Technical > Matt Shaff's Engine Shop

sbc HP per cubic inch

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digster:
Matt
  Many variables but in your years of dyno sessions have you seen any patterns develop as to best sbc bore stroke (sweet spot).
I've been making 700hp @ 6000 RPM. 4.125 bore X 4.00 stoke. My set up needs 750hp @ 7500 RPM. My new heads and cam will get me there.
Going to freshen up a bit in the off season. Just wondering if I need to re invent the wheel bore and stroke wise or if the 434 chev is still a good choice for this range? Thanks   

masracingtd1167:
A lot of the bracket guy's that I know run that same bore and stroke and run very fast with it . A good pair of heads should really make good power . There are some really good 23 degree heads out there .  2http://www.speierracingheads.com/ 

digster:
Thanks 1167.
 I run Brodix - 12 15 degree heads. My Old heads flowed 360@ .700. The new 12's are a solid casting with more porting. They flow 390@ .700.
I'll get my goals with a few updates to the old engine. Starting to second guess the set up. With comments like.  Not enough rod ratio (6 in rod). Not enough piston dwell time. Need a shorter stroke and spin it harder. Not sure if I agree with these guys. Some good things are hard to change.
 

masracingtd1167:
I didn't know you were running a rolled over head . You should be able to make big power with a head like that . I use an 18 degree head on mine but I do run a shorter stroke 3.625 and a 4.155 bore . I agree you might have to spin it a little higher to get the results that you want . I think you should be able to make over 800 HP with it .

Frontenginedragsters:
Digster:
 As we all know the engine is a air pump.
Dyno testing shows us that as long as torque continues to rise with RPM then the HP numbers rise also.
Its how the math works on a dyno. Torque x RPM divided by 5252.
It would help to know what heads, intake and camshaft you are running now.

Matt

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