Don Terrill’s Speed-Talk

What is the best flowing small block chevy exhaust manifold to use? Class rules limit to factory exhaust manifolds.Do the 90's lt1 manifolds work o.k. or are the old ram horns still the best? Thanks

Best I've ever seen are the old 2 1/2" Ram Horn Corvette manifolds. Chevrolet still carried them up until a few years ago. They were so good that many tracks with cast manifold rules made them illegal.

You can go to www.castheads.com to see the information they have. The previous poster was accurate in stating the 2 1/2 inch ram horns are the best of the "cast" manifolds, but most all circle track "stock" divisions have outlawed them. Good luck.

Wonder if they are better than the newer lt1 manifolds?I would use the rams horns but since they are center dump they are hard to get a decent pipe to it.

IME the ram horns are best, but as you know you'll almost surely have to make mods to get them on
the car. Note that blue88 specified the 2 1/2 outlet ram horns. The smaller ones and those with a angle
at the outlet are inferior.

I don't think the LT1 wil be bad, but never tested them against Ram horns

Last time I needed ram horns, Enginequest (EQ) had new castings of all the various ram horns.

thanks guys.

I tested a bunch and the LT1 were one of the worst. The older corvette 2 1/2 center dumps then were the ones to run. I have not tested this one but i'm willing to bet it's better then the older vette ones.

I run a stock cast iron class myself and just visually the LT1's look very small. The manifolds I run are off of a 87 V2500 chevy truck. IF you see these manifolds you will be cvery surprised how large they look.

Weather or not they actually flow better I have not tested but I have to think if the volume is larger they should flow better.

My rules say not center dumps so I am have no comparison to thoses.


or for some 87 chevy vans they had these...there are a stock header type manifold but most rules don't allow them...my rules say they must be cast iron.



Good luck

3V Performance wrote:I tested a bunch and the LT1 were one of the worst. The older corvette 2 1/2 center dumps then were the ones to run. I have not tested this one but i'm willing to bet it's better then the older vette ones.

ALL34200 exhaust manifolds.jpg

Tom,
I believe that photo is of the units made by All Star, I would think those are better than the oem units-

cpmotors wrote:

3V Performance wrote:I tested a bunch and the LT1 were one of the worst. The older corvette 2 1/2 center dumps then were the ones to run. I have not tested this one but i'm willing to bet it's better then the older vette ones.

ALL34200 exhaust manifolds.jpg

Tom,
I believe that photo is of the units made by All Star, I would think those are better than the oem units-

Yes they are. I agree but have not tested them myself yet.

May not be allowed, but I saw some SS pipe individual runner 350 SB headers that are stock on I want to say, 1-ton four door cab long wheel-base DOT state trucks, say early '90's????

Heck, I didn't even know they existed?

Now, I recently did see a pair of cast-iron 350 big truck, (car type), LOG exhaust manifolds that are BIG TRUCK "swept back and out" and to me are way better than our logs.

I don't have any idea what years they are used on tho, sorry.

pdq67

It baffles me how the LT1 manifolds could be the worst of the bunch, since the LT1 motors themselves were a pretty high horsepower engine...during the 90's. Seems if the exhaust was such a restriction, they would not have been producing 265 hp.

blue88 wrote:It baffles me how the LT1 manifolds could be the worst of the bunch, since the LT1 motors themselves were a pretty high horsepower engine...during the 90's. Seems if the exhaust was such a restriction, they would not have been producing 265 hp.

I don't think that 265HP would be considered a high HP engine. But regardless of that they are fine for street were you are turning considerably under 5000 RPM most of the time. Now if your are buzzing at all they are very restrictive.

My 2 cents

we dyno tested about every sbc stock exhaust manifold available on a 355, 9-1, 2 barrell stock cast intake w/modified plenum and port matched ,2-G sean smith carb, 455 lift cam, steel crank, forged piston, 2 into 1 exhaust set up on a limited motor a couple years ago,..these were the exhaust manifolds we tested,..LT1, rams horn 2 1/2, truck log, 90's camaro over the port manifolds, tube type 1 ton truck manifolds,...

the tube 1 ton truck manifolds were the best with the LT1 & rams horn about the same,...everything else was way off the mark,...our conclusion as to why the LT1 worked as well as the 2 1/4 rams horns was the design,...and both the LT1''s and the rams horns had alot more torque from 3500-6000 rpm than the tube truck manifolds,..from 5500 on to a max of 6700 the large tube truck manifolds were superior...

340 hp max @ 5500 rpm

the tests were done with 3 different rochester 2-g carbs as well,..so every manifold had at least 3 runs..

so maybe flow isnt everything?...considering the very restricted motor we tested them on it seems to be the case..