ls1transam84

iTrader: (1)

I have got a 98 LS1, stock: bottom end, lifters, rocker arms, heads (853 and 806 shaved .02), head gaskets. The new parts consist of: Comp push rods (7.4"), double roller chain, and LG Motorsports X2 cam. This is the second cam I have tried in the motor. The first was a Cam Motion ground cam specs were 226/232 575/588 112 LSA 108 center line. With both cams I have hit the pistons with the valves. I know the X2 will work four of my buddies have it in there LS1s with no problems. I have used up all of my ideas of why. I have used different heads, checked the chain, push rods, rocker ratio, different timing settings ect., you name it I have probably tried it. I am out of ideas if any one has any please help. I have got to get this motor together.
Thanks

PREDATOR-Z

Either heads are milled, or valves are bigger than stock, (or both), or you are running a thinner gasket than stock, or you're installing the cam wrong or the cam is not ground properly.

Need more info on head specs and gaskets

Patrick G

iTrader: (14)

Solve your problem and flycut your pistons.

allngn_c5

iTrader: (3)

There shouldn't be any reason to flycut the pistons using the g5x2 cam.

5ltrBetr

iTrader: (3)

Perhaps you are not lining the cam up correctly. The double rollers I have seen have timing marks to setup the cam straight up or 2-4 degrees advance/retard. Maybe you are setting it 180 degrees out? Just a thought. The timing mark on the crank sproket should be pointing straight up and the "0" mark on the cam sproket should be pointing straight down, in line with the timing mark on the crank sproket. Otherwise, I'd have a hard time seeing how those low lift numbers could be hitting the pistons. I am running .598/.595 using 241 heads cut .020 with not even close contact. I think you have something mechanically out of place.

allngn_c5

iTrader: (3)

+1

PREDATOR-Z

LIFT HAS NOTHING TO DO WITH PTV CLEARANCE AT THOSE DURATIONS

But your dual crank sproket could have something to do (using wrong dot)

Juiced

iTrader: (2)

Actually the tappet lift a 110/106 TDC has everything to do with PTV.

It you are installing it on a 108 LCA and are 4* advanced then you are decreasing the PTV by .12 assuming it's a xe-r lobe, depending on the size of your intake valve and how much they have been milled that could very well be your problem.

PREDATOR-Z

MAX LIFT occurs at BDC (Bottom, meaning cylinder is the furthest away from BTDC or ATDC where contact occurs)
LSA and ICL are a byproduct of VEs which have little to do with lift.
The common relation is as lift increase, some duration increases, but it is minute.

I wish poeple would get this straight.
PTVC is related to duration size and valve events, not to .050 cam lifts.
As mentioned above it is tappet lift that matters.

ALLBOTTLE

iTrader: (13)

Yes, max lift does occur at BDC, but the Lift at TDC is what is going to determine the amount that intake and exhaust valve is open.


1) If your head has .200 free drop (intake) and have pistons .010 out of the hole (common in the ls1) and a .040 gasket you have a total of .230 maximum clearance at TDC.

2) Take the .230 and subtract it .070 as a margin of safety and you have .160

3) Find out your Intake/exhaust center line angle (110 as an example) Find the Tappet lift for the lobe at 110... .076 (for a popular 236 comp XE-R lobe)

4) .076 tappet lift x 1.7 rocker ratio= .129 valve lift at TDC..... This lobe will clear.

5) take the same lobe at 106 centerline... tappet lift is .091
.091 tappet lift x 1.7 rocker ratio = .155.....

hmmmm.... by moving the ICL by 4 degrees you've reduced PTV by .026

no imagine if the cam is installed 4* advanced thats another .026 you've taken off your PTV.

please explain how tappet lift at TDC has nothing to do with PTV?

moeZ28

iTrader: (7)

Are you positive the heads have only been milled .020" ? When I got my used ported heads, they were milled .060", and they guy I got them from didnt know that they were milled. I had to measure them versus a stock head to see the difference. Also, if its not a stock shortblock and you put it together, did you get the right size pistons for your rod length, or the right rod length for your pistons or for your stroke? Any of that could affect PTV.

PREDATOR-Z

You are correct
But there is a difference in tappet lift and .050 cam lift

The initial post #5 refered to .050 lifts and not tappet lift (see highlight)

So in post #7 I said .050 lifts (size) are pretty much irrelevent in this matter.
This is where lots of poeple get confused.

Post # 8 brought tappet lift to the table
Perhaps I should have been more clear that I was reffering to .050 cam lift size and not tappet lift.

I edited my post so there is no confusion.

ALLBOTTLE

iTrader: (13)

Just here to help...lol

Maybe people will read both post and learn a bit.

XpEdItIoUs

iTrader: (44)

good one alex.

ls1transam84

iTrader: (1)

I talked to LG himself and he informed me that the stock litters have .1 preload. So when I was using the soft spring I wasn’t compressing the lifter enough and that is why it hit. He also said the same thing as Alex @ CMS said, if I had .18 to .2 at a valve drop I would be fine. The dots are where they should be, heads are milled .02 for sure, gaskets are right (.056). I am a little unsure still about the whole thing but it has to be ready by august for the TA Nats. When I put the Patriot springs back on and clayed the motor I came up with .16 ish on the intake and .2 ish on the exhaust, the lifters were collapsing. I measured a lifter with the spring out and fully collapsed and there was .2 diff from all the way up to fully collapsed. So if what he is saying is true I should end up with .06 or so intake and .1 exhaust. Dose this sound right? Thanks for all the advice; this thing has kicked me hard.

PREDATOR-Z

You never said anything about using lightweight springs.
To use lightweight springs you need to also use a modified hydro lifter with the plunger welded or the internals filled solid. Also use a p-rod adjustable checker set to 0 lash

Then rotate the motor (piston clayed of course, organic clay).
Then measure clay. That is your PTVC

Another way is to use a dial indicator, which is more accurate.

ls1transam84

iTrader: (1)

I used a lifter with the internal spring removed so it was initially collapsed and an adj p-rod. First I adjusted to no lash and was good. Next just for safety sake I put the pass side together with dual springs so on, rolled the motor over and hit. So to check again I measured the difference in plunger distance (stock to collapsed) and adjusted my p-rod so (.2, 7.4 to 7.6) HIT HARD. That is what has got me, is why did the valves hit to start, with the stuff in it and doesn’t now. Could the lifters been stuck? I have done everything up to now and have gotten no real constant result other than the valve drop and now the vpc I am getting (when I clayed it last). I know the parts I have are good and in right (they have been put together by 6 different people) but more time than not I have hit, but after a hit or two it quits and I get the .16 and .2 vpc. With the first cam I had from cam motion when I first put it in and rolled the motor it hit with the same stuff I have now, but it shouldn’t have and nether should this one. Is the info LG gave me true? thanks

PREDATOR-Z

You do not use a collapsed lifter, you want to mimic full pump (no preload), so either fill the insides so the plunger doesn't drop or weld it. I micro welded mine.
Then as I said 0 lash the meter and check again. This way your p-rod geometry is centered in the cups and rocker areas.

allngn_c5

iTrader: (3)

I am glad to be on this site. I just learned a ton from Predator, and Alex. Thanks fellas.

ALLBOTTLE

iTrader: (13)

Honestly is sounds like user error.

Take a step back and get the proper tools and start from the beginning.

You need a lifter @ zero lash to simulate lifter pump-up at pressure.
Set # at TDC, adjust your pushrods and turn the cam over by hand with the tester spring installed to see if you are hitting, repeat on the exhaust vlave.

Once you've done this then you'll know if you have to fly-cut to get the proper PTV.