Engine: Cylinder head porting WTTW...

[Mike Van Veghten]

That's...."Word To The Wise...
Those of you doing your own porting...

I thought I'd check the common wall thickness (exh. to int.) before "rounding" off that part of the intake bowl wall. This is with using either the stock 1.750" dia valve and espicially the R3, 1.875" dia. valve.

On one pair I'm now reworking, I found "one" intake port that was very thin (as checked SEVERAL times with my sonic checker). And that was with NO grinding yet. I even lightly smoothed the wall to get rid of any roughness, at least on the port side. No help..!
I was told (by a pro) about .095" to .100" was about as thin a wall as you'd want to go.
Well, this one port was already only .180" thick to start with. .080" isn't nearly enough to fully "round" the bowl of the port.
All the rest of the ports are .220" to .240" thick at the common wall...which is about enough to round off the bowl..and leave suffecient wall thickness.

Was this caused by rust, casting porosity, a bad casting plug....no clue....but I've already got enough money into these heads to NOT take the chance and loosing a head. I'm not Pro Stock racing....so...I'd rather loose a coupla CFM than a head.

And just to drive this home a little more, one of the high dollar (moved the valve over) sets I'm reworking, was also thinner than I'd like....and this was with moving the valve over..."away" from the exhaust..!

While not as pretty...might be a good idea to leave that part of the intake bowl a little flat..!

As someone around here always says...your heads, your money..do as you see fit.
I thought I'd just pass along the information I found this morning.

Mike

[Skybolt]

Which port was that? Was it the same for the other heads or just one? Were the heads 570's as the ones I saw you doing were 570's? Where exactly was the thinnest part that you are going to leave flat? Does this mean you will do the same for all other ports on those heads as to get similar flow characteristics?

[Mike Van Veghten]

Which port was that? -
Second from the right.

Was it the same for the other heads or just one? -
The second head (of the pair) was simillar, but not nearly as thin.
As noted above, I've also had a pair of heads that was thin in that area...all eight ports.

Were the heads 570's as the ones I saw you doing were 570's? -
Different heads than the ones you saw, but yes, also 570's.
In my early venture into Stude heads, I found that the 570's seemed to be the most reliable, wall thickness wise. Looks like even they can be hit and miss.
Glad I bought the Sonic Tester....!

Where exactly was the thinnest part that you are going to leave flat? -
As noted above, the common (int. to exh.) wall in the intake bowl. From just under the solid area (common iron to both ports) into the bowl as far as my probe would go....near the roof.

Does this mean you will do the same for all other ports on those heads as to get similar flow characteristics? -
I stopped and thought about this for a couple of hours. I ended up splitting the difference..! While I didn't open the rest up fully, I did go a little farther than the "bad" and the second to the worst port. In thinking about all of the differences I've seen over the years in heads and manifolds...hell...even Edelbrock made an intake manifold that had different sized intake ports for half the engine from the other half..!
Intake manifolds are the worst. Both duel AND single plain manifolds....out of the box...each runner flows a different value (in "most" manifolds...not all !). Remember the big block Chevy heads...? Two good ports and two marginal ports. Up until the aftermarket started evening up the ports....that took twenty years...!
So yea...two ports are one width and the rest are a little wider in the bowl.

Mike