Piston to head clearance

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
User avatar
Walline
Member
Member
Posts: 183
Joined: Thu Apr 29, 2004 5:19 pm
Location: Kansas

Piston to head clearance

Post by Walline »

What is the closest anyone has ever ran in a 7000RPM max automatic drag car? I was going to try .035. Any thoughts? THANKS!!
User avatar
speedtalk
Site Admin
Site Admin
Posts: 986
Joined: Mon Apr 21, 2003 2:43 pm
Location:

Post by speedtalk »

I've seen some stocker guys run a fuzz closer than that. Keep in mind that piston to wall clearance plays a role - .003 can be closer than .010
In Memory of Don Terrill
SpeedTalk Owner/Admin
Lasher...
Member
Member
Posts: 199
Joined: Sun Feb 01, 2004 10:00 pm
Location:

Post by Lasher... »

I have run my last SBC at .019 down the hole and an .015 steel shim gasket with steel rods and the pistons @ .002. I know one guy on another forum who is running .027 total with steel rods. One person I know ran .025 but thats about the closest he would go... even at that on his 355 it showed as small amount of contact......... I may have to freshen up an engine for my better halfs car and I had planned on .028 to .030 depending on how things machine up... but hers is a low RPM daily driver........ I have never run alum rods but they may require more clearence than a steel rod would. I cant offer any help with alum or ti rods.

EDIT : BTW all those examples I gave above were SBC's. Other engines may require some different numbers.
maxracesoftware
Vendor
Posts: 3627
Joined: Sat Feb 14, 2004 4:04 pm
Location: Abbeville, LA
Contact:

Post by maxracesoftware »

on a Chevy 1968 Camaro running in NHRA SS/IA Class with 350 sbc

http://www.maxracesoftware.com/Jimmy_Faul_Wheelie.jpg

http://www.maxracesoftware.com/Camaro_68_JF.jpg

http://www.maxracesoftware.com/Danny_Helmer.jpg


4.065 Bore (4.000=Stock)
3.493 Stroke (3.480=Stock)
362 cid

BME pistons at .010" piston-to-wall clearances

NHRA BluePrint Specs = .018" HeadGasket -.002" min Decks

ran this combo at -.011" deck clearance = .029 " total deck clearance w/.010 piston-to-wall

on Dyno at 600 rpm/sec tests to 7500 rpms
pistons were not hitting decks yet

at DragStrip, shifting at 7500 at crossing at 8300+ rpms
pistons were lightly hitting decks , especilally as racer lets off throttle while still in high gear after finish line

went to Mr. Gasket .022" thicker headgasket
the Chevy's seem to "run faster" with pistons on verge of hitting decks or as much as very lightly hitting decks

not recommended for average racer !!
which would be at least .035" total recommended deck clearances
w/steel rods + light pistons ...to bare min of .050 to .060 for alum rods
.045" would be on verge w/alum rods
MaxRace Software
PipeMax and ET_Analyst for DragRacers
https://www.maxracesoftwares.com
Post Reply