Minimum safe port wall thickness

[BILL-C]

Just wondering what other head porters use as a minimum safe port wall thickness in aluminum 23* sb chevys in bowl on common wall between exhaust and intake ports. How thin have you gone without problems? How thin did you go and HAVE a problem? There isn't any water there on heads in question. I'm a little worried about both excessive heating from exhaust port to intake charge and cracking.

[mag2555]

First some questions of my own if you do not mind?
1) what heads and valve sizes are we taking about and what port runner volume are they now?

2) how much do they flow now ( are they stock ?) and how much more are you looking to yank out of them?

[BILL-C]

We are in the middle of making a new cnc program to port Brodix dragonslayer 200 castings and came across a little bit of core shift. If we mirror image the intake ports and offset to standard bore space we will end up with the port thickness between intake and exhaust port in bowl area on one of the end cylinders at .060 in one spot. It looks like end cylinder core is .020 out of place.Seats and guides are correct.We can either put the port where it is supposed to be and settle with .060 thick at small spot in question, or move port location to follow shift of casting[ like you were hand porting] and keep port thickness at .080 minimum. The thinnest i have ever seen a casting ported to in this location is .045 by another shop for a drag race only app and has lived for a year so far without issue. Has anyone gone too far and had a problem? Where is the line that should never be crossed?

[statsystems]

We are in the middle of making a new cnc program to port Brodix dragonslayer 200 castings and came across a little bit of core shift. If we mirror image the intake ports and offset to standard bore space we will end up with the port thickness between intake and exhaust port in bowl area on one of the end cylinders at .060 in one spot. It looks like end cylinder core is .020 out of place.Seats and guides are correct.We can either put the port where it is supposed to be and settle with .060 thick at small spot in question, or move port location to follow shift of casting[ like you were hand porting] and keep port thickness at .080 minimum. The thinnest i have ever seen a casting ported to in this location is .045 by another shop for a drag race only app and has lived for a year so far without issue. Has anyone gone too far and had a problem? Where is the line that should never be crossed?

I've had to repair some 18* stuff with port intruders because they were about .080 thick.

IMO they should have installed the port intruders first.

[Cubic_Cleveland]

I’ve had to repair a pair of Edelbrock 15° Victor SBF heads that were around .040” in that area and had cracked between both bowls. There was no water anywhere near the cracks, but it took 16 inserts, 16 guides and some weld to repair! This was a turbo charged 440cui drag engine making around 2000hp on meth and had survived 4 seasons of hard racing. Maybe we could have left the cracks as it didn’t appear to leak gas, but how could you warrant them not going further and finding water eventually, or an inset falling out...

[BILL-C]

I am going to play it safe and follow the existing port casting on end port. It's a bit more work, but would prevent a few more grey hairs.

[BILL-C]

Thanks for replies.

[Krooser]

I'm wondering why the head mfg.'s don't check for core shift before they ship those heads. It's not like Brodix is selling a Chicom knock-off... these sell for real money!

[BILL-C]

Darn near every ready to run casting has some core shift. Oem,aftermarket, iron, and aluminum. They are as good as they need to be for the intended application.Some are way worse than others. That is why we usually start with a pro-port ultra small opening raw casting when we can. I'm just a glutten for punishment and am chasing a PITA market that most cnc guys don't bother with. Anyone familiar with how heads are cast can verify how difficult it can be to make precise pieces, especially towards the end of the life of the casting tooling.

[BILL-C]

The brodix castings are like swiss watch parts compared to some of the cheap import castings i have played with. Brodix has good stuff.