SuzukiSavage.com - dremel the intake port ?

batman

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dremel the intake port ?
11/25/17 at 21:56:28

We've covered the exhaust port a number of times ,but I've not heard much about the intake port. The bottom of the head bolt (under the carb) sticking up into intake as been ground down by a few ,but besides that most have not ventured any farther ,thinking that there was little/or no room for improvement .That is not entirely true . Unlike the exhaust, the fuel mix is pushed toward the top outside radius of the passage and this is where we can make the most improvement. The valve guide and boss are in this path and by reducing it(carefully) and making it a bit more aerodynamic and grinding the walls a bit and all the way around near(but not larger)than the valve opening. This will increase the density of the fuel /air mix sitting behind the valve until it opens and is jammed into the cylinder, which boosts compression (TO 9:1)torque and horsepower( 2.5HP). somewhat less effective is to also remove some material from the sides of the passage at 3 & 9 o'clock, and toward the middle of the inside radius to increase flow in the center of the passage. I don't know how any of what I said could be done without removing the head and valves, but you might get that far into the motor someday .

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Dave

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Re: dremel the intake port ?
Reply #1 - 11/26/17 at 03:43:27

I did some work on mine - but not a lot. I sharpened and smoothed the divider where the inlet splits to the two ports, I did a bit of smoothing where the seats are installed in the head, and I believe a did a bit of work to narrow the guides (later model guides are already tapered on the end).

When you replace the stock 40mm carb with a 36mm Mikuni, the intake port has a larger diameter than the carb and rubber spigot/flange that holds the carb onto the head......so there is a very sharp step/change in size between the rubber flange and the port - this has to be creating some turbulence in the intake. It may be worthwhile to make a piece of aluminum that fits between the flange of the carb spigot and the head that creates a smoother transition.......I am not sure if there is enough rubber in the flange to allow some blending to occur.

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Christof13T

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Re: dremel the intake port ?
Reply #2 - 11/26/17 at 08:56:01

I looked real hard at the intake while I had the GF doing the port work on the head, and came to the conclusion that any minimal gains from working the intake port were not worth the risk of making a damaging mistake. I had her smooth out the end of the stud and called it a day.
I could not be happier with the results. Of course upgrading to the 97mm piston probably had a little something to do with the extra testicular fortitude now present.

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batman

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Re: dremel the intake port ?
Reply #3 - 11/26/17 at 09:06:06

Dave I'm not sure that a little turbulence in the passage is all that bad , your rubber carb mount being smaller than the opening in the head shouldn't cause that much,you will always have some due to valve stem and guide anyway. Using a 36mm carb instead of the stock 40mm also has the advantage of the higher velocity dropping faster which increases it's pressure at the back of the valve as does enlarging the passage just above the valve. All of which should increase torque and hp . It seems to me that what you did was right on the money. I mentioned widening the walls and easing the inside radius but this will have much less gain than what you've already done and may not be worth doing .

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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: dremel the intake port ? Reply #4 - 11/26/17 at 09:18:08 http://ultimateaircooled.com/tech/11333-dimpled-intake-manifold-intake-port-h...
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Christof13T Full Member Offline SuzukiSavage.com Rocks! Posts: 211 Vicoria, Texas Gender:	Re: dremel the intake port ? Reply #5 - 11/26/17 at 10:10:59 justin_o_guy2 wrote on 11/26/17 at 09:18:08: http://ultimateaircooled.com/tech/11333-dimpled-intake-manifold-intake-port-h... Did you know that dimpling technology to reduce surface drag was developed in an attempt to mimic the skin of a shark? Very interesting stuff Justin.
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batman Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 3806 osceola new york Gender:	Re: dremel the intake port ? Reply #6 - 11/26/17 at 15:14:42 No polishing of the intake is ever suggested ,the ruff casting of the walls doing the same as dimpling would, that is creating a boundary layer at the walls inside of which the fuel stream flows faster.
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Ruttly

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Re: dremel the intake port ?
Reply #7 - 11/26/17 at 19:25:25

Fuel entering into port will pool mostly around valve guide , a rough casting or dimpling gives the fuel a high points to be drawn up and reatomized instead of passing into cylinder as raw fuel. This doesn't mean you can't make it flow better,just don't get carried away removing that nice casted surface. Now engines that run alcohol or nitromethane it's a different story.

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Ruttly Serious Thumper Offline Thumpers Rule Posts: 5112 Manteca , CA Gender:	Re: dremel the intake port ? Reply #8 - 11/26/17 at 19:37:22 I did some port matching with the rubber manifold for the Vm36 and have a smooth transition and also made a heat shield to keep some of the head & cylinder heat off the carb,well I modified one from a SR500 to fit. So it's gasket,heat shield,manifold all port matched together. Cool fuel is better than hot fuel !
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Dave YaBB Moderator ModSquad Offline SuzukiSavage.com Rocks! Posts: 18101 Camp Springs, Kentucky Gender:	Re: dremel the intake port ? Reply #9 - 11/27/17 at 08:18:11 I found a photo of what I did to the intake port on my Cafe' bike. The port was not polished - the sanding marks were retained to retain a somewhat rough surface. (On the next one I might bead blast the surface to provide the roughness).
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