long tube headers

[turbo2256b]

In general the 1 5/8 primary non equil length shorties are the best. The shorty equi lengths not realy worth it with all the turns and twists, they had to go to 1 5/8 just to do better than the 1 1/2" shortys.

[gadget73]

I think the equal length gained like 1hp over the non-equal on a stock motor, for all the nonsense involved in fitting them and changing the spark plugs. There used to be a chart around somewhere of headers on a stock HO, and the best gains were a 1 1/2" equal length. I think it picked up 6 hp or something over the stock HO header. The non-equal was 4 or 5 hp over stock.

End of the day, it was small gains for the effort. With better heads, it would make more difference but the stock exhaust port size and shape just doesn't move enough air to really justify huge efforts.

[turbo2256b]

Stock HO headers are perty much a joke just look at all the dents and crushed areas in the tubing. Bet the old 289 hipo cast iron ones woud do better. If I still had all my data on flow rates based on pipe dia and bend radii and number of bends the non eqi 1 5/8s fewer bends more straight sections would flow more than a bundle of snakes with a lot of minum bend radii. All those bends also affect the return wave that helps extract the next pulse so eqi lenght headers so each indivual pipe with different bends is going to have a different return pulse.

[johnunit]

I think the equal length gained like 1hp over the non-equal on a stock motor, for all the nonsense involved in fitting them and changing the spark plugs. There used to be a chart around somewhere of headers on a stock HO, and the best gains were a 1 1/2" equal length. I think it picked up 6 hp or something over the stock HO header. The non-equal was 4 or 5 hp over stock.

End of the day, it was small gains for the effort. With better heads, it would make more difference but the stock exhaust port size and shape just doesn't move enough air to really justify huge efforts.

Pipe sizing is a whole different thing, too. 1 1/2 would probably stop being ideal near the top of the rev range on a stock engine, and then 1 5/8 is outgrown surprisingly quickly. I think when I was playing with the mega-bucks engine sim a few years back, I found that by the time I went GT40 or ported heads on my 351W I was better off with 1 7/8.

[turbo2256b]

Pipe sizing is a whole different thing, too. 1 1/2 would probably stop being ideal near the top of the rev range on a stock engine, and then 1 5/8 is outgrown surprisingly quickly. I think when I was playing with the mega-bucks engine sim a few years back, I found that by the time I went GT40 or ported heads on my 351W I was better off with 1 7/8.

A lot of those apps just go for max power which could leave a lot of midrange in the dust. So peak power coud improve 20HP but at a loss of 40 50 HP in mid range areas. Its just like too big of an intake system costs low and mid range in the same way. Cam choice same deal.

[johnunit]

A lot of those apps just go for max power which could leave a lot of midrange in the dust. So peak power coud improve 20HP but at a loss of 40 50 HP in mid range areas. Its just like too big of an intake system costs low and mid range in the same way. Cam choice same deal.

This was Engine Analyzer Pro, so I was basing it on the whole rev range from 1500 RPM to whatever the engine I was simulating could survive. I think for header sizing I was looking for not hurting power above 2500 or 3000rpm.

[packman]

Anderson Motorsports makes 1-3/4" shorties. I am considering these if the Dougs Tri-Y don't work.

Packman