Deck clearance
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Instructor
Joined: Dec 2017
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Deck clearance
well you’ve talked me into it...I’m spending $900 on pistons, and $500 on machine work to bore 30 over grind my old crank and balance...heck I’m already going 30 over anyways. why don’t I just buy a scat rotating assembly and stroke my 454 since the kit is around $1500? It seems it would be crazy not to.that’s why I love it here, you guys have a ton of combined wisdom....
anyhow I’m trying to figure out compression and need to know deck clearance if the different crank as I believe stock 454 is .030 deck clearance but was it deck clearance with a stroker kit?
anyhow I’m trying to figure out compression and need to know deck clearance if the different crank as I believe stock 454 is .030 deck clearance but was it deck clearance with a stroker kit?
Last edited by Muzzyzx7rr; Dec 13, 2017 at 07:25 PM.
Race Director
Joined: Jul 2015
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From: SW Florida.
the deck clearance is in the block deck...originally. GM set them .016 to .020. with stock piston pin heights, you will get the same clearance. a LOT of aftermarket piston makers are making their pistons .010 or more higher so people don't have to deck the block to get zero deck height. so whatever pistons you are buying, you need to find out what pin height they are using. 4.0 or 4.25 stroke...
Thread Starter
Instructor
Joined: Dec 2017
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the deck clearance is in the block deck...originally. GM set them .016 to .020. with stock piston pin heights, you will get the same clearance. a LOT of aftermarket piston makers are making their pistons .010 or more higher so people don't have to deck the block to get zero deck height. so whatever pistons you are buying, you need to find out what pin height they are using. 4.0 or 4.25 stroke...
It says the stroke is 4.25”
Thread Starter
Instructor
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Race Director
Joined: Jul 2015
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From: SW Florida.
I meant, whichever stroke you are going with, you need to contact the piston manufacturer and find out if they are lowering the pin height to zero deck the piston and, if so how much. the pin height is an eighth inch higher for 1/4 longer stroke. but if it is .010 lower, the deck height is around .005 to .010 instead of .016 to .020 like stock. AND if somebody decks the block shooting for zero deck and gets pistons already zero decked with pin height, now you have pistons sitting .010 or more up above the deck.
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
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From: New Braunfels Texas
You need to install the crank and bearings along with a piston and rod.....bring the piston to TDC. Measure how far the piston is in the hole with a piston bridge and indicator. Do this on all four corners and record. Write it on the deck of the block and on a piece of paper. Give these numbers to your machinist......this will allow the machinist to "square deck" the block. This is called a "mock up".
As far as choosing your pistons, stick with standard manufacutres compression heights. (C/D). I am not aware that any manufactures have made the pistons higher in the bore....but this does not mean it has not happened.
Basically a Big Block Chevy is called out by racing manufactures to have a 9.800 deck.
So 9.800 - (4.250/2)- 6.385= piston C/D (Compresion distance) which in this case is 1.290.......since most factory blocks are 9.815 to 9.820....whack the difference off the block and you are done.
A quick look of the SRP catalogue shows that they like a 1.270 C/D and call the block out at 9.780.....which is fine.
Eagle makes a 6.405 rod to make your deck 9.800.....which will give some meat for later if you want to do it that way.......either way....do the math and trust it.
Jebby
As far as choosing your pistons, stick with standard manufacutres compression heights. (C/D). I am not aware that any manufactures have made the pistons higher in the bore....but this does not mean it has not happened.
Basically a Big Block Chevy is called out by racing manufactures to have a 9.800 deck.
So 9.800 - (4.250/2)- 6.385= piston C/D (Compresion distance) which in this case is 1.290.......since most factory blocks are 9.815 to 9.820....whack the difference off the block and you are done.
A quick look of the SRP catalogue shows that they like a 1.270 C/D and call the block out at 9.780.....which is fine.
Eagle makes a 6.405 rod to make your deck 9.800.....which will give some meat for later if you want to do it that way.......either way....do the math and trust it.
Jebby
Last edited by Jebbysan; Dec 13, 2017 at 08:18 PM.
Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
212157 SRP pistons, with 115cc combustion chambers, it's close enough to 10.5:1 compression it'll scare you. It is .060 over for 496 ci. Pump gas friendly too. All forged rotating assembly and H-beam rods. Including the boring and balancing, you'll be close to what you're looking at for stuff that has been used and revived. I went with Eagle crank and rods at the suggestion of the machine shop.
Last edited by TimAT; Dec 13, 2017 at 08:35 PM.
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As mentioned...9.800 is normal height of block. Most shops will deck it to where you end up with pistons .005" down in the hole. My engine has the pistons .009" OUT of the hole. The difference for piston to head clearance can be made up with various head gaskets. Typically folks shoot for .035"-.040" total clearance. Mine is usually tighter...but I'm a little out there sometimes!
1.270" is typical compression height for a 4.250 stroke with a 6.385" rod. That will put you at 9.780" if everything is perfect and you'll have pistons .020" down in the hole. Better if they are up closer to zero...so tell machinist what you're looking for.
When ordering crank....make sure to get one with center counterweights. Much better on long stroke deals.
I'm assuming you're looking at the all forged setup? Crank, rod and pistons?? You want to build a solid bottom end.
Ck Competition Products and Ohio Crank. Might also call Chris Straub..he can sell you the whole package at one time balanced and all.
JIM
1.270" is typical compression height for a 4.250 stroke with a 6.385" rod. That will put you at 9.780" if everything is perfect and you'll have pistons .020" down in the hole. Better if they are up closer to zero...so tell machinist what you're looking for.
When ordering crank....make sure to get one with center counterweights. Much better on long stroke deals.
I'm assuming you're looking at the all forged setup? Crank, rod and pistons?? You want to build a solid bottom end.
Ck Competition Products and Ohio Crank. Might also call Chris Straub..he can sell you the whole package at one time balanced and all.
JIM
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Le Mans Master
Joined: May 2006
Posts: 9,993
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From: League City Tx
Well that escalated quickly.... lol
At least you decided to add the 4.25” crank before you chose the cam.
You are REALLY gonna need to do some head work now....and need more cam then originally discussed, and more converter to match.
At this point, you can save yourself a lot of headache/trouble and money by just buying a 496 from VortecPro for $7800 and make a proven 650hp....the R&D is already done for you and you are not relying on local machine shops, hoping they are getting the **** right.
You’ll love the 496 tho.
At least you decided to add the 4.25” crank before you chose the cam.
You are REALLY gonna need to do some head work now....and need more cam then originally discussed, and more converter to match.
At this point, you can save yourself a lot of headache/trouble and money by just buying a 496 from VortecPro for $7800 and make a proven 650hp....the R&D is already done for you and you are not relying on local machine shops, hoping they are getting the **** right.
You’ll love the 496 tho.
Thread Starter
Instructor
Joined: Dec 2017
Posts: 239
Likes: 17
Well that escalated quickly.... lol
At least you decided to add the 4.25” crank before you chose the cam.
You are REALLY gonna need to do some head work now....and need more cam then originally discussed, and more converter to match.
At this point, you can save yourself a lot of headache/trouble and money by just buying a 496 from VortecPro for $7800 and make a proven 650hp....the R&D is already done for you and you are not relying on local machine shops, hoping they are getting the **** right.
You’ll love the 496 tho.
At least you decided to add the 4.25” crank before you chose the cam.
You are REALLY gonna need to do some head work now....and need more cam then originally discussed, and more converter to match.
At this point, you can save yourself a lot of headache/trouble and money by just buying a 496 from VortecPro for $7800 and make a proven 650hp....the R&D is already done for you and you are not relying on local machine shops, hoping they are getting the **** right.
You’ll love the 496 tho.
Yes it escalated very quickly lol
Melting Slicks
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From: Spring Park MN
Thread Starter
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Racer
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As quench doesn't add a bit of power the deck clearance/quench isn't important. Spend some time in an automotive machine shop and you'll quickly find modern engines with their 4 valves per cylinder and HEMI's don't have any quench and they'll run circles around our C3's. There was a time in which engine builders believed quench increased the burning speed but that was proven wrong 50 years ago when Mopar re-introduced their HEMI.
Le Mans Master
Joined: Aug 2017
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From: Cool Northern Michigan
False again. Why don't you just start your statement with: True or False?
It would be a lot better for all of us.
Quench is the distance between the block decking, piston top and the the flat surface of the cylinder head. It has nothing to do with the chamber size, volume, or design. A Hemi can still have quench.
And the smaller the better. It does add power.
It would be a lot better for all of us.
Quench is the distance between the block decking, piston top and the the flat surface of the cylinder head. It has nothing to do with the chamber size, volume, or design. A Hemi can still have quench.
And the smaller the better. It does add power.
Last edited by HeadsU.P.; Dec 14, 2017 at 09:13 AM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
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From: New Braunfels Texas
False again. Why don't you just start your statement with: True or False?
It would be a lot better for all of us.
Quench is the distance between the block decking, piston top and the the flat surface of the cylinder head. It has nothing to do with the chamber size, volume, or design. A Hemi can still have quench.
And the smaller the better. It does add power.
It would be a lot better for all of us.
Quench is the distance between the block decking, piston top and the the flat surface of the cylinder head. It has nothing to do with the chamber size, volume, or design. A Hemi can still have quench.
And the smaller the better. It does add power.
Quench is very important to run compression and hold off detonation.....Hemi has no quench as it is a round open Hemispherical chamber.The center counterweight helps make it easier to balance external if necessary.Jebby