Porting for larger Cross Section
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 1,131
Likes: 106
From: laingsburg MI
2020 C3 of the Year Finalist - Modified
Porting for larger Cross Section
Is there a safe way to increase (measure) the port min. cross section, without hitting water? I already have gone into the pushrod wall (welded up)... I think my 385 c.i. could use a larger c.s. I have edelbrock performer rpms, that are ported to a measured 193 cc intake runner. I think that the 6000+ rpm is breathing limited...
Race Director
Joined: Jan 2000
Posts: 13,017
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Well, for the first question.....I think you really have to have an idea of head thickness....and now you know that one! Just use some inside calipers to stay back from that level. You can also use head bolt sleeves if that is a tight area. I have some heads ported by AFR many years ago with them. My BBC brodix heads have been ported through head bolt holes too.
Here's some real interesting reading on the subject. This site has some of the major heavy hitters on it. Darrin Morgan from Reher/Morrison, Larry Meaux from Meaux Racing heads etc.
http://speedtalk.com/forum/viewtopic...er=asc&start=0
Hope this helps some....
JIM
Here's some real interesting reading on the subject. This site has some of the major heavy hitters on it. Darrin Morgan from Reher/Morrison, Larry Meaux from Meaux Racing heads etc.
http://speedtalk.com/forum/viewtopic...er=asc&start=0
Hope this helps some....
JIM
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 1,131
Likes: 106
From: laingsburg MI
2020 C3 of the Year Finalist - Modified
a lot of good info. This will assist in calculating the ideal c.s. minimum, then I will have the real world ex. of how to open port area at the pinch, without going into water or weakening the roof. The roof thickness (longturn area) can be measured with calipers? What about weakening the area beneath the valve springs?
I am not familiar with head bolt sleeves, can you explain more?
Thank you for your consideration
I am not familiar with head bolt sleeves, can you explain more?
Thank you for your consideration
Race Director
Joined: Jan 2000
Posts: 13,017
Likes: 2,261
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Yes they make long curved calipers that can reach around and measure the thickness of the head. Similar to ones that can measure piston dome thickness. You do have to be careful under spring pockets...they can crack if you cut too thin.
They make sleeves that you can press into the head bolt and pushrod holes...to seal off the holes when you port though them.
On Big Blocks, they often just leave it open. There is a bolt right by the pinch point in the port that needs to be opened up and it breaks into head bolt holes in two ports. It sounds weird, but it doesn't cause any issues. The head bolt seals the hole from vacuum and oil leaks. Putting a sleeve in place in that case would put you right back where you were before you opened it up. Check Brodix and AFR for the sleeves if interested.
JIM
They make sleeves that you can press into the head bolt and pushrod holes...to seal off the holes when you port though them.
On Big Blocks, they often just leave it open. There is a bolt right by the pinch point in the port that needs to be opened up and it breaks into head bolt holes in two ports. It sounds weird, but it doesn't cause any issues. The head bolt seals the hole from vacuum and oil leaks. Putting a sleeve in place in that case would put you right back where you were before you opened it up. Check Brodix and AFR for the sleeves if interested.
JIM
