Exhaust manifolds for a 383 winter makeover

Lee · 01-16-2002, 12:10 AM

Its wintertime here and I need an excuse to spend time in my garage....
When I did my 383, I wanted my '75 to look like a stock L48 and go like hell. So, I left the stock 2" ramhorns on it. The car goes great (mid to high 13's), but I cant help but think they must be strangling the poor thing. So, how much performance improvement would I get from the 2-1/2" ram horns or some of the newer tubular exhaust manifolds. The car has ported 2.02 heads and a 2-1/2 low restriction exhaust system (with a 2" flange welded on at the manifold end to connect to the stock size). Of course it has all the other stuff too like a 71 4 bolt block, forged flat top pistons, medium riser intake (painted cast iron orange) cam, holley double pumper etc. etc., so those 2" hole must just kill it.

Any suggestions short of a set of headers? (unless I got 100HP out of them!)

Also, has any one used roller tip rockers? Their cheap, a nice weekend project and tempting, but will you feel the difference in your butt?

Thanks, Lee

tapio · 01-16-2002, 10:17 AM

Quote:

Also, has any one used roller tip rockers? Their cheap, a nice weekend project and tempting, but will you feel the difference in your butt?

Thanks, Lee

About the rocker question, pls see http://forums.corvetteforum.com/zerothread?id=214561

yoslambo1@cs.com · 01-16-2002, 12:24 PM

when i added 1.6 roller rockers i definetly noticed a difference. ide go for it! p.s when i added headers & free flowing exhaust i felt an even better gain! :D .....383 on the way! :D

JCL · 01-16-2002, 03:30 PM

Lee. Not sure you'll see "100" HP, but maybe headers and sidepipes would kill two birds. You'll get some HP (guess maybeeeee 40 to 50) with the right baffle/muffler set up, and a fantastic sound and looks. The big one on the market is Hooker.(i've got these) But if i had it to do again, they would be Stahl. I like the collect idea UNDER the frame, so the sidepipe is a long smooth looking tube !! Just a thought............ JCL :cool: :cool: :chevy

Lee · 01-18-2002, 11:10 AM

Thanks JCL, but the sidepipes would squelch the "looks like an L-48" plan. Tempting though... I don't really expect 100HP, but I am wondering if I would get 10-20HP by going to the 2-1/2 inch manifolds? I really want to keep this as a sleeper, but getting into low 13's or high 12's would be fun too. :hat

Lee

Clink69 · 01-18-2002, 04:13 PM

Those manifolds are killing your power. Even small headers would open that thing right up. You need to make sure the intake is flowing good and open that exh up. Check out my 383 build up . Note, besides the headers/sidepipes, you can't see any of it from the outside.

Yes you will feel some difference using 1.6 roller tips. Using these the peak flow will be maintained for a longer period of duration.

Check out pics of my buildup and specs in my sig. My is almost scary fast on the street.

http://forums.corvetteforum.com/zerothread?id=219513

:flag

[Modified by Clink69, 1:14 PM 1/18/2002]

mountainmotor · 01-18-2002, 04:34 PM

Lee if we knew what cam you are using it would be of help.Is it a single or dual pattern?
What are the specs?

Lee · 01-18-2002, 07:45 PM

mountainmotor: I rummaged around in the garage for an hour looking for my cam specs, but no joy. Its in there somwhere but I am recovering from a recent move. Seems to me it was a bit more aggressive than a stock 350-350 horse style, but not really wild. The car pulls hard up to 6500,( I don't care to know how long it would pull above that...) Still lots of low end torque. Does that help? It might take me a week to find the cam card.

Lee

ol,RJ · 01-19-2002, 04:43 AM

your cranking a 383 to 6500rpm with stock style exh manifolds!!!!!!!
they have to be hurting your peak HP.
you NEED headers....

mountainmotor · 01-19-2002, 12:09 PM

I like how you want to keep this a sleeper.Sounds like you have a good combination as is!
The maintenence of headers and the hassle of them has lost it's luster with me so to speak.I must be getting old! :)

Lee · 01-19-2002, 01:35 PM

Yeah mountainmotor, I don,t really want headers either. The 2-1/2" style ram horns are an easy bolt on. The only other thing I might consider is a more recent vette manifold or a set of "shorty" style headers that are essentialy a tubular ram horn with a 2-1/2 collector.

BTW, The motor does pull hard to 6500, but the shift point on my TH400 is around 5500-5800 RPM. Thats a less expensive shift point....

Basically, I want to get another 20 to 40 HP out of this motor for around $1000 and keep it streetable (from my wifes perspective that is...)

Lee

corvgreg · 01-20-2002, 05:09 PM

If you want to keep the sleeper look, get the 2 1/2" rams horns. I think there are companies out there that modify these to flow better, but I can't think of any but Extrude-Hone at this time.
Greg