desktop dyno please
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desktop dyno please
hi guys - my old DD ( was replaced 3 years ago ) has a 428 cj and would like to know the hp i was making - looking to freshin up the engine and put it in a 4x4 im building - ok so the specs
428 CJ - stock stroke
.060 over bore
balanced
comp cams 268H cam
Edlebrock performer RPM intake ( port matched to heads )
Holley street 770 cfm
ported and polished 390 heads ( off a late 68 stang ) shaved .020
sorry no casting # - will go look if i need to -
10.7 compression ( if my numbers are right )
and i have the original cj heds - but one was f#$ked ( cracked )
is it worth finding another set / one - or are the edelbrock heads a good choice ? any info - thanks - dan
428 CJ - stock stroke
.060 over bore
balanced
comp cams 268H cam
Edlebrock performer RPM intake ( port matched to heads )
Holley street 770 cfm
ported and polished 390 heads ( off a late 68 stang ) shaved .020
sorry no casting # - will go look if i need to -
10.7 compression ( if my numbers are right )
and i have the original cj heds - but one was f#$ked ( cracked )
is it worth finding another set / one - or are the edelbrock heads a good choice ? any info - thanks - dan
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food for thought
i though i might add that the truck is a 73 f100 long bed 2wd - slight lift with 33.12.5 tires and a c6 - Strange 9" with 4:10 and a detroit - ran 13.93 @86MPH at the the local track ( with borrowed 30 " slicks ) ran to the 6000 prm shift in first then smoked in second - third was painfull - truck was towed home due to tranny issues ( lost every gear but R ) - havent drivin her since - also think i burned a ex valve because low compression on # 7 ( leak down / air can be heard in the headers ) - will find the time slip if i can ( was 3-4 years ago ) - was a killer ride - thats why i think it will find a new home in my 4x4 ( with 44 inch tires / weekend killer )
Post Fiend
Joined: Jan 2003
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From: Iowa
I'll assume you're running headers and mufflers. Assuming a good port and polish on the 390 heads, you'd gain nothing with Edelbrock heads except you'd lose some weight off the front end.
In desktop dyno, I'm getting an even 400hp @ 4500rpm, and 512ft-lbs @ 3000rpm. If you put CJ size valves in the 390 heads, make that 422ft-lbs @ 5000rpm, and 515ft-lbs @ 3000rpm
With that cam and that compression ratio, I hope you like pinging! Because that's what that motor will do a lot of. It needs a bigger cam. I suggest the Comp 292h. That way you'll at least be in the ballpark for dynamic compression ratio for pump gas. Plus, you'd be able to keep the rpm's up to keep the tires clean.
In desktop dyno, I'm getting an even 400hp @ 4500rpm, and 512ft-lbs @ 3000rpm. If you put CJ size valves in the 390 heads, make that 422ft-lbs @ 5000rpm, and 515ft-lbs @ 3000rpm
With that cam and that compression ratio, I hope you like pinging! Because that's what that motor will do a lot of. It needs a bigger cam. I suggest the Comp 292h. That way you'll at least be in the ballpark for dynamic compression ratio for pump gas. Plus, you'd be able to keep the rpm's up to keep the tires clean.
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thanks for the info - i was running 92 oc. and moved the timing back - when i was a at the track i was on 101 oc and some agressive timing curves - and it would ping on the 92 when i towed or when it was hot out ( high 90 + ) - the headers are 1 7/8 hooker super comps - and 2 1/2 " - h pipe - 40 flows also - can this engine be bores .080 ? or is sleving the only good option - concidering real 428 cj blocks are getting hard to find -what compression should i shoot for ? i was thinking 9.5 or 9.0 -
FE "Freakin Expensive"
Joined: Dec 2003
Posts: 6,461
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From: Smith Mountain Lake, VA
Well I wouldnt do a 390 block at .080" over without a sonic check....and you can run the CR uo there..I think Polcat is running around 11 to 1 with Iron heads even..but the cam he's running bleeds off some of the CR.. He runs 93 Octane with the timing turned back on the street and Fast Gas at the track with the timing turned up..
RJ
RJ
Post Fiend
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From: Iowa
So what block are you running now? A 390 block or a 428 block?
In either case, the answer is the same. Get it sonic checked, and bore the least amount needed, with consideration given to available piston sizes.
In either case, the answer is the same. Get it sonic checked, and bore the least amount needed, with consideration given to available piston sizes.
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the block is a 428 cj - it was bored .060 insted of .040 when i had it done last due to #8 had a broken piston that scored the cyl ( was .030 when i got it ) - dont really want to go .080 over as the pistons would be $ - so i was going to sleave it and go with stock or .030 - i want to replace the heads as im pretty sure i have a burned valve and the valve heights were all screwed up afteri got the valve job ( i hate that machine shop ) - he said he couldnt help it as the seats were f up -
