Author Topic: Deck height VS quench  (Read 567 times)

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Fordman

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Deck height VS quench
« on: July 12, 2018, 09:15:17 AM »
For the ideal quench of .038-.043 how much does deck height play into this. I have a deck height of .032 on one side and .042 on the other (assembled to measure current DH, block has not been decked yet). Most opinions I have found in searching is to zero deck and adjust quench with head gaskets. Does the engine care if I run the piston say.028 in the hole and use a .015 head gasket?. I would rather deck the block as little as possible. Thanks for your time....John

Barry_R

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Re: Deck height VS quench
« Reply #1 on: July 12, 2018, 10:46:23 AM »
Only thing is that the really thin head gaskets are sometimes a bit sketchy.  I have also used the extra thick Cometics (.066 etc) and let the pistons climb .020 out of the deck on packages where you do not want to cut the original deck any further.

gt350hr

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Re: Deck height VS quench
« Reply #2 on: July 12, 2018, 02:00:32 PM »
  There is a new trend toward  pushing the piston out of the block as much as .020 and running a thicker gasket . The "theory" is to pull the combustion pressure spike away from the bottom  of the gasket , thinking it reduces the chance of that pressure "lifting" the head and compromising the gasket at the block surface. AGAIN this is a new trend and NOT followed by everyone. "I" haven't done it myself to prove or disprove it.
« Last Edit: July 13, 2018, 09:42:25 AM by gt350hr »

HvyFt4spd

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Re: Deck height VS quench
« Reply #3 on: July 12, 2018, 04:49:09 PM »
  That's interesting, everything old is new type of deal I guess. At RAM that was noted to be something learned at the engine classes Smokey held in the 70's. In 02 before working there myself I wanted a block O-ringed for nitrous and was given the idea of pushing the piston above the deck at least .010 as an alternative. I'm not aware of a downside from it being done that way but wonder what the margin of pressure variance is.

gt350hr

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Re: Deck height VS quench
« Reply #4 on: July 13, 2018, 09:51:57 AM »
  As long as minimum piston to head clearance is maintained there isn't a negative effect. The idea is the pressure doesn't have "direct access" to the gasket/block mating surface. Engine builders have used deck spacers in the past to allow longer strokes/ rod length. Unless the block is sleeved into the spacer , the limit is keeping the top ring in the block. This would allow and increase of .200-.300 in "block height. Kaase has done this a few times on his Engine Masters entries. Works fine.

cjshaker

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Re: Deck height VS quench
« Reply #5 on: July 13, 2018, 11:41:04 AM »
Might work on a high performance engine with a limited life-span between tear downs, but I wouldn't want to try it on an engine that I intended to put lots of miles and many years on. I would think carbon buildup on the above-deck part of the piston crown would eventually start to wear the cylinder wall and cause issues with ring seal, along with cylinder wall scoring. It happens on typical high mileage engines, so I think it would be even more pronounced with one that had pistons that went above the deck.
Doug Smith


'69 R-code Mach 1, 1965 427 MR Sideoiler 2x4, 4-spd Toploader, 4.30 Detroit Locker
2 1965 Galaxies with 390s
1970 F-350 390
1958 Ford Ranch Wagon 390

cjshaker

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Re: Deck height VS quench
« Reply #6 on: July 13, 2018, 11:45:20 AM »
A couple pictures of Kasses' engine from last years EMC.



Doug Smith


'69 R-code Mach 1, 1965 427 MR Sideoiler 2x4, 4-spd Toploader, 4.30 Detroit Locker
2 1965 Galaxies with 390s
1970 F-350 390
1958 Ford Ranch Wagon 390

Posi67

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Re: Deck height VS quench
« Reply #7 on: July 13, 2018, 11:56:07 AM »
My friends 472" Windsor has the pistons .075 out of the hole and a .120 thick gasket. Works well but it's in a race car. Of course, this does nothing to help answer Fordman's question.   

gt350hr

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Re: Deck height VS quench
« Reply #8 on: July 13, 2018, 02:30:53 PM »
A couple pictures of Kasses' engine from last years EMC.





       I had a bit to do with that project. In '77 I found a pair of heads machined like that at Holman Moody in Charlotte. I ended up buying too much and ran out of money so I let a friend buy them. I mentioned them to Jon when he was Dyno's crew chief back then because NHRA gave a weight break to "inline" valve heads and I knew that one would flow air. Dyno passed on the idea but the unique nature was stuck in Jon's memory. The rest is history.

HvyFt4spd

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Re: Deck height VS quench
« Reply #9 on: July 13, 2018, 02:52:41 PM »
 Speaking head spacers with big strokes M/T did that in 64 on 289's. What's funny about that is it leaves guys scratching there heads when they are so lucky as to find the blower manifolds. Due to the deck spacers a clearly Windsor intake is often too narrow for a 351 that didn't exist yet and too wide for the 289 noted by the part number.

 

 

Barry_R

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Re: Deck height VS quench
« Reply #10 on: July 14, 2018, 06:15:15 AM »
First time I ever saw head to block spacers was at a drag boat race in Columbiaville, MI +/- 1980.  They were about two inches thick on a Pontiac Ram Air V headed, blown alcohol boat lettered as "Fool's Way", along with similar crankcase "extensions" on the sides of the pan rails.  I stared at that concoction for about an hour trying to understand what I was looking at.  Never saw inside of it, but that sucker sounded like a nitro motor and owner the water beating out a ton of Boss 429 and BB Chevy powered stuff.