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choptop0130

800cc intake and exhaust port matches!!!!!!!!!!!!!!!!!!

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So i am at the point that i am thinking about popin the intake and exhaust off my 800cc to see if port matching them or if they need matching! The exhaust shape is like a D shape, kinda strange to me but are wanting to know if anyone has looked at these motors before and if they have poor matching from the factory and could benefit from this expotentialy! if the intake manifold is smaller than the intake of the head but by just a little then i'm good with that, if the exhaust is a little bigger than the exhaust port, i'm good with that too, so, anybody been into one and does anyone know who carries the gaskets for both? Thanks Guys!!!!!!!!!!!!!!!!!!!!!!!!!!!

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The ports shouldn't be bigger as you described. If there is a step in the intake or exhaust flow, This sets up considerable turbulance in the flow which holds back the flow. This is true rather the air hits a wall it has to jump down or a wall it has to jump over. they both set up turbulance. Kind of like water flowing down a nice smooth flume, very fast, as compaired to water flowing down a rocky river, slowed way down because of all the turbulance created. The ports should match, reguardless which side it's on, Where the port is smaller, match it to where the port is bigger. This may be at different areas on the same port. The more unobstructed the flow the more air you get thru thus more power.

Lenny

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Lenny, for the most part i agree with what you are saying however a few years ago i was able to set in on some would consider to be "secret" workings in racing and was able to watch several different motor configurations hence 2,3,4,6,8,10, cyl motors with die in the fuel run in a black light room, the lesson i learned was unreal, a motor inhales and exhales almost as we do and the gas that comes out the top of carbeurators is unreal. The point being the when correctly placed reversion dams in the flow path makes a motor a much more effecient machine! This is not as prodominant in fuel injection motors but still present none the less so for the configuration i was speaking of would be exceptable for me. My 355 dirt motor with intake and exhaust ran on the dyno with the mods made our gasket mods on the intake and header adapter mods yeilded a 18 H.P. differnce and 12 ft. lbs of torque. That is with out a jet change.

So that's a little on a subject of the past i'm glad to be away from........we use to call it going to the fights and hope a race breaks out LOL! Just trying to see if anyone has been into one and seen first hand if it is off by much and how bad! I called silverbullet over a week ago and left message for rick to call me on the cams but no return call, this isn't the first time that's happened, maybe busy or vacation or something but maybe when he gets time i will hear from them, it would be definietly interesting to see what those cams would do for my type of racing! Might let me knock down that shifting thing i have to do down 20 or 30 shifts per lap lol!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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so heres a dumb ?? but I will ask anyway. all this talk about matching the exhaust and intake your not talking about just doing the manifolds you also talking about removing the head and natching it there as well right????

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Yesl, the head too and in my case I cleaned up the head all the way to the valves so it was a less curvy path to get there. Your right about the air dams but that is only when they are carefully placed by computer or thru experimenting. Not placed right they would hurt performance. They are not there because they flow more air but I beleive to help counter the effect of the intake valves not opening in exact timing with top or bottom dead center and conditions caused by ram effect. I would think that ram effect on an engine is rpm specific and at certain rpms that bounce back could also be an issue. Dams could counter this issue. Also, back pulsing up the intake from the combustion chamber wants to be stopped. Two cycle engines use a reed valve which acts like a dam to stop back pulsing. I'm going to shut up here because the complexities of highly developed intake systems is beyond my learnings. I'm sort of guessing based on my feel for physics.

Lenny

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Really a good analogy lenny, and pretty close there as well, our race engines have benefited from this practice for a few years now, as well it makes them have a real crisp raspy sound that just throws people for a loop! We are big fan's of david vizard a world renowned mechanical engineer that applied alot of theories to racing, he also made a believer outa us on dimple motors and fire sloted pistons with less timing! The more timing you got in a motor the more it is trying to fire the motor to go bsckwards when fired on the compression stroke. With all the correct applications applied to a motor it will stand about 22 to 27 degrees of timing before it starts to go hott, it is a MUCH more complete burn done this way and the swirl affect is capitalized on greatly, atomozation is acheived easier thru this set-up, if ya get a chance take a look at his articles on the net, it is to some "bsckwards" thinking but in a v-8 with the correct camshaft specs the motors are beasts!!!!!!!!!!!!!!!

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Matching the intake ports is a very good idea, but you need to be very careful when you start to work inside the intake ports of the head itself. Yes there are benifits to be had from porting the head itself but the shape of the ports are configured from past experience and then programed into a computer to get good flow, but keep in mind that this is done to be able to comply with emissions. There is alot to be gained by porting heads for HP you just need to keep the shape close to original, especially on the intake side because it relies on vacumn not pressure like the exhaust. I did some port work many years ago long before multi valve heads came out but before the advent of these type of heads it was pretty straight forward, now there is alot more swirl effect on the air going into the cylinder and it is very easy to ruin this effect. If you want to port the heads I myself would find someone that does it for a living and has a very good rep because once it is done if it's wrong you will be buying a new head. If you go the route of forced induction, if you do, you need to tell them what type of setup you will use because if memory serves me it makes a differience.

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Really a good analogy lenny, and pretty close there as well, our race engines have benefited from this practice for a few years now, as well it makes them have a real crisp raspy sound that just throws people for a loop! We are big fan's of david vizard a world renowned mechanical engineer that applied alot of theories to racing, he also made a believer outa us on dimple motors and fire sloted pistons with less timing! The more timing you got in a motor the more it is trying to fire the motor to go bsckwards when fired on the compression stroke. With all the correct applications applied to a motor it will stand about 22 to 27 degrees of timing before it starts to go hott, it is a MUCH more complete burn done this way and the swirl affect is capitalized on greatly, atomozation is acheived easier thru this set-up, if ya get a chance take a look at his articles on the net, it is to some "bsckwards" thinking but in a v-8 with the correct camshaft specs the motors are beasts!!!!!!!!!!!!!!!

I watched a 2hr Youtube video of one of David Vizards seminars.

Good stuff and very edicuational, I recommend that anyone interested in best preformance out of their engine watch his stuff. Going to watch the rest of his videos myself. I like the way he thinks, He bases all of his thinking around the physics then he confirms it with extensive testing. A lot of people talk physice but they don't really understand it, but he does. Every little detail is physics to him.

Lenny

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