Slant Six Forum :: Limitations of stock exh. manifold for performance

Quote:

Extrusion honing adds a couple of hp on the std manifold but as you said...

When I first started playing with my slant, I checked a few online stores about extrude honing. OMG... it was in the neighborhood of $600.00 to do one!!! I am sure if I shipped them a hundred manifolds the cost would be much better. For that kind of money i'll buy up a bunch of stainless mandrel bent tubes and start welding up a header.

Ouch

Why is stuff so expensive over there?

I had mine done for R200 ~ $29 and it is the same process - first wondered but these guys do manifolds casted for the local motor industry

Author:	emsvitil [ Fri Nov 30, 2007 12:36 pm ]
Post subject:
Quote: Quote: Quote: Extrusion honing adds a couple of hp on the std manifold but as you said... When I first started playing with my slant, I checked a few online stores about extrude honing. OMG... it was in the neighborhood of $600.00 to do one!!! I am sure if I shipped them a hundred manifolds the cost would be much better. For that kind of money i'll buy up a bunch of stainless mandrel bent tubes and start welding up a header. Ouch Why is stuff so expensive over there? I had mine done for R200 ~ $29 and it is the same process - first wondered but these guys do manifolds casted for the local motor industry I'd just port match at the manifold/head (make sure manifold is slightly larger at all points for anti-reversion ledge) and use a sanding-flap wheel to smooth things out............

Author:	CARS [ Fri Nov 30, 2007 1:06 pm ]
Post subject:
Here is the price list I went off of http://www.gethoned.com/parts.php?get_p ... automotive There may be cheaper places out there but I bookmarked the site because the little pictures of the process are mesmerizing

Author:	Aggressive Ted [ Fri Nov 30, 2007 1:50 pm ]
Post subject:	Stock exhaust manifold
I am with emsvitil, for a street car build. Make sure the gasket matching is done the way he explained, from the intake to the head, the head being right at the gasket size, the intake being a little smaller to reduce reversion. On the the exhaust, make sure the exhaust manifold is gasket matched and leave the head alone, or if you do port it leave it a little smaller to reduce reversion. I cleaned up inside the exhaust as far as I could reach and reamed it out, cleaned out the ridges, bumps, etc.....you don't need to go crazy, but a general clean up sure makes a big difference. I was running my exhaust manifold stock up until about a month ago when I put on the Aussie Carbon fiber manifold gasket. Then I gasket matched it and cleaned up a bit. It has more zip (faster response) around 2500 rpm on up.

Author:	MikeY [ Mon Dec 03, 2007 8:35 am ]
Post subject:
Thanks everyone for the replies. If the stock exh. manifold is only good for about 4000 rpm, it sounds like making even 150 hp would be tough, as that would require 197 ft/lb at 4000 rpms.

Author:	sandy in BC [ Mon Dec 03, 2007 9:22 am ]
Post subject:
You can make much more than 150hp with the stock manifold. The head is where the power is.

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Limitations of stock exh. manifold for performance https://slantsix.org/forum/viewtopic.php?t=25997	Page 2 of 2

Author:	Aggressive Ted [ Mon Dec 03, 2007 1:37 pm ]
Post subject:
MikeY, With the mods I have made on my build Doctor Dodge says I should be a 160 HP with the Single barrel Holley. I am very happy with the performance output. A stock motor puts out 200 ft pounds of torque at 2000 rpms and about a 100 to 148 HP depending on the year and carb and the way they used to measure output. So the stock manifolds aren't that bad for a street car. Doctor Dodges Split manifolds are the next step to take. PM me your email and I will send you a output chart.

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