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Ram horns exhaust manifolds came with 2 1/2 outlets where the exhaust manifolds that fit an A-body chassis came with only 2 inch outlets.
I wonder what the difference would be with a set of Chevelle cast iron manifolds versus headers would be ?My guess would be it's way more than the 20 HP shown here.
 

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I bracket race a 65 Impala with a mild 355 and a TH400 with a stock torque converter and a 3.55 gear. This is essentially a street car, and my son and I drive it on the street all the time. The engine is 10:1 with a Lunati 219/227 @ .050 hydraulic roller and vortec heads. With headers and a 2400 stall, it went a best of 13.22 @ 101.5mph. With stock converter and ported rams horn manifolds, it has gone a best of 13.78 @ 100.5. The 60 ft time dropped from 1.80 to 2.10 with the stock converter, so that explains the bulk of the ET difference. I estimate the headers were only worth .10 in ET and 1 mph. I shift at 6000 with this rig.

At the risk of stating the obvious, the more cubic inches and the more RPM you turn, the more the rams horn manifolds will restrict power.

I am also currently building a 64 C10 truck for bracket racing and nostalgia events. Engine is a 355 with flat top pistons and stock, unported camel hump heads with 1.94/1.50 valves. I'll be using ported 2.5" rams horns. The cam is an off-the-shelf Clay Smith hydraulic roller that they grind specifically for stock camel hump heads and factory rams horn manifolds. Specs are 223/237 @.050 with lift .544/.534. I hope to be on track by August, I'm excited to see what it will do with 4.11 gears and 2400 stall. Clay Smith says power peaks at 6400 in a 327 and 6200 in a 350 with this cam.

I love the stock look and vintage vibe of the rams horn manifolds, and I love how they clean up the engine compartment and make the car so much easier to work on. It's worth losing a few horsepower in my mind.
 

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That's good information, BUUUUUUUUUUUUUUUUUUUT, 2 1/2in Ram Horn (or ANY Ram Horn) manifolds CANNOT, repeat, CANNOT be used on ANY Chevelle, because the front frame cross member is immediately below where the outlet would be for a Ram Horn manifold. MAJOR BUMMER!!!!!!!!!!!!!!!
In his 60-64 Chevys By The Numbers, Alan Colvin shows a a factory drawing/casting number for a 2 1/2in log style manifold, but after much searching and many inquiries, I've never been able to locate a single 2 1/2in log style manifold for a Chevelle.
 
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It's been my experience with board members that the majority like all hotrods and even though their favorite might be Chevelle, they usually have other hotrods. This Chevelle board in referenced all over the net as a "go to place" for info. Straub Tech posting this here is for the good of the hotrodding community. A member buying a C3 or Square body (Very popular these days) can use this information to make a decision.

Happy Motoring!!!!
 

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Interesting...i believe it picks up torque everywhere not just at WOT every car except the daily has had them. (Long tubes)

Spent a ton of time doing a set of 2.5" rams horn (porting) and was diappointed to hear he really felt no difference. May have been on a bench or dyno but kinda of a waste fwiw

Very difficult to get into the actual horn area and the bosses are in the way. I mean you can for the most part but getting substantial material out...meh.
Maybe thats why guys used to Extrude hone?
Off topic some just saying.
 

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It's been my experience with board members that the majority like all hotrods and even though their favorite might be Chevelle, they usually have other hotrods. This Chevelle board in referenced all over the net as a "go to place" for info. Straub Tech posting this here is for the good of the hotrodding community. A member buying a C3 or Square body (Very popular these days) can use this information to make a decision.

Happy Motoring!!!!
thats the reason i like to come to this forum. love this kind of information. i have 2 big block chevelles that were built from information from people on here. i am building a 70 c10 and just finished my 383 for it. been waiting all week for you to post the results. ill be porting a set of manifolds next week. thanks for keeping us little guys informed
 

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Ram horns exhaust manifolds came with 2 1/2 outlets where the exhaust manifolds that fit an A-body chassis came with only 2 inch outlets.
I wonder what the difference would be with a set of Chevelle cast iron manifolds versus headers would be ?My guess would be it's way more than the 20 HP shown here.
That's good information, BUUUUUUUUUUUUUUUUUUUT, 2 1/2in Ram Horn (or ANY Ram Horn) manifolds CANNOT, repeat, CANNOT be used on ANY Chevelle, because the front frame cross member is immediately below where the outlet would be for a Ram Horn manifold. MAJOR BUMMER!!!!!!!!!!!!!!!
In his 60-64 Chevys By The Numbers, Alan Colvin shows a a factory drawing/casting number for a 2 1/2in log style manifold, but after much searching and many inquiries, I've never been able to locate a single 2 1/2in log style manifold for a Chevelle.
It's been my experience with board members that the majority like all hotrods and even though their favorite might be Chevelle, they usually have other hotrods. This Chevelle board in referenced all over the net as a "go to place" for info. Straub Tech posting this here is for the good of the hotrodding community. A member buying a C3 or Square body (Very popular these days) can use this information to make a decision.

Happy Motoring!!!!
What I was trying to point out and the reason Tom said what he said is that the Ram horns flow way better than any Chevelle cast iron manifolds will flow.The log type's 2" outlet is a big jam compared to a Ram horn's 2 1/2" outlet.So the difference between a log type exhaust manifold and a set of headers would be way greater than hat the difference the Rams horns experience.That's all I was trying to point at.
It would be interesting to see what the difference is on the dyno between a set of rams horn and log type Abody exhaust manifolds would be.I think that may also apply to Nova's and Camaro's too but I'm not sure maybe Rams horns could be made to fit the F and X body cars.
 

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Think the crossmember is in the way on Fbodys. Had the logs on a 67 rs, was given a set of rams horns and decided they wouldnt work. That was 30 yrs ago so memory is a little foggy.

Anybody know if the 90s LT1 exhaust manifolds exit to the rear or center?
KNow lots of the C4 guys use them as the L98 tubular manifolds suck.
LT1 pieces supposedly work pretty well.

Do the sanderson or speedway copies have larger ports internally?
 

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The outlets on the rams horns for a Chevy II are angle 45 degrees towards the rear, I think, and I think those were never cast with 2.5" outlets, but I'm not 100% sure.
Thought mine had straight manifolds, butt you might be correct. It's been over 3 decades since I owned mine so I couldn't say for sure.
 

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90ish Impala Roadmaster LT1 manifolds they exit in rear Dorman makes them


Camaro


Looks like the corvette is still center dump.
 
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