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Head Recommendations

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Head Recommendations Empty Head Recommendations

Post  Stimie on December 14th 2019, 9:27 am

I've been collecting parts for about a year now 2 kids in college race car money gets real thin. Dropping the block off at the machine shop after the holidays. I've got a DOVE A block with a Scat forged assemble 4.5" crank and flat top pistons. I'm planning on having the 2,3,4 main conversion to done on the block. I don't have a cam yet however the pistons are cut for .800 lift with the Kaase or Ford SCJ style head. The question I have is head choice. Are the SR-71 heads that much better than the SCJ? There's better than a $1000.00 difference between the two. The car will be a track only car (62 ranchero). I would like to get the car well in to the cat into the 9's.

Stimie

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Post  rmcomprandy on December 14th 2019, 9:57 pm

Stimie wrote:I've been collecting parts for about a year now 2 kids in college race car money gets real thin. Dropping the block off at the machine shop after the holidays.  I've got a DOVE A block with a Scat forged assemble 4.5" crank and flat top pistons. I'm planning on having the 2,3,4 main conversion to done on the block.  I don't have a cam yet however the pistons are cut for .800 lift with the Kaase or Ford SCJ style head. The question I have is head choice. Are the SR-71 heads that much better than the SCJ? There's better than a $1000.00 difference between the two. The car will be a track only car (62 ranchero). I would like to get the car well in to the cat into the 9's.

Being "better" is all about the application where the heads are to be used.  
The SR-71 is a much better fitting for an "all out" race head for that "type" of aggressive high valve lift engine, than the SCJ could ever be.
However, Way to much head for a lot of applications.
It looks to me like a P-51 head would be a better fit for your application.

rmcomprandy

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Post  Dave De on December 14th 2019, 10:06 pm

Well I've run all three of them (SCJ, P-51, and SR-71) on the same short block. There are definite power differences when stepping up. I ran bottom 9's with all three. Highly worked over SCJ's will perform similar to P-51's out of the box. Highly modified P-51's will perform similar to SR's out of the box. I have not modified my SR's yet. Your pistons valve reliefs are probably to small diameter wise for the larger SR intake valves.
Having said that and experienced that your best selection is to use P-51's. Another factor is that the pushrod guides on the SCJ's need to be cut and welded to get good rocker geometry. P-51's are pretty much good to go out of the box. They are plug and play as good as Edelbrock but with much more performance.

Ive run all three heads on a 580 with 13.5 compression and E-85 with a similar or identical camshaft.
Dave De
Dave De

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