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11mm to 12mm Head bolt/stud conversion

whatsup62

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Anyone here done this? Is it really needed? What kind of power with no issues are guys running with the 11mm's?
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2-tone

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1k rwhp with a whipple with the smaller studs. I plan on adding 100-150 more at some point in the next year. Hoping I don't find their limit.
 

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in my opinion it's not necessary unless your looking for pro-mod power. i have built 6 coyotes that hang out around 1000-1200 hp and have never lifted a head. the ones that break seem to be unlucky with broken crankshaft or other lower end mechanical failure.
 

Will@Whipple

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1000 Wheel seem's to be the average power that the 11mm head stud's will survive, beyond that the 12mm stud's ( Down to the Main Journal's Like the Gen 1 11-12 block's and Gen 2 5.2L Blocks) is highly recommend along with other cylinder head retention procedure's to help with head lift.
 

olaosunt

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Another reason to look at the Voodoo block if you are planning a 5.2 build (rather than boring and sleeving a post 12/pre 18 block .
The PW lined blocks seem to be holding up past 1000 whp without the need to sleeve .
 

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olaosunt

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Thanks for the info !
Is it possible to do the 12 mm conversion with the motor in the car (I doubt it ) ?

What are the the other “head retention
procedures “ ?
I am lifting the heads in my KB car at just below 1000 whp with the 11 mm heads studs so looking for options without pulling motor .

I do have another assembled long block(sleeved 15-17 block with the 11mm head studs ) which will replace the one in the car now .
Will I need to take it apart to do the conversion ?
 

Will@Whipple

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Thanks for the info !
Is it possible to do the 12 mm conversion with the motor in the car (I doubt it ) ?

What are the the other “head retention
procedures “ ?
I am lifting the heads in my KB car at just below 1000 whp with the 11 mm heads studs so looking for options without pulling motor .

I do have another assembled long block(sleeved 15-17 block with the 11mm head studs ) which will replace the one in the car now .
Will I need to take it apart to do the conversion ?
Anytime, and no this service can not be done in the car it must be done on a CNC Machining Center for proper depth/position. The block must be 100% bare as well because it locate's through the main's so you would have to have your other assembled long block fully apart as well.

Other option's for improved cylinder head sealing is O-ringing the Sleeve's so you can use a stainless steel ring around the cylinder's with the OEM MLS head gasket's this procedure must also be done with the engine bare as well. This is by far the best option out there under high boost.

If you wanted to try something without pulling the motor I would suggest trying the JE Pro Seal MLS head gasket's they look very promising.

Hope this help's!
 

olaosunt

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1000 Wheel seem's to be the average power that the 11mm head stud's will survive, beyond that the 12mm stud's ( Down to the Main Journal's Like the Gen 1 11-12 block's and Gen 2 5.2L Blocks) is highly recommend along with other cylinder head retention procedure's to help with head lift.
Anytime, and no this service can not be done in the car it must be done on a CNC Machining Center for proper depth/position. The block must be 100% bare as well because it locate's through the main's so you would have to have your other assembled long block fully apart as well.

Other option's for improved cylinder head sealing is O-ringing the Sleeve's so you can use a stainless steel ring around the cylinder's with the OEM MLS head gasket's this procedure must also be done with the engine bare as well. This is by far the best option out there under high boost.

If you wanted to try something without pulling the motor I would suggest trying the JE Pro Seal MLS head gasket's they look very promising.

Hope this help's!

Thank you so much !
I already tried those head gaskets when I swapped the heads ( went from GT 350 to GT heads ) when I replaced a blown head gasket.

I guess too late now for current motors .
I debated using the Voodoo block (unsleeved ) vs sleeving a 15-17 block for the last 5.2 block .

I gues there are pros and cons to both but I know now which block I would choose if I was to build another one . Lol
 

Will@Whipple

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Anytime! Oh very nice. So far so good with those head gasket's ??

There is pro's and con's to both like you said and if you really want to make some serious power and not stress about the block the best thing as I'm sure you know is the BEAR Coyote Block or the new Predator 5.2L Block :)
 

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Will@Whipple

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olaosunt

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Anytime! Oh very nice. So far so good with those head gasket's ??

There is pro's and con's to both like you said and if you really want to make some serious power and not stress about the block the best thing as I'm sure you know is the BEAR Coyote Block or the new Predator 5.2L Block :)
Still lifting the heads despite the gaskets and ARP head studs .
I like the predator block . How different is it from the old vooodo block ?
Both use the 12 mm head bolts .
 

Will@Whipple

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Still lifting the heads despite the gaskets and ARP head studs .
I like the predator block . How different is it from the old vooodo block ?
Both use the 12 mm head bolts .
Oh man, well that's not good those gasket's where supposed to help keep it sealed when the head's lift.

Well the Gen 2 5.2L block ( Current production GT350 block ) and the upcoming Predator 5.2L Block are actually different but both new 5.2L blocks do have the longer cylinder head thread's from the factory, along with increased structural support and improved PAC liner's
 

olaosunt

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Oh man, well that's not good those gasket's where supposed to help keep it sealed when the head's lift.

Well the Gen 2 5.2L block ( Current production GT350 block ) and the upcoming Predator 5.2L Block are actually different but both new 5.2L blocks do have the longer cylinder head thread's from the factory, along with increased structural support and improved PAC liner's
That’s interesting . I had assumed the Gen 2 5.2L block WAS the predator block .
Do you know how the predator block is different ?
 
 




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