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Old 06-27-2005, 03:31   #1 (permalink)
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Piston Valve Clearance

I'm running flat tops and I'm 99.9% sure I only have exhaust valve reliefs in the piston tops.

"Roughly" speaking if I ran upto a 600 thou intake valve lift (~240* dur'n) will this potentially come close to the 100 thou piston clearnace limit? Block's been decked (I'll have to check how much when heads come off.....I think it's slightly below zero), and heads will be new unskimmed.

I'm aware of the variables and the only way to know 100% is to check the final assembly with a dial gauge. Just gathering rough info from peoples' experience.

Cheers
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Old 06-27-2005, 03:36   #2 (permalink)
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Re: Piston Valve Clearance

I've run a cam with .680 and had no probs using flat tops that were .010 down the bore.
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Old 06-27-2005, 04:00   #3 (permalink)
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Re: Piston Valve Clearance

When i checked my clearance, the intake valve was heaps closer to the piston than the exhaust valve, and i had 2 valve reliefs.
If it is some new alloy heads you have in mind, i found mine had more clearance from the closed valve to the deck of head, than the steel heads i used to run. From just swapping to alloy heads, i picked up heaps more piston to valve clearance, running a lot bigger cam.
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Old 06-27-2005, 06:28   #4 (permalink)
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Re: Piston Valve Clearance

Quote:
Originally Posted by TruBlu351
I'm running flat tops and I'm 99.9% sure I only have exhaust valve reliefs in the piston tops.

"Roughly" speaking if I ran upto a 600 thou intake valve lift (~240* dur'n) will this potentially come close to the 100 thou piston clearnace limit? Block's been decked (I'll have to check how much when heads come off.....I think it's slightly below zero), and heads will be new unskimmed.

I'm aware of the variables and the only way to know 100% is to check the final assembly with a dial gauge. Just gathering rough info from peoples' experience.

Cheers
I have never seen exhaust valve reliefs in aclevo piston .Whether you have one relief or two they are put in for the intake valve. 600 lift should not cause any dramas with the stock valve reliefs.What pistons are you running?
I ran a solid of .623 lift and 260 @ 50 with no problems and standard reliefs in a l2379 trw forgie.
I would be more concerned with the exhaust valve clearance on any engine that i built . The intake valve is usually quite safe but rather the exhaust valve is the one that cops a hiding. As the exhaust valve is closing the piston is chasing it up the bore . If the engine experiences uncontrolled valve toss during an over rev situation then there is the possibility of Ex valve contact .
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Old 06-27-2005, 08:07   #5 (permalink)
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Re: Piston Valve Clearance

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Originally Posted by russxr67
I have never seen exhaust valve reliefs in a clevo piston.


...long duration + high lift = exhaust valve relief.

(Residue marks are from clay testing P-V.)

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Old 06-27-2005, 19:16   #6 (permalink)
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Re: Piston Valve Clearance

I've got some short deck hypereutectics on 6" rods. In retrospect I know I should have gone forged, but we'll just test these and hope for the best. No valve bouncing authorised! At least the rev limiter is in place already.

The plan is for new alloies, allhoys, alloys - you know what I mean! So they will have some decent clearance being new heads. They obviously have the potential to make good HP, but I think I'll limit their potential to 500fwhp (~.600ish cam) considering these pistons. The rest of my bottom end is fine.
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Old 06-28-2005, 05:56   #7 (permalink)
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Re: Piston Valve Clearance

davis : Congratulations, that must be your shortest post ever (besides the pic)

trublu351
I am running single valve relief pistons on 6" rods with zero deck height and cam is 248 @ 50 with 605 lift and AFD 2v's

No hole in the piston yet!
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Old 06-29-2005, 00:40   #8 (permalink)
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Re: Piston Valve Clearance

Thanks guys. Yeah, looks like I'll be good to go then. Cheers.
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Old 06-29-2005, 01:21   #9 (permalink)
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Re: Piston Valve Clearance

Quote:
Originally Posted by TruBlu351
Thanks guys. Yeah, looks like I'll be good to go then. Cheers.

If you have problems with clearance, set the roller rockers to 50 thou lash
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Old 06-29-2005, 18:19   #10 (permalink)
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Re: Piston Valve Clearance

Im sure my mechanics told me before but what is the minimum piston to valve clearance you should have??? Cause im running the clevo 3v heads my pistons are relieved for valve clearance we checked the clearance with the plastasine when we did the first rebuild i got to excited when i saw that the valves only just touched the plastasine and ripped it off before my mechanic got to measure the clearance amount. serfice to say he doesnt what me near the motor this rebuild
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