[bob460]

Soon ill have my 545 (p51 heads,10.8 comp,hyd roller cam,950 carb), which makes 635hp at 5800 and 640tq on pump fuel ready for some custom made headers. My question is what size should i use 2, 2 1/8 or 2 1/4 inch and which is better for the street 4 into 1 or tri ys. As im worried the car is pretty low so im thinking of using tri y. What do yous think.

 

[bigblok86ranger]

Not trying to be a dick but why is hp and tq so low with such a big engine? Something seems mismatched. I would expect 100hp more out of that combo of cubes and heads.

I would think 2 1/8" would be a good size for the primaries and I have heard properly set up tri-y's are usually worth ~10-15hp.

 

[bob460]

Its a hydraulic roller cam perfect for the street the specs of the cam were roughly 256 duration 620 lift 112 lobes i think, a solid roller would have made a little more but not 100hp more.

 

[bigblok86ranger]

As long as your happy with it thats all that matters apparently you weren't going for max hp, Like many people do.

 

[White Lightning]

For your cubes (and the deciding factor will be "what RPM range will you be running in"?) I'd suggest a set of 2" primary tubes, a 4 1/2" true merge collector and tubes in the 28" to 32" range. If you step up in cam and carb specs and want to run higher RPMs (more CFM) then the 2 1/8" primary tubes and a shorter tube length might benefit your combo. Remember, velocity and exaust gas temp are our friends! LOL Hope this helps.
Rob

 

[bob460]

Just talked to the guy who is going to build it and said to go 2 inch stepped into 2 1/8 inch into 3 1/2 collector ceramic coated, he also said that a well designed tri ys which they use on sprint cars might be even better with the low revs and heaps of cubic inches it will make more torque. See what happens.