Question : Boosted 3400/3500 Mani's vs Headers

[zofo61]

I am buliding a boosted 3400/3500 hybrid using the entire 3500 topend and an RSM Vortech kit. MY question is ..........what would be the real difference between using two front 3500 exhaust mani's vs a set of expensive headers. Could anyone estimate the HP difference and or the flow difference taking into consideration 8-12 pounds of boost with the 3500 top end............back pressure?...........you get the idea.

[IsaacHayes]

3500 mans will flow better than logs (less back pressure), but the headers will give you a scavenging effect which will help to pull the exhaust out of the cylinders so that no remainder of it is left over, and the piston doesn't have to work so hard to push it out.

You will see a gain with headers over 3500 tubular manifolds. The 3800 SC crowd upgrades to headers and sees gains, and their manifolds stock are much like the 3500 tubular ones. Just to give you an idea.

[zofo61]

Thanks........my cam profile is going to add some duration to the exhaust valve as well ....just tossing the idea around.........dont want to spend the money on the headers if i dont have to...........anything other than the TOGS I had before is a real compromise in quality...I've seen the S&S and the Pacesetters and they are half the quality of the TOGS...........dunno......not there yet but I can get another front 3500 mani and just dont know if I am going to go that route............decisions decisions......

[Joseph Upson]

You can't compare the turbo exhaust to the supercharged engine exhaust since the turbo is in the way to change the scavenging effect. In the case of a turbo the 3500 manifolds will probably leave very little room for significant improvement because they are built so well, lots of area and a smooth collective merge. Generally the less space you have between the turbo and the exhaust ports the better. If you run pretty high boost the difference is likely to be more significant.

I'm building headers because it will reduce the plumbing between the exhaust ports and allow me to relocate the turbos closer to the engine. I wouldn't spend a lot for a custom set in this scenario because of what I've read and how exhaust flow characteristics between a supercharged engine and turbocharged engine differ.

What's most important for the turbo engine is that your boost pressure to exhaust pressure ratio is as close to 1:1 as you can get it at your intended peak power output.

[zofo61]

Thats all well and good ,I guess ,but I am not using turbos I am using a Supercharger. Therefore, the question is still up for futher discussion.........but thanks for your input.

[Joseph Upson]

Thats all well and good ,I guess ,but I am not using turbos I am using a Supercharger. Therefore, the question is still up for futher discussion.........but thanks for your input.

I missed that. As stated previously you'll benefit from headers over the stock cast iron manifolds.

[RedZMonte]

cast manifolds are not very good flowing. Turbo or supercharger a good set of tubular manifolds/headers will always gain power. do you have to get headers to make power... Nope. Can you make more power.... Yep.. is it worth the extra $$....? thats up to you.. its hard to estimate the power increase you will get because no one has really done it.. the 3800's are gaining an average of 15-20hp... but again its imposible to say on your setup. especially if your adding a cam. the more work done to the engine (ported heads, ported intakes, cam, compression, ect...) the more power gains you can expect.

S

[kwhauck]

RedZMonte are you in colorado?

[RedZMonte]

RedZMonte are you in colorado?

Yep. I think we have spoke a coule times at badimere. I have the Red Turbo Z34 Monte and i used to have a White 3800 S/C swapped Lumina Z34.

Shane

[kwhauck]

hmmm.....i guess i don't remember, i would think i would remember both of those vehicles.....you planning on racing again this next season, like club clash or anything?

[RedZMonte]

hmmm.....i guess i don't remember, i would think i would remember both of those vehicles.....you planning on racing again this next season, like club clash or anything?

Probibly make it up there sooner or later. I also have a 04 Subaru wrx STI. I usually meet up with a few of the Club GPer's.

Offically hijacked thread FTW!

S

[zofo61]

Probibly make it up there sooner or later. I also have a 04 Subaru wrx STI. I usually meet up with a few of the Club GPer's.

Offically hijacked thread FTW!

S

Maybe you two should exchange phone numbers or start a new thread...just a suggestions....there is an IM function to this site as well

[johnnymossville]

^^^^ I was thinking the same thing. lol

[kwhauck]

zofo61, sorry to hijack yoru thread, but back on topic i am also on a supcharged buildup and could probably offer some suggestions, how about you give some details of your buildup, internals, HP goal, head work, blower unit you will be using, etc.......

[zofo61]

No worries...........
3400 bottom with stock balanced crank and stock balanced rods with Arias Forged Pistons. Custom cam profile to be determined......mainly more duration on exhaust side a little bit on intake.....I am letting my machinist deal with that( I cant seem to get Ben to configure me a profile or suggest the different rocker ratios so I am left with a local builder who does the big boys but is willing to play with a sixer). 3500 top end UIM, LIM Heads slightly ported and polished ....little bit of bowl work. RSM Vortech kit with 65 mm TB and I have injectors from 19, to 28, to 36 to choose from........tuning will be local at a dynotuner that uses HP tuner software http://www.vmptuning.com other than that I have no idea what numbers this will bring..........?