Bad head for my 512 stroker

[pentastarpro]

Short block is done. Heads are done, well I thought so. Cleaned, maged, ported, gasket matched, polished, hard exhaust seats, milled to cleanup, paint, & freeze plugs. While lapping valves I found small dot in #2 intake seat so back to machinist (I do most my work). Each time we touched it, it got bigger - POROSITY!
In all the B & RB stroker builds I never saw a defect in the seat area. These are 4006452 castings (76'-78') from a motorhome with the additional 1/8" water holes around spark plugs to match the block.

Yeh yeh, I know buy a set of aluminum & forget it. Not me, i'm hard headed(sic).

Machinist will try cutting for replacement seat but where there is poroisty it usually runs through to water.
Anyone ever run into this before?
Anyone in socal have a spare head to match my good one? If not I will start over with a set of small chamber 3462346 castings I was saving for another 451 B stroker.

 

[AJ/FormS]

ouch

 

[IQ52]

Never seen a small chamber 346. Musta been milled a bunch.

 

[PRH]

It’s probably just a small void in the casting.
A seat will likely be all that’s needed.

 

[pentastarpro]

My machinist is trying the seat replacement first.

The 3462346 castings came in two sizes, 79.5cc & 81.5cc, however you can reduce the volume even more with flat valves rather than tulip but with a weight penalty. My reference to "small chamber" may have been misleading. Nothing compares to the 2708915 @ 73.5cc.

Thanks for the comments.

 

[Rmoore]

My machinist is trying the seat replacement first.

The 3462346 castings came in two sizes, 79.5cc & 81.5cc, however you can reduce the volume even more with flat valves rather than tulip but with a weight penalty. My reference to "small chamber" may have been misleading. Nothing compares to the 2708915 @ 73.5cc.

Thanks for the comments.

so how does this big cubic in run with the factory heads !! Plenty of torque I’m sure

 

[RustyRatRod]

My machinist is trying the seat replacement first.

The 3462346 castings came in two sizes, 79.5cc & 81.5cc, however you can reduce the volume even more with flat valves rather than tulip but with a weight penalty. My reference to "small chamber" may have been misleading. Nothing compares to the 2708915 @ 73.5cc.

Thanks for the comments.

ooo 2cc difference. That'll add power.

 

[PRH]

Those “79.5c “ and “81.5” cc numbers look like what you’d see in an NHRA tech bulletin........ which are usually way different than reality when it comes to BB mopars.

The virgin open chamber Mopar heads I’ve measured that still had the OE valves were in the 88-91cc range.

It takes a fair amount of milling to get one in that 79-81cc range.

Could there be some oddball thing out there with noticeably smaller chambers?
Sure...... never say never........ but 88-90 is what you’re going to get from just about any untouched open chamber BB Mopar head with the OE valves you come across.

 

[pentastarpro]

This "big cube" (507) is still in assembly rack. No vehicle yet. Head looks excellent after repair. Really pays off having a senior machinist that knows the process. Need a few more items to button this one up. Getting close.
My non-precision cc procedure is using a large syringe, not a burette , so my measurements have been 82-84cc w/OE tulip valves. Close enough for me.
"2cc, that'll add power" at my age, just as long as I'm the first one to coffee shop in the morning. Hi