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.035" Quench for steel-rod big block... #1282848 08/10/12 12:22 PM 08/10/12 12:22 PM
Joined: Jan 2003 Posts: 15,439 Val-haul-ass... eventually B BradH OP Taking time off to work on my car
BradH OP Taking time off to work on my car B Joined: Jan 2003 Posts: 15,439 Val-haul-ass... eventually	This is a 3.75"-stroke over-bored 440, steel rods, and forged pistons w/ .006" clearance. It's expected to turn 7000-7200 through the traps. I've traditionally run zero deck height + .040"-thick gaskets, but was wondering if there would be any benefit to tightening it up to .035" w/ a thinner MLS gasket. There's never been any indications of piston-to-head interference w/ .040".

Re: .035" Quench for steel-rod big block... [Re: BradH] #1282849 08/10/12 12:44 PM 08/10/12 12:44 PM
Joined: Oct 2007 Posts: 4,213 New York polyspheric master
polyspheric master Joined: Oct 2007 Posts: 4,213 New York	IIRC Jenkins said that if you don't need more knock suppression tighter clearance increases pumping loss. How much probably varies with the quench surface area and how the edges are prepared. Boffin Emeritus

Re: .035" Quench for steel-rod big block... [Re: BradH] #1282850 08/10/12 04:18 PM 08/10/12 04:18 PM
Joined: Jul 2010 Posts: 2,091 Delray beach, Florida P Performance Only top fuel
Performance Only top fuel P Joined: Jul 2010 Posts: 2,091 Delray beach, Florida	i don't personally feel there's enough benefit to reduce the quench to .035 vs. .040 thre's most certainly a downside though if the piston starts contacting the head. as the bore and piston wears over time, the piston skirt to wall clearance will increase and hence more piston rock. machine shop owner and engine builder

Re: .035" Quench for steel-rod big block... [Re: Performance Only] #1282851 08/10/12 06:40 PM 08/10/12 06:40 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	Dan has a really good point, so if you do it you had better be taking the heads off regularly to see if there are any witness marks. I really don't think you'll see more than a couple of hundredths which can get lost in the tuneup and track conditions. R.

Re: .035" Quench for steel-rod big block... [Re: dogdays] #1282852 08/10/12 06:49 PM 08/10/12 06:49 PM
Joined: Jan 2003 Posts: 6,591 Canton, Ohio S Sport440 master
Sport440 master S Joined: Jan 2003 Posts: 6,591 Canton, Ohio	Not worth the risks with just a .005 change.

Re: .035" Quench for steel-rod big block... [Re: BradH] #1282853 08/10/12 09:59 PM 08/10/12 09:59 PM
Joined: Jan 2012 Posts: 12 MN 7 73outlaw member
73outlaw member 7 Joined: Jan 2012 Posts: 12 MN	Just last week buddy of mine gernaded his 451,guess how??!! I pulled it down and it has .030-.035 piston to head clearance,not good now have a pile iron. Never made a pass down the track. WTF was the builder thinkin????? I would say less than 5hp is in .005 keep her north of .040

Re: .035" Quench for steel-rod big block... [Re: 73outlaw] #1282854 08/10/12 11:27 PM 08/10/12 11:27 PM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	If you try, suggest you check all 8 holes for clearance as slight variaton cylinder to cylinder could cause a big oops. I wouldn't try it.

Re: .035" Quench for steel-rod big block... [Re: ahy] #1282855 08/10/12 11:44 PM 08/10/12 11:44 PM
Joined: Jan 2008 Posts: 795 Glendale Az D Darryls-Demon super stock
Darryls-Demon super stock D Joined: Jan 2008 Posts: 795 Glendale Az	My .030 over 440 is at .035 before piston rock but the motor has only seen 6800 RPMs and it has Crower steel billet rods.

Re: .035" Quench for steel-rod big block... [Re: 73outlaw] #1282856 08/11/12 12:27 AM 08/11/12 12:27 AM
Joined: Dec 2004 Posts: 103 3 340roadrunner member
340roadrunner member 3 Joined: Dec 2004 Posts: 103	Quote: Just last week buddy of mine gernaded his 451,guess how??!! I pulled it down and it has .030-.035 piston to head clearance,not good now have a pile iron. Never made a pass down the track. WTF was the builder thinkin????? I would say less than 5hp is in .005 keep her north of .040 wow that really sucks for your buddy! Sounds like hes a dork though... can't he tear down his own engine? Next you'll tell me his cars pink or something.. I agree .035 quench is too little.

Re: .035" Quench for steel-rod big block... [Re: BradH] #1282857 08/11/12 01:25 PM 08/11/12 01:25 PM
Joined: Aug 2003 Posts: 43,335 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,335 Bend,OR USA	Brad, rock the pistons both ways and shoot for .039 piston to head for pump gas with .002+ rod bearing clearances I have never ran rod bearings tighter than .0025 and I have seen witness marks on my piston edges my pump gas street motor with .003+ rod bearing clearances and .039 piston to head clearances cold on the edges I switched to a set of .042 Cometics MLS Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: .035" Quench for steel-rod big block... [Re: BradH] #1282858 08/11/12 03:02 PM 08/11/12 03:02 PM
Joined: Jan 2003 Posts: 16,932 NC 440Jim I Live Here
440Jim I Live Here Joined: Jan 2003 Posts: 16,932 NC	There is not a lot of gain, and you would have to take lots of care and measurements to see if it would be successful, IMO. I run with 0.037"-0.038" piston to head and it was fine. You could see it keeping the quench area of the pistons cleaner than the part under the combustion chamber. My 2-cents for your application is have it in the range 0.037"-0.040"

Re: .035" Quench for steel-rod big block... [Re: 440Jim] #1282859 08/19/12 01:54 PM 08/19/12 01:54 PM
Joined: Jan 2003 Posts: 15,439 Val-haul-ass... eventually B BradH OP Taking time off to work on my car
BradH OP Taking time off to work on my car B Joined: Jan 2003 Posts: 15,439 Val-haul-ass... eventually	I'm going to stick w/ the tried-n-true .040" composition gasket on the 452 block since it's been zero decked. The pistons I ended up getting for the 451 "should" end up .005" down if the original decking was done accurately. In that case I'll have to decide on whether to have the block cut more, or run a .036" MLS on that engine to pull the quench down a bit.

Re: .035" Quench for steel-rod big block... [Re: BradH] #1282860 08/19/12 05:23 PM 08/19/12 05:23 PM
Joined: Jul 2010 Posts: 2,091 Delray beach, Florida P Performance Only top fuel
Performance Only top fuel P Joined: Jul 2010 Posts: 2,091 Delray beach, Florida	Quote: I'm going to stick w/ the tried-n-true .040" composition gasket on the 452 block since it's been zero decked. The pistons I ended up getting for the 451 "should" end up .005" down if the original decking was done accurately. In that case I'll have to decide on whether to have the block cut more, or run a .036" MLS on that engine to pull the quench down a bit. if the compression ratio and camshaft give the desired cylinder pressure, .045 quench is more than adequate. is .005 quench going to make a difference in how the combo runs? not likely IMO if everything else was spec'd out to work together. i can tell you we've done hundreds of big block street combo's using .045 just in case they need a future deck clean up and they all run just fine. most of thise combo's are edelbrock, SR or 440-1 headed combos. most use 93 octane but some can get away with 89 octane. it's all in the cylinder pressure. machine shop owner and engine builder

Re: .035" Quench for steel-rod big block... [Re: Performance Only] #1282861 08/19/12 05:34 PM 08/19/12 05:34 PM
Joined: Jan 2003 Posts: 5,486 SoCal Brian Hafliger master
Brian Hafliger master Joined: Jan 2003 Posts: 5,486 SoCal	I just did 2 identical small block stroker builds, first one had 10.2:1 and cam was 241@ .050 hyd and second was 10:1 with same cam. Everything else was the exact same from carb to pan...3HP difference and 7Tq. Yes the 10.2:1 engine made slightly more, but you'd never feel it. The first engine will operate at much higher elevationi than the second hence why the bump in compression. I agree, .040-.045 will be such a small amount of quench and compression...you'll only see it on the dyno chart. Brian Hafliger

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