Posted By: Wedgeman
Minimum quench ? - 12/29/12 11:05 PM
What would be the minimum clearance between piston and head ? is .019 too little using H beam scat rods ?
Dan
Dan
Minimum quench ?
Posted By: CSK
Re: Minimum quench ? - 12/29/12 11:14 PM
need .040
Posted By: emarine01
Re: Minimum quench ? - 12/30/12 12:31 AM
Quote:Thats about .010 too close
What would be the minimum clearance between piston and head ? is .019 too little using H beam scat rods ?
Dan
Posted By: skrews
Re: Minimum quench ? - 12/30/12 12:59 AM
.040
Posted By: Cab_Burge
Re: Minimum quench ? - 12/30/12 01:17 AM
Quote:Probally to close
What would be the minimum clearance between piston and head ? is .019 too little using H beam scat rods ?
Dan
What psiton type and materials are yours and how much piston to cylinder wall do you have now? My pump gas 518 C.I. stroker with .0065 piston to cylinder wall clearance was rocking over enough to make it look like it was hitting the edge of the pistons on the combustion chamber edges when warmed up (190F) and revved up above 7000 RPM with .035 cold checking clearances( make sure and rock the piston all the way to the outside of the block and the same on the inside(cam side) 
I increased the head gasket thickness .008 to get .043 minimum 
I was trying to follow the recommendations of using .035 with steel rods and forged pistons That worked fine on the iron, open chamber 906 heads, not so good when I swapped the heads to a set of close chamber Eddy RPM aluminum heads 
Posted By: d-150
Re: Minimum quench ? - 12/30/12 01:18 AM
just use head gasket to make up difference .036 minimum but .040 optimum
Posted By: JohnRR
Re: Minimum quench ? - 12/30/12 01:55 AM
way too close , you want to get as close to .040 as possible
Posted By: 5spdcuda
Re: Minimum quench ? - 12/30/12 02:41 AM
I've run .038 on a 4.030 bore with .0025 piston to wall and stock rods with no problems. At .035 I would get nervous.
Posted By: BSB67
Re: Minimum quench ? - 12/30/12 03:37 AM
Quote:
need .040
Really.
Posted By: emarine01
Re: Minimum quench ? - 12/30/12 03:38 AM
We ran .032 on 4.030 bore cast piston stock rod with .004 skirt cl to 7k and never hit with W2 econos open chamber, some have posted .028 on a tight small block, The quench effect will fall off rapidly after .040.
Posted By: quickd100
Re: Minimum quench ? - 12/30/12 03:39 AM
I set up a 440 with KB hyerutectic's at .035. Mild hydralic cam, steel rods, never see's 6000rpm. Works great but was a pain in the butt setting the quench distance that close.Dave
Posted By: MR_P_BODY
Re: Minimum quench ? - 12/30/12 03:47 AM
Quote:
I've run .038 on a 4.030 bore with .0025 piston to wall and stock rods with no problems. At .035 I would get nervous.
I ran .032 on a 4.070 bore and it just touched at 8000 rpm
in one spot... I hit it with a die grinder on the heads
and it was fine
Posted By: Wedgeman
Re: Minimum quench ? - 12/30/12 03:57 AM
Ok
Thanks for all the responses !
Dan
Thanks for all the responses !
Dan
Posted By: emarine01
Re: Minimum quench ? - 12/30/12 04:06 AM
Most of the time a piston strikes the head its from the piston rocking
in the bore, I know this will not sit right with some but if the piston just kisses the head it will just rock back
This is not the best thing but I have seen a fellas 383 sbc @ .028 turn 8500 for years with the pistons hitting the head... it just leaves little marks 
in the bore, I know this will not sit right with some but if the piston just kisses the head it will just rock back
This is not the best thing but I have seen a fellas 383 sbc @ .028 turn 8500 for years with the pistons hitting the head... it just leaves little marks
Posted By: Adobedude
Re: Minimum quench ? - 12/30/12 04:40 AM
.040 to be safe. As per previous post...Piston rock.
Posted By: RemCharger
Re: Minimum quench ? - 12/30/12 10:38 AM
When you can read the piston # on the head its just right.
Posted By: moper
Re: Minimum quench ? - 12/31/12 04:44 PM
Quote:
When you can read the piston # on the head its just right.
That's what I always heard for race engines too...
On my street/strip stuff I run .030-.040 depending on the compression hieght and bore size. Tighter is better and with good equipment and operator it's as easy as having the machining operations done.
Posted By: polyspheric
Re: Minimum quench ? - 12/31/12 05:36 PM
Guess where the .001" safety clearance you should have had went to?
It's deducted from your top ring land height, if you're lucky.
It's deducted from your top ring land height, if you're lucky.
Posted By: dodgeboy11
Re: Minimum quench ? - 01/01/13 12:06 AM
Depends on the piston type, cylinder clearance, intended rpm and rod type and quality. I'm running .035" on a small block with KB hypereutectic pistons and about .0025" clearance on the skirts. Runs great. I wouldn't be afraid of .030" on that one either. But you start opening up the bore and using forged pistons, you'll want more clearance because of piston rock and growth. I suggest shooting for zero deck and running the quench at whatever your gasket thickness is. On a Fel-Pro it'll typically be .039".
Posted By: Leon441
Re: Minimum quench ? - 01/01/13 05:35 PM
Quote:
When you can read the piston # on the head its just right.
Yerp, I place marks on my pistons just for this. Run it close as I dare. Then pull the heads and see if I can go some more. Once I know I continue to run that. If I suddenly start seeing marks with the borescope I know there is something wrong.
What you can get away with depends on bore, piston to wall, rods, and what makes you nervous.
Posted By: b1dartsport
Re: Minimum quench ? - 01/01/13 06:47 PM
If you are making the quench real tight make sure you check all of the pistons,I use a deck bridge. I have seen some crank throws out of index as much as .003 which means clearance would not be the same for all 8 pistons. Just my
Posted By: moper
Re: Minimum quench ? - 01/02/13 02:34 PM
Quote:
If you are making the quench real tight make sure you check all of the pistons,I use a deck bridge. I have seen some crank throws out of index as much as .003 which means clearance would not be the same for all 8 pistons. Just my
I agree 100%. My block prep always includes a line hone and square decking with good equipment to properly set the deck height and the entire assembly should be mocked up to verify there aren't any "taller" holes due to rod length, stroke length, or stroke indexing issues. I've found total lengths off more than .003" before - especially with lower dollar or factory parts.