Cast Exhaust Manifolds (Approximately)

[Orange Crate]

Originally Posted by 4u2nv

I'm real close to buying this 350 with the rams on it , I don't know if they are aftermarket or not , do these give just as good of performance as headers ??

Basically no they are not better than headers, it depends on how the engine is built and how it is going to be used. I built mine for torque at low RPM. The 2.5" outlet manifolds are decent below about 4500.

[Willshook]

Originally Posted by dagnabbitt

Someone on here did an airflow calculation that indicated that of all the ram horns they made, the 2.5" Corvette ones are the only ones that actually are as good as having headers.

I don’t know what the measurement was, but it’s not about flow. Since the ports all exit into a “log”, the exhaust pulses are stepping on each other and there is no scavenging effect.

This is why headers have individual, long tubes - to separate the exhaust pulses and to create negative pressure, both of which add power - again, gains relative to the build level of the engine.

Even shorty headers are better than “log” manifolds as they still separate the exhaust pulses.

[dagnabbitt]

Its just a personal preference for me. They look good, last 50 years or so, and they don't leak. They seem to belong on an old truck, too. I admit that I also like to be a contrarian.

People do tend to lump all manifolds together, though, when the Corvette ones are quite a different animal.

According to some tests, Corvette manifolds can add 10+ horsepower in stock form over regular manifolds, which I think would make them as good or better than shorty headers. With mods they can make 20+ hp more.

Not as much hp added as long tubes, but certainly good enough for me. Unless we are talking about a built engine I am not sure you would notice the difference.

[4u2nv]

Originally Posted by dagnabbitt

I think that they do. Someone on here did an airflow calculation that indicated that of all the ram horns they made, the 2.5" Corvette ones are the only ones that actually are as good as having headers. That's all I needed to hear: I hate constantly messing with headers.

I have them with 2.5" pipes and mufflers, as the above poster notes, that helps. No restrictions from header to tailpipe.

I can't get dualls on my truck , the gas tank is on the drivers side and it's in the way
I would be better off using the ram horns and the cross over pipe ?? I guess

[Accelo]

The newer headers are not the junk we purchased when I was young. Stainless steel mounting flanges and stainless or Alumized pipe. The lower flange is also a much better designed with some using the round ball style connections.
Yes, they still can be a PITA with clearance fitment issues and automatic shifting rod placement and or clutch linkage issues.
Still I agree, if driving many miles without issues and easy installation the cast-iron manifolds are the way to go. If max power is your game, long tube headers can not be beat.

[Orange Crate]

Originally Posted by dagnabbitt

Its just a personal preference for me. They look good, last 50 years or so, and they don't leak. They seem to belong on an old truck, too. I admit that I also like to be a contrarian.

People do tend to lump all manifolds together, though, when the Corvette ones are quite a different animal.

According to some tests, Corvette manifolds can add 10+ horsepower in stock form over regular manifolds, which I think would make them as good or better than shorty headers. With mods they can make 20+ hp more.

Not as much hp added as long tubes, but certainly good enough for me. Unless we are talking about a built engine I am not sure you would notice the difference.

Exactly, I like all these reasons, also this thread was started as information about what is available in the after market. If anyone wants to debate manifolds versus headers then a new thread could be started ( not by me). As I stated in post 14 these manifolds really helped my 406.

[Tom]

Originally Posted by Orange Crate

Why can we not do this in this country anymore?

Because nobody is willing to pay what it would cost for a quality worker [$$$] to make good [more $$$] stuff. You can get well made steel headers for less then what that manifold would sell for I bet.

Originally Posted by 4u2nv

do these give just as good of performance as headers ??

No. But they give better performance then normal manifolds.

[Orange Crate]

Originally Posted by Tom

Because nobody is willing to pay what it would cost for a quality worker [$$$] to make good [more $$$] stuff. You can get well made steel headers for less then what that manifold would sell for I bet.

It's a rhetorical question.....

[Mike C]

I TIG brazed a plate over a connecting rod “exit hole” on a 3.0 Mercruiser. Was quite an interesting project. Very interested in seeing how your repair works out.

I went from headers to manifolds on my Jimmy. Not a perfect apples to apples because I made a couple of changes. 331” engine, 210 @ .050 symmetrical camshaft, 8004 intake and JET stage II Q-jet. Headers were Heddman 1 5/8” long tubes. Exhaust was 2 1/4” with some unknown turbo mufflers from a parts car I had.

I used reproduction manifolds from Speedway (this is circa 1999) which did not have that odd bump in the port (nor does that appear on the pic on their web site currently. At least as best I could tell.) I think I paid $50 each and they are about $75 now. I used 2 drivers side mounts if memory recalls because that was the cheapest way. Bandsawed the generator mounts off and ground fairly smooth. Had local exhaust shop build a 2 1/2” exhaust with what were at the time DynoMax Hemi Turbo mufflers. These have a 20” case.

On my truck, my highly tuned and experienced () “butt-o-meter” noticed no change in power. If anything maybe slightly more low end? Not enough to notice in reality. On a lower power engine like my .030 327 incher (325 hp, maybe 350 at crank?) the 2 1/2” manifolds and same size exhaust equal the headers with the slightly smaller exhaust.

Like any other vehicle mod, “your mileage may vary”.

[69cam]

Who makes/sells the exact reproduction manifolds the op mentioned?

[Orange Crate]

Originally Posted by 69cam

Who makes/sells the exact reproduction manifolds the op mentioned?

Corvette Central

[LS short box]

Just a thought.
I hang out over corvetteforums.com. a good bit.
If the manifold is the same as Corvette manifold maybe see if some one has one for sale?

[Orange Crate]

Originally Posted by Mike C

I TIG brazed a plate over a connecting rod “exit hole” on a 3.0 Mercruiser. Was quite an interesting project. Very interested in seeing how your repair works out.

I went from headers to manifolds on my Jimmy. Not a perfect apples to apples because I made a couple of changes. 331” engine, 210 @ .050 symmetrical camshaft, 8004 intake and JET stage II Q-jet. Headers were Heddman 1 5/8” long tubes. Exhaust was 2 1/4” with some unknown turbo mufflers from a parts car I had.

I used reproduction manifolds from Speedway (this is circa 1999) which did not have that odd bump in the port (nor does that appear on the pic on their web site currently. At least as best I could tell.) I think I paid $50 each and they are about $75 now. I used 2 drivers side mounts if memory recalls because that was the cheapest way. Bandsawed the generator mounts off and ground fairly smooth. Had local exhaust shop build a 2 1/2” exhaust with what were at the time DynoMax Hemi Turbo mufflers. These have a 20” case.

On my truck, my highly tuned and experienced () “butt-o-meter” noticed no change in power. If anything maybe slightly more low end? Not enough to notice in reality. On a lower power engine like my .030 327 incher (325 hp, maybe 350 at crank?) the 2 1/2” manifolds and same size exhaust equal the headers with the slightly smaller exhaust.

Like any other vehicle mod, “your mileage may vary”.

It is not working out. The casting is so contaminated it just blows out. It's the same using AC or DC. OK, OK all you expert welders, just calm down, I've done my research and followed all the tips and tricks. It might be alright to get the truck started again but it will NOT be going down the road with this repair. I had a similar problem once while trying to weld an old cast aluminum part, there was so much junk imbeded in the casting. Come on January....

[Mike C]

The one manifold and just use it for a month would be less than I paid for the silicon bronze TIG rods! Something to consider just in case that January deliver is delayed…

Back in the late 90’s was about the time the repro 2 1/2” manifolds showed up. $50 for the imports or $300 for the “restoration” manifold. But at least they are available!

[Orange Crate]

Originally Posted by Mike C

The one manifold and just use it for a month would be less than I paid for the silicon bronze TIG rods!

I do not understand this statement!

[AcampoDave]

Once you find exhaust manifolds of quality, a trip to Jet-Hot would help their longevity. I had mine done in the "Silver polish" a while ago. I'm still happy with them.

[Mike C]

Originally Posted by Orange Crate

I do not understand this statement!

Rather than waiting a month (or who knows how long) just buy a re-pop manifold and use it until the expensive one comes in. That way you don’t have to wait. The silicon bronze rod I bought to weld the engine block cost more than a $75 manifold.

[Orange Crate]

Originally Posted by Mike C

Rather than waiting a month (or who knows how long) just buy a re-pop manifold and use it until the expensive one comes in. That way you don’t have to wait. The silicon bronze rod I bought to weld the engine block cost more than a $75 manifold.

OK, got it now, I'm a little slow....so my plan laid out here is to use the repaired piece to get the truck back running and then wait....