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Username Post: SBC valve lift question        (Topic#235208)
C10 Sleeper 
Valued Contributor
Posts: 3426
C10 Sleeper
Loc: Redding Ca
Reg: 03-17-09
02-08-10 08:11 AM - Post#1858480    

Just out of curiosity I have been thinking about how much valve lift can a Small block chevy take with flat top pistons before actually hitting the pistons. Now I know there are many variable that come into play but lets say you have a 350 .030 over with a 2.02/1.60 set of basically stock 64cc heads that have never been milled and the block was decked just enough to clean it up.

Im not saying I want to do this to push any mis matched engine combos but I am planning a full out race motor for the near future and need some basic info to play off of and the rule book is going to be pretty strict on some things.

Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 16291
Age: 67
Reg: 03-16-01
02-08-10 08:16 AM - Post#1858486    
    In response to C10 Sleeper

your forgetting that both the cams duration and Lobe Separation Angle will effect the resulting clearances, generally cams under about 220 duration at .050 lift with under a .470 lift and a 112 or wider LSA will clear

Edited by grumpyvette on 02-08-10 08:23 AM. Reason for edit: No reason given.

"13th Year" Gold Supporting Member
Posts: 16176

Loc: Colorado Springs, CO
Reg: 08-08-04
02-08-10 09:22 AM - Post#1858523    
    In response to grumpyvette

Generally, a stock head with stock springs can stand up to just short of .50 inch of lift (.470 on vortecs) without major issues - like hitting the piston (depends more on the cam timing really), coil bind, valve float, etc.

Your heads will require machine work and better springs to improve on lift figures.

Your sanctioning body should have limits in their rulebooks, and if it is a near stock class they should be .50 inch or so.

C10 Sleeper 
Valued Contributor
Posts: 3426
C10 Sleeper
Loc: Redding Ca
Reg: 03-17-09
02-08-10 11:15 AM - Post#1858576    
    In response to Vaughn

I am not worried about springs or modifications to the heads to accomidate bigger springs to handle lift. The current rule book will be changed somewhat by next year when the car will be on the track. we can run any set of heads cubic inches are limited to 360 and must use a vic jr manifold with a flat top piston and any cam shaft as long is it isnt a roller. The motor is going into a circle track car that weights about 2500 pound and there is no engine claiming. In the past I was running a 6.30 rear gear turning about 7000-8000 RPMs if I remember correctly.

C10 Sleeper 
Valued Contributor
Posts: 3426
C10 Sleeper
Loc: Redding Ca
Reg: 03-17-09
02-08-10 11:29 AM - Post#1858584    
    In response to C10 Sleeper

here is one of the cams I was considering its a solid flat tappet cam.

advertised duration int/ex 302/310
duration at .050 278/286
valve lift .550/570
lob seperation 106*

what are your opinions on PV clearance? I will have my machine shop set up the heads with the proper springs so there shouldnt be an issue other than if there is a chance that something will collide due to lack of proper clearance. I am trying to get into the ball park so I dont have to order multiple cams or have my pistons machined for more clearance if I dont have too.

"4th Year" Silver Supporting Member
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Age: 60
Loc: Altavista, Va.
Reg: 07-05-08
02-08-10 01:08 PM - Post#1858634    
    In response to C10 Sleeper

I had a dirt track friend a while back who really liked Lunati SPA2-292-302 It has .550 in. and 571 ex.

Dedicated Enthusiast
Posts: 5628

Reg: 05-27-08
02-08-10 02:07 PM - Post#1858662    
    In response to aghaga

Don't forget that valve regrinding gives more clearance for lift of the valves.

Super Senior Member
Posts: 4962
Loc: paradise
Reg: 09-05-03
02-08-10 07:56 PM - Post#1858937    
    In response to C10 Sleeper

i have a .537 lift, 243@.050, 112 lsa with flatops and maybe .042 piston to head clearance. but thats with world heads so the end result may not be the same.
70 L camino 350 all forged,174 baby blower, g-force 5 spd, road rage suspension. Pray first before all else fails.

C10 Sleeper 
Valued Contributor
Posts: 3426
C10 Sleeper
Loc: Redding Ca
Reg: 03-17-09
02-09-10 09:00 AM - Post#1859185    
    In response to bobb

OK thanks that is kind of what I wanted to see.

Posts: 240

Age: 23
Loc: central IL
Reg: 05-01-08
02-09-10 10:57 AM - Post#1859235    
    In response to C10 Sleeper

lunati solid roller

5.66/5.78 lift
110 lsa
16 lash

13cc dished kb 9.8:1

i know i got dished pistons which obviously help
83 silverado c-10 short bed
383ci lunati cam, dart heads, 750 demon, cal-tracs bars
8.2902 @ 83.15mph 1/8 mile 3950lbs

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