View Full Version : Horsepower 383 Sbc?
How much hp do you think my soon to be finished 383 actually 384.5 cu.in will make?
Edelbrock Rpm 64cc straight plug heads, Air-gap intake, Holley 750 vacuum sec, Comp cams Xe268r solid roller, 1.52 roller rockers, fully balanced engine, static compression 9.89
rocketman
02-25-2006, 05:18 PM
400-430.
Sparky67
02-25-2006, 06:03 PM
How much hp do you think my soon to be finished 383 will make?
Edelbrock Rpm 64cc straight plug heads, Air-gap intake, Holley 750 vacuum sec, Comp cams Xe274r solid roller, roller rockers, fully balanced engine, static compression 9.7
Hmm, I would say 445 to 455 HP. I admit that my 383 solid roller just made a little bit more.. 612 hp with dyno sheet. It is a little more radical than your build, but I had another 383 that had similar specs and it made around 455 hp on the dyno.
Jeff
streetk14
02-25-2006, 09:31 PM
The dyno in my head says 450 hp :)
Lowend
02-26-2006, 09:03 AM
I'm guessing in the mid 400's. That is really low compression for that engine setup.
Are you using dished pistons to get compression that low? With flattop pistons your comrpession should be in the mid 10's
-18cc pistons are used, but the compression is a unknown for me because the engine block has been machined and i dont know by how much. The smallest number possible is 9.7 my is guess: 9.8 - 9.9
The engine made 233 rwhp and 260hp @ flywheel :banghead: everything is new or in very good condition.
What´s wrong?
jerome
08-03-2007, 10:19 AM
so you dynoed it in the car and dynoed it on a stand?
was the carb tuned at the dyno?
was timing set correctly, does it bog when you drive it?
need more info on the problem to start guessing.
Jerome
ponchopwr70
08-03-2007, 10:41 AM
Somethings wrong. My 388 made 318 rwhp with my crappy exhaust, and I have old school type heads.
jasonsnova
08-03-2007, 11:51 AM
seems off i would of guessed 440 fwhp....????? something isnt right!
6'9"Witha69
08-03-2007, 01:24 PM
That thing has some serious issues. Are the springs correct to the cam? What about timing? Carb adjustment? Check the ignition system including full 14 volts to the coil (this is VERY important). What size exhaust and headers are you running?
josh@scotts
08-03-2007, 02:00 PM
yo ponch i think your heads are robbin ya..
josh@scotts
08-03-2007, 02:04 PM
and for 383 , is vacuum secondarys workin go double pump 750
ponchopwr70
08-03-2007, 04:46 PM
Josh they are prob hurting a little but they have been ported and polished by a very good machinist. I just bought 1-3/4 headers and 3" oval x-pipe, my exhaust is def killing it. I'll dyno it in a month or so but at least I'm in the 12's (on street tires) Hey 383 I would check your timing and if your vacuum secondries are opening like others have said.
Steve Chryssos
08-04-2007, 10:49 AM
The engine made 233 rwhp and 260hp @ flywheel :banghead: everything is new or in very good condition.
What´s wrong?
I'm sorry to hear that. Never guess at compression. Start here:
http://www.rosspistons.com/calculator.php?Units=English
If you don't have all the answers to fill in the blanks--get them from your piston manufacturer/engine builder.
From there check the stupid stuff first--starting with a check for wide open throttle. At 9:1 with a good hydraulic cam and a 170cc runner head (which is what you have), you should be able to generate 1 HP per cube. 10:1 (which I don't think you have), 200cc heads and a roller, you should be able to generate 1.15-1.2 HP per cube.
At 260HP something should have appeared very wrong on the dyno if you have a problem such as ignition timing, ring seal, bad cam lobe. Lazy, "popping/farting/banging", smoking, nosing over, etc. Any of that happen?
Damn True
08-04-2007, 11:00 AM
Another thing to check would be the degreeing of the cam.
Nope, the car and engine runs like a dream and the carburator is tuned with broadbandslambda. The valvetrain is the correct one for the cam, exhaust size: 1.5/8 to a dual 2.5" pipes. 13.5volts to the Hei distributer.
So probably there must have been something wrong with the dyno itself.
Morgan
08-05-2007, 06:42 AM
Your engine specs are not too far off from mine and I made 502 HP on pump gas at 5900 RPM. Also made 495 Ft Lbs at 3400 RPM.
You can see the dyno printouts on my website if you are interested.
The printouts looks exactly like mine, strange. My peaktorque was at 3300 and peakpower at 4930 but with totally different numbers.
Steve Chryssos
08-05-2007, 08:17 AM
Well if it's running smooth, then I'm concerned that your compression is way off. Maybe they shipped you a set of 72cc heads? Should be easy enough to confirm based on part number. Might be cast into the head under the valve cover. 72cc plus -18cc dish plus your healthly cam would give you very low static compression and dismal dynamic compression.
If the heads are right then worst, worst case scenario, you have 9:1 which should still make 100HP more at the flywheel. Your engine and chassis numbers are in line for the most part, so I would keep digging for an answer.
Edelbrock 60899 is the heads i have and use (64cc), KB pistons that i use (KB135) have a -18cc dish that will make 9.71 in compression (well in the recommended area from the cam manufactuer: Comp cams) The block is milled 1 hundreds of a millimeter as well.
A have reason to believe (after some snooping around) that the dyno i tested doesn´t work probably with automatic transmission without lockup or that the numbers can`t be accurate (says enginebuilders i have talked to) :hand:
I will check if the secondaries opens as they should.
I have changed the secondary spring so that they open earlier at lesser vacuum.
The differance was noticeable but just that.
malihoochie
08-13-2007, 01:44 PM
How was the HP at both flywheel & the rear wheel determined? I am shocked that you could lose only 27hp through the driveline.
andrewb70
08-13-2007, 03:19 PM
Time to get the car scaled and take it to the drag strip. The MPH is a very accurate indicator of HP.
Andrew
DarkoNova
08-13-2007, 07:16 PM
Time to get the car scaled and take it to the drag strip. The MPH is a very accurate indicator of HP.
Andrew
That's what I was thinking. It's also what I was told. I've got a pretty stout 355 and I only got 265 hp at the wheels. The guy said he's had guys come in with built 383's with high compression, big cams and AFR heads and make the same power. I didn't believe him, but it looks like maybe he was right. My guess is his dyno is totally off. What kind is it? Supposedly Mustang Dynos give pretty low numbers.
I plan on finding a local dragstrip and making a few passes to see what's up. You should probably do the same.
Matt
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