1989GTATransAm

iTrader: (3)

I had a set of custom short/mid tube headers made to fit my car and allow me to use the exhaust termination boxes. Here are the results from the engine dyno.

The test was against a set of 1 3/4 inch long tube headers versus my chassis fit custom made 1 3/4" short-mid tube length headers. Joe Sherman could have wrote the script ahead of time on the results.

Basically my headers were down to the long tube headers at 3500 rpm 438tq/292hp to 406tq/271hp. From that point on the custom headers started to make a comeback and at 5000rpm the long tube headers were at 469.6tq/447.1hp and the custom headers 462.2/440trq. From then on to 6500rpm it was somewhat of a seesaw. The longtubes averaged 1.4 more horsepower over that span versus my chassis fit custom headers.

So with my 4000rpm stall I don't think I will be giving up much power at all for the rpm range I will be running down the track. Peak torque was at around 5000rpm and peak horsepower was at 6500. Shift point will be at 6800rpm as that is when the power starts to nose over.

Best dyno numbers with the long tubes was 526 horsepower at 6500 and 471 torque at 5200rpm.

Best dyno numbers with the short tubes was 524 horsepower at 6500 and 466.5 torque at 5300rpm with the same conditions.

We switched to Mobil one and let the intake manifold cool off but kept the oil hot and we managed to squeeze out 535 horsepower out of the short tube headers. This motor only likes a total of 30 degrees timing.

So bottom line above peak torque there is virtually no difference. Below peak torque you start to give up some power and torque. A lot of us have to much power down low and are trying to kill torque. So let's say I'm quite happy how things turned out. When this motor goes in my car I will loose very little power from the dyno with the these headers. The power loss will come from the accessories and the drive train.

LilJayV10

iTrader: (5)

Interesting post. I have read of several people going 10's on shorty headers.

Do you have pics of your shorty headers? I am wondering what they look like compared to my dyno don headers.

Shinobi'sZ

It's great that you did this kind of test. Do the custome 1 3/4" (assuming not Dyno Don's) headers that you have terminate where the stock Y pipe connects to the stock exhaust manifold or did you take them down to the cats?

Thanks

1989GTATransAm

iTrader: (3)

They are custom because I'm using exhaust termination boxes. They have to be constructed in a certain fashion in order fit and the collector pipe to exit into the boxes. No they do not go to the cats. I have no doubt that Dyno Don's short tube headers would perform the same way.

There have been other people reporting the same results with a nice set of short tube headers. Mainly above peak torque there is no difference. My headers were not coated with a thermal ceramic coating either for the test. I think once they are coated that will help them some more.

They can be seen in this video of the dyno pull.

http://www.youtube.com/watch?v=WTT4Jf3CqFQ

And in this thread.

https://www.thirdgen.org/forums/tpi/...o-results.html

ericjon262

how do you define a short tube header? I would refer to the headers in your other thread as mid length, those are the longest shorties I have ever seen.

1989GTATransAm

iTrader: (3)

"those are the longest shorties I have ever seen."

Look at the very first sentence at the top of this thread. I called them short/mid length tube headers. On average they are probably a couple of inches longer than Dyno Don's regular short tube headers. They also have more bends in them which is not the best for the exhaust system.

ericjon262

sorry, I was skimming. they look like top notch pieces, I would love something like them for my car, but I don't have anyone in my area who makes headers, and I don't have the time to do it myself.