Vales hitting pistons w/X2 cam, HELP!?
#1
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Vales hitting pistons w/X2 cam, HELP!?
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
Thanks
#2
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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
Need more info on head specs and gaskets
#3
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Solve your problem and flycut your pistons.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
#5
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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.
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Originally Posted by 5ltrBetr
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.
+1
#7
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Originally Posted by 5ltrBetr
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.
But your dual crank sproket could have something to do (using wrong dot)
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Originally Posted by 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)
But your dual crank sproket could have something to do (using wrong dot)
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.
#9
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Originally Posted by Juiced
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.
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.
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.
Last edited by PREDATOR-Z; 05-09-2007 at 12:19 PM. Reason: clarifying
#10
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?
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?
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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.
#12
TECH Senior Member
Originally Posted by Alex @ CMS
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?
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?
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.
#15
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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.
#16
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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.
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.
#17
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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
#18
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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.
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.
#20
Originally Posted by ls1transam84
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.
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.