Valve to piston clearence?

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Dec 16, 2003 | 10:21 AM

ImBatman

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Joined: Oct 2000

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From: Lake Wylie, South Carolina

Valve to piston clearence?

I am going to double check this anyway but wanted to get an idea of a possible problem with the clearence. Here are the piston, head and cam specs. Again the block is a +.030 454.

Cam
Intake Exhaust
Valve Adjustment 0.016 0.016
Gross Valve Lift 0.568 0.578
Duration At 0.015 Tappet Lift 274 280
Valve Timing At 0.015
Open Close
Intake 31 63
Exhaust 74 26
These Specs Are For The Cam Installed At 106 Intake CL
Intake Exhaust
Duration At 0.05 236 242
Lobe Lift 0.334 0.34
Lobe Separation 110
Piston
Teflon coated hypereutectic race pistons.
Piston specs: Compression@.030" bore
10.91:1 w/100.9cc heads
10.09:1 w/109.4cc heads
9.32:1 w/119cc heads
.210" dome, 2 valve relief
For stock stroke crank
1.640" compr. distance
Deck clearance .025
Skirt clearance .0015
Heads
Series Performer RPM Oval Port
Int. port vol. 290cc
Exh. port vol. 110cc
Chamb. vol. 110cc
Deck thickness 9/16 in.
Int. valve size 2.19 in.
Exh. valve size 1.88 in.
Valve spring dia. 1.55 in.
Rocker stud dia. 7/16 in.
Pushrod dia. 3/8 in.
Maximum Valve Lift .700 in.

Dec 16, 2003 | 10:50 AM

GDaina

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From: In Dreams There Is Truth Ohio

Re: Valve to piston clearence? (BlackRat)

minimum valve to piston clearance should be .1"

Dec 16, 2003 | 10:54 AM

ImBatman

Thread Starter

Safety Car

Joined: Oct 2000

Posts: 4,282

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From: Lake Wylie, South Carolina

Re: Valve to piston clearence? (GDaina)

Is there anyway to roughly estimate that with the above info? Again I will be physically checking it I just wanted to see if this combo may give clearence issues.

Thanks
Wade

Dec 16, 2003 | 11:11 AM

norvalwilhelm

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From: Waterloo ontario Canada

Re: Valve to piston clearence? (BlackRat)

You can't guessimate clearance by looking at the specs. Most of the time there is enough but it must be checked.
I prefer to mock up the engine and put checker springs in the cylinder being check, set valve clearance then add an extra .100 feeler gage under the rocker arm then slowly turn the engine over continually stopping, pushing down gentley on the valve feeling for the pisoton. If the motor turns over with the extra .100 on the valve stem you will not have a problem .
This check in only when the piston is plus or minus 10 degrees on either side of tdc.
I do not like the platercine under the valve. You could miss something.

Dec 16, 2003 | 11:21 AM

69 N.O.X. RATT

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From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192

Re: Valve to piston clearence? (norvalwilhelm)

I like to put a small flat piece of clay on the top of the piston (1/4 to 3/8 in. thick). Put your haed gasket on and bolt the head down on that cylinder, crank the motor over a few times and pull it apart, then you have an actual measuremet for P/V clearance. I like at least .100 for intake and .130 for exhaust (stell rods). With the small cam you are using and the rest of the parts you have I will bet you will have closer to .25 P/V clearance, but check to be sure.

Dec 16, 2003 | 08:41 PM

blunsford

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From: Indianapolis IN

Re: Valve to piston clearence? (69 N.O.X. RATT)

I thought it was .080 for intake and .1 for exhaust with steel rods. BTW you need to use modeling clay, not play dough. Coat the top of the piston with a light coating of oil so it comes off cleanly them mic the part the valve hit.
I think the figures 69 NOX quoted may be for aluminum rods????

Dec 16, 2003 | 10:09 PM

JRD77VET

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Joined: Apr 2002

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From: Zionsville, PA NRA Life Member

St. Jude '03-'04-'05-'06-'07-'08-'09-'10

Re: Valve to piston clearence? (blunsford)

Quote:

I think the figures 69 NOX quoted may be for aluminum rods????

69 NOX specified steel ( stell) rods in his reply. I agree with his numbers . :yesnod:

Those were the numbers I used when I built motors.

:seeya Jeff

Dec 16, 2003 | 11:22 PM

blunsford

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From: Indianapolis IN

Re: Valve to piston clearence? (BlackRat)

It apparently depends on the source. After all the varying opinions I looked it up in two sources.

Howards Cams Install guide says .080 intake and .1 exhaust.
How to Hotrod big blocks says .1 intake and .125 exhaust.

That's for steel rods of course. Howards says to add .030 to those clearances when aluminum rods are used.

Personally, I'm comfortable with the .080 and .1 since I won't be doing over 6K revs. I suppose if I was going to rev to 8K or above I'd be more likely to use the .1 and .125 numbers.