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| Limitations of stock exh. manifold for performance https://slantsix.org/forum/viewtopic.php?t=25997 |
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| Author: | MikeY [ Sun Nov 25, 2007 6:16 pm ] |
| Post subject: | Limitations of stock exh. manifold for performance |
A stock exhaust manifold can be followed up by a good exhaust system, but nevertheless, can never be as good as Dutra duals or headers. With a 225 slant, what are the realistic limits such as rpms, induction (NA), cam size, etc., beyond which the stock exhaust manifold is just too much of a restriction and bigger, "better" parts are not going to gain very much? I'm also speaking in terms of a nice, balanced, 99% street SL6. Thanks! |
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| Author: | sandy in BC [ Sun Nov 25, 2007 7:10 pm ] |
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As long as you are running a 2 barrel 300cfm or smaller the stock manifold is prolly fine. If you never get above 4000 rpm the stocker is prolly fine. |
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| Author: | Joshie225 [ Sun Nov 25, 2007 9:45 pm ] |
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At one time I ran a 225 with a Holley 390 on a Clifford intake, 264° Comp Cam, 1.78" intake, 1.45" exhaust valves, milled head and a stock exhaust manifold with 2 1/4" pipe and Walker Dynomax Super Turbo muffler. It ran better and made more power with the good head and stock exhaust manifold than it did with a stock head, Clifford shorty headers and generic 2 1/4" parts store muffler. Unless you can find someone with an engine built like yours that replaces a stock manifold with headers and makes no other significant changes you won't know how much power you're giving up. I ended up with the stock manifold because when I was doing my head upgrades I traded my short Clifford headers for long ones that I couldn't fit into the car. I had to resort to the stock manifold to make my race and it ran great! |
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| Author: | 68barracuda [ Mon Nov 26, 2007 2:47 am ] |
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Did a sim run only added 465 holley turned 90 degrees with plenum devider - dual plane and freeflow large bore - cannot spec size with this version - exhaust Std 8.8CR head and cam - for RSA STD @ 2000 rpm 78hp 205ft/lb Peak HP 123 @ 3500 Peak TQ 207 @ 2500 Improved induction and Exhaust - without headwork @ 2000rpm 100hp 262ft/lb Peak HP 150 @3500 Peak TQ 262@ 2000 Bare in mind that some of the stuff like header lenght and diameter cannot be spected in this version, but it does give an indication |
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| Author: | Miser [ Mon Nov 26, 2007 5:15 pm ] |
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i thought i'd post this here while we're on the subject, instead of making a new thread. what is the best way/type of clamp to make a straight piece of exhaust pipe hold still while cutting? an f-bar type clamp like this? http://www.harborfreight.com/cpi/ctaf/d ... mber=92490 i'm using a sawzall because that's what i have, and it really tends to make exhaust pipes move around when cutting |
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| Author: | dakight [ Mon Nov 26, 2007 5:27 pm ] |
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I've never tried a bar clamp like that but I suppose it would work if the jaws are deep enough. I think a bench vise would work better just be careful to not distort the pipe. You could make a fixture of plywood and 2x4s too. Of course, a chop saw is the proper tool but I don't have one of those either. |
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| Author: | rock [ Mon Nov 26, 2007 5:36 pm ] |
| Post subject: | well miser... |
Well Miser, My jaw opened up about like that clamp when I looked at the pic....I gotta say using a bar clamp, all I had on hand or not, would not cross my mind. Kinda like using a claw hammer to cut glass. The bar clamp is for stock with flat sides, not tubing. you would be better off to use the sawzall to cut a half circle about the radius of your tubing in each of two halves of a wood block, pop the cutouts over the tubing like a pair of clamp jaws, then use the bar clamp to hold the wood parts on the tubing. tubing is often cut with a tubing cutter. network a bit and a local mufffler shop will cut it for you. Or rent or buy a Rigid tubing/pipe cutter big enough to cut what ever diamter you have, clamped by your wood blocks and bar clamp. Or use a hacksaw. Really, if you are gonna start fabricating you need some tools, and Harbor Freight and pawnshops are ok places to get a few tools. We all know the pain of not having bucks to buy tools, but you really are gonna need more than a bar clamp and sawzall to do metal work. Haunt flea markets, equipment auctions, and estate sales. Sadly, increasing numbers of 80 year old guys are leaving tools behind now. Ask friends for help on a project as simple as tubing cutting And early on, get a good vise to replace the bar clamp. Even a Chinese vise is better than none til you can get an old Columbian. One of the most used tools I have is a 4 inch grinder, and I see one is now on sale at Harbor for $16! That tool plus a drill press will enable you to do lots of stuff, then if you get a small oxy/acetelyne set you can begin to move from the pre-stone age into being what one forum member calls himself "A tool using mammal!" rock '64d100 |
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| Author: | Shaker223 [ Mon Nov 26, 2007 7:07 pm ] |
| Post subject: | |
This is what I used to cut and make my exhaust. Not heavy duty but very functional for the home garage. http://www.harborfreight.com/cpi/ctaf/C ... pricetype= |
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| Author: | Doctor Dodge [ Mon Nov 26, 2007 7:40 pm ] |
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I have a "roller cutter" chain type pipe cutter, it works well. DD http://www.etoolcart.com/browseproducts ... D2031.HTML |
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| Author: | Charrlie_S [ Tue Nov 27, 2007 4:36 am ] |
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I have a chain type cutter, also. Last week I needed to make up some pipes to direct the exhaust out of the engine compartment, from my Clifford shorty headers. The chain cutter did not like to cut "U" bend pipe. The Sawzall, was not very controlable. I wound up using one of those small air body saws. The regular blades are too short, but a hacksaw blade broken in half, worked real good. |
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| Author: | sandy in BC [ Tue Nov 27, 2007 8:59 am ] |
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Bench vise and hacksaw? |
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| Author: | MikeY [ Wed Nov 28, 2007 1:03 pm ] |
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Anyone else want to add their thoughts? |
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| Author: | 68barracuda [ Wed Nov 28, 2007 11:08 pm ] |
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Extrusion honing adds a couple of hp on the std manifold but as you said - a good set of headers, with a good inlet helps a lot - one without the other does not realize the full HP potential - it has been said in the past Open up the ports and up the cr while you at it and the grin factor goes ballistic Everything hooked onto the slant head, and with the default slant head config is limiting, one way or an other - if you are aiming for high output, or optimum volumetric efficiency. 
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| Author: | CARS [ Thu Nov 29, 2007 6:46 am ] |
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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.
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| Author: | 68barracuda [ Fri Nov 30, 2007 12:27 pm ] |
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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.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 |
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