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Help with Big cube pump gas build..

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gt350hr
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Help with Big cube pump gas build.. Empty Help with Big cube pump gas build..

Post  nascar429 June 4th 2020, 11:15 am

Hi All..

In the planning stage starting to gather parts for a strong ( hoping 800HP-ish ) pump-gas 93/94 octane street/strip build 588ci to 598ci 11 to 1 comp
I already have A460 block, Mafia manifold and a Bobby at competition carb built 1150 Dominator runs beautiful on everything i tried it on..

Scat Forged 4.500 crank i have as well.

Rods to order H beams 6.700 or 6.800 Manley, Scat ..or possibly a Molnar 6.750 and a 1.300 compression height ?..umm  

pistons probably Diamond will need around a 35cc dish.. question with that much dish is there a preference in which compression height to use 1.260 or 1.360 ?   

rings 1/16 1/16 3/16 or possibly a thinner 0.43 ring package.?

Heads drooling over SR-71's.. but my head is saying P51 or possibly AFR, TFS 325's may be a better fit for this build...any thoughts guys?

I can give more details on the car if i haven't bored you to death Lol  Rolling Eyes peoples thoughts on custom camshaft  i suppose i'm getting ahead of myself till the heads are chosen.



Any advice would be appreciated.


Last edited by nascar429 on June 4th 2020, 10:11 pm; edited 2 times in total (Reason for editing : too much rambling sorry..)

nascar429

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Post  Gregaust June 5th 2020, 5:10 am

Sounds like a plan I have if I build myself something again, 598 , SR-71 etc Smile

With a 4.500 crank my preference would be the 6.8 rod which would require a 1.26 piston giving a 10.310 height.

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Post  nascar429 June 5th 2020, 6:32 am

Gregaust wrote:Sounds like a plan I have if I build myself something again, 598 , SR-71 etc Smile

With a 4.500 crank my preference would be the 6.8 rod which would require a 1.26 piston giving a 10.310 height.

At the moment my thinking is the same 1.260 piston..

I built a pump gas 580ci SCJ headed deal with a 6.800 rod for a Black Landau in the march 2018 issue of Street machine.. it's still going strong. no fouled plugs in 3 years ( crane HI 6 ignition the best inmo ) sweet 1050 2 circuit Dominator also the pin is in the oil ring at that compression height, but has not been a problem.

the 588ci 598ci i'm building is going into a survivor cosmic blue Xa gs sedan for a good friend..I have a set of SR-71 heads here for my own build..the owner after seeing them has pretty much tunnel vision now  Shocked haha ..i'm not sure i can change his mind to try anything else oh well..Kaase doesn't have any in stock at the moment so i have a little time to make a decision on heads etc, we will see.

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Post  rmcomprandy June 5th 2020, 11:25 am

1mm, 1mm, 2mm would be my ring pack choice.

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Post  nascar429 June 5th 2020, 12:17 pm

rmcomprandy wrote:1mm, 1mm, 2mm would be my ring pack choice.



Is there a brand you have a preference for with that ring pack design ? it will be a 4.600 bore..

Your opinion advice is appreciated.

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Post  gt350hr June 5th 2020, 1:04 pm

At 1.260 C/H you can expect a round dish about 3.800 dia at .180 deep + a valve relief to get your volume. A mirror image dish will not leave enough material thickness. Ring lands will be fine for any ring combination but the pin will be in the oil ring unless the 1x1x2 ring set Randy mentioned is used.

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Post  nascar429 June 5th 2020, 1:23 pm

gt350hr wrote:   At 1.260 C/H you can expect a round dish about 3.800 dia at .180 deep + a valve relief  to get your volume. A mirror image dish will not leave enough material thickness. Ring lands will be fine for any ring combination but the pin will be in the oil ring unless the 1x1x2 ring set Randy mentioned is used.

Thanks for the thorough break down of your thoughts..some good points.

After messaging Kaase today seems they prefer a 1.360 C/H with 4.500 stroke.. in your opinion would it be advisable to try to keep the pin out of the oil ring if possible?

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Post  rmcomprandy June 5th 2020, 5:15 pm

nascar429 wrote:
rmcomprandy wrote:1mm, 1mm, 2mm would be my ring pack choice.



Is there a brand you have a preference for with that ring pack design ? it will be a 4.600 bore..

Your opinion advice is appreciated.

To me ... any engine of that caliber will have custom pistons.
You can designate any ring pack you want, (along with gas ports).

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Post  Busted Knuckles June 9th 2020, 8:19 am

No problems with the rings in the pin bore. It was a concern when these first came out but it's been proven OK.

As long as you don't plan to spray hell out of it, the 1.260" pin height will be OK. If you're going to empty your bottle of nitrous on every pass, move that top ring down and give the top ring some cooling and piston deck some thickness.

Big inch engines love big heads and big cams. You almost can't over-do it.

I'd invest in stock in your favorite tire manufacturer....

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Post  hbstang June 9th 2020, 11:06 pm

my .02 says for almost the same money the sr-71 heads make it a no brainer!no need for shaft rockers or stud girdles.its not easy to get over 1,000 on pump gas,but i think these heads will do it.
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Post  Mark O'Neal June 9th 2020, 11:16 pm

nascar429 wrote:
gt350hr wrote:   At 1.260 C/H you can expect a round dish about 3.800 dia at .180 deep + a valve relief  to get your volume. A mirror image dish will not leave enough material thickness. Ring lands will be fine for any ring combination but the pin will be in the oil ring unless the 1x1x2 ring set Randy mentioned is used.

Thanks for the thorough break down of your thoughts..some good points.

After messaging Kaase today seems they prefer a 1.360 C/H with 4.500 stroke.. in your opinion would it be advisable to try to keep the pin out of the oil ring if possible?

The pin being in the oil ring doesn't matter, as long as you don't forget the oil rail support.

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Post  gt350hr June 11th 2020, 1:36 pm

nascar429 wrote:
gt350hr wrote:   At 1.260 C/H you can expect a round dish about 3.800 dia at .180 deep + a valve relief  to get your volume. A mirror image dish will not leave enough material thickness. Ring lands will be fine for any ring combination but the pin will be in the oil ring unless the 1x1x2 ring set Randy mentioned is used.

Thanks for the thorough break down of your thoughts..some good points.

After messaging Kaase today seems they prefer a 1.360 C/H with 4.500 stroke.. in your opinion would it be advisable to try to keep the pin out of the oil ring if possible?

Let's see ,
Kaase designed the head , tested the head and is now suggesting what to use. That is enough for "me" to go with what they suggest.

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Post  rmcomprandy June 11th 2020, 2:47 pm

gt350hr wrote:
nascar429 wrote:
gt350hr wrote:   At 1.260 C/H you can expect a round dish about 3.800 dia at .180 deep + a valve relief  to get your volume. A mirror image dish will not leave enough material thickness. Ring lands will be fine for any ring combination but the pin will be in the oil ring unless the 1x1x2 ring set Randy mentioned is used.

Thanks for the thorough break down of your thoughts..some good points.

After messaging Kaase today seems they prefer a 1.360 C/H with 4.500 stroke.. in your opinion would it be advisable to try to keep the pin out of the oil ring if possible?

  Let's see ,
      Kaase designed the head , tested the head and is now suggesting what to use. That is enough for "me" to go with what they suggest.

Personally, the length of the bore on the block being used will have a huge influence upon the rod length and piston compression distance .
I don't want over a 1/3 of the pin diameter hanging out of the bottom of the bore at BDC.
It has been done though, for short periods of time. With a "barrel skirted" piston it will go a little longer.

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Post  wayney June 13th 2020, 4:08 pm

in my opinion SR-71 would be the head of choice. or boss heads.

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