[L98]: How much lift before piston modification?
Thread Starter
Team Owner
Joined: Mar 2000
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From: Boston, MA
[L98]: How much lift before piston modification?
Theorize a stock L98 with only a new camshaft. How much total lift is possible before you have to start modifying the pistons for clearance?
Thanks. :)
Thanks. :)
Melting Slicks
Joined: Apr 2000
Posts: 2,793
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From: Elizabeth City, NC
Re: [L98]: How much lift before piston modification? (scorp508)
Not sure exactly but it is well over .560 The stock valves are nice and small, they would probably permit somewhere in the range of .570-.590 cam even with the extra 20-30thousandths clearance.
Melting Slicks
Joined: Apr 2000
Posts: 2,793
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From: Elizabeth City, NC
Re: [L98]: How much lift before piston modification? (scorp508)
Still good, you should know that Scorp. How many guys are running that 219 cam. It's not going to hit. Quit stressing.....
Melting Slicks
Joined: Mar 1999
Posts: 2,535
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From: Rochester NY
Re: (LPDesRoche)
Your 219 with .560 lift. You are fine there. I am running the 219 cam on my LT1 with 1.6rr. No problem here. I ordered a custom grind blower cam for my 383ci LT1 its Xtreme Energy 214/224 @.05 .569/.606 LSA 114 with 1.6rr. I hope its will clear my JE-28cc heavy duty blower pistons.
Bruce
93LT1 Conv w/ZF6
top end mods
jetted 150hp NX
Blown 383ci is coming very soon Spring 2002
Bruce
93LT1 Conv w/ZF6
top end mods
jetted 150hp NX
Blown 383ci is coming very soon Spring 2002
Le Mans Master
Joined: Mar 1999
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From: delmont pa
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Re: [L98]: How much lift before piston modification? (scorp508)
the valves are closest to the pistons at 10 degrees before top dead center for the piston. put the piston at 10 degrees before top dead center and with a light valve spring move the valve up and down and check the travel with a dial indicator. if you do not have a indicator just use feeler gage to check the distance between the valve stem tip and the rocker tip. this will work for all but the most radical cams.
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Re: [L98]: How much lift before piston modification? (scorp508)
Brian, you may need professional engine help soon.
One small mistake could cost you alot of money.
Example: I've been doing this stuff for over 35 years and I still went to Cartek. Best move I could of made. You can't know it all.
One small mistake could cost you alot of money.
Example: I've been doing this stuff for over 35 years and I still went to Cartek. Best move I could of made. You can't know it all.
Melting Slicks
Joined: Apr 2000
Posts: 2,793
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From: Elizabeth City, NC
Re: [L98]: How much lift before piston modification? (mackeyred96)
The easy way to check it is to remove a spring place the head on the engine with according piston at TDC. Measure the distance from the valve seal to the tip of the valve. Then drop the valve into the cylinder until it touches the piston, measure the new distance from valve tip to seal. Subtract, then subtract another 30 thous. (general accepted overkill clearance). You will have what you are looking for. If you do it without a head gasket, you have even more room to spare.
Burning Brakes
Joined: Nov 2001
Posts: 1,189
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From: Austin TX
Re: [L98]: How much lift before piston modification? (scorp508)
There's more to it than just the amount of lift. The amount of duration
can affect valve to piston clearance, as well as where you install the cam
(in terms of advance/retard). Different cam lobes have different rates of
acceleration on opening the valves which can cause the valve to get closer
to the piston, all else being equal. On the intake stroke the intake valve
is "chasing" the piston (intake valve is opening while the piston is moving
down the cylinder). On the exhaust stroke the piston is chasing the valve
as it closes. There's alot going on there.
There's more to it than just gross lift.
You also have spring coil bind to deal with. This could become a problem
before you start having piston interference.
You have to check clearances with whatever combination you are going to
run.
Dan
can affect valve to piston clearance, as well as where you install the cam
(in terms of advance/retard). Different cam lobes have different rates of
acceleration on opening the valves which can cause the valve to get closer
to the piston, all else being equal. On the intake stroke the intake valve
is "chasing" the piston (intake valve is opening while the piston is moving
down the cylinder). On the exhaust stroke the piston is chasing the valve
as it closes. There's alot going on there.
There's more to it than just gross lift.
You also have spring coil bind to deal with. This could become a problem
before you start having piston interference.
You have to check clearances with whatever combination you are going to
run.
Dan
Melting Slicks
Joined: Apr 2000
Posts: 2,793
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From: Elizabeth City, NC
Re: [L98]: How much lift before piston modification? (danno85)
But thats not what he asked, or what I described. Like I said it was just a simple way of checking. The next best way is to clay the piston top and give the motor a full rotation with all parts in place and measure the clay. But with the lack of duration on the 219 cam, the method I described will get you exactly where you want to be. No need to break out the calipers and feeler gauges and other machinist tools when someone else already did.
Burning Brakes
Joined: Nov 2001
Posts: 1,189
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From: Austin TX
Re: [L98]: How much lift before piston modification? (LPDesRoche)
But thats not what he asked, or what I described.
I should have quoted it.
Scorp didn't mention any specific cam, so I was responding in more
general terms.
Using your method, if you have clearance at max lift with the piston at
TDC then yes, you're fine. However, if the valve hits with the piston at
TDC then that certainly doesn't mean you wouldn't have adequate clearance
with the engine running, because the valve does not come the closest
while the piston is at TDC. Therefore, if you don't have enough clearance
using your simple method you can't draw a conclusion either way.
Scorp simply asked "what's the max lift a L98 will handle", and my point
is that there is not a simple answer to that question.
If the question were "will xyz cam work", that's different.
Dan
Burning Brakes
Joined: Nov 2001
Posts: 1,189
Likes: 2
From: Austin TX
Re: [L98]: How much lift before piston modification? (88-406)
On a stock L98 coil bind will be an issue long before piston to valve clearance. To check it, I put my dial indicator on a push rod only, along with the checking springs on the valves then rotate the engine till max lobe lift is observed "Worst Case" then I'll move the dial indicator to the valve tip and measure travel till it strikes the piston with me pushing the valve by hand.
KM
KM
at maximum valve lift. On the intake valve it occurs at some point while the
valve is opening (and the piston is "on it's way down" the cylinder), and
on the exhaust valve it occurs while the valve is closing. This is why a change
in duration, lobe ramp (opening/closing the valve "faster"), and cam
timing (advance/retard, change to LSA) can all affect valve to piston clearance
even though the lift may be the same.
The easiest way to accurately check valve to piston clearance is to use clay
on the piston, which is what I'm doing here:
http://home.austin.rr.com/dancurrie/mm6.jpg
If the heads are already on and you want to check it then you can adjust
the valve to spec and then insert a stack of feeler gauges between the rocker
and valve equal to the min. amount of clearance you want, and slowly turn the
engine over by hand to check for binding. You have to be careful doing
this on hydraulic lifters though because the plunger in the lifter will bottom,
which won't give you full valve lift. This test method is best done using a solid
lifter even on a hydralic camshaft.
Dan :)
Safety Car
Joined: Apr 2001
Posts: 3,525
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From: Houston TX
Re: [L98]: How much lift before piston modification? (scorp508)
Scorp,
As stated several times below, the best way to determine if an unknown cam will work would be to mock the combination with clay and a solid roller lifter on the hydraulic roller cam. This requires purchase of some additional parts. With that being said, I ran a similar combo to what you are describing above; LPE219, 1.6 ProMags, 91D-Ports angle milled to 51cc, on factory '87 pistons. I ran this combo in several positions (straight up, 4° adv, 2° adv) and checked each time with no issues on clearance.
My advice, check everything, but the same combo has worked for me and others.
BTW, I thought you were going with aftermarket SRP pistons, or a 383 combo. Is this not the push any longer?
Best of Luck,
Aaron
As stated several times below, the best way to determine if an unknown cam will work would be to mock the combination with clay and a solid roller lifter on the hydraulic roller cam. This requires purchase of some additional parts. With that being said, I ran a similar combo to what you are describing above; LPE219, 1.6 ProMags, 91D-Ports angle milled to 51cc, on factory '87 pistons. I ran this combo in several positions (straight up, 4° adv, 2° adv) and checked each time with no issues on clearance.
My advice, check everything, but the same combo has worked for me and others.
BTW, I thought you were going with aftermarket SRP pistons, or a 383 combo. Is this not the push any longer?
Best of Luck,
Aaron
Pro
Joined: Dec 2001
Posts: 715
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From: NYC NY
Re: [L98]: How much lift before piston modification? (scorp508)
Scorp, if you find out what you believe to be an accurate maximum lift and duration on your setup I like to hear it. That is if you find it somewhere other than in this thread.
P.S. thanks for emailing me back about my registration problems.
Jeff
P.S. thanks for emailing me back about my registration problems.
Jeff
