HP increase manifold->headers

[mhjo]

I have done some tuning up on my 289 (performer intake, new cam, MSD etc..). Still, I am running on stock manifiolds. justwonder:

how much HP increase will I gain by:

- installing HiPo manifolds
- Shorty headers
- Tri-Y headers

Will I notice any increased exhaust noise in passenger compartment by installing headers?

 

[rbohm]

hipo manifolds add about 15 hp, shorties perhaps 20-25, and tri-y's about 25-30. and yes you will have an increase in interior noise, though how much depends on how the exhaust system is designed, and the mufflers you use.

 

[allcarfan]

I think those numbers may be a bit generous to be honest. With those three different setups you listed, you should not ask how much more HP you will get but how they will effect your torque curve...thats what is going to make you faster.

15hp across the board is going to make your car a better performer than 25 more peak HP.

out of those three, i suggest the tri Ys....great for bottom end torque. Interior noise would be nominal. If you are worried about it though, just put sound sound dampner between your firewall and carpet.

 

[GaPonyFarm]

The Tri-Ys are pretty much proven to work best on slightly modified small blocks. You figure K-Code 289s used Hi-Po Manifolds, Shelby could have done the same but opted for Tri-Ys for racing... I'm guessing he had a good reason. I'm simply not a fan of shorty headers.

No scientific evidence, just historical. BTW, you can get ceramic Tri-Ys for around $150.00, IIRC, from Va Classic Mustang.

 

[golf4283]

get full length's. you will get the most power out of all them.

 

[calpolymustang]

long tubes are good for top end, but tri-ys scavenge better so the bottom end is better. with stock heads, it shouldnty make much difference. on a 289, 2.25' pipes should help more than the unnessasary 2.5', which hurt torque on a small stroke engine. the sound is a better reason to get headers than just the HP, its not going to be a night/day improvement, but the sound will make it seem beefier