Re: Piston/Valve clearance, how tight have you run?
[Re: quickd100]
#1710088
12/13/14 02:30 PM
12/13/14 02:30 PM
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Joined: Feb 2011
Posts: 4,302
Nebraska
72Swinger
master
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master
Joined: Feb 2011
Posts: 4,302
Nebraska
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My 6.1 is sitting at .069 on the intakes. I'm gonna run it.
Mopar to the bone!!!
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Re: Piston/Valve clearance, how tight have you run?
[Re: quickd100]
#1710091
12/13/14 03:41 PM
12/13/14 03:41 PM
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Joined: Feb 2011
Posts: 4,302
Nebraska
72Swinger
master
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master
Joined: Feb 2011
Posts: 4,302
Nebraska
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That is tight tight ^^^^^^. Don't want to kill the quench, so I guess its cut the pistons time or roll the dice.
Mopar to the bone!!!
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Re: Piston/Valve clearance, how tight have you run?
[Re: quickd100]
#1710092
12/13/14 03:41 PM
12/13/14 03:41 PM
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Joined: Jan 2003
Posts: 9,985
Frostbitefalls MN (Rocky&Bullw...
gregsdart
master
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master
Joined: Jan 2003
Posts: 9,985
Frostbitefalls MN (Rocky&Bullw...
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Dave, I think that is too tight. For sure on the exhaust, as any failure of the valve to follow the cam and ya got trouble. With only 0.040 piston to head, when a lot of that is eaten up at speed you are down to about .020 or .030 from crashing the exhaust valves. Any inconsistency in valve depth in the heads will add to the problem, along with any other items that are a bit off.
Last edited by gregsdart; 12/13/14 03:46 PM.
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Re: Piston/Valve clearance, how tight have you run?
[Re: quickd100]
#1710094
12/13/14 04:01 PM
12/13/14 04:01 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
I've got one on the stand right now that REAL tight. Trying to decide if I should try it or not. Intake is at .045 and exhaust is at .060 WITH lash. Quench is at .040. Motor is a 426 wedge with the low compression Max-Wedge pistons, compression works out to 13.72-1.    Dave
Throw a little thicker gasket on it.. yeah we all try
for .040 quench but a bit more isnt gonna kill you
but a crash of a valve sure will... I ran a SB with
.045/.055... it cleared but the valves were right
there on the pistons.. I actually had to clearance
3 pistons on the first tear down where I could see
a slight touching... I didnt even bother with a re-balance..
that was with tight piston to bore pistons... rocking
the piston will tell you more
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Re: Piston/Valve clearance, how tight have you run?
[Re: gregsdart]
#1710096
12/13/14 10:39 PM
12/13/14 10:39 PM
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Joined: Jan 2003
Posts: 16,923
NC
440Jim
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,923
NC
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Quote:
Dave, I think that is too tight. For sure on the exhaust, as any failure of the valve to follow the cam and ya got trouble. With only 0.040 piston to head, when a lot of that is eaten up at speed you are down to about .020 or .030 from crashing the exhaust valves. Any inconsistency in valve depth in the heads will add to the problem, along with any other items that are a bit off.
I agree. For a super stocker or some class rules that might be fine. But if you don't check and replace valve springs, etc. very often you could hurt something real bad. Over rev it by accident (water box, missed shift, tire spin, etc.) same damage. Not worth it for most of us, IMO.
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Re: Piston/Valve clearance, how tight have you run?
[Re: quickd100]
#1710097
12/13/14 11:09 PM
12/13/14 11:09 PM
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Joined: Nov 2003
Posts: 1,362
Out of the State of Confusion
blue_stocker
pro stock
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pro stock
Joined: Nov 2003
Posts: 1,362
Out of the State of Confusion
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Having run S/SS for several years I know and have formed my own 'dimples' when the P/V clearances were TOO close (.040"). In stock, we take lots of chances because we're stuck with non-reliefed/flat top pistons and quite often, run-what-you-brung situations with our engine parameters, which can end up with disastrous results (getting the aforementioned 'dimples'/ forging our own reliefs or worse, ouch). Nonetheless, a good rule-of-thumb is .080" piston to valve at the closest point. Some say .080" intake, .100" exhaust, so if you have the option to modify/machine the tops for bigger/deeper pockets, do it! I've also talked to a few engine shops that state absolute minimum piston to head clearance should be .050" in a steel rod engine. I've run as close as .037" with a wobbly .008" skirt clearance to boot without crashing. So...what is the 'correct' clearance? Whatever you can get away with without catastrophic engine damage/failure. Just be aware that the results could be less than positive should you have inaccurate measuring techniques or your choice of clearances be inadequate!
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Re: Piston/Valve clearance, how tight have you run?
[Re: blue_stocker]
#1710098
12/13/14 11:18 PM
12/13/14 11:18 PM
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Joined: Mar 2006
Posts: 9,824
MI, usa
dvw
master
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master
Joined: Mar 2006
Posts: 9,824
MI, usa
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Quote:
Having run S/SS for several years I know and have formed my own 'dimples' when the P/V clearances were TOO close (.040"). In stock, we take lots of chances because we're stuck with non-reliefed/flat top pistons and quite often, run-what-you-brung situations with our engine parameters, which can end up with disastrous results (getting the aforementioned 'dimples'/ forging our own reliefs or worse, ouch). Nonetheless, a good rule-of-thumb is .080" piston to valve at the closest point. Some say .080" intake, .100" exhaust, so if you have the option to modify/machine the tops for bigger/deeper pockets, do it! I've also talked to a few engine shops that state absolute minimum piston to head clearance should be .050" in a steel rod engine. I've run as close as .037" with a wobbly .008" skirt clearance to boot without crashing. So...what is the 'correct' clearance? Whatever you can get away with without catastrophic engine damage/failure. Just be aware that the results could be less than positive should you have inaccurate measuring techniques or your choice of clearances be inadequate!
True enough. Why would ANYONE try this on a non class style motor? They must have money and time on there hands. Nothin more fun then dropping a valve, well maybe kickin a rod.
Doug
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Re: Piston/Valve clearance, how tight have you run?
[Re: dvw]
#1710099
12/13/14 11:32 PM
12/13/14 11:32 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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It is easy to forget this rule: Retard the cam get more room on the intake valve --EASY -- sometimes it is just a case of having cam advanced a little too far -- This can pull you out of a jam and sometimes. ---you find that engine runs better than you imagined with cam in a different position Fun to note-- that on a dyno --if you take your time and move a cam around a little you discover things that do not fit conventional wisdom ( which is Highly Over rated) Many cams we know and love like the 590 solid and the world famous .650 lift Comp solid , a cam that is a Herb McCandless original--It loves being in a 440 at 100- 101 range and a 500 at about 104--then it will rock but straight up you would have to turn big RPM to get the juice out of it-- 
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Re: Piston/Valve clearance, how tight have you run?
[Re: quickd100]
#1710101
12/15/14 12:47 AM
12/15/14 12:47 AM
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Joined: Sep 2014
Posts: 4,457
Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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Intake valve clearance does not need to be any more than what your piston to head clearance is. If you can run p/h that is all the intake needs. It is "impossible" for them to hit, unless you have a valve float issue, or some other such problem.
For the exhaust, it is p/h clearance plus .040. Any more than that and you are wasting compression.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Piston/Valve clearance, how tight have you run?
[Re: dizuster]
#1710105
12/15/14 04:49 PM
12/15/14 04:49 PM
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Joined: Sep 2014
Posts: 4,457
Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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That's why I don't uses chains. Period.
If your valvetrain is correct, p/h clearance is enogh for intake p/v clearance. If it's not, use the MoPar standard .100 intake and .120 exhaust.
I've seen junk with more clearance than that hit. So it's a matter of right is right.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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I thought that I was the only one that did stuff like that!!!! BOTH intake & exhaust on my Gen 3 Hemi were .067"-.070" It's ran fine with No issues @ 8000 RPM. 
Also I am thinking that the valve may bend when stamping.