particles in the fuel filter but now the 2nd fuel filter has remained clean and problem still persists.

gotta_believe

I did replace the fuel filter and problem still persists.

gotta_believe

I think that the fact that the problem seems to be getting worse (occurring at lower and lower speeds ) should tell me something is wearing out or getting more broken or something!

Peterbuilt

How's the SOCK at the end of the pickup tube in the tank?

CanadaGrant

My guess is a fuel pump going bad. I had a similar problem that turned out to be a carb inlet filter with an anti drain back check ball in it that was too restrictive but yours is getting worse.

gotta_believe

The fact that the problem persists even with a new carb installed tells me it isn't a carb problem..

Is there any way it could be not enough spark for some reason?

gotta_believe

Tank and sock are new but will test the sock integrity again just to be sure it isn't a factory reject.

REELAV8R

Milan454

Check for timing chain slack. Could be chain jumping teeth???

BLUE1972

If it's still stock, put a jumper from 12v to the + of the coil and see if it gets better, if it does it's electrical. Resistance wire, condenser or coil.

I agree it appears to be a fuel issue.

I just had a similar issue on my 85, 838 w/carb , my MSD box went bad. Drove me nuts.

Cavu2u

My money is on a failing fuel pump.


Steve

gotta_believe

We did the fuel flow check by cranking engine with carb tube disconnected but maybe that doesn't tell us everything that happens under load.

We will install new fuel pump with different Roch Quad carb and see what happens.

gotta_believe

wouldn't that produce misfiring and/or backfiring? Those symptoms are not happening. The engine just struggle to continue increasing RPMs.

gotta_believe

This is really helpful. We'll try it when I get garage time on Nov19th. Really appreciate this hint on how to narrow the problem.

gotta_believe

Farmingdale !!! I am in Dix Hill. Maybe you know my mechanic, Gary Galardi. Deer Park.

Rescue Rogers

Put a fuel pressure gauge in there as well. I had a brand new pump fail after a few weeks, only new because of the pressure gauge

REELAV8R

So it doesn't act like it runs out of fuel then recovers then does it again over and over until you back off the throttle? Not sure what you mean by struggles to increase RPM. I was under the impression it was cutting in and out.