mxzxracer16

Hey guys I really could use some advice here. I'm no stranger to engines in general and all things automotive, but embarrassingly I'm getting my a$$ whooped on one of my built NA 540 engines.

Here's a run down of what's going on and what I've tried.
-Engine is burning cylinder 2 where its black and loading up, under revs there is a noticeable misfire that's on the 2/4/6/8 bank. Plug the plug after running and it's cooler then the other plugs and black.

Tried plug wires / plugs / swapped caps / swapped carbs from other engine / replaced the lifters. Engine has aluminum heads, Victor Jr intake / Holley 950 / constant fuel pressure at 8psi / compression is 135 across the board / leak down shows some blow by into the crank case but approx 15% none thru the valves / Gil exhaust manifolds / bigger cam roller motor / MSD distributor and box.

My questions are, can an internally leaking exhaust manifold on that bank cause the issue of misfire / can the msd ignition cause a single cylinder issues / or what in the heck should I do check next? Any advice would be emmensly appreciated. I'm really at a loas and tired of swapping parts and getting a plug that loads up and starts missing. The boat will ride well but at upper throttle trying to push the engine it's about 500rpm off max Rpms "5700" at WOT due to the cylinder misfiring out.

Thanks

SB

iTrader: (1)

Could be exhaust. Not uncommon.

Did you swap the My Sparks Die ignition boxes ? Are they hooked up same as each other ? Voltage to the box over 12V ? Wired direct to battery ? In dist, under rotor, is it rusty ?

mxzxracer16

Thanks for the response. I pulled the distributor, and there was some corrosion, I cleaned it up and tested each trigger wheel and seemed OK, also I reclocked the distributor to see if the misfire would change cylinders and staid the same. The ignition box is wired to battery 12v. I sort of have wished I found a mechanical issue with the engine at this point because I'm getting no where.

MILD THUNDER

iTrader: (3)

I noticed your fuel psi is set to 8psi. Thats a little high. Is there any fuel dripping from the boosters at idle? It it really rich at idle by any chance?

What are you running for igntion timing?

sutphen 30

I'd look at the exhaust gaskets,head and riser,,any leak and it will suck water back.Is the exhaust dry to the tips?to test the ignition,,put the timing light on each cylinder and watch the light on the dampener and see if the miss is seen in the timing light.

253

Cut the fuel pressure back to 6.5 and try it.

mxzxracer16

Thanks guys for all the insight. The timing light trick I never thought of to see if the misfire is on the ignition side rather then the fuel / mechanical side. Ill check that. Thanks. Also ill drop the fuel pressure regulators on the aeromotive pumps and the carb is not leaking from the boosters or not atleast from what I have been able to see. After this I think I'll pull the manifold on that side and check. Its in fact IMCO manifolds with just 1 water feed into the manifold, and water must just pass thru the top of the manifold into the exhaust? I forget since i repowered it years ago.