[v869tr6]

If I drill a 0.625" hole down to within 1/2" of the deck between the ports, will I break into the ports on a unported head?

[73 TRANSAM]

No you won't, this is for a water mod to cool the heads better. I did one on each side of the middle exhaust port.

[v869tr6]

Originally Posted by 73 TRANSAM

No you won't, this is for a water mod to cool the heads better. I did one on each side of the middle exhaust port.

No this is to press a 0.625" OD chrome moly tube into the bolt hole, so the clamp load will be on the deck.
I could pull the exhaust off and measure, but I would rather not if I don't have to..

[blaktopr]

I have a cut up head I can try it on later if nobody else knows

[Tom Vaught]

Look forward to that info Chris.

Tom V.

[v869tr6]

I called Edelbrock and asked, tech said it is a casting but should have at least 0.200" on the outside of the bolt hole.
I should be good, thanks

[73 TRANSAM]

I did these on my heads after talking with Charlie. The tubes will show on both side of the middle exhaust ports. But it shouldn't leak as it is pressed fit. Good luck.

[v869tr6]

Originally Posted by 73 TRANSAM

I did these on my heads after talking with Charlie. The tubes will show on both side of the middle exhaust ports. But it shouldn't leak as it is pressed fit. Good luck.

Are your heads ported?
What size tube OD?

[steve25]

How the heck much flow are you looking to yank out of the Exh ports on these heads?
I see no need to port back that center divider so thing so as to need extra Bolt support.
There is more then enough port wall meat on the opposite wall to maintain the needed port area by just grinding along gentle curve into that outboard wall!

On these heads ( the high comp version) the Exh valve bowls are nice and deep, this means that with the right bowl shape and valve & seat angles the flow cone around the valve closes back up as it should before the crown of the short turn, this in turn means you can do some shuffling around of the Exh flow without paying a flow loss price.

[slowbird]

If you're pressing in a tube why does it matter if you break into the exhaust ports?

[73 TRANSAM]

My heads are Butler WP 59cc. My pistons are .145 below the deck to compensate for the heads.

[john marcella]

The bolt-hole is .530 at minimum , you're going to put a .625 in. So at best your gona have .052 radial register for clamp load. Its gona crush.
Still it may be better as it might split the load between the top of the existing bolt hole and the bottom of your tube register.
If you having a problem I would go bigger. Doesn't matter if you break into the port. I do it on almost every set. Not just on Pontiac either and still run no tubes whatsoever.

[73 TRANSAM]

I believe the size that I used was .750 moly tubing. It is a .120 wall. I would not use .625 as it doesn't have enough meat on it. I also went 1.25" deep as I didn't want to hit the helicoil on the outer exhaust port..

[BruceWilkie]

Originally Posted by 73 TRANSAM

I believe the size that I used was .750 moly tubing. It is a .120 wall. I would not use .625 as it doesn't have enough meat on it. I also went 1.25" deep as I didn't want to hit the helicoil on the outer exhaust port..

This^^^ It should also keep most of the shank of the fastener off the tube and allow less heat conduction to the fastener.

[steve25]

Does not anyone think that having 1400 degree Exh gases right on a Head bolt call for rethinking the clamping load that said bolt can provide?!
Also the Exh flame gets down to the Heads gasket area around that bolt and its not made to handle that.

I would machine down a 1/2" OD cast iron Valve guide to do the job if it where me.

[charlie66]

Originally Posted by v869tr6

If I drill a 0.625" hole down to within 1/2" of the deck between the ports, will I break into the ports on a unported head?

Ed.. I used .120 wall .750 tube . Fixed my head bolt sinking problem 100 %. Tube did not break though exhaust ..

Good luck!

[73 TRANSAM]

Originally Posted by steve25

Does not anyone think that having 1400 degree Exh gases right on a Head bolt call for rethinking the clamping load that said bolt can provide?!
Also the Exh flame gets down to the Heads gasket area around that bolt and its not made to handle that.

I would machine down a 1/2" OD cast iron Valve guide to do the job if it where me.

I am not running a head gasket. I'm running Marty's sealing rings on my setup. Also I don't think it would leak as it is a pressed fit design. I'm always afraid of cast iron as I don't think they're stronger than a steel.

[v869tr6]

Originally Posted by john marcella

The bolt-hole is .530 at minimum , you're going to put a .625 in. So at best your gona have .052 radial register for clamp load. Its gona crush.
Still it may be better as it might split the load between the top of the existing bolt hole and the bottom of your tube register.
If you having a problem I would go bigger. Doesn't matter if you break into the port. I do it on almost every set. Not just on Pontiac either and still run no tubes whatsoever.

Thanks John, looking at the 0.058" wall I was a little worried I would get the stud stuck in moly vs alum....would be ugly.

[v869tr6]

Thanks, Charlie and 73Transam, I will order some 3/4" 0.120" wall How much deck thickness did you guys leave on the center bolt hole?

[73 TRANSAM]

Mine was about 1.25" as I do not want to hit the helicoil on the two outer exhaust ports. I believe Charlie is about an inch from the deck.