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AllisUpstate 
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 Topic: Should I Polish D17 Intake Manifold?
Posted: 01 Dec 2011 at 6:44pm |
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I recently purchased a US made manifold for our D17 IV. The interior of the casting is pretty rough, especially as compared to the old manifold.
Any ideas as to whether I should try to smooth out the roughness of the intake tract? I'm not trying to port and polish a drag racer or anything, but I'm wondering if the engine performance might suffer from a pretty rough intake manifold flow path.
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AllisUpstate
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Posted: 01 Dec 2011 at 6:45pm |
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AllisUpstate
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Posted: 01 Dec 2011 at 6:45pm |
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Oops, not only posted a blank, but this is a gas engine.
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John (C-IL)
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Posted: 01 Dec 2011 at 6:59pm |
You can solve all of those problems by using the edit functions under post options and then instead of having 3 post you would have had only one edited one.
Smoothing out the intake manifold would probably not be of much benefit. Making sure that the mainfold and head ports are properly aligned would be the best use of the time you would have spent smoothing out the manifold runners.
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AllisUpstate
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Posted: 01 Dec 2011 at 7:09pm |
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John, Thanks. I will make sure to look closely at the alignment.
Sorry about the 3 posts. I get mixed up (it doesn't take much) between the Post Reply and Quick Post options.
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powertech84
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Posted: 01 Dec 2011 at 8:08pm |
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Intake manifolds almost never should be polished, ported yes, but polishing decreases the atomization of the fuel.
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AllisUpstate
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Posted: 01 Dec 2011 at 8:20pm |
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Powertech,
Thanks for the advice. I grew up reading so many motorcycle mags, where the intakes were polished until shiny, and the D17 manifolds were pretty darn crude, especially compared to the original I took off. I worry a little about fuel condensation in the crevices and such. But if you think it won't matter in performance, I won't worry about it.
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powertech84
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Posted: 01 Dec 2011 at 8:32pm |
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If there are large ridges, it wouldn't hurt to knock them down a bit, but i wouldn't expect any noticable performance changes. Most of my porting experience comes from automotive heads. I know nothing at all about motorcycle engines, but i would be curious to understand what the differences are, and why they would want them so smooth. The only one i suppose i would see the point of polishing would be a reed engine, or a direct injected engine of some type.
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KGood
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Posted: 02 Dec 2011 at 9:03am |
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Just on a side note when we were building our tugger engines the biggest problem the experts found was the sharp 90 degree angle were the bore for the riser from carb meets the horizontal runner. They said thats bad and rounded it out somehow. We were going for less restriction to get more air because of big cubes. The biggest manifold we found was the original for a D17LP.
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427435
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Posted: 02 Dec 2011 at 10:45am |
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Be sure there isn't any loose sand or sl*g on the inside before you bolt it on.
Edit: For some reason, the "a" keeps getting replaced by an asterisk. sl*g is not a bad word!!!
Edited by 427435 - 02 Dec 2011 at 10:47am
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Mark
B10 Allis, 917 Allis, 7116 Simplicity, 7790 Simplicity Diesel,
GTH-L Simplicity
Ignorance is curable-----stupidity is not.
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injpumpEd
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Posted: 02 Dec 2011 at 12:11pm |
 powertech84 wrote:
Intake manifolds almost never should be polished, ported yes, but polishing decreases the atomization of the fuel. |
for natural aspirated gas engines. turbo & non turbo diesels will benefit from polishing intake since no fuel is in the intake charge. minimal difference at best unless a really hopped up engine.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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wi50
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Posted: 02 Dec 2011 at 4:53pm |
I took a stock manifold, carb, head, and I made adapters to fit my Superflow flowbench and I tested the parts to see what they flow in their stock form.
Going from memory the carb I tested was from a Gleaner E and would flow just shy of 100 CFM
The stock manifolds I've tested would flow around 105-115 CFM @ 28" depending on the brand of aftermarket one or the original AC ones. Takeing a flame shaped carbide and working the corners where the carb neck joines the manifold, and the corners wehre the manifold turns to go into the head one can get an easy 140 cfm through a stock manifold without much work. If I work a little harder and weld the corners up on the outside and really cut a nice sweeping D shaped radius inside I can get quite a bit more. With a larger carb flange and neck and some real trick work building some deflecters one can get over 200 cfm through one. It's all in what the rest of the engine and parts require and can support and how hard one wants to work.
This doesn't mean much for your stock cylinder head, cam and engine. The manifold will choke the head a little bit, but the carb will choke things even more. You're not going to see any big gains but go ahead and knock those corners out of the maniofld a bit and radius them it's not going to hurt a thing.
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"see what happens when you have no practical experience doing something...... you end up playing with calculators and looking stupid on the internet"
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Gatz in NE
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Posted: 02 Dec 2011 at 5:10pm |
427435 wrote:
......
Edit: For some reason, the "a" keeps getting replaced by an asterisk. sl*g is not a bad word!!!
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what do you get when you type Shift 8 (asterisk) ? and what do you get when you type an uppercase A ?
If those are screwed up too, your keyboard is probably at fault. Plug in a sub and see if that works.
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