Problem With 454 Mags
 

:( long story hate typing so here it is:
twins: just rebuilt 1 works fine. i change the elctronic module in distributor on one, guess which one i'm having problems with.
it will pop when i give it throttle pass 3500 rpm it is missing on number 7 cylinder (i pulled spark plug wire while it was running
no change
i've checked valve lash and these are new cams and lifters in engine.
herer is what i replaced so far either by taking it off good engine or new?
carb
cap and rotor
modules (electronic and the one on riser)
plugs
wires
i have timing set @ 10 intial 24 module
checked push rods on #7 cylinder (this is the one that seems to be the problem)
boatfix.com (george) great guy by the way has helped me out alot, says to try putting timming light on sparkplug wire where problem is, which i will try this weekend.
here is what i think might be happening possible water in cylinder after it is running. maybe a head gasket?
anyone have this problem? i sure would like to talk to you.

thanks in advance to all motorheads that are going to try to help me

Re: Problem With 454 Mags
 

You might want to check firing order, cap can be wired for left or right rotation.

Re: Problem With 454 Mags
 

bin there done that (about 15 times)
i'm also going to change distributors from running engine

Re: Problem With 454 Mags
 

Could be a weak or broken inner valve spring---doesn't matter if the springs are new, you may have a "dud"...they usually start popping/causing trouble right around 3000-3500rpm or so.

FYI, I was having a intermitent miss this summer right around 3000-3500rpm or so as well, but it wasn't because of a broken spring.....did a compression check, changed the plugs, checked the cap/rotor, changed pulg wires....it was water in my fuel---I hadn't inspected the fuel/water seperators in a while and they were full of water. Once I emptied them out the miss still didn't go away until about 30 more miles of boating---then it finally disappeared.

Re: Problem With 454 Mags
 

you maybe right i will check fuel too
if motors are using same tank won't they both have problems?
oh yea have 165lbs compession in that hole too.

Re: Problem With 454 Mags
 

I have dual/seperate tanks, but the other fuel/water sep was pretty close to being full too---but was just happening with one engine. I have the KE coalesant (spelling?) fuel filters.

Do you have the Merc 454cid Mag 365hp engines with the old Rochester carbs??? It's been a very long time since I have had a Rochester carb in my hands, but if I remember correctly don't they have the fuel filters that are located within the carb itself? If I am right, then those should probably be inspected/replaced as well.

Re: Problem With 454 Mags
 

Did you crank the engine while you checked the push rods? Mine acted like that with new cam, lifters and rockers. I had a rounded cam lobe.

Re: Problem With 454 Mags
 

changed carb from one side to the other, so its no change there. i watched push rods too, this rebuild has been a nightmare (3) times my machineshop guys are clueless
i might get another set of valve springs and put them in if nothing else works. i got to say this that if i could have found big block chysler exhaust for the boat,,,i would have put 2 blown 440 in it.

Re: Problem With 454 Mags
 

What does the tach do when this popping starts?

Is it popping out the intake or exhaust or both?

The engine with power steering generally has a deeper fuel pickup, so it will get all the water first when you have a water in fuel issue.

BT :cool:

Re: Problem With 454 Mags
 

My Other Engine Has Ps Pump
Tach Bounces All Over The Place