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Running a sbc with the common wall head bolt hole exposed

General engine tech -- Drag Racing to Circle Track

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rewguy
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Running a sbc with the common wall head bolt hole exposed

Post by rewguy » Thu Oct 10, 2019 11:35 am

I know that you can run it if ONE port is exposed.....but can you run it if both ports are exposed to the same head bolt hole? I think so.....but double checking here.....thankyou!!

mt-engines
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Re: Running a sbc with the common wall head bolt hole exposed

Post by mt-engines » Thu Oct 10, 2019 12:28 pm

Yes

Walter R. Malik
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Re: Running a sbc with the common wall head bolt hole exposed

Post by Walter R. Malik » Thu Oct 10, 2019 8:53 pm

rewguy wrote:
Thu Oct 10, 2019 11:35 am
I know that you can run it if ONE port is exposed.....but can you run it if both ports are exposed to the same head bolt hole? I think so.....but double checking here.....thankyou!!
Intake wave tuning will be off slightly but, there is no other problem with actually running it.
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SchmidtMotorWorks
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Re: Running a sbc with the common wall head bolt hole exposed

Post by SchmidtMotorWorks » Thu Oct 10, 2019 9:52 pm

Port leaks can be costly, on those Gen 3 hemis with the flap valve controlled 2 length setup; if the seals on the valves stop working, it can cost 30HP.
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mt-engines
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Re: Running a sbc with the common wall head bolt hole exposed

Post by mt-engines » Fri Oct 11, 2019 9:01 am

SchmidtMotorWorks wrote:
Thu Oct 10, 2019 9:52 pm
Port leaks can be costly, on those Gen 3 hemis with the flap valve controlled 2 length setup; if the seals on the valves stop working, it can cost 30HP.
How does that at all compare against the common wall bolt in the cylinder head?
of course when you change the tuning length of the runner you can be off bunch.

Have you done a back to back? I have for multiple customers. Because after max effort porting crap happens when you are doing what you can to get the size. In one instance sleeving the bolt hole lost us 4hp on the top end. This was an 800 hp 400"sbc

The reason i had to sleeve it was because a few of the customers flipped out when they saw the hole. After freshen up and the sleeves installed, we placed it on the same dyno. That was as back to back as i have tested this scenario.

PRH
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Re: Running a sbc with the common wall head bolt hole exposed

Post by PRH » Fri Oct 11, 2019 10:34 am

One of the local builders closed his shop several years ago, but continued to do select builds for some of his long time customers.
Mostly dirt oval builds.
He had sold off all the big equipment, so he was pretty much just doing the assembly.

He was bringing me many of the heads for seat work and valve refacing.
There were several sets of heavily ported SBC Dart iron heads where the bolt was exposed to both ports.
Those heads were still winning a fair share of races.
Somewhat handy with a die grinder.

SpeierRacingHeads
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Re: Running a sbc with the common wall head bolt hole exposed

Post by SpeierRacingHeads » Fri Oct 11, 2019 11:15 am

Every SBC CNC head I sell has the bolt hole exposed. muchtodoaboutnothing

You should see a heavily ported GM 615X for Comp. Has 3 windows in the port.
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mt-engines
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Re: Running a sbc with the common wall head bolt hole exposed

Post by mt-engines » Fri Oct 11, 2019 11:40 am

SpeierRacingHeads wrote:
Fri Oct 11, 2019 11:15 am
Every SBC CNC head I sell has the bolt hole exposed. muchtodoaboutnothing

You should see a heavily ported GM 615X for Comp. Has 3 windows in the port.
exactly

Orr89rocz
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Re: Running a sbc with the common wall head bolt hole exposed

Post by Orr89rocz » Fri Oct 11, 2019 12:49 pm

SpeierRacingHeads wrote:
Fri Oct 11, 2019 11:15 am
Every SBC CNC head I sell has the bolt hole exposed. muchtodoaboutnothing

You should see a heavily ported GM 615X for Comp. Has 3 windows in the port.
Yup i even ran 30 psi thru it and all seemed fine

levisnteeshirt
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Re: Running a sbc with the common wall head bolt hole exposed

Post by levisnteeshirt » Sun Oct 13, 2019 7:29 pm

Off idle throttle response effected ?

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