headers

[Mr. Belve]

What is the performance difference bet having 13/4" primarys to 2"? The motor is a st/strip 440.

[Ausydad]

I think it's gonna have a lot to do with the cfm's you're pulling through. If you have a large plenum intake with big carb and high flowing heads, maybe 1 7/8 or 2" would work. If you have a 6bbl set up with mild cam and no more than pocket ported heads, 2" may be much and hurt your performance. So, it depends on your RPM range and cfm flow as to which will give you better performance. How 'bout some more specs to look at and help with?

[Dart]

A lot of it has to do with your primary tube length...

If you are running the fenderwell 2" headers the primary tubes are like 54 miles long and those will certainly not help. You will need some serious heads, compression, and cam for it to go.

PRO had the fenderwell headers on his 383 and it wouldn't rev over 4800rpm.

[Tarrbabe]

Dart, I dont know what experience you have with headers, but size will not limit RPM. Performance during RPM will be affected, but RPM will be dictated by other factors. Only time I had headers limit RPM was when they came loose from heads and engine wouldnt rev past 3500 and backfired. I used 1 3/4" on my 340, Hooker. Worked very well.

[Dart]

I am not saying that the headers were the only factor. The 383 was fairly mild and the heads were stock. The 2" primary tubes compounded the other problems...does that make sense?

[Tarrbabe]

I understand the combination of mis-matched parts but from your post, I got the impression you were blaming the headers. You talked of the 383 with problems, I feel that the 440 needs the 1 7/8 or 2" for a healthy engine. If you are running a stock 440 you can get by with 1 3/4" and they will help the performance. Add pocket porting, intake, carb. and a street/strip cam, and I belive the additional size is needed to adjust to the additional in-charge. Mis-matched parts are the biggest problem facing hot-rodders (in my opinion, and Mother Mopar, that's why they put out the package setups for all the different classes). I don't follow everything mopar says but they spent millions working out things to help us and I like that they help when they can. I'm hope I don't come across like I'm preaching, but I belive sharing information is our greatest assets. - Just thinking out loud.

[jelsr]

Not saying yea or nea for anything, just FYI. A given engine will have a given power band. Shorter primaries will move the band up the scale, longer will do the opposite. Same with larger and smaller. My engine (see below) is relatively large and I'm running small dia long primaries. It will pull like a bear from 3000 to 6000 and then noses over noticeably. Oval track requires quick exits from the corners not high velocity at the end of the straights. The big thing is to make everything match and work together as Tarrbabe pointed out.

[Tarrbabe]

Old Engine Book -
General Performance - 1 3/4" x 36"-42" primaries, 3" x 12" collectors
361-383-400 Bracket 1 7/8" x 36" primaries, 3' x 12" collectors
440 Bracket 2" x 36 primaries, 3 1/2" x12" collectors
383 - 400 4 bbl Super Stock
2" x 34" primaries, 3 1/2" x 12" collectors
440-6bbl and 426 Max Wedge Super Stock
2 1/8"x36" primaries 3 1/2" x 12" - 18"
426-440 Grand Nat. 2 1/4" x 36" primaries 3" x 12" w-H pipe