aaronc7

I have the comp cam adjustable length pushrod and am getting zero lash between 7 3/4 and 8 turns. 6.8 + ((7.75+8)/2)*0.050 + 0.082(preload) = 7.275 required pushrod length. I believe I have done everything correct... just looking for a sanity check on here. I checked cylinder 1 and 6, intake and exhaust both. All measurements were within 1/4 turn of each other. I ensured each was at their respective TDC firing position for the check... I even put the stock pushrods in and turned the motor over to be sure I was indeed on the base circle of the cam for the checks.

This short of a pushrod does not seem all that common which is why I am a bit skeptical that I am doing something wrong.... here's a list of relevant info that I can think of.

2003 C5Z
Stock bottom end LS6
243/LS6 heads ported and milled 0.030" by AI
OEM GM headgaskets
EPS 226/230 .604/.604 113 +3 on HiRev lobes
New "LS7" lifters
Stock rockers with trunnion bearing upgrade

Thoughts, ideas, need more info?

Thanks!

k24556

Mmmm. The heads were milled 030 so that moves the rocker trunion 030. If you had a valve grind, then the seat moves closer and the valve goes in further. If each one was moved 010, that gives you 050. Then you end up at 7.75 before the work. The machine shop can grind the valve stem tip some, but I don't think there is .050, maybe .025. Are ls7 lifters taller? Are they pumped up with oil so you know you are getting a good measurement. I'm hoping you haven't torqued the heads so you can check p.v.t to make sure that big cam won't put a calve in a piston. If not drop a stock lifter in and check

my point is to go back to all the changes you made. Now is not the time to hurry.

64drvr

Do you have a dial caliper to measure the pushrod length checker?

aaronc7

I don't think mine is long enough to measure the entire length. I verified the part number online and it is indeed 6.800" base length and 0.050" per turn. Why do you ask?

aaronc7

A little searching on LS1tech... I've found some posts that suggest the LS7 lifters are 0.050-0.060 "taller" than the standard ls1 lifters. If you couple that with the ballpark math from k24556 above, then I guess that puts me in the ballpark. No idea on LS6 cam base circle vs this EPS cam.

dblerman

When I did my heads/cam swap I found that even at TDC dot to dot the lifter wasn't on the base circle of the cam, it was a few degrees off. The method I used was I put two pushrods/rockers on a cylinder, and rotated the engine, when intake valve begins closing the exhaust will be on base circle, when exhaust valve begins opening intake will be on base circle.

243 heads
228R comp cam
LS7 lifters
7.400 pushrods

aaronc7

Which cylinder were you checking when at "dot to dot"?

For my own sanity, I might as well double check using the EO/IC method, although I'm pretty certain I did verify that the cam was on the base circle.

vettenuts

Dot to dot with the cam at 6 o'clock is cylinder #6 at TDC, not #1 so that might make a difference depending on how you measured.

vettenuts

I don't think the numbers are unreasonable but I would also check the rocker wipe patter before measuring to ensure the rockers are optimally placed. With stock rockers and a cam, this can require lowering of the rocker stand, not shims.

aaronc7

Vettenuts, I was hoping you'd chime in. You're in about every single thread I've come across the subject and always had good info.

When I came across posts such as "I've never ran pushrods shorter than 7.300...you're doing something wrong!" it made me question myself a bit.

But then again it also seems like many people just throw in whatever pushrods or what someone recommended to them and never actually measure.

I'll look into lowering the rocker stand, don't think I've read much discussion about that with the stock rockers.

Thanks

64drvr

Personally, I'd double check the measurement. maybe semantics, but i just marked the pushrods on a piece of paper and measured the marks on the paper with a dial caliper, requiring me to cut off the first 3-4" because mine is also not 8".
I hate to even list it since it's an LS7 and no two situations, even equal builds should be taken as gospel...
but on my LS7, i had the heads milled .030, EPS cam, fresh LS7 lifters. stock 7.800, required 7.775's IIRC....possibly 7.750's. point being the change was not huge. granted, you're going from LS1 to LS7 lifters.

not to insult your intelligence but if anything i would remeasure, ensuring the checker is fully seated in the cup of the lifter and the cup of the rocker, and that you are indeed on the base circle of the cam.

dblerman

Either way, I prefer the EO/IC method, it takes 100% of the guesswork out of whether you're at TDC and on the base circle (especially if you don't have your timing cover off).....I also use this method for torquing the rocker arms.

vettenuts

I can't use this method for rockers since I run the Yella Terra's and they are installed in pairs necessitating the cylinder be at TDC for the rocker pair being installed.

vettenuts

aaronc7, I would also find out if AI did anything to the seats. Not questioning their work, as they are excellent, but if the seats were dressed a bit then as stated in an earlier post by k24556 the stems may be a tad higher which again lessens required pushrod length.

Finally, the LS7 lifters are a stock replacement. As I recall, in replacing an original LS1 lifter with an LS7 lifter you end up with a little larger preload. I seem to recall this was due to the pushrod cup being higher relative to the original LS1 lifter. Do some searching for the LS7 preload by "Eric D", who I believe works for GM. He posted a table of lifter part numbers with some of the specifics.

vettenuts

Found it, see post #6. Link to lifter dimensions

aaronc7

Thanks. Yep I have that picture saved to my desktop and where I came up with my target preload of 0.082".

We will see what happens I guess. I just ordered some 7.275s from BTR. Overnight shipping, they get here tomorrow. Trying to wrap this up before Saturday when I'm heading out of town for a couple weeks for the holidays.

vettenuts

If you have a dial indicator, you can install one dry pushrod and measure the preload. If it is OK, remove and properly prepare for installation. Make sure to blow out the oil hole. I use Redline Assembly Lube on both ends and the valve tip during installation.

aaronc7

Figured I would follow up in this thread. I didn't actually measure preload, but I did install the 7.275 pushrods... all of them did have some preload, so that's a good thing I guess.

Finished everything up just now and took her for a quick spin. Made a quick exhaust video... keep in mind this is tune revision 1 and stuff has not been dialed in yet at all.

Stroker87

that sounds awesome!

are you going to dyno or street tune?

my car is an 03 I have ported 243's, fast 92, ls2 Tb already just waiting to go on been looking for a cam so i'm very interested in your results and drivability

RonSSNova

Your EPS cam is similar to mine. You will like it.

I simplified things. Set on base circle, adjusted the checking pushrod for 0 lash, removed and measured with 8" calipers. Added my desired .060" preload to the measurement and ordered pushrods.

I checked the orig lifters against the LS7, they were identical.

Have fun!

Ron