'Bochawa72

I finally got my car on a dyno and the 383 I bought from T&L(now out of business) doesn't perform anywhere near the promised numbers. The dyno sheet I got with my motor showed 460hp and 450tq. Now in the car and on a mustang dyno it put out 258hp/294tq. At the time of purchase the practices of T&L were not known to me. Well I know now and the recent disappointing dyno run has got me wondering what I have under the hood. Here's the dumb question. Is there any way to tell what I have without pulling the motor and taking it apart.?

SuperBuickGuy

that's well within spec - losses in the power train can be 25%-35% (sometimes even more depending on gear ratio). The numbers you have on the motor are (probably) without anything attached to the motor. Things like transmissions are huge power users (especially automatics)...

Also, dyno numbers - was it with accessories? with electric water pump? with exhaust?

and now that I've typed all that, your motor is about right - maybe could use a tune to maximize potential, but even so.... it's pretty close.

with the limited info you've told - you could probably get the rwd hp to 300-315 with tuning and maximizing things like exhaust (headers, high-flow mufflers, large pipes), underdrive pulleys, better air intake (like cold air)....

427Hotrod

Mustang Dyno's read lower than Dynojets in addition to all the other things noted. You can pull a valve cover to see what heads are on it for sure unless they are aluminum with markings on the outside.

Run a compression test....

Tell us what you *think* is in the motor and give us the RPM that it peaked TQ and HP or post the runs for us to see.

What was timing etc?

Headers? Manifolds? Carb, trans etc? Give us some details..


JIM

'Bochawa72

Good points guys. I understand the mustangs read lower than the dyno jets. But I was expecting around 25% loss. Not 45% and 35%. I'm not sure how it was tested by the builder to get the 460/450 base numbers.

My car was used at a race shop for a EFI project. I had the FAST XFI system installed. It was run on the dyno before the install then run again after the install/tune. The before test showed 260/300 and that was with a RPM Airgap under a Holley 770 CFM Street Avenger.

Here's a bit more detail on my 383 set-up. I have 215cc Dart Pro 1 alum heads. Comp cams 276HR-12 hyd. roller cam. 10.25 compression. I'm running Hooker SuperComp sidepipes with the STS baffles. 355 gears in the back and I've got a TKO600 with .64 overdrive. I forget where I had the timing set and I don't know where it ended up after the EFI install.

That should cover it. I don't have the before and after EFI dyno sheets yet but I do have the sheet I was sent with the engine from the builder.


So do the new numbers(258/294) still sound right? I'm hoping to get the new dyno sheets soon. I'll be sure to post.

Doug1

I have spent a little time looking at 383 strokers on craiglist, then I realized how difficult it is to know, since everything is internal only. The fact that his builder is out of business is big time red flags, I hope what he is concerned about is not what actually happened...

fishslayer143

what your builder sent you , is a Gross HP number, engine only, no accessories, headers only.. with a manual trans you should not lose 25% to parasitic drivetrain loss.. it should be more like 15-20% at your power level.. or about 90HP loss..so your current numbers are low , you should be 40-50 hp higher .... that dyno sheet may not be really from your motor....that said, a 383 can be a very strong motor, mine dyno d at 525Hp in my 81..

Doug1

uh oh...Bochawa is gonna wanna kill someone