Whats your compression ratio?

[blykins]

Probe pistons will run you $400. That's what I bought mine for. They are forged. Flat tops with floating wrist pins. Like I stated before, Edelbrock heads, ROL head gaskets, pistons sit .005" in the hole. Compression ratio is 11:1, 8.27:1 DCR with my cam. Very good quench as measured. Excellent pistons....I've used them in two builds.

[ZOERA-SC7XX]

KB flat top pistons make about 10.0:1 w/69 cc heads for a 428 FE, and are under $400 per set. I think that's about dead-on for street use w/93 octane fuel.

[blueovalfanatic]

Originally Posted by blykins

Probe pistons will run you $400.

Do you have a part number or anything? Part number 14472-030's are $455, 10:1 with 72cc heads. Are they the same as yours?

Thanks,
Greg

[decooney]

10.8:1,with aluminum heads and a tad larger cam to help bleed off a bit.

[maverick]

From the response in this post, a mid to upper-10 ratio (naturally, engine blueprint based around said c.r) can be "safe" with 93 oct. and timing not set too high.

Resonable assumption?

[aldersonjames20]

Based on this thread, I went and filled up my SPF with 100 race fuel the other day... cost me 60 bones for 12 gallons. I noticed very little if any difference in the way it drove, ran, and sounded compared to the 93 I normally put in it. Now I realize that if I was going to be road racing and sitting at 5-6K rpm for extended periods its better for the engine, and i can't really see if its healthier for the engine without comparing plugs after a drive with each, but I just am not prepared to spend the money for anything over the cost of 93 for normal driving. Hope I am not doing harm, but it sounds like its fine based on my engine setup and drivability.

James

[blueovalfanatic]

Thanks for the help everyone. I decided to go with Probe SRS pistons (#14472). Finally, the engine build is officially underway!

Greg

[Excaliber]

I notice this when I run higher octane: The engine shuts down quietly when you turn off the key, no 'dieseling' or 'run on' with higher octane fuel. Now a lot of the 'run on' problem can be cured by simply having a low idle rpm, which pretty much closes off the carb throats 'starving' the engine. But with MY cam AND dual fours I have to keep my idle rpm around 1000. Thats 'just enough' for the engine to continue to draw in a little bit of 'fuel\air' through the carbs and theres 'just enough' hot carbon in the combustion chamber to ignite that fuel\air and cause the dreaded 'run on' condition.

When I'm using 'race gas', ZERO problem, shuts right down, even at 1100 to 1200 idle rpm. Why? Higher octane fuel is hard to ignite, another way to say it is, it's more stable. You COULD surmise that it 'burns cleaner' leaving fewer deposits to ignite said fuel, maybe. But no, I think whats happening is it's simply 'harder to ignite'. I routinely shut off the key and 'dump the clutch' with the car in gear when shutting down. I've done it so long I don't even think about it anymore, until I let someone ELSE drive and they DON'T, then I'm freaking out when the motor 'runs on'!

Using octane boosters has NOT helped this condition, even using well above the recommended amounts. Conclusion, octane booster aint doing squat for me!

[blykins]

Greg, I'm running a 428, but those are essentially the same pistons. Flat tops with 4cc valve reliefs.

BTW, can you send them back? I have a guy that will sell them for about $50 less than what you paid....they will drop ship from Probe.

Email me....

[JAM1775]

I have a 2002 built 351W , Comp roller cam , ported 190cc Brodix heads, Ross flat forged pistons, AL Flywheel, 3 step colder spark NGK V plugs running, 32 degrees total timing running 11:1 on 93 pump gas. I've accidently revved and started to roll out in 3rd, no chatter. I also have used 75 hp nitrous ( 3 degrees out) and 100hp (4 out) only on high rpm 3rd/4th gears. The motor currently has 14,000+ miles with no noticeable issues. I do add cheapo Champion Octane Booster in summer but that's just a quirk of mine.