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Old 04-05-2016, 08:53 PM
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Thoughts on build and HP estimate? Thanks

Hey guys im new to this site and recently got into engines and want to make a hobby of it. Here is the specs im considering and questions:
*Its a 93 350 SB bored 0.060
*279 Thumper cam
*Comp cam springs (cam specified)
*High energy Hyd lifters (cam specified)
*Premium '50' series 1.5 ratio rocker arms with 3/8" stud
*stock crank
*Summit racing Carb and manifold kit (03-0199)
-600cfm carb 4 barrel
-dual plane intake
-electric choke and vacuum secondary
The motor will be mostly a street truck and cruising rarely racing other than playing on the road hahaJust curious as to what to expect from HP an TQ and how this build would work out, i know some people dislike the bore .060 and the thumper cam for their own reasons but lets not talk about that. Advice for different parts would be appreciated aswell. Thanks!!

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Old 04-06-2016, 03:36 AM
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If this is a 93 truck motor, you will need some different heads.The swirl port heads that are on it quit breathing @ 4000 to 4500 rpm.Your cam will just barely be getting into it's powerband by the time the heads die out.They also can only support, a little over 300 HP due to their poor flow.They are designed for low rpm torque, not high rpm HP.
If you already have heads but forgot to mention it, which heads do you have? Casting #, or, brand.
Also,your block is very likely a roller ready block & easily converted to a roller cam/lifter setup. I strongly advise you to consider doing so for performance & longevity.

Last edited by jokerZ71; 04-06-2016 at 04:03 AM.
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Old 04-06-2016, 03:46 AM
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AND.... If you are "just playing" on the street, you may want to consider building the motor for lowend torque anyway. Very rarely will you ever get fully into the power band where that cam will actually be doing any work. Build the motor to work between 1500 and 5500 RPM and it will be much more "fun" to drive on the street.
Mark
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Old 04-06-2016, 10:35 AM
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Quote:
Originally Posted by jokerZ71 View Post
If this is a 93 truck motor, you will need some different heads.The swirl port heads that are on it quit breathing @ 4000 to 4500 rpm.Your cam will just barely be getting into it's powerband by the time the heads die out.They also can only support, a little over 300 HP due to their poor flow.They are designed for low rpm torque, not high rpm HP.
If you already have heads but forgot to mention it, which heads do you have? Casting #, or, brand.
Also,your block is very likely a roller ready block & easily converted to a roller cam/lifter setup. I strongly advise you to consider doing so for performance & longevity.
Yes i did forget to mention heads, the heads i have in mind are Summit Racing heads part number is SUM-152123 cast iron they have 72cc combustion chamber and 165cc runners. Intake valves are 2.020in and exhaust are 1.600in
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Old 04-06-2016, 10:48 AM
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Quote:
Originally Posted by Chevy2500HD View Post
Yes i did forget to mention heads, the heads i have in mind are Summit Racing heads part number is SUM-152123 cast iron they have 72cc combustion chamber and 165cc runners. Intake valves are 2.020in and exhaust are 1.600in
I don't know a lot about that head,but,it appears to be a repro of the old "camel humps" with hardened exhaust seats.
My concern would be that the 72cc chambers may not allow adequate compression to let that cam live up to it's potential.It depends largely on the type of pistons you choose,their pin hgt,& the gasket thickness.
Assuming you use a 6cc flat top piston and engineer a quench(distance from piston top to deck surface plus the gasket thickness) in of about .040",your static compression will be in the 9.5:1 range,however,that cam has a 63* IVC(intake valve closing),which will actually have the real running compression(DCR) down close to 7.5:1.This will make your lower rpm power/torque very soft until you get up into the higher rpm range.That cam is gonna perform it's best with a static compression closer to 10:1.
A 64 to 67cc chamber would get you closer to that.
I know you don't wanna hear it,so,I'll only say it once,you could do a lot better on your cam choice,especially for the use you have stated.

Last edited by jokerZ71; 04-06-2016 at 11:02 AM.
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Old 04-06-2016, 11:26 AM
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With a 64cc head,your SCR will be in the 10.5:1 range,but,due to the late timing of that cam,your DCR will be close to 8.5:1.This would be a lot better,but,depending on how efficient those chambers are,you could start to have detonation problems on pump gas with those iron heads.It will be borderline.You would be far better off choosing an aluminum head.
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Old 04-06-2016, 04:38 PM
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What transmission are you running & what rear gear? That cam is gonna need a higher than stock stall, if an automatic & most likely some steep gears, especially if you have bigger tires.
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Old 04-06-2016, 08:57 PM
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X 2... For same money can get into much more powerful and efficient Vortec iron heads...
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Old 04-07-2016, 12:26 PM
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Aluminum heads, 64cc and 180cc intake runners would be my choice. Dart and World make some nice heads for an attractive price. Shop around a bit. You may do better with a Comp Cams XE series cam over the Thumpr.
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