Engine misfiring - cant find cause

Andrewrv8 · Post by **Andrewrv8** » Mon Nov 03, 2014 6:59 pm

I fitted a 4.6 into my p6 recently running with edelbrock 500. It ran rough and seemed to misfire on 4 cylinders (5,6,7+

. Using a p6 timing cover and distributor (electronic). Believing it could be due to warped heads I removed the engine and fitted another. Replacing the cam with a new 4.2 item and steel timing gears and duplex chain etc. Strangely this engine suffers with the same rough running and misfire on cylinders 5,6,7 +8. This surely is no coincidence. I,ve swapped leads etc to eliminate failing leads. Any suggestions? thanks

ChrisJC · Post by **ChrisJC** » Mon Nov 03, 2014 8:11 pm

Is the Eddy 500 a double barrel carb on a dual plane manifold?, one barrel of which feeds cylinders 5,6,7,8?

Chris.

Andrewrv8 · Post by **Andrewrv8** » Mon Nov 03, 2014 8:22 pm

It is a 4 barrel, was on a dual plane but I've now changed manifold to an old unit I had. Not too sure what it is but has intake holes for nos and is dated 1987 underneath. Looks like left side of carb feeds left bank and right feeds right bank. Hope that makes sense. Think it could be carb related? The fumes are terrible

ChrisJC · Post by **ChrisJC** » Tue Nov 04, 2014 6:16 pm

If it's dual plane, one carb should feed the inner two on one bank and the outer two on the other bank. And the other carb the rest of them.

If one carb is doing one bank, it'll never work very well......

Chris.

Andrewrv8 · Post by **Andrewrv8** » Wed Nov 05, 2014 5:54 pm

Chris, I agree with you, but it worked on my last engine with holley 600 without any misfiring issues. Not the best manifold I admit. The first 4.6 I fitted I used an Eddy performer and it still misfired. Just tried an different coil - no improvement

Andrewrv8 · Post by **Andrewrv8** » Sat Nov 22, 2014 11:00 am

Problem solved!! I feel rather silly but I had not noticed a vacuum port on the rear of the carb (presumably for brake servo?) which was wide open

Runs like a watch. Will upload on youtube over the weekend

sidecar · Post by **sidecar** » Sat Nov 22, 2014 5:56 pm

Andrewrv8 wrote:Problem solved!! I feel rather silly but I had not noticed a vacuum port on the rear of the carb (presumably for brake servo?) which was wide open
Runs like a watch. Will upload on youtube over the weekend

That is a big hole at the back of the carb! Anyway its good that you'e sorted it out!

Andrewrv8 · Post by **Andrewrv8** » Tue Nov 25, 2014 2:00 pm

Yes, ahem thanks. I still cant work out how to get pics on here but here is a link to the car on youtube -

SimpleSimon · Post by **SimpleSimon** » Wed Nov 26, 2014 12:18 pm

Andrewrv8 wrote:Problem solved!! I feel rather silly but I had not noticed a vacuum port on the rear of the carb (presumably for brake servo?) which was wide open
Runs like a watch. Will upload on youtube over the weekend

It takes a man to admit he cocked up

she spins up nicely in that vid

mgbv8 · Post by **mgbv8** » Wed Nov 26, 2014 9:37 pm

SimpleSimon wrote:
Andrewrv8 wrote:Problem solved!! I feel rather silly but I had not noticed a vacuum port on the rear of the carb (presumably for brake servo?) which was wide open
Runs like a watch. Will upload on youtube over the weekend
It takes a man to admit he cocked up she spins up nicely in that vid