exhaust port daming?

[first timer]

i have no idea what the techincal is called but i rember hoomgar posting somtin about flating the bottom of the exhuast ports out so it smooths the exhaust flow into the pipes.

my question is why bother with the head and ports at all can i just weld a plate to the inside of my header pipes, look at this website here and look at the pipe openings they are useing as a background image.

http://www.akrapovic-ai.si/main/catalog/products-catalog.htm

it just seems easier then foolin with the head.

i don't think i am goign to mess with anything but this is just a discustion post.

-ryan

 

[Dink]

IUf you take a look at the exhaust port shape on a 16 valve 1100 head the ports are shaped like that!
So in fact what you would be doing is actually called "port matching", this is done to smooth flow and increase horsepower.
Dink

 

[Billy Ricks]

I've never heard of damming exhaust ports. It's done all the time to intake ports on drag bikes. It's not a steet mod though.

 

[Hoomgar]

I've never heard of damming exhaust ports. It's done all the time to intake ports on drag bikes. It's not a steet mod though.

Billy, see Dink's post above. It is actually a very common street mod these days. The bikes Dink mentions and newer ones come that way from the factory now but older bikes like mine need the mod if you want this improvement. Performance shops that work on vintage super bikes are doing these jobs year round on a regular basis. It doesn't get talked about much because for some reason it seems to be the mystery mod among vintage bike owners yet it is nothing new. But loads of people are finding out about the improvement gained from it now more than ever.
Joe Paparo does several of these a year now on vintage super bikes.

I can get you more information on it from some performance shops around here if you so desire?

 

[Billy Ricks]

Mark,
Thanks, but my bike has them cast into the head. I don't doubt it gets done. I do wonder though what they are using to build up the dams. Epoxy is used in the intake runners, but I have doubts as to whether epoxy would hold up in the exhaust ports.

 

[Dink]

Billy as I understand it they weld into the floor of the port, then heat treat the head and start porting, the idea is to flatten the floor and build the height, and also to extend the length of the port divider, preferably to sharpen it up too.
Dink

 

[Hoomgar]

Mark,
Thanks, but my bike has them cast into the head. I don't doubt it gets done. I do wonder though what they are using to build up the dams. Epoxy is used in the intake runners, but I have doubts as to whether epoxy would hold up in the exhaust ports.

Works like a charm. They use a special high heat epoxy.

 

[Anonymous]

They make a plate that bolts onto big block chevys exhaust when you use a certain head. It raised the floor of the exhaust to promote better velocity. I've been away from cars for years and can't remember which head it was.

 

[gsbill]

Yo Yo Yo....Headwork is done with a flow bench...You cannot change the shape of your head without knowing if you are making improvements..THE FLOW BENCH...It is a time consuming process best left to only experienced personel..The flow bench measures air flow through the head and also allows for the actual flow of air to be adjusted for optimum performance. You cant just weld in metal or epoxy the floors and expect good reults..You may do more harm than good.

 

[Hoomgar]

Yo Yo Yo....Headwork is done with a flow bench...You cannot change the shape of your head without knowing if you are making improvements..THE FLOW BENCH...It is a time consuming process best left to only experienced personel..The flow bench measures air flow through the head and also allows for the actual flow of air to be adjusted for optimum performance. You cant just weld in metal or epoxy the floors and expect good reults..You may do more harm than good.

I took that as the obvious but that is a good point Bill that I wouldn't have thought needed mentioning. I didn't consider that someone would try this on their own without knowing what they are doing. But you are right, if they did it could spell disaster to performance. The pro's use the flowbench and several other flow tools that measure the throughput of the port as they "tune" it.

This kind of work is best left to someone who knows exactly what to do. Don't attempt it on your own thinking it is just a mater of putting it in there and then bolting up. There are loads of dynamics to it. I wouldn't even think about it.

 

[lhanscom]

Here's another link for info on this stuff.
http://mototuneusa.com/thanx.htm

 

[cbxchris]

Bill when we ran either gas/nitrous or turbo/nitrous bikes we tried several different port shapes,sizes etc. We came to the conclusion when you are using a artificial blower be it nitrous or turbo the port work has less and less to do with it. What we finally got to running on our funny bike was 1150 heads with 2mm over exhaust and 1mm over intakes. We just blended in where the seat work was done. Absloutely no port work other than that. It made no difference on the dyno or the track. Of course a carb bike would benefit greatly but you also have to have the cams,valves,carbs,cam timing and pipe to go with it. You also have to have the proper piston to work with a camshaft. I think on a strictly stock bike if all you do is port it you are wasting your time.

 

[Anonymous]

They make a plate that bolts onto big block chevys exhaust when you use a certain head. It raised the floor of the exhaust to promote better velocity. I've been away from cars for years and can't remember which head it was.

it is both the rectangular and oval port heads for chevy. they would provide better high end flow numbers but reduce low end torque ever so slightly.