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In search of 1HP per Cubic Inch
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Author:  mopar_nocar [ Sun Jun 17, 2007 3:52 pm ]
Post subject:  In search of 1HP per Cubic Inch
want to build my second ever hopped up slant. i would like to build it to make 1 HP per cubic inch.(Naturally aspirated) how about a recipe from the more experienced out there in slant land? on hand thus far, i have 1.7/1/44 oversized valves and that's about it.

i'm probably going with a 10" or 9" convertor behind it, in a 904. 3.55 gears are already installed, and current weight with a SB is 3200 (w/driver).

in all, 1HP per Cubic Inch should put me into the mid to low 15s range, which is FINE. faster would be even better, but NOT required.

sb
Author:  mopar_nocar [ Sun Jun 17, 2007 7:38 pm ]
Post subject:  wow
28 views and no responsese. guess this is the wrong forum. sorry.

sb
Author:  tophat [ Mon Jun 18, 2007 6:55 am ]
Post subject: 
I am no expert but a few suggestions.
4bbl intake. hyperpacks are VERY expensive now, but aftermarket intakes are affordable.
As much cocompressions your fuel can stand, prolly mill the head and block.
Port the head.
Dutra duals or headders
as for the cam somebody else will have to chime in

1 hp per inch is doable but not easy without poweradders

hope this gives you a start, and sparks some interest from others
also do some searches here, lots of good info in the archives


I would like to try 1 hp per inch with my 170 once I pull it out of my dart (that is a ways off)
Author:  Dan-o [ Mon Jun 18, 2007 8:37 am ]
Post subject: 
1hp per cylinder is easy, any well built/desined motor should be cabable of that. it when you're doing 1.5+ thats hard.
Author:  slantzilla [ Mon Jun 18, 2007 9:57 am ]
Post subject: 
Mine is well over 225 N/A. 1 per is relatively simple.

Mild port job on the head to match the O/S valves. You may want to ditch the 1.44's and go with a 1.50". Mill the head at least .060"

Offy intake and a 390 Holley. I've run low 14's w/a 390 on motor, and 12.00 on spray.

Headers.

Cam with around .500" lift and about 230*@.050" Stock 340 valve springs will do well. You will probably need a set of custom length pushrods from Smith Brothers.

Mill the block at least .100" and stick with stock rods and pistons.

That should put you right where you want to be for motor. :D
Author:  Doc [ Mon Jun 18, 2007 10:34 am ]
Post subject: 
A basic rebuild with more compression and a cam is all that is needed with the short block.
The real power will come from the cylinder head.
DD
Author:  mopar_nocar [ Mon Jun 18, 2007 1:13 pm ]
Post subject: 
cylinder head: gasket match intake and exhaust, tapering down into the port....pocket porting behind the valves, smoothing up the combustion chambers (will i need to unshroud any with the 1.7/1.44s?).
mill it .060

did i miss anything on the head work?

sb
Author:  Doc [ Mon Jun 18, 2007 2:24 pm ]
Post subject: 
Back-cut the valves, use thinner valve stems.
Thin-out the valve guide boss in the pocket.
Relieve the combustion chamber walls (sides) around the valve heads and seats.
"Line of sight" port passage work to help reduce the bend. (and improve flow)
Multi angle valve seat grinding. ("3 angle valve job")
Set the valve spring pressures at the minimum needed for the cam profile you use.
DD
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