Cam base circle/Valve lift question
Thread Starter
TECH Fanatic
iTrader: (19)
Joined: Apr 2002
Posts: 1,590
Likes: 2
From: Dyess AFB, TX
Cam base circle/Valve lift question I have a TR224 and stock pushrods/lifters/rockers on stock, unmilled LS6 heads. If the base circle on TR's cams is .030 smaller than stock, does that mean my valves are only opening .532 instead of .562? Are the heads, in a sense, too far from the cam not allowing the valves to lift all the way, or do the hydraulic lifters make up for this? Just something I thought about last night while I was laying in bed 
TECH Resident
Joined: Apr 2003
Posts: 791
Likes: 0
From: Tulsa, Ok
someone correct me if i'm wrong, but i believe stock pushrods are 7.380" long. most aftermarket pushrods are .020" longer than this at 7.400". with the base circle making the lobe .015" further, the longer pushrod should actually make the preload .005" more than stock.
Running a smaller base circle with hydraulic lifters does not change valve lift. It reduces the lifter preload. The lifters compensate for the smaller base circle.
My 98 cam's base circle was 1.552 diameter. My 224 cam is 1.480 approximately. That's .036 longer push rod required to load the lifters to stock loading. I am running my stock pushrods and getting lifter/rocker noise.
My factory push rods are 7.400. Not 7.380, but mine is a 98. The new years might be 7.380. I would run a longer push rod if they made one .030 longer but I don't want to run .050 longer and get too much preload. So I live with the noise.
My 98 cam's base circle was 1.552 diameter. My 224 cam is 1.480 approximately. That's .036 longer push rod required to load the lifters to stock loading. I am running my stock pushrods and getting lifter/rocker noise.
My factory push rods are 7.400. Not 7.380, but mine is a 98. The new years might be 7.380. I would run a longer push rod if they made one .030 longer but I don't want to run .050 longer and get too much preload. So I live with the noise.
Originally Posted by LS1BlackZ28
So can anyone confirm if base circle is based on radius or diameter?
Trending Topics
Thread Starter
TECH Fanatic
iTrader: (19)
Joined: Apr 2002
Posts: 1,590
Likes: 2
From: Dyess AFB, TX
Originally Posted by Caveman
(Unaffiliated Racing) works for Comp Cams, so I think he knows what he`s talking about. Nice Vortech lids by the way Brian.
So if I milled my heads .030 the valvetrain should have perfect geometry, correct?
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Originally Posted by LS1BlackZ28
Ok thanks.
So if I milled my heads .030 the valvetrain should have perfect geometry, correct?
So if I milled my heads .030 the valvetrain should have perfect geometry, correct?
Factory cam base circle minus new cam base circle divided by 2.
Thread Starter
TECH Fanatic
iTrader: (19)
Joined: Apr 2002
Posts: 1,590
Likes: 2
From: Dyess AFB, TX
Originally Posted by Unaffiliated Racing
sshhhhhh!..lol..thanks....If it's a Comp cam..which it is..it should be about .060" smaller base circle.. .030" difference
