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Discussion Starter · #1 ·
While I've got the engine torn down, I've decided to upgrade the pistons. They're currently Silvolites (1443, sealed power # 400NP) with a recessed head .160” deep X 3.445” dia. and a ratio of 8.5:1. I'm wanting a higher cr, but I'm not sure what size I need. Hyper pistons are fine, I don't plan on spraying or spinning the engine to high and I need to run pump gas. I've priced the Speed Pro pistons and they seem to be what's best for my needs. Any suggestions on a streetable cr? Any help is appreciated, thanks.

-sb 400 block over 0.040 (408).
-Comp ratio?
-AFR Eliminator 195/65cc heads
-Lunati Voodoo 60104
-Edelbrock RPM Air Gap Intake manifold.
-Long tube Flowtech headers.
-2 1/2" full exhaust with a H-pipe.
-Carter AFB competition series 750 cfm carb.
-MSD 6A box.
-MSD plug wires.
-Turbo 400 trans.
-Hughes Performance 2,500 stall.
-12 bolt posi rear, Richmond 3.55 gears, Eaton carrier.
 

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You should probably go with a flat top with some valve reliefs, that cam is going to want some compression. Your rear gear and converter are just about right. Good call on upgrading.
 

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Won't hurt, you could probably handle some extra with those afrs. As it is I'm at about 10.3:1 on 87 octane with my dart iron eagles, no pinging.

I have those exact same heads going onto my 383 with the lunati 60112, let me know how those things wake your motor up.
 

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Zach,
When you mention Speed Pro pistons...which one's are you considering?
Hypers or Forged?
If it's a hyper, Speed Pro sells a -12.5 cc dish that will put your CR around 10.2 depending on deck height/gasket thickness....p/n #H615CP40
The flat top hypers, H616CP40, with a -6cc valve relief, will yield a CR of around 10.8
I personally like the SP hypers with the coated skirts for a mild build.
 

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Discussion Starter · #7 · (Edited)
Sorry about that, I'm leaning towards the hypers. I don't plan on spraying or getting too high in the rpm range. I can always save a little longer and go forged if there's a reliability issue.
 

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BTW...running a Voodoo 60104 cam in an AFR headed (180cc) 383 with Speed Pro hypers in my bro-in-law's '69 Malibu.
TH350, 3200 stall and 3.73 gears, 10.2 CR, 750 DP Holley...ran a 12.65 @ Silver Dollar.
 

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Discussion Starter · #9 ·
BTW...running a Voodoo 60104 cam in an AFR headed (180cc) 383 with Speed Pro hypers in my bro-in-law's '69 Malibu.
TH350, 3200 stall and 3.73 gears, 10.2 CR, 750 DP Holley...ran a 12.65 @ Silver Dollar.
Thanks guys, looks like I'll be getting the Speed Pro hypers. Bill, with traction/tuning do you think my 3,560 lb (w/ driver) '70 can get lower than those numbers? He has more gear and stall, but I will have more cubes and bigger heads. Also, how highway compatable are 3.73s?
 

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Thanks guys, looks like I'll be getting the Speed Pro hypers. Bill, with traction/tuning do you think my 3,560 lb (w/ driver) '70 can get lower than those numbers? He has more gear and stall, but I will have more cubes and bigger heads. Also, how highway compatable are 3.73s?
Sure, why not? You're driving a '70, aren't 'ya!! ;)
The '69 is a loaded, full bench seat, A/C car and weighs over 3800 lbs with driver.
The 3.73's are really right on the edge of being comfortable for long distance highway driving. In fact, we trailer the 130 miles to Reynolds...
You'll like the cam and FYI his power brakes work fine.
 
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