I remember somebody posting a link to a calculator that told you the optimum size for the primaries and collectors (not the length but the diameter) but I can't seem to find it anymore. Can somebody help me out. Thanks

 

Gee, this is ONLY about 3-1/2 years late, but maybe it'll help someone out...

HeaderDesign.com

(I found this thread while doing a related search...)

 

If you subcribe to that jargon to determine what header to use on a street car, then you have way to much time on your hands.

That info is just for an allout max output race situation.

 

For 3rd gen cars with the following:
350=1 3/4" headers
305=1 5/8" headers

 

wow lol...thanks i guess

 

Do you really want to go with the 1 5/8" header in a camed lb9, or is the 1 5/8" header sufficient for most street applications both in 305s and 350s? I have been sort of trying to figure this out for sometime since I am trying to select a set of headers for my car. I know that many people here have chosen the hooker 2055s, which have 1 5/8" primaries.

 

My choice for the '82 is 1 3/4" to 1 7/8" step headers, 34" tube length and a 3 1/2" collector---only other thing I'm considering is using a merge collector but I haven't really found any good test data on them other then the usual manufacturer's hype...???? But, this will be a 383 solid roller cammed, AFR 195 heads, 12.8 CR on E-85... Obviously a whole lot more header then the average 350 with a mild cam would ever need....

 

Depends on the combo. The primary diameter is directly related to the CFM of the exhaust port on the head.

1 5/8" are fine for most guys. I ran 1 5/8" headers for a number of years when I had a thirdgen and trapped 119-120mph in the 1/4.

Some guys at the time, such as Traxion if I recall, were running 1 3/4" long tubes, but I was running 10mph faster than them so I often wonder if it was overkill. Then again, they had better heads than me.

There is some merit to primary length tuning, but not with the camshafts you guys are running.


-- Joe

 

So would it be worth the money to invest in a set of hooker 2055s, which are tuned, vs lets say the hooker 2460s, which are not tuned? Also, since Dyno Don's headers have 1 3/4" primaries, will that be overkill for my engine and kill performance?
My heads are pretty much stock, with comp cams xr258hr12: 206*int/212* exh. @.05" tappet lift .480"int/.488"exh. lift with 112* LSA?

 

What do you have now?

I don't think 1 3/4" primaries are going to do much for you. And the tunes vs not tuned, if you are referring to the length being equal or not it doesn't matter. Whats worse, having 8 primaries equally the wrong length, or 8 primaries of slightly different lengths? Neither.

I don't know about Dyno Don's headers. I'd compare price, and go from there.

My 119-120 mph thirdgen strip car ran hedman 68470 headers. I had swapped to SLP 1 3/4" with zero improvement. This is on sportsman II heads with a somewhat lazy exhaust port. IF you had say, AFR 195s and a 224+ degree camshaft I'd opt for 1 3/4".


-- Joe

 

Right now I am running the stock exhaust manifolds that came with my 91 lb9 t5 dual cat formula. I know they are a big restriction. I am looking for a set of headers with provisions for the air injection. I want to keep the car emissions legal. My car has been lowered so I don't think I have the clearance for long tube headers. From the choices shorties out there, I have heard that the hookers have some of the best fit in our cars. I want to be able to take full advantage of the cam that I've put in there.