How thin is too thin, bowl porting thickness ??

Guest · Post by **Guest** » Sat Jan 29, 2005 5:33 am

Ok, have a straight six head here & the fellow wants to install bigger intake valves etc, I've checked bowl thickness & required grinding in the bowl after machining the seat, haven't started yet but it works out there will be about .100 thickness left in the bowl wall after grinding bowl blending etc on average, is this getting too close for comfort or am I being paranoid ?

John Haskell · Post by **John Haskell** » Sat Jan 29, 2005 12:52 pm

You're good to go. The areas of concern will allways be at the core split & at the bottom of your throat cut when cutting heavy material. You will never know how thick this area is, but when you start grinding, you either are prepared to fix this stuff if you go through it or you shouldn't be doing it. This port break through is so common in this line of work, us old hatters don't even get shook up over it. ------ Have your customer get you an old part & cut it up if he is into it. That's what is done here.

Guest · Post by **Guest** » Sat Jan 29, 2005 4:41 pm

thanks John, just wanted to run through this with someone before attacking it with the cutters, the core is fairly consistant with no shift

bill jones · Post by **bill jones** » Sun Jan 30, 2005 1:12 pm

-how did you determine the the thickness of the bowls?
-How large is the surface area that you found to .100" thick?
-Are you going to install seat rings?
-What type of head is this?
-Are you going to port the head of just do the valves and bowl blend?

Guest · Post by **Guest** » Sun Jan 30, 2005 5:58 pm

It's a Hemi 265 ci straight six ( Bill Jones is probably thinking what's that? )

borrowed a sonic

Full porting job

bill jones · Post by **bill jones** » Sun Jan 30, 2005 8:42 pm

-I can't recall ever seeing an inline himmy head, but obviously it's something that you probably wouldn't have access to cut up another head just to look at it.
-If you can believe your sonic tester I would wonder how much of an area is this .100" thick.
-Just yesterday one of the guys at Chapmans was telling me that he couldn't get accurate sonic test measurements on a 440 chrysler cast iron block yet they never had a problem on any other head or block.
-I wouldn't worry about the .100" at all but it's the always the little surprises that get you.
---------------------------
-I have ported just enough SBF windsors (and 2V cleveland heads) to know that just about when you get the ports to where air is starting to do what you want it to do that you find a water hole, like the 291 heads on the other thread.
-It doesn't bother me anymore to have to braze up a cast head because I have the equipment and the procedure down real good, but the customer really should the final say about getting greedy on thin castings.
-it's just that the customer needs to be prepared for that extra expense.
----------------------------------
-If this engine supercharged, thin areas could be an issue.
-I've had to braze up seat ring bores where they've broken into the water jackets from being real thin once you get cutting in there.

Guest · Post by **Guest** » Sun Jan 30, 2005 9:19 pm

Going on the shape of the bowl area the thinnest part on the side wall of the bowl would be approx a bit more than 1/2 inch in area on each side of the bowl, nothing really I guess to worry about

I've done plenty of welding before but would prefer not to have to do it

and no it's not supercharged

bill jones · Post by **bill jones** » Sun Jan 30, 2005 9:33 pm

-I'd have to assume that the ports are all symetrical, that they look identical, don't have 3 lefts and 3 rights?
-If they are symetrical then chances are better than if you had lefts and rights, because of coreshift.
-----------------------------------
-I did a pretty serious job once where we cut up one half of SBC Bowtie head, dissected a pair of left/right ports, and proceded to port the heads based on what I found.
-The problem was that I dissected the wrong half of the head and the other half left me with a quarter sized hole in the bowl wall next to the exhaust bowl.
-That was the worst job I ever had to try to repair.
-I took the other half of the cut head, ported it and found the same exact problem.
-I never could get that fixed so the pair of heads with two big holes had to be sent to someone better than me to get fixed.

Guest · Post by **Guest** » Sun Jan 30, 2005 9:49 pm

this head isn't a left / right so ok there

sometimes I've had to disappoint a customers power dreams & maximum cfm for the sake of not hitting water, it makes so much extra work, I have however in the past welded to add / change port shape to make good gains in cfm, but these days don't get involved with it much