GTFORMULA

iTrader: (94)

just got 03 ls6 cam do you really need .050 longer pushrods or can the lifter plunger take up the extra room. I need solid facts not opinions Thanks everybody

GTFORMULA

iTrader: (94)

with stock height ls1 heads

Adrenaline_Z

The camshaft does not determine the pushrod length, unless you have changed
the base circle diameter of them cam.

Lifter preload is set with the lifter on the baseline of the cam lobe.

The pushrod length will vary if the lifters are not stock dimensions, or the
rocker tip does not align with the valve stem.

The latter can be a product of valve height, head gasket thickness, decking, etc.

You will want to check the rocker arm alignment on the valve stem after
setting pre-load (non adjustable, or adjustable valve train?), then
determine the need for a change in p-rod length after cycling the valve through
the entire lift motion.

2xLS1

iTrader: (25)

To answer your original question, no. I am running the 02+ LS6 cam in my 00 with stock pushrods with no problems and have installed it in other cars with stock pushrods with no problems. I believe someone here did all the math with the different base circles one time and came up with 7.427 to be the length to maintain the exact same lifter preload as the stock LS1 set up.

Dan_the_C5_Man

Yes, to do it right, you do..

It's curious how "2xLS1" contradicts himself in his post. (says "no" but then states they should be 7.427" (correct)). And it seems "Adrenaline_Z" has done the same thing in his post as well; he states "only if the base circle of the cam changes.." Umm, o.k., the LS6 cam's base circle IS smaller, so how does that equate to not requiring new push rods?

I went with 7.425" on my LPE GT2-3 cam. That cam has at least as small a base-circle as the Z06 cam, which is smaller than a stock LS1 cam.

GM engineers (you know, the guys that designed these engines) made up the difference on the valve side, w/ longer valves.

Lots of folks run the stock PR's with LS6 cams on LS1 motors.. That does not prove it is the "correct" way.

2xLS1

iTrader: (25)

He asked if he needed .05 longer push rods. That's how I'm not contradicting myself.

Adrenaline_Z

OK buddy, once you learn the difference between base circle diameter and
base circle, then you can start bashing others.


EDIT: If you knew anything about setting pre-load, the lifter would be at the
same point on the base circle of either cam.

It may also help you to read the entire post where it states to check
the rocker tip alignment on the valve stem throughout the entire lift cylce.

I guess pushrod length is only checked on the base circle huh?

Thanks for coming out.

redtail2426

iTrader: (10)

the only base circle measurment needed is the base circle of the lobes.The ls6 ncam has a smaller base circle diameter on the lobes then the ls1 does.this smaller base circle will allow the lifters to sit further down,reducing lifter preload.you technically just measure the lobe base circle and divide by two to get lobe base circle radius.If the base circle radius of the ls1 cam is .776 and the base circle radius of the ls6 cam is .745.then you would need a pushrod that is .031" longer to maintain original lifter preload.these numbers are not the actual measurments so do not use them.This is just an explanation of how to properly measure your need pushrod length.This will also only work on an engine without milled heads or block,aftermarket rockers etc.

Adrenaline_Z

True, no arguement with your math; but he's going to use an LS1 head with a Z06 cam.

Are you really going to trust the math without checking the seat depth,
or rocker alignment after assembling the engine?

redtail2426

iTrader: (10)

rocker alignment and seat depth are not an issue if the stock ls1 heads are stock(no adjustable rockers and such).the only thing that will change valvetrain geometery on a stock ls1 head is adjustable rockers.the stock rockers simply get torqued to 22 lb ft and geometery on the valve will be constant between cam changes as long as the preload on the lifters is correct.all he has to do if thats all he is changing is the cam is measure the lobe circle radius and compare it to the stock lobe circle.its as simple as that and works perfect.

Adrenaline_Z

You're putting alot of faith in the casting process and component toleranaces.
I'd be double-checking in every case.

We've already determined that the valve lengths are different and the base circle
diameters
are not equal.

Again, that's confidence if you can predict a push-rod length without checking
the final assembly on the engine.

We should invite some hard core engine builders to this thread just to get a
professional opinion. I'd be interesting in their view as well.

redtail2426

iTrader: (10)

i would to remembering that this is only for an engine that is completely stock with no milling and stock rockers.also remember that the ls1 and ls6 pushrods are the same length.that is why the valves on ls6 heads are longer,because there cam lobes are smaller,instead of making a whole new pushrod length they just added it onto there newly designed lighter weight valves to maintain proper preload..I did see a calculator once that would do the math for you and it worked the same way that i stated.But please someone who knows what they are talking about chime in and give an opinion.im curious as well

GTFORMULA

iTrader: (94)

Thanks for the input guys all this technical stuff is funny, especially when people argue . I really apprieciate your input. BUT all I want to know is will it work and has anyone ever done it. Im trying to do this as easy, and without buying unnecessary parts. Thanks everybody

redtail2426

iTrader: (10)

another point i will stress that may put this to rest is that if an engine is being totally rebuilt or heads even removed,interchanging heads and gaskets and what not then i would not use the math idea,but instead use a pushrod length checker.The math idea will only truley work correctly if the engine is stock and has not been disassembled since it rolled off the factory floor.this will not work on extensive rebuilds.

redtail2426

iTrader: (10)

to answer your question you will need some 7.4's.Stock length pushrods are 7.38".thats why when people do cam swaps they use hardened pushrods that are 7.4" as this makes up for the smaller base circle.i will be measuring a set of stock pushrods to verify that they are 7.38 but have done a lot of searching on the forum and as far as i know from this site stock pushrods are 7.38"

Trans Am Kid

I had my heads milled .027 when I ported them and used 7.40 pushrods to have the correct length. If your heads untouched you will need to get the 7.425 pushrods.

Chris81

iTrader: (1)

Mine works fine with Manley 7.40's

Ryan02SS

iTrader: (3)

I used the run the LS6 cam with stock pushrods. To get perfect valvetrain geometry running the LS6 cam w stock LS1 heads you need a 7.427" pushrod. I ran the stock PR's and ran into no problems at all. I have my oil analyzed after use and no changes were noticed. Thunder Racing's Hardened PR's are actually 7.415" long if you are looking for an off the shelf pushrod.

Dan_the_C5_Man

Thanks for everyone that chimed in. Again, to the folks I "bashed", the consensus of this thread so far (in my mind anyway) is 7.425's to do it "right", but yes you could get away w/ 7.400 and no it won't grenade.

My reasoning for my purchase of longer PR's was I wanted to replace the stock pieces w/ hardened items; why in the world would you not take advantage and buy the "correct" length in the processes.

schultzsj

iTrader: (1)

If you dont change anything but the cam, casting processes and component tolerances are not relevant. These things only matter if you are changing other components that could vary such as valves, heads, head gaskets, lifters, Etc. along with the cam.

Why would the valve lengths be different when it sounds like he is using his same heads? The base circle diameters are certainly different but by a known or determinable amount.

Again, if you change nothing but the cam, there is not confidence involved. The required change in pushrod length is simply the difference between the two cam base circle diameters divided by two.

To summarize, you can ACCURATELY predict the required change in pushrod length based on the difference between the two cam base circle diameters if you only change the cam (which seems to be what he is doing).

Steve