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Old 08-19-2012, 07:25 AM
ArtNJr ArtNJr is offline
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Vehicle: 1998.5 Dodge 2500HD 4x4
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Engine: 1998-1998 359ci (5.9L) Cummins ISB 24-valve Diesel I6 235hp 420lb/ft (manual), 215hp 420lb/ft(auto)
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Quote:
Originally Posted by Dodge Boy13 View Post
hey im looking into headers for my 98 5.2l just looking for some suggestions as to the similarities and differences and which would be better and brands
Dyno tests conclusively show that headers with less than 30" long primary tubes do not make anywhere near as much power as headers with 30" or longer primary tubes. Also, the tube diameter needs to be the same as the exhaust port to speed exhaust gasses out -- large tube headers are ONLY for engines designed to run high rpms all the time, are supercharged, etc. -- large tube headers just kill low-end power on a normally-aspirated engine without serious head work, cam, etc.

And the small valves / combustion chambers on the 318 engine require small tube but long length header tubes -- 32" long for best HP, 36" long for best torque. Then add a NASCAR style X pipe in the middle of the exhaust system to balance out the uneven firing order of each bank of cylinders -- more HP & torque both & better fuel mileage too.

The engine itself is an "even-fire" engine, firing every 90 of crankshaft rotation, but if you look @ the firing order, 1-8-4-3-6-5-7-2, you will see that the exhaust pulses coming out of the right head & the left head are uneven. Just consider what's coming out of the left head in terms of engine firing order: 1 - - 3 - 57. Cylinder 5 "robs" air from cylinder 7 since they fire one right after the other & #7 tends to run lean. On the other side, #8 "robs" air from #4 since they fire one right after the other, but the 5-7 problem is worse.

How do you fix that? Better intake manifold & headers which are designed to equalize the amount of air (fuel mixture on a carbureted engine) which goes into each cylinder & it can get VERY complicated. But headers with small diameter tubing (same size as the exhaust ports) & at least 30" long will make a major difference in how the engine runs. (Best way to go is a 4-2-1 setup on each side). And although the X pipe is the best way to go, if you just put an H pipe in that'll make a big difference -- a piece of pipe which goes from the left exhaust to the right, after the headers & before the mufflers.

Not trying to "toot my own horn" here, but I'm an engineer who's designed & made exhaust systems for over 40 years & have been to the dyno many, many times, so I know what works, what doesn't & why. (My diesel truck has an exhaust of my own design that out-flows anything on the market for that engine).

Any of the name brands will work well -- as long as they're designed as I described -- the big-name companies have put a lot of work into their products. And I'll give a shout-out to Bassani exhaust as owner Darrell Bassani made the pipes for my Land-Speed-Record Harley-based engine, based on a combination of my design & his CAD-CAM equipment -- I don't have CAD-CAM (computer-aided design / computer-aided manufacturing) programs like he does.

But I asked him to make the pipes too long on purpose because we were going to cut 'em back on the dyno anyway -- look @ the dyno chart's HP / torque curves, cut off an inch (or less) & run the bike again. I knew where I wanted my peak HP to be (7200 rpm) so we just cut the pipes back a little @ a time until they dyno showed peak HP @ 7200. They ended up being within 1/2" of my calculations ;-) But @ the Bonneville salt flats, 1/10th of a mph can be the difference between getting a record or not (got 3).

So anyway, Bassani, Doug Thorley, Hooker, etc. all make good products & there's a LOT of engineering that goes into them. Just remember small diameter & 30" long (or more) for your truck & an X pipe or an H pipe in the exhaust after the header collectors & before the mufflers (doesn't really matter where you put it). "Been there, done that, got the T-shirt"
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