mk3cn4

iTrader: (3)

Ok, in my 2002 Ls1 I have a dial gauge set up riding on my intake lifter, no rocker. Before the measurement, I press down on the lifter pretty solidly to make sure it's all the way down. When I rotate the engine by hand and measuring the lift on the pushrod, I am getting numbers pretty close to each other, right around 0.266". In case it matters, after the pushrod comes up and I keep rotating engine to where it should drop, it doesn't drop on it's own, I have to manually push it down.

So, supposedly I take that number and multiply by rocker ratio (1.7) and that's my lift.

.266 * 1.7 = .4522

When I do the same thing on my exhaust I average around .236, which is:

.236 * 1.7 = .4012

Now, I'd prefer not having people throw me a bunch of guesses like "that's probably the leakdown from the plunger" or whatever, I want this to be a repeatable science. If it's leakdown from the plunger, what value do I add? I assume I don't add base radius.

What am I missing?

Please someone who KNOWS please tell me, I have two jobs and have been working on this for 3 nights after work now and I need to identify this cam enough to #1 NOT LIE to someone when I sell it and #2 have it tuned. I NEED to know and there's no way I can take this cam out.

I think one big clue is that it's very likely aftermarket since the intake and exhaust are so different, stocks are pretty close to each other IIRC

Thanks guys.

Thread that started this:

https://ls1tech.com/forums/generatio...-camshaft.html

therabidweasel

iTrader: (5)

Why push the lifter plunger down? Why not leave it up? I don't see how adding a variable plunger height height is something that is needed.

How hard must you push the lifter down? If it's much at all that isn't good either, but I suspect the plungwr

therabidweasel

iTrader: (5)

Is coming up on you. Sorry about the double post. Mobile.

outkast6991

iTrader: (34)

First spin the motor slowly with your hand on the pr pushing down until the lifter is on the base circle of the cam. When the lifter isn't moving down your on the base circle. Now set up the indicator on the edge of the lifter or the tip of a pr. Rotate slowly until max lift. Multiply that number times 1.7 and that's your valve lift. If your doing it right it should be 100% repeatable. Hope this helps man

outkast6991

iTrader: (34)

I'm guessing you weren't on the base circle when you zero'd the indicator

mk3cn4

iTrader: (3)

I was pretty careful to be well past the lobe in both directions when I measured, the samples were taken rotating forwards and backwards over the lobe making sure it was at a solid low point each time at startup, and I would always start where there was no movement for first turn or two to ensure it was at zero (I can only turn little bits at a time, doing this alone).

The reason I am pushing the pushrod down is because after each test the pushrod goes up and stays there, dial guage spring not strong enough to push it back down, and to repeat the test I have to push it back down and rotate the engine to make sure it's bottomed on the base circle (no movement when I rotate).

I'll try to take another video and post it. I'll do anything to get this answered at this point!!!

Maybe it's not possible to get an accurate measurement with a plunger in the mix?

mk3cn4

iTrader: (3)

That sounds exactly like what I did. I'll try to do another video like I mentioned and maybe you guys can spot me doing something wrong.

outkast6991

iTrader: (34)

I was able to get very accurate results using the method I described. If your sure your correct then it should repeat time after time. Are you on the edge of the lifter or in the cup?

mk3cn4

iTrader: (3)

I am doing it similar to the attached picture (which was my first attempt), except NOW I have taken the rocker arm off, and have the pin of the dial gauge resting in the hole of the pushrod ball, where the dial gauge pin is aimed to shoot straight down the pushrod (if that makes sense), and I've moved from the exhaust as pictured to the intake one valve over.

So, I'm not resting right on the lifter, I have the pushrod in between. Now that you mention the cup, maybe that's contributing too, maybe I'm slipping into and out of the cup.

outkast6991

iTrader: (34)

Ok. Are you seeing any lateral movement of the pr? You have to be perfectly in line to get the indicator to measure all movement. Are your first numbers repeating? Or are you getting different measurements

therabidweasel

iTrader: (5)

Ok man, seat the lifter back on the cam, but what you don't want to do is push the plunger inside the lifter down. Stock lifters are pretty soft. Like outkast says, your measurement should be repeatable. Good luck, you'll figure it out.

outkast6991

iTrader: (34)

A dial indicator shouldn't be collapsing a lifter. As said above if your measuring right the results should be repeatable

mk3cn4

iTrader: (3)

Okay, just got back in from the garage with more info. Took off another rocker (exhaust this time) and it's pushrod was "springy", meaning I could push it down on its lifter and it would give several mm but spring right back up. So, measured that one trying to leave it "sprung up" and got 3 consistent measurements of right around 0.281 which is still wrong, works out to be .477 which is smaller than stock even.

I have to get to bed now (11pm here) and won't be back at this until (at least) tomorrow, maybe later, anyone having any other ideas I'd really appreciate it.

EDIT: CRAP just looked it up and that's right where stock is. Maybe this is a freaking stock cam in this thing. Boy am I going to be PISSED if that's true. My next step is to try to repeat this on an intake valve (the cheatr cam has big difference between intake and exhaust) and if that shows repeatable results near stock I'll just trust that. If it's very different (like larger) then I'll continue my quest.

Thanks everyone.

outkast6991

iTrader: (34)

It does seem like a stock cam. Glad you got some repeatable results though

therabidweasel

iTrader: (5)

Outkast, he says in the original post he was pushing the lifter down. He was just reseating the lifter on the cam but I thought he might be compressing the plunger too...just wanted him to be aware how soft the stockers are.

Good luck op, glad you're making progress.

mk3cn4

iTrader: (3)

Am at work now so won't get a chance to do anything until late tonight or maybe tomorrow night, but my plan will be to find an Intake pushrod that springs up when pushed just like that exhaust one did, and and for consistency do the test on it while it's in the "sprung up" position just like the exhaust one was.

I am going to assume right now that this will be the trick: to get accurate measurements find a rod that moves and is "springy". That last measurement felt solid, and lines up exactly to stock. If it measures to be stock intake lift (should be 0.274 intake according to: THIS) then I'm pronouncing this cam stock, which means I was probably ripped off.

My next step will then be to just bolt this sucker back up leaving the stock springs on, returning the PAC springs I just ordered (they didn't even arrive yet), and take it to the track and check the trap speed to double check there isn't an unexplained 30 horsepower there for the final verification (I was afraid to do that originally because I saw the stock springs on what was supposed to be a cammed car and didn't want to drop a valve).

I knew when I bought this car there was something fishy, but the guy just kept convincing me over and over and I trusted him.

outkast6991

iTrader: (34)

hey man i hope my post didn't come off as me coming at you. that wasn't my intention at all. i was just trying to help the OP with a procedure that has worked for me. Hopefully the OP will get the info he needs

therabidweasel

iTrader: (5)

Nah man, didn't take it that way at all. Wasn't coming back at ya either

Op, good luck man I hope it is cammed and you weren't ripped. If so, you already got the sprngs on the way, so a cam is just a little...

mk3cn4

iTrader: (3)

Ok, just to let everyone know, I did an intake pushrod test tonight and got some mid 270's, seemed relatively consistent.

This has convinced me that this is a stock cam.

Also explains why it runs so well on stock springs.

So, seller lied.

I wish this seller was an LS1tech member because I'd love to call him out and publicly thrash him, but no such luck. Just some random dude in Virginia with some timeslips that may or may not have been his.

Oh well. Thanks guys for the help!! If nothing else this was a good learning experience. Now I can just button this thing up and start driving it without fear of busting a spring.

outkast6991

iTrader: (34)

There is a lot to be said for stock reliability. It sucks he lied to ya but it will come back around to him. Enjoy your new ride and when you do stick a cam in it at least it will be what you want and done how you want. Good luck man