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Head Question
For the last 5 years I've been running a stock piston 400 in my 3800 lb Aspen. It has run 12.80 @ 106.
My combo is 400 stock piston 494/292 cam M-1 Dual plane intake 3310 750 holley, 78/82 no power valve Pocket and exhaust ported 452 heads windage tray 3000 converter 3.91 gear My question... I just got a set of 516 heads given to me today.. I guess they have the smaller (1.74) exhaust valve... Will the I gain much by swapping these closed chamber heads on the motor ( it should work out to a full point in compression) even though they won't be ported??? If I have time I might clean up the bowls..I don't know.. |
#2
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Regardless of what people say here those heads can be made to flow with any production headported or not! But to get the results you want money needs to be spent at the machine shop! Go with 2.14 & 1.88 valves and spend maybe 50 hours with I die grinder (I did) and you can have a set of heads that will flow with the best of them. I supopse will support 600 H.P no problem! The heads will also result in 3/4 point more compression over open chamber heads (906,452 etc). The small chamber will be fast burn remeber to polish the chamber as much as possiable. Make a mirror with them. You can spent a unlimited time porting heads Just remeber the bowl area and short side radias is were it lies as power gains! Over stock heads I belive there may be 3 to 5 tenths floating in there! If done right over stock heads!
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516's are a good head. Some have posted info here that says they are crappy, and some that says they are great. All I know is that ALL aftermarket heads are closed chamber design, as seen on the 516.
You won't see a full point of compression though. I inputed the numbers at www.kb-silvolite.com and find with the 516's(and a .040" head gasket) your up to a little less than 8.2 to one comp.(up from 7.5) Stock piston only comes to within about .110" of the deck. I don't agree with the idea of needing bigger valves. As I've brought up before here, the 500 horse 427cid SB chevy crate motor only uses a 2.08 intake and 1.60 exhaust, just like the 516. Also a more recent hotrod showed a naturally aspirated racing boat engine that made over 1000 horsepower by 6000 rpm. The collectors on the headers were enormous, it was about a 30000 dollar race engine, with just less that 600 cid displacement. The exhaust valve on this monster? 1.80" That's it! In any case, I don't think the 1.60 valve will limit the horsepower you make, but if you are wooried, you'll need to put seat's in the exhaust valves anyway(the head casting is about as hard as cheese, and will sink badly if run with unleaded), so that's a good opportunity to step up to the 1.7? the newer b/rb heads came with. |
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