Rebuilt 454 w 502 heads keeps loosing spark
 

Newly rebuilt 454, w brand new 502 gm
Heads, I lost spark on 4 plugs, guess there fouling out they are Ac delco mr43xxx plugs the tip seems shorter then my last plug and ideas what is causing this motor has ran max 5 hours, all cylinders compression checked fine 140 etc. thanks

have you changed plug wires&dist cap lately?

Is it actually losing spark or are the spark plugs fouling out????? Big difference.

I have fire coming out of distributer, they are fouling out bc if I change spark plug I then get spark when grounded, today I changed power valve and it seemed to solve issue... But now next problem the steering wheel and whole boat vibrate from 1500-3800 rpm then smoothed out to wot at 5000 rpm, it's a fresh rebuild- put in new motor mounts- aligned out drive.... When I put in neat real motor does same thing

I'd be looking for faulty plug wires possibly arcing, cap and rotor, or other ign related issues.

To check for a blown powervalve, float to high, stuck needle and seat, etc, run engine and look down the carb at idle, should not be pouring/leaking gas from the boosters.

Was this that 454 shortblock you were looking at from the place that some advised to steer clear of?

Also saw you dropped the engine when the chain let go during install. That can be a issue.

The motor fell slightly skimmed the oil pan nothing insane the
Jacks seal failed... The engine only vibrates between 1500-3700 it smoothed out after that, any ideas? U guys still thinking electric

Just bc a couple ppl
Complain about a shop doesn't make it ****, u build 200 motors etc. couple ppl
Complain give me a break

Hard to tell whether its a vibration from misfire or from something out of balance over the Internet.

Was this engine balanced with the damper that's on it? Internal balance of external balance? Pull the drive and run the engine, to eliminate a possible ujoint issue if its a bravo setup

The machinst is telling me to pull the motor, im ready to drop it off and let him do the install bc then he has no one to blame... The bravo ran perfect with last motor and we looked at u joints when doing alignment... the new motor vibrated right of the bat... If the motor is off balance would i have noticed it while running on the ground??? i put a flat head screw driver on out put of coupler and didnt see and bouncing etc... could this mean internally coupler failing when it has a load??? But if so how does it push boat to wot at about 70 mph?