I have a 1970 350/350hp L46. I am considering changing the 2" exhaust system. Will 2 1/2" exhaust manifolds with 2 1/2" exhaust pipes give any noticeable performance increase over stock 2" exhaust manifolds with 2" exhaust pipes. Also, would there be a large differnece between tri-y headers and the 2 1/2" exhaust manifolds.

 

I would always go the header way if I could. You'll gain a few ponies but probably nothing that you'll feel in the seat of your pants. Exhuast upgrades are always a good ideal, tho. Larry

 

CK, the largest problem is, most any honest header mfgr will tell you about gaining NOTHING in actual HP from using their headers, WITH ANY MUFFLED, CATISTROPHIC converter syste, too much back pressure, so therefore the header advantage is destroyed....

so, do the headers IF you are doing other mods, or just want to look cool on show night, other than that the rams' horns are fine....

this from my header mfgr.....

sans the sales BS....


GENE

 

I am running a set of early 2 1/2" ram horn manifolds that have been extrude honed inside to open them up.
I have them on a 78 pace car with a full 2 1/2" exhaust out the back, they work great and I still have the stock look without the worry of dragging them on a curb.
I looked at some dyno results with these manifolds aginst some headers and there was only like a 5 hp loss with the manifolds on a mild small block at 5500 rpm.
I did not think that the loss was that great to me to keep the manifolds.

Thanks, Mark G

 

I added indents to my right Jet-Hot coated Heddman header near the collector when I drove my warmed over '80 L48 too quickly over a speed bump in a parking lot... wouldn't have that problem if I had my OEM exhaust manifolds... But it sure looks nice seeing those ceramic coated pipes hanging underneath from 20 feet away... and popping the hood to see those headers 'shine'... I bought the headers that have the A.I.R. fittings in event future owner or regulations necessitate install of cat(s).

 

I have headers but if you have a good set of 2.5 ram horns i would jet coat them reinstall & chg the rest of the exhaust system & mufflers.

 

350hp with 2" pipes? Poor engine, she's suffocating.

 

Remember that's gross horsepower, not net. 2" actually won't strangle that engine much.

 

I'm interested in using these manifolds but I have some questions. The only 2.5" rams horn manifolds I see fit 62-63 327 corvettes, will they also fit a 350?
See this link:
http://www.shop.com/op/~Dorman_Exhau...5?sourceid=298

Or how about these:
http://www.martelbrothers.com/catalo...r-p-14859.html

I'd like to connect to a stock 78 corvette 2.5" exhaust, will I still need spacers, heat risers, etc?

If the engine is a ZZ4 will the head angle throw the exhaust to manifold alignment off?

Thanks,

Kipp

 

Here's another option that I've been considering for the balance of stock look and performance.

http://www.castheads.com/corvette_systems.php

I don't think I linked it right, but the website is there.

 

That's the best price I've seen on these manifolds (shop.com/mid $50s each).

As for hooking them up on a stock 78 exhaust system, I wouldn't work too hard on doing this. I doubt very much you will see much if any gain from using these on the stock 2-1-2 exhaust on a 78. The 78 L-82 had 2.5" pipes, but they squeeze down to the 2" opening of your stock manifolds.

If you do go for these (I am looking at doing these as well), you should plan on having a new 2.5" exhaust made up for you at a local shop, or doing it yourself. I would suggest a nice tru dual system with dual cats depending on the state you live in. If you need to pass a visible inspection for emissions, I have seen versions of these manifolds that have the AIR tube pads on them which can be drilled and tapped for their installation and stock look.

As for the performance of Rams Horns vs headers, Vizard says you can get about 60-70% of the benefirt of headers with the rams horns if you match the port sizes to the heads. He goes over the process in 'How to Build Horsepower.'

For proof of just how much you can do with these, another forum member (BIG632 I think) has posted some threads and dyno results of his 383 stroker motor that lists 375RWHP (not shabby at all) and uses 2.5" rams horns (massaged) and true duals. That thread is a great read by the way.

Good luck and keep us informed!

 

I would use shorty headers instead of the Ram's horns. A little less weight can't hurt.

 

Thanks to all, for your input & advice.

 

which are you going to use ??

 

I don't know about dyno figures, but I do know "seat of the pants"...I have a modified 350, dual quads...I just recently installed chrome shorty headers, a new 2 1/2" crossover pipe back to the first union, cat is gone and I already had Dyno-Max muffs on her. There was a noticable change in acceleration once she could breath properly....NOTICABLE!
Just my 2 cents....

 

Another option would be to keep the 2 inch rams and instal 2 1/2 exhaust. Any muffler shop can fit 2 inch to 2 1/2 flange at rams outlet. It would be less restrictive than what your running now and save you some $$. I currently have headers on mild 350 and am converting BACK to manifolds for more clearance and the fact that the headers need replacing anyways. Just a thought

 

I switched from open hooker headers to headers with 1 7/8th primarys and I noticed a huge difference. lol my headers are almost as big as your exhuast.

 

MY 80 L82 had an air pump so I try to retain the injection ports in case laws change and I need to have it inspected.

When I bought the car it had headers and the heat was more in the engine compartment, they would suffer from leaks every so often and they would hit speed bumps with the car lowered. I did go back to rams horns but on the 2 inch had air injection.

Last week I ran my car on the dyno to get a baseline on the ZZ4 and found what appears to be a 50 hp drop with the 2 inch rams horns. Wanted to run 2.5 inch which flow much better but no air injection.

This week I ordered a set of high flow manifolds from Sandersen headers that are their design, flow well, have injection ports and I could get them ceramic coated to drop temps further. Will run them on the dyno in the next 4 weeks.

 

cool post the numbers

 

those martel bros ramhorns don't look anythiung like stock ramshorns to me. or am i missing something.