Pistons for a Blown 351C?

CloneRanger · Sep 13, 2004

Hi Guys, what pistons do people use in Blown 351Cs? I've been looking, but I can't find anything off the shelf with more dish than 13cc? I don't particularly want forged pistons because of the piston slap issues when cold...
Want to get down to about 8:1 compression with OC heads, and not really comfortable about doing it with a Felpro 0.078" headgasket...
Any Ideas?
Thanks
Ben

nosaj122081 · Sep 13, 2004

You're really asking for it if you wanna run an open-chambered blown motor without forged pistons. In fact, I ABSOLUTELY would advise against it; it'd be a grenade indefinitely. If you want any more dish than 13cc though, you'll probably either have to have them custom made or machined.

CloneRanger · Sep 14, 2004

I'm not seeing the problem with OC heads? 10-12psi is fairly mild boost levels... I'm not thrilled about having forgies in a daily driver....

Hack · Sep 14, 2004

I believe that OC heads are more prone to detonation when compared to CC heads. I don't know anything about forced induction on a 351C. Have you talked it over with the manufacturer of the blower? They should have some good information.

fastcoupe68 · Sep 14, 2004

try probe industries

nosaj122081 · Sep 14, 2004

CloneRanger said:
I'm not seeing the problem with OC heads? 10-12psi is fairly mild boost levels... I'm not thrilled about having forgies in a daily driver....

Open chamber heads suck for detonation... They knock like crazy (know from experience with 'em) on even lower compression NA motors. With 10-12 PSI of boost, it'd be a disaster without forged. I wouldn't even consider hyper or cast pistons.

CloneRanger · Sep 14, 2004

I'm building a custom setup using an Eaton off of a SVT lightning and a custom EFI manifold....
Problem is, as soon as you go to dished pistons, you lose your squish effect from the CC heads, so you might aswell have OCs...
I suspect half the problems with OC's reputation for detonation largely comes from putting lumpy pistons to get the compression up, giving bad chamber shaping...
I DO NOT want to use forged pistons. 0.002-0.006 clearance versus the 0.001 for a hyper? I don't want a motor that rattles like an old bucket of crap on start up....

nosaj122081 · Sep 14, 2004

CloneRanger said:
I'm building a custom setup using an Eaton off of a SVT lightning and a custom EFI manifold....
Problem is, as soon as you go to dished pistons, you lose your squish effect from the CC heads, so you might aswell have OCs...
I suspect half the problems with OC's reputation for detonation largely comes from putting lumpy pistons to get the compression up, giving bad chamber shaping...
I DO NOT want to use forged pistons. 0.002-0.006 clearance versus the 0.001 for a hyper? I don't want a motor that rattles like an old bucket of crap on start up....

Nope, the open chambers are just BAD... I ran flat tops, 'bout 9.5:1, still knocked with a Lunati Bracket Master II cam. The chamber itself is poorly shaped for detonation purposes, it isn't pistons. You're looking at the wrong kinda dished pistons for closed chamber heads; you want a D-dish, not the generic circular dish.

Hyper pistons are still CAST, and are very brittle... I would never run them in a boosted engine, EVER, as it has too great a potential for a catastrophie... Hypers are great for factory stock and near stock applications, but I would even feel bad selling a set to a guy that was running boost. Forged are still the sturdiest pistons, bar none, and thats why everyone uses them with boost and nitrous... FYI, since you're using a Lightning blower, they had forged pistons factory, same with the new Cobras. And every turbo car I've owned. Never once heard a rattle. If you run hypers and OC heads I'd run race gas all the time to be safe.

http://www.flatlanderracing.com/kb_hyper.html

3spd on floor · Sep 14, 2004

whats the problem with forged? all stock 5.0s from like 87-92 had them, and they dont have any piston slap issues. the myths about forged pistons are just that, myths. you dont hear new cobras rattling like old buckets of crap, do you?

slapper · Sep 15, 2004

CloneRanger said:
I DO NOT want to use forged pistons. 0.002-0.006 clearance versus the 0.001 for a hyper?

With 10-12 pounds of boost, you might want to give yourself a little more piston/wall clearance than .001.
I would also open up the rings more also. I knew a guy that ran hypers with about 6 lbs of boost. It ran good for a year or so until he got a bad tank of gas on a hot day. Cracked the cylinder bore longitudinally when the piston blew it's top and sprayed the cylinder with aluminum.

Pistons for a Blown 351C?

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