Dished or Flat top pistons

[87 V20]

Ok, so I started tearin apart my 400 sbc to put my aftermarket parts on and , as I thought, it has dished top pistons. Just wanderin is it gonna be worth the time and money to put flat tops in it.

Its a standard bore 400, with vortec heads, and a rv cam.....just curious how much of a difference power wise it would make. Im not boostin it so I wanted higher compressin just didnt know if id justify spendin the extra time and money...thanks.

[454Man]

If you stepped up in cam size swell. Other wise the RV cam is good with your current setup. Others will chime in.

[CanadianC10]

With higher compression expect to never run regular octane again, anything around 10-1 will detonate when hot , at the same time aluminum heads can handle 11-1

[rich weyand]

Concur: you don't need higher compression with a torquey cam.  Higher compression is for more horsepower high in the rpm range.

[87 V20]

ok. thanks alot guys. I feel like a little kid on Christmas day, cause its my first restro and im about to drop a decently built 400 in her....YEEEHAAAW!!!

[VileZambonie]

Are the heads you are running stock GM Vortec heads? Have you modified them and added steam holes? A detonating 400 is not going to make you happy. If you want a tire fryer you should really look at the whole package not just the cam and compression ratio. Do you have 3.42:1 ratio and what size tires? Are you using the 700R4? TBI or carbureted?

[87 V20]

gm vortec heads off a 97 or a 98, 373 gears, sm465 tranny, and I called a couple machine shops in the area and every one of em said steam holes aint necessary just run a 180 t-stat. Their all old school guys and said theyve run em with and without steam holes and said they didnt notice a difference either way...ive gotta good coolin system also...oh and 35 inch tires, and a tbi with bigger injectors and a modded chip...


Its a 87 v20 pickup truck...really buildin for torque for pullin

[HAULIN IT]

Flat top pistons with the Vortec heads will get you more compression than your going to want...depending on gasket thickness, piston to deck height, ect. you could end up near 11 to one. 10.3-6 is likely. Be conservative, a heavy 4x4 will rattle easy under load. Lorne

[VileZambonie]

I agree Lorne. You are going to have a pinger for sure and a 180° Thermostat isn't going to solve your problem. You either need to drill the block or drill the heads. Fel-Pro has a head gasket with provisions for this. Also remember to install the bypass.