melting spark plugs help help
 

just finished my motor and it runs great except it is melting the rear spark plug and not sure why.

the plug it self is melting not the electrode weird thinking its pre ignition but not sure. motors still got good compression this is the second time and its only happend in the # 8 cyl.

sbc .30 over rhs heads and procharged 6 psi maybe its running lean? currently running a msd with 30 deg timing at 3000 and a ngk br7ef.

please any help would be awesome.

fixx
 

your running way lein,,,are you running jet extensions in the carb and did you up the jet sizes from stock..you may also have to open up the hole behind the power valve..need to know what carb your using..

Way lean or detonation.

Depending on your compression ratio may also want to step up to -8 or-9 plugs. Just a little colder

30 deg timing is part of your problem,egt,s are probibally sky high.add some timing and some fuel,you need to tune off the leanest cylinder.

the carb is a holley 4150 im pretty sure. in a carb enlosure box with a single plane weiland intake. no power valves blocked them off and used larger jets 82 prim 90 secondary.
proform base plate.

motor is 8.1 to 1 compression dish pistons 72 cc heads.

i am going to step down to a ngk 5r724-9 two steps colder than now.

what is the problem with the timing being at 30 deg? where should i run it at? i thought boosted motors needed timing removed from them on the total?

yes the carb is good and it has jet extensions

Im looking at a set of RHS heads for my 408 sbc... how do you like them??

Is the float notched?

Put some fuel in it. Are you running a boost referenced fuel psi regulator? Is the float notched? I'd figure the fuel out asap. If you haven't hurt a ring land, tuliped a valve yet, its probably coming.

As far as Timing, marine stuff can be a little different than what guys do on the street. On the street, they pull timing out at max boost, which allows them to run MORE boost. Reason is, well, because they can. They never are at WOT under full boost long enough to start melting things. Too much timing and they'll detonate in a drag race though. In a marine engine, with sustained wot, not enough timing will make the EGTs sky high. All the marine supercharged books here clearly state not to use a boost retard device, basically because of what I said above.

I do not know small blocks, and what kind of timing they like. Mercurys supercharged carb'd stuff for BBC's was

525SC=35* total 5.5 psi of boost
600SC=33* total 6psi of boost
800SC=28* total 8psi of boost