blowing the floor out..porting

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sr5bidder

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the exhuast port is really restricted ... i ground the floor out to a more round shape the original shape was like a d shape
 
Improvement? Wellllll... yes and no. Maybe.

Without an inside micrometer and a flow bench, it may or may not work. Grind too much, and you can make the flow "stall" between the valve and head outlet.

Some '80's-90's GM aluminum heads (Corvette) use a D shaped port from the factory. Ford 351 Cleveland 4V heads sometimes use port plates or a special epoxy to achieve the same thing. I have a factory '83-85 Mustang 5.0 carb intake that has raised runners that are smaller than the head port. It has to do with volume vs. velocity.

Something like this:
http://www.mpgheads.com/port_plates_a.php
or do a Google search for "351C port stuffers".
 
MotoArts said:
Improvement? Wellllll... yes and no. Maybe.

Without an inside micrometer and a flow bench, it may or may not work. Grind too much, and you can make the flow "stall" between the valve and head outlet.

Some '80's-90's GM aluminum heads (Corvette) use a D shaped port from the factory. Ford 351 Cleveland 4V heads sometimes use port plates or a special epoxy to achieve the same thing. I have a factory '83-85 Mustang 5.0 carb intake that has raised runners that are smaller than the head port. It has to do with volume vs. velocity.

Something like this:
http://www.mpgheads.com/port_plates_a.php
or do a Google search for "351C port stuffers".
Click to expand...

^^^ what he said:tup:
 
You have to keep in mind that the exhaust flows different than the intake because of heat. You are not going to help the engine at all by messing with the exhaust. Why do you think it is that a 1 mm intake valve is offered, but no oversize exhaust. Clean up the sharp edges and casting imperfections, then polish it glass smooth and leave it at that.
 
Do not blow the floor of the port out. Do not mess with the short side radius unless you are merely blending it. You can clean up & narrow around the guide & make sure that the long side radius is very nicely blended. Airflow whether it be intake or exhaust has a tendency to flow along the roof of the port. Also, a good valve job would be the key to seeing good improvement.
 
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too late fella's. its gonna be hard to tell if it has any effect on power because when I install this head I will be also putting a wiseco piston in with higher compression.
It is a spare head I had anyhow I started to grind the carbon build up in the exhaust port and got carried away, i have not torn down the engine yet.

anyone know how to get the bind needke bearing out for the cam?
 
Midway if you think about it its like smokey yunick said the more you get in, and the more you get out the more power. sounds to me like that involves the exhaust.
 
97warrior350 said:
Midway if you think about it its like smokey yunick said the more you get in, and the more you get out the more power. sounds to me like that involves the exhaust.
Click to expand...

Do some more reading on porting and the basics of flow through an engine. The exhaust is more efficient than the intake side because of the heat involved. I am no porting expert by any means, but have ported lots of stuff over the years. Everything I have ever studied warns against opening up the exhaust. If you get the exhaust too big it hurts the scavenging. This is very important on overlap when the scavenging is helping pull in more air/fuel mix. Most anything you read on exhaust porting says to raise the roof of the runner. Heat always rises. Opening up the floor area probably is bad for flow.
 
this is a 4 stroke, scavenging is realated to 2 stokes for all I know?? Do the valves overlap in timing?

I was just thinking folks all the time are putting big money into exhaust systems that flow more freely, so what would be the difference between the begining of the system (head) and the end (slip on)

also there are alot of threads hear on grinding the weld inside the header flange as a mod, do ya'll just grind the top of the weld?

I may get some pics of my work soon, the floor was the easy part the roof is hard to sand so I am not done. I may need to go over to harbor frieght and see if they have any small flapwheel barrels for my dremel
 
sr5bidder said:
this is a 4 stroke, scavenging is realated to 2 stokes for all I know?? Do the valves overlap in timing?

I was just thinking folks all the time are putting big money into exhaust systems that flow more freely, so what would be the difference between the begining of the system (head) and the end (slip on)

also there are alot of threads hear on grinding the weld inside the header flange as a mod, do ya'll just grind the top of the weld?

I may get some pics of my work soon, the floor was the easy part the roof is hard to sand so I am not done. I may need to go over to harbor frieght and see if they have any small flapwheel barrels for my dremel
Click to expand...

Well, yes & no man. A 2 stroke is a whole different animal in that it's exhaust is an extension of the engine & not just an addition. 4 strokes do have overlap, more with longer duration cams & what not but it's really difficult to relate the 2 engines, they accomplish the same thing but go about it totally differently.
I don't think anyone is saying that the exhaust side isn't important on these engines, it is, it is on every engine. What I was thing to say earlier is that typically a port will flow the majority of it's volume along the roof of the port. This isn't to say that the floor is unimportant, it is. It's so important that if you mess with it then what you do can be detrimental to how the roof of the port flows & then you have a problem. In short term, basically a mild blend of the port floor is all that is necessary.
Also, we all do blend the entire header as the exhaust port turns rounds as it exits.
 

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'00 WO-YA! said:
Do not blow the floor of the port out. Do not mess with the short side radius unless you are merely blending it. You can clean up & narrow around the guide & make sure that the long side radius is very nicely blended. Airflow whether it be intake or exhaust has a tendency to flow along the roof of the port. Also, a good valve job would be the key to seeing good improvement.
Click to expand...

i see what you mean ...I just took the head off the warrior and there is sticky stuff in a very defined area on the roof of the exhaust port... the bike was smoking real bad ...the valve guides and seats appear to have been replaced in this head it may have a bigger intake valve too i will check...and besides all the carbon and goo it seems in better shape than the other I was grinding on

I will work on this head as suggested
 
well I found alot of ridges where the new valve seats where installed sharp little buggers right behind the valve seats both intake and exhaust and smoothed them out

There are sharp little ridges around the face of the valve seats in the combustion chamber that might seem cause flow turbulance when the valve opens ...should I knock the sharp lip off these areas?
 
well I got everythin buttoned up on sunday I would have finished on Saturday but when I traveled down to O'rielys to get a new plug I stoped in the right stuff for a 18 pack of beer and to say the least nothing else got finished on Saturday except the 18 pack.

I put the original head back on and a piston and cylinder I had bought off ebay about a year ago, it had a wiseco 1mm over oiston with no indicated wear so I did a very light hone and installed it with new circlips.

It fired right up and does not smoke any more! I had a brief period of smoke about 15 minutes into the rings setting up, it smoked lightly for about 2-3 minutes, I hope that does not return but so far so good

I must have done something right as it feel like it has alot more power and the carb adjustments I was chasing to make it run good are all gone ( I guess it was low compression and all that carbon build up).

Now I need to find a rear caliper and a right upper a-arm
 
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