What Pistons?
 

I have a 540 Merlin bored 30 over, edelbrock alum heads 118 cc, 871 bds 6.5 lbs boost, twin Holleys throttle body size 930, rod length 6.385, bore 4.53, stroke 4.25, scat crank, lightning exhaust. Any recomendations on what pistons I need would be greatly appreciated. Had Srp 142985 pistons, keep melting, wondering about compression. Thanks

i use j&e or weisco forged blower pistons,both brands are top quality parts.

I would FIRST figure out why you are melting pistons.... no piston in the world can handle a bad tune. Now I am not insulting whoever did your tuning, what I call tune has alot of variables: total compression, total timing, fuel grade, carb jetting, etc.

Melting pistons is caused by extremely high temps. Timing could be too high at boost. You didnt say if you had intercoolers, so you might have really high air temps and too much timing at boost could cause this condition.

Too low of octane fuel usually causes detonation which will usually result in pistons breaking peices, not melting.... but it is not uncommon.

How much total timing do you run? Is there any intercooler?

:eek: Your running 9.5:1 on that blower motor with those pistons and cc heads according to SRP

http://www.srp.com/cat/auto/chevy_bb/flat_top_inv.shtml

I've never owned a blower motor but from all I've read about them in magazines it seems they always run more like 8 or 8 1/2 to 1 compression using dished pistons.That's unusual to actually be melting pistons.

not unusual at all. in this case if he has a static 9.5 comp ratio, then at full boost he has roughly 18.7 to one which, unless he is running 130 octane along with water injection explains his collection of ash trays

LMAO!

No disrespect to boatguy94.

Might want to look at the JE 257943

http://www.jepistons.com/cat/je/auto...inv_dome.shtml

I run 9.5:1 compression and 5psi. This results in a 12.5:1 dynamic compression. With 6.5psi and 9.5:1 static you would be at about 13.5:1 dynamic. Not outrageous but you would need to be conservative on the tune. Timing around 30 total and a/f ratios under 12 at WOT and at least 93 octane. What timing and a/f are you running to melt a forge piston? Also if it is efi I would have a hard look at the fuel curve.

Niceguy is right on. I can attest to no piston will survive a bad tune and most pistons can survive a conservative tune. I run hypereutectics with my setup and it run strong with no piston issues. But the setup is 11.7, 29* and 93 oct.

BT