I just took my car for a drive after a winter of installing 5.3L GTP stage 2 ported heads, Comp XER 281 cam, long tubes, ORY, PCM4Less tuning, SLP MAF, porting the TB, LS6 intake and a Textrailia clutch and Aluminum flywheel. It REEEAAALLLYY runs good but I'm getting some spark knock going thru the gears but I have 1/2 a tank of 87 octane from last year in it. I think the old 87 in it is causeing the spark knock but I wanted your guys opinion. So do you guys think that could be causing the spark knock?

 

y was u running 87 octane for ?

 

Especially with new heads that very well may have raised your static compression ratio and a cam that very well increased your dynamic compression? Throw in a bottle of octane booster. It worked when I did a head/cam swap in my Gen.I/LT1 hybrid with a half tank of 87 octane.

 

87 octane+LS1=BIG PROBLEM lol, dont ever use anything put premium in a LS1, or any performance V8 really.

 

yeah. you need to run some octane booster through it. I guess you have a lot of driving to do to get it out of the system. or even better go find som 104 or 100 octane and fill it up. that is what I did. when I did my h/c/i swap back in the day. it only ran like crap for a little bit. haha.

 

I did, just that after I posted that, seems to be getting better.

 

Shoot I never ran 87 in our car even when it was stock?!?!?

 

octane booster isnt ****. its only .? of a point not ?. points. and its not good for valves and etc leaves orangish residue

 

I always run 87 in my car when it was stock. No knock retard at all, I checked it with the snap-on scan tool I have.

 

you do not need to be running 87 on an LS1 period! 91-93 minimum.

 

Its true that 87 isnt what you should be running, but in a stock application, the ECU just kicks in the low octane table and gets you by. Now that youve got higher compression, all bets are off. I still have KR with 93 that im chasing down, i cant imagine you having luck on 87, especially old 87. Id go to the local home depot and buy a gallon of toluene or xylene and mix it into the tank along with topping off with premium. That should bump the octane up to a premium grade level.

 

Higher compression and a bigger cam don't go very well with 87 octane.

 

NEVER run 87 octane. Stock or not.

Even if you do, (for some reason I don't know), you'll probably LOSE fuel economy.

What, to save $2 per tank of gas??

 

Should have used a little forethought and filled up with 93 for the last tank of the driving season. BTW the gas mileage was unchanged from 93 to 87 on my car when it was stock.

 

I agree with you for teh most part, but lower octane actually has a higher BTU output. Assuming you can stay with the high octane table, youll actually have better milage on 87, theoretically, but as soon as you try to go WOT, or lug up a hill, youll ping to all hell.

 

one thought ....

when you use a hand held programmer it changes (as most know) the fuel and spark curve and it says (if it doesn`t have have dual fuel grade tuning) to not use lower than 91 or as a hyperteck if I`m not mistaken 93 octane or detonation (some noises might be heard and shakes felt) due to the reprogrammed computer advanced spark that in many cases will not tolerate low octane fuel ....

bottom line ask PCM4LESS if the tuning was on 93 octane and running 87 MIGHT be the problem .... just a thought.

(next time anybody does that with a 87 octane in the tank my advice take out the remaining fuel the old hose sucking way and fill it up with 93 or what it was tuned on)

hope it helps.

 

My thermostat stuck on me and it shot up to 240 instantaniously And now I'm getting coolant in the exhaust! No coolant in the oil, probably a head gasket. I just hope the heads and block are ok. It only ran about 3 miles to get home. I'm going with ARP head studs or bolts this time. If I cracked the block on the install it would be losing coolant into the oil correct?

 

Ttt!!!

 

If you had put "winter-blend" 87 in your tank before storage then that would explain the knock from the fuel.
You may have had some detonation though, and that would explain the failed head-gasket.
Make sure you get your block and heads re-decked flat before bolting it back together.

I like 87 octane myself, but I'd suggest draining your tank completely before running the car again. Use whatever is in your tank for the lawn-mowers.

 

dude what were you thinking???? 87 octane, don't you realize you gotta pay to play.
Put some Amoco ultimate or Shell V-Power both 93 octane, but the only fuels I burn.