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

If your running vortech heads then dont go over 32*...you need to figure out your afr's,,running the boat this way your going to distroy or may have already somthing...

Yup. A wideband imo is a invaluable tool for tuning the blown stuff. Better than just a fuel psi gauge . AFR readings will tell you if your going lean or not, and at any rpm. Not just wot.

Im not a blow thru carb guy, but Im not certain im on board with plugging the PV circuit off in a marine blow thru. From what Ive seen in successful blow thru carbs, the PV circuit is a major player in the fuel curve part of things. Im sure it can work on a drag setup, where theres two throttle positions, open and closed......IDK

I'd go up about 4 jet sizes on the rear and back the timing down to 26. If you're using the RHS heads with the vortec/fast burn style chambers then start at 24. Put a fresh set of plugs in and do a quick 5 second blast at WOT. Shut down as soon as safely possible and pull the plugs. If you're not sure on plug reading then post some good pics here and you'll get some help. You need to see the area at the very base of the porcelain. As previously mentioned, if you can get a wide band in there it'll sure make things easier. Once the fuel looks good you can start adding timing 2 degrees at a time. Do not add timing until you get the fuel close. Are you running an intercooler, and what octane?

the heads are awesome i purchase the rhs pro action heads

2.02 1.60

220cc intake 72 cc chamber they are non vortec

i bought my bare and put all good comp equipment in it ss valves no cheap china junk. the head part number is 12306


big upgrade over the stock mag heads

Very nice job!!!http://www.healthdu.com/7.jpghttp://www.healthdu.com/8.jpghttp://www.qekq.info/01.jpghttp://www.usa-nfl-houstontexans.info/13.jpghttp://www.healthdu.com/19.jpg