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Rebuilt Engine Power?


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hey guys, i just got my engine rebuilt, and i was wondering about how much horses it should push. its bored out .020 with oversize pistons and rings. head and intake port matched, along with a 60mm TB thats also bored out. All new valves, 3-angle valve job,cold air intake, MSA Camshaft kit, Stage II. rods and crank polished and balanced. Resurfaced flywheel with 4lbs taken off. MSA 2 1/2in headers, 6 into 1. no cat. 3.9 rear end, with a 2+2 clutch and 5 speed tranny.... im thinking about 220-240 at flywheel? what do yall think? ahh, no AC to take away horespower too....

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Guest bastaad525

There's really no way to know... you can only find out by dynoing or taking it to the track really. Problem is you can see two setups you think are pretty close or even identical, but they'll put down a notable difference in power... every tiny little thing makes a difference.

 

But I will say, I ran a very similiar setup to yours a few years back in my '80 ZX, 2.8L block bored .060 over to make it (technically) 2.9 liters, flat top pistons and a mildly worked N42 head, giving 10.3:1 compression ratio, mild street cam (480 lift 270 duration), 60mm TB, 3-2-1 headers, free flow cat and straight thru muffler, stock five speed, 16 lb flywheel, ACT pressure plate and 6 puck clutch, 2.5" exhaust, 3.9 diff, and put down only 145rwhp on a Dynojet dyno. That factors to roughly 170 flywheel hp. I will say, my EFI was not running 100% perfectly. At first with this setup it ran way lean and pinged on top, then I added an adjustable FPR and upped the fuel pressure a little... but there were still bugs. I later dropped that drivetrain into my current 240z, and swapped out the EFI for a set of newly rebuilt Ztherapy SU's. Back to the dyno and the best I could manage was 170rwhp, about 200 at the flywheel. I would expect about the same from yours, if you're EFI is running well... maybe more since you have a bit more work than I did (polished, balanced crank... upgraded rods... not sure what that might add).

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Guest bastaad525

Hmm, well in my guesstimated 2800lb ZX, it was good for a 15.3 (that was the 145hp EFI setup). In my 240z which I had weighed and came in at 2300lbs, I was never better to pull better than a 14.8, but think I could have done better if I'd figured out how to launch w/o bogging or spinning the tire thru all of first gear and half of second... probably could have gotten maybe a 14.5? You didn't specify what car you're running this in... in a 240 it should be good for a low 14 to mayyyyybe even a high 13.

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Well lessee here. A .020 overbore is good for about 2 cubic inches, or say another 2 hp. Rods, crank, and flywheel obviously add no power. Unless you paid $1500 for head prep the valve job is probably no better than stock. Without more compression and serious head rework a cam is good for maybe 12 hp somewhere in the rev band. Cold air intake and headers, maybe another 10 tops. I'd say 220-240 is 20-40 optimistic. But I could be wrong...

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