Max out of the hole

General engine tech -- Drag Racing to Circle Track

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sccagt1racer
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Max out of the hole

Post by sccagt1racer » Wed May 16, 2018 6:34 pm

I'm assembling a ls engine for a friend and from my calculations its going to be .012 -.015 out of the hole. I have a .051 head gasket right now and could go thicker if needed. How much is too much out and what is the min quench I'll be safe at. Ive been told .038 -.040. Its a ls6 with a wiesco forged piston. wiesco 6.125 rod and stock crank. Its going to see a max rpm of 7200 road race car.

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af2
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Re: Max out of the hole

Post by af2 » Wed May 16, 2018 6:44 pm

Not advanced. You can get any thickness gasket you need. Get it assembled and figure from there.
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Re: Max out of the hole

Post by jed » Wed May 16, 2018 8:40 pm

I have built several with the piston .012/.015 above the deck and used a .046 gasket with no
Reported problem.
Put it to get her and drive it like you stole it.
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Re: Max out of the hole

Post by PackardV8 » Wed May 16, 2018 9:12 pm

Your combination should be OK.
Its going to see a max rpm of 7200 road race car.
Are you going to install the limiter chip and a locking tell-tale tach? Never believe a driver or a friend on a race track. They only shift when they're ahead.
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Re: Max out of the hole

Post by Geoff2 » Thu May 17, 2018 6:35 am

I am currently building an engine & have deliberately had the block decked so that the pistons are 0.010" out of the hole. 0.039"head gasket. Trying to cheat the octane fairy. Engine will be limited to 6000 rpm.

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Re: Max out of the hole

Post by mag2555 » Thu May 17, 2018 1:03 pm

.015" out of the hole means it will grow to .020" when at normal temp, but if you have Aluminum heads concider it a wash!

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Re: Max out of the hole

Post by houser45 » Thu May 17, 2018 1:08 pm

Leave it with the .051”

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Re: Max out of the hole

Post by CGT » Thu May 17, 2018 3:10 pm

sccagt1racer wrote:
Wed May 16, 2018 6:34 pm
I'm assembling a ls engine for a friend and from my calculations its going to be .012 -.015 out of the hole. I have a .051 head gasket right now and could go thicker if needed. How much is too much out and what is the min quench I'll be safe at. Ive been told .038 -.040. Its a ls6 with a wiesco forged piston. wiesco 6.125 rod and stock crank. Its going to see a max rpm of 7200 road race car.
Aluminum block? I have done quite a few that were .006 to .008 above deck and used a .036 cometic..aluminum head, aluminum block LS. Your clearances above will be fine, even if its iron.

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Re: Max out of the hole

Post by Rick360 » Thu May 17, 2018 3:52 pm

mag2555 wrote:
Thu May 17, 2018 1:03 pm
.015" out of the hole means it will grow to .020" when at normal temp, but if you have Aluminum heads concider it a wash!
Wow, I gotta see the math on that. :-k

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Re: Max out of the hole

Post by af2 » Thu May 17, 2018 4:17 pm

Rick360 wrote:
Thu May 17, 2018 3:52 pm
mag2555 wrote:
Thu May 17, 2018 1:03 pm
.015" out of the hole means it will grow to .020" when at normal temp, but if you have Aluminum heads concider it a wash!
Wow, I gotta see the math on that. :-k

Rick
Ya me too. On a typical blown Brad we see .014" growing from hot to cold. HMM If the piston was out it will stay out!
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Re: Max out of the hole

Post by RCJ » Thu May 17, 2018 4:56 pm

I've run 100s of laps with a motor that is .027 out of the hole with a.070 cometic gasket..040 is what shoot for.

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Re: Max out of the hole

Post by af2 » Thu May 17, 2018 5:55 pm

RCJ wrote:
Thu May 17, 2018 4:56 pm
I've run 100s of laps with a motor that is .027 out of the hole with a.070 cometic gasket..040 is what shoot for.
Re working a 489 that is using a .061" Felpro and will get the same one at .039" total clearance using Aluminum heads now.
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Re: Max out of the hole

Post by pamotorman » Thu May 17, 2018 9:10 pm

sccagt1racer wrote:
Wed May 16, 2018 6:34 pm
I'm assembling a ls engine for a friend and from my calculations its going to be .012 -.015 out of the hole. I have a .051 head gasket right now and could go thicker if needed. How much is too much out and what is the min quench I'll be safe at. Ive been told .038 -.040. Its a ls6 with a wiesco forged piston. wiesco 6.125 rod and stock crank. Its going to see a max rpm of 7200 road race car.
the aluminum block will grow .005 so you will be .005 less than room temp measurement

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Re: Max out of the hole

Post by MadBill » Thu May 17, 2018 9:43 pm

There have been a number of S/T threads on ideal piston/head clearance and 0.040" seems to be well-accepted as a good target for iron blocks with steel rods. Most feel ten thous 'too much' is way better than five thous too little, but there are numerous builders that are prepared to fly much closer to the sun; down to 0.030" and even a tad less. :shock:
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Re: Max out of the hole

Post by xanadu » Thu May 17, 2018 10:10 pm

Closest ive gone is .028" on an iron headed ford 351C. Im still scared when i think about it.

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