hammertime

iTrader: (1)

If you are using a hydraulic lifter, and not using a "checking spring", spring pressure should force your lifters to bleed down enough that you would not have contact. You should be measuring greater than actual running clearance if that is the case. Also, most cams are cut on a smaller base circle than stock, requiring a longer than stock pushrod to get the lifter pre-load back where it belongs.

Installing a cam dot-to-dot will not help you find a cam that is ground incorrectly, or a timing set that is off. Manufacturing defects can happen, and something definitely does not look right with the results you are getting. I would degree the cam to see exactly what you have before going any further. Even if you just catch an installation error, you might save yourself hours of chasing your tail.

If your chamber volume checks out, check that your valves are in fact 2.00". When the vendor says "check, but you should be fine" and you have actual contact while checking, you've got a problem somewhere.

Good luck!

ramairJP

iTrader: (3)

Using the stock pushrods in your setup is creating some error in your measurement. To use clay correctly you need to use a solid lifter - shimmed or otherwise - and a PR adjusted to zero lash with the cam on the base circle and the rocker arm torqued. I prefer the check spring approach set up in a similar manner using an adjustable PR. Roll then engine to TDC and then check up to 15 degrees on the appropriate side per valve - ATDC pr BTDC - in 1 degree increments with a dial indicator on the spring retainer. If you're using a check spring with too long off a PR it will push the spring open and show less PTV clearance. That cam with milled heads and LS7 lifters will probably need a shorter PR than 7.425".

For comparison, my cam is 230/232 110+1 on stock 853 heads and had .070" intake clearance and .090" exhaust clearance, so it is just tighter than the acceptable limit. I used 7.425" intake PRs and 7.400" exhaust PRs on stock LS1 lifters.

whtnuklz

iTrader: (8)

I just checked the cc's on the heads and it was just over 61cc. The guy who owned them before had to have had them milled, even though he said they were untouched.

whtnuklz

iTrader: (8)

when i measured for pushrod length at zero lash the checker was at 7.350. i went with a 7.425 which will give me .075 preload.

BaddBird

iTrader: (6)

Did you have a valve job done on your heads?

chrs1313

iTrader: (24)

you do not need preload to check ptvc...

if you are using the duals springs to check you need to use a solid lifter...just take apart an old one and put washers inside of it...then use your adjustable pushrod checker and clay...

or use checker springs and a regular lifter...

ptvc clearance should be alot greater than contact though...

put it this way my setup is 57.5cc with a .040 gasket and ms4 size cam on a 110+3 and I had -.020 clearance...flycut for .110 and now have .090...

whtnuklz

iTrader: (8)

yes I had a valve job done

whtnuklz

iTrader: (8)

I was not trying to preload my lifters to check ptv. my post about pushrod length was in response to another post about my pushrods being too long. tomorrow I'm taking a couple old lifters and making them solid to get an accurate check

redtail2426

iTrader: (10)

good idea,use a solid lifter,and a checker spring.I use a light checker spring and the feeler gauge method,seems to be the easiest for me.Clay method works fine too though

Squirts11

iTrader: (14)

I felt the clay method was much less precise to measure accurately, as I had .020" less clearance when I measured via dial indicator/magnetic base, checker spring, and solid lifter (to simulate full lifter pump up).

Exactly. I took lifter preload into consideration for my ptv measurements, as at high rpms the lifter can fully pump up w/ oil (thus the entire pushrod length, including the added length for preload - say .075", would need to be taken into account). More or less, worse case senario.

As said above, ensure you check the entire range of 20 degrees before TDC to 20 degrees after TDC.

technicalninja

iTrader: (1)

I would verify cam timing before cutting on the pistons.

Your vendor has already posted that you should have enough clearance.

Cam timing can seriously effect PTV clearance.

Dot-Dot is not good enough IMO.

Verifing intake centerline is what I would do next.

95% of the time everythings fine and you just wasted an hour of work.

That other 5% is where you end up finding troubles like yours....

whtnuklz

iTrader: (8)

I've never degreed a cam before so this process is new to me. I have an LS2 timing set will this work or do I have to buy an adjustable timing set if the grind on the cam is off?

Squirts11

iTrader: (14)

You'll have to have some form of adj timing set, otherwise you won't be able to make adjustments to the ICL if needed.

djfury05

iTrader: (30)

In any case be glad that you made the correct choice by not taking a vendor/sponsors opinion on what "should/shouldnt work." I learned the hard way. Instead of checking ptv like I should have I asked many sponsors and took their opinions and started my motor and didn't have enough clearance. This has led to me spending $3000 on getting the motor rebuilt and my heads fixed and labor to get it all back together as opposed to just a few hundred for checking ptv and flycutting. No matter what happens be proud that you made the right choice and you are saving yourself a lot more money this way even if it does mean more delay.

technicalninja

iTrader: (1)

If the grind is off I'd contact the vendor before buying new parts.
It is also possible for the timing set to be off.
If your intake centerline (ICL) is way off (+/-3 or more) from where it's supposed to be I'd do more investigating before purchasing an adjustable timing set to compensate. You might stick your old timing set on it to verify the new and old set are close to the same readings (the old set should show mild retardation due to wear/chain stretch).

The LS2 set should work fine. I am a big believer in an adjustable set but for the purpose of giving me more "options" regarding cam timing and not to solve a PTV clearance issue.

Always find out the "why". Never throw parts at a problem. Never modify before having a complete understanding of why the modifications are needed (sometimes modification is the only way but verify first). Never completely trust anything you read on the internet. You are the builder of your engine and compatability of the assembled parts is solely dependant on you!

Trust your vendor more than anyone else but still verify! They cannot do the "verification" due to distance. Everyone has the occasional screw up. They may be trusting yet another company if they didn't grind the cam themselves. Your application might be just enough different to be "the exception to normal" regarding the cam selected.

The most valuable tool you own is your brain. Educate it if needed! My education never stops. I learn new stuff all the time. It's been 30+ years since my first motor overhaul (getting OLD ). I may have been wrenching longer than you have been alive. NEVER stop learning.....

You will need a degree wheel, a piston stop, and a dial indicator that can measure total valve lift at the retainer.

A crank snout adaptor makes this easier but is not a requirement.

The March 2011 issue of Car Craft magazine has a pretty good write up of how this is done on a LSx engine. They are checking for total lift on the side of the lifter body but the same point can be found at the spring retainer on an assembled motor.

This article has a excellent description of how to truly verify you've found TDC and how to use this same method to verify you've found max lift (intake centerline) on the cam.

This check (intake centerline only!) can be done with hydraulic lifters on an assembled engine.

Verifing cam profile at .006 / .050 and accurately checking PTV clearance requires a "solid" lifter with "lash" set to exactly 0. no preload and no extra clearance.

In your case (due to the strange PTV clearance and the fact that your already "heads off") I'd go the solid lifter route first. Verify intake centerline then check it at .006/.050 (your cam card will have timing #s at one or the other). I also verify the range at .050; this is the total number of degrees between .050 off seat to .050 before close. This spec should be dead on to what the cam card says. What you are doing is verifing the cam to it's published numbers (mapping it). If it's different than the card shows contact your vendor before doing anything else.

What bothers me the most regarding your posts is the fact that your vendor said "enough clearance" (guessing at least .100) and your head CCs say it's been cut .020-.025 so even with the cut head you should see .075 and not "contact" as you have.
You are using an old head gaket when doing the clay method, correct?
Are the valves the stock size?
Having a valve job done usually drops the valve further into the seat and increases PTV (a tiny little bit).
It is possible to screw this up as well if larger valves were installed and the valve seat wasn't cut properly (deep enough) for the larger valves.

Something is "off" on your set up (per your vendors comments) and I would figure this out before modifing the pistons. You still may need to modify the pistons but I'd figure out the "why" before doing it.

I've always "degreed" the cam before checking for PTV clearance.

In 20 years of degreeing cams I've found 2 new cams from reputable companies that were "wrong". One had an incorrect base circle, the other was a mis-labeled grind. Like I said before 95% of the time the cam is correct and checking is a waste of your time. As long as you already have the tools it costs nothing and if you don't have the tools you will need them later as long as you intended to continue to do this type of work.

Having the ability and tools to properly degree a cam is every bit as important as checking the PTV clearance IMO. Maybe more so. You can "make changes" in performance with cam timing adjustments.

Hope this helps...

Intercooler2

iTrader: (24)

Tools are on the way. Just notch it can't hurt at all. It's out where you can get to it real easy.

whtnuklz

iTrader: (8)

Looks like I'll be cutting them pretty soon.

chrs1313

iTrader: (24)

cut, mill, run a .040...only way to go...