I been working on porting these heads. I stuck a exhaust gasket up to the exhaust ports. eek! I think I need a bridgeport to cut out all that iron. How should I go about it????
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I been working on porting these heads. I stuck a exhaust gasket up to the exhaust ports. eek! I think I need a bridgeport to cut out all that iron. How should I go about it????
Dans66Stevens:
I been working on porting these heads. I stuck a exhaust gasket up to the exhaust ports. eek! I think I need a bridgeport to cut out all that iron. How should I go about it???? How does the gasket match to the headers? Are you sure you have the right gasket?
I have a set of Big Block felpro gaskets. They fit my Bassett headers perfect. I could remove about 1/8 on three sides.
There are alot of different opinions on this, but if the port is smaller than the headers, some porters will recommend leaving them that way. The mismatch has an anti-reversion effect. And if you have the D port exhaust, you should not grind the port floor round to match the header. The heads are disigned with the D port because they flow better that way compaired to the old style chevy 0 ports.
These are the round ports. Im going to just leave them alone.They have to be better then when I started.
Dan, Did you ever get those CMI headers to work?
wsm9808:
There are alot of different opinions on this, but if the port is smaller than the headers, some porters will recommend leaving them that way. The mismatch has an anti-reversion effect. And if you have the D port exhaust, you should not grind the port floor round to match the header. The heads are disigned with the D port because they flow better that way compaired to the old style chevy 0 ports. I agree with that observation. Many credible sources for porting/polishing say that if the exhaust port is smaller than the header to leave it alone. The same goes for a smaller intake manifold port into a larger cylinder head intake port.
But this has had my curiousity peaked lately with my BBC motor. Someone installed a Rect.port tunnel ram on a large oval port head (049). To me it would seem that there is a great disturbance of air-flow when the mixture rushes past the intake/head matteing area. Hmmmm... This is probably why I am ditching that intake for correct version. Many people have performed this Rect.port intake/oval port head match, but I don't necessarily buy the idea.
Any one have some credible input to this?
~Ty
HotCrusader, its funny you mentioned this. I have a friend who posts here on the boards all the time. He has a Hydro with a 468 BBC. He runs a oval port head with square port tunnel ram. The boat runs over 100 mph.
He has a old Hot Rod magazine with a dyno test that found 20 ponies from this combo.
I agree it seams kinda strange. It goes against all things I have ever heard. But Im going to try it on my 427.
Dan, I did the exact same thing back in the early 80's with a 396 and an Edelbrock TR2X, I ran 90 in a flat with it, it does work!.. :)
I ran that combo about 11 years ago. 427 BBC oval heads and square port Cragar (SSI) blower manifold.
Could not find an oval blower manifold back then. Seemed to shove enough in to make it go pretty well.
After I did that I got curious so I decided to go one step further, I did a build up of epoxy on the outer surface of the ports so I could smooth out the blend and raise the roof a bit and without any tuning changes, I got 3 more mph out of it, thought that was pretty cool, I wished I would have kept on experimenting with it!.. :cool:
Wow...So I suppose my motor was set-up with some care. I did find out that my cam is not an Erson but a Crower. Hmmmm....Part#297HDP 01244.
My crank is a cast version and the pistons are cast as well. Oh well....
Well, at least you got a good cam!.. wink :D
My machine shop guy thinks Im nuts!!!! eek! He says there is no way that set-up will make more power. This was a week ago.
The other night he says I may just try it out. wink He is getting smarter. :D
Thunderbutt, as far as the headers go they are Stellings Stainless steel. I have not tried to do anything with them yet except to polish them. They look great hanging in my shop. :D
The Schiada is in my storage building with about 3 feet of snow piled in front of the building. burningm
Ask him if he's ever tried it before! :rolleyes: just because he's a machinist, that don't mean he knows anything about making power!.. :D
I run my hydro with this setup, square to oval and it makes good horsepower. I've run two motors with this setup and both have worked well. The article that Dan was talking about was in an 80's edition of ***boat, and was writtin by a dragracer. His theory was that abrupt wall that the fuel and air hit caused a turbulance effect breaking up the fuel and air mixture. He did put bigger exhaust valves in the heads for greater exhaust flow. Maybe someone from ***boat could find this article. I may still have the article, will have to dig.
Exactly!.. :) Never seen that article, I'd like to raed that!.. :)
[ March 09, 2003, 07:21 PM: Message edited by: GofastRacer ]
This machinist friend of mine has built some very fast cars. Another words he is know Dummy. wink
We talked the other night about the epoxy. He said if you made the runner flow better he thought it would help. Just kinda interesting.
Well, since the castings are thin at that point, when you blend the manifold you have quite a curve in the head. With a build up you can straightened the port out more making it a straighter shot. The only reason I did it was that my heads were all beat up and I was going to shit can them anyhow, figure what the heck, why not try it, I was supprised at the outcome!.. wink :D
Dan,
If you could make a gradual taper from the manifold to the head with some epoxy you could have a tapering effect which could in the speed of the air and fuel. Any increase in air velocity in the intake port would help as long as didn't go up past 368 ft per second for the rpm range wink that you wanted to achieve. A lot of head porting guru's have a hard time achieving this port velocity.
kojac... wink
kojac:
Dan,
If you could make a gradual taper from the manifold to the head with some epoxy you could have a tapering effect which could in the speed of the air and fuel. Any increase in air velocity in the intake port would help as long as didn't go up past 368 ft per second for the rpm range wink that you wanted to achieve. A lot of head porting guru's have a hard time achieving this port velocity.
kojac... wink
OOOps
I meant to say an increase in air speed. Of course you already knew that.
Kojac... :)