more on my crappy dyno runs. Advice solicited

[jerry S]

when my car was in PA, it laid down 351 rwhp on a dynojet at 6200 rpm. I got it here and swapped out the distrib and ignition for a MSD 6AL and a pro-billet distrib. Also, the fuel pump had gone bad from the time it left to the time it got here and the putz who worked on it first put on a Scott Drake fuel pump because "it's concourse correct" (like I give a FF).

So I take my car in for a second tune because it is a dog. It puts down 280 then 293 rwhp on a dynojet at 5400 rpm and then dies like a pig at anything over that.

1. could the Scott Drake Fuel pump (I think it is 80 gph or so) not be able to deliver sufficient fuel at 6000 rpm?
2. Is my total timing way off following the install of the MSD? I don't recall which springs we installed.
3. Could it be a carb problem?

 

[2bav8]

Another possibilty is the brand of dyno used. Different dynos types give different results.

An example, I had a 289 a long time ago that dynoed at 180 HP at the rear wheels on a Mustang Dyno. Then, it was tested on a Dynojet and it had 260 HP at the rear wheels with no tune.

 

[jerry S]

Another possibilty is the brand of dyno used. Different dynos types give different results.

An example, I had a 289 a long time ago that dynoed at 180 HP at the rear wheels on a Mustang Dyno. Then, it was tested on a Dynojet and it had 260 HP at the rear wheels with no tune.

both are dynojets. Don't know about the models, but they should be pretty consistent.

 

[ForceFed70]

Falling flat like that above a certain RPM is a common sign of a fuel pump that cannot keep up. It's easy to test tho... get a fuel pressure guage, and play around on the freeway. If your fuel pressure drops below 4PSI, then your pump is unable to keep up.

 

[PoliceInterceptor]

2. Is my total timing way off following the install of the MSD? I don't recall which springs we installed.

I think the fuel pump is probably the problem over 5400, I think Carter makes a nice, somewhat correct looking unit that puts out 110GPH, however.

The Pro Billet for my FE came with the heavy silver springs and a 21-degree stop installed. If you still have the silver springs, you probably do not have the entire advance in before 4000-4500, with the 21-degree stop you probably need to be in the 14-16 initial range starting out to get reasonable total. It is probably not causing the falling flat problem but it could indeed be leaving quite a few ponies in the stable.

Trying another rev limit pill in the 6AL might also be worth a shot, never know what a bad one could cause, of what kind of day the guy putting the stickers on them had.