Convertible milling job on D-ports
 

So... anyone done it ? Have pictures or info on the subject... can't seem to find any info on it.

Was tinkering with the idea and wanted to try it on a junk head in one of the 5 ax mills at work, chop some off and do a new flange layout.



Kris.

Whats the benefit?

This is to make it easier to make an up/down and forward turbo headers.

I have seen several attempts with doing a machined off cast iron flange and a tube stuck into the exhaust port. Mostly RA-V deals from many years ago.

If you had new virgin castings then a good cast iron welder could probably what you are after if he also machined up a cast iron mounting flange that would allow the ideas you are proposing.

Has been done with SB Chebbys a few times.
A friend did that with a twin Turbo Corvette set of manifolds. Turbo flange on upside down manifolds.

Tom V.

Almost 60 years ago Mickey Thompson did that to a number of his Pontiac engines. His catalog even listed the weld-on flanges for guys who wanted to DIY.
[Of course we didn't call them D-ports at the time- just Pontiac ports]

Was not aware Jack that Mickey offered the Cast Iron Flange for sale. Thanks

Tom V.

I was under the impression there would be no welding needed ?.. only a drill & tap deal after the big milling job ... worst case some custom inserts threaded into the head sides for the header/manifold clamping.



Kris.

Some years ago I had a set of "D-Port" cast iron heads cut (top to bottom) right in the middle of the #1 exhaust port and the #7 exhaust port. I was basically using that cut up head to have a mounting pattern for some supercharger brackets.

There is a nice solid chunk of iron at the top of the exhaust port in the head but there is a very large water jacket at the lower part of the head under the bottom of the exhaust port.

So how are you going to seal up that water jacket? What happens to the head cooling if you remove that water jacket?

May be a way around that issue but not a simple one like you describe in your post.

Tom V.

Thanks for the reply Tom! See now I’m getting somewhere ... that’s the sort of detail I’m seeking


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How do they do it on the CV-1 heads? Relocate water jacket?

Maybe they can post up the mods that they make with their ALUMINUM heads so that they can do a normal port and a high mount exhaust port. The intake runners are in a different spot so obviously the water jacket has to be somewhat different vs the factory cast iron head.
Thought I read that the topic was Cast Iron D-port heads, not the other heads.

Tom V.

Yes... other heads will have different coolant cavities so no help there..but roughly speaking yes it’s a similar deal/goal


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No pictures .. huh ?!?!

I don't know how much of the exhaust flange you want to cut away (or why), but if you mill from flush to the head at the bottom of the exhaust ports with the majority being cut off the top of the ports -then I don't see why you would hit the water jacket. I'm assuming that you want to remove most of the roof of each exhaust port to straighten and shorten the port? If this is what you want,then I believe you could fab a new flange and bolt it to the head using countersunk Allen head bolts.

This was his Original Plan.

I posted that with a Flange he had a chance of making it work.

I believe originally he thought he could just screw right into the head and attach the headers that way. Correct???

Tom V.

Yes Tom... a bit too far fetched ain’t it ?

Happy 4th !


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No criticism toward you at all, I looked at that deal myself back in 1978 when my buddy did his Corvette with the Twin Turbos mounted on up-side down manifolds.

Happy 4th to you and your family.

Tom V.

I looked into doing it too, and using a flange seemed like the best way, something like the Stahl adapter flanges that are used on SBC's to mount bigger diameter headers. I came to the conclusion that as far as turbocharging was concerned it didn't matter if there was 2" of cast iron exhaust port or 2" of steel header tube. Maybe for n/a combos the straight shot out of the milled head into a straight header tube (instead of the 120 degree port bend) could give a small power increase.

Here is a Picture of the 68 Corvette with the "Custom Fabricated" Chevy Exhaust Manifolds
(New Parts) with Turbo Mount Flanges welded on. The Engine was Fuel Injected.
The picture just shows the position of the turbos in the vehicle. This Pic and build was in 1978
the engine was a 327 engine, the engine made slightly over 600 hp. Did not stop worth Chit.
That was 40 years ago.

Click on pic to make larger.

Tom V.

Convertible milling job on D-ports
 

Are you attending Norwalk Tom ?

That looks like quite the ride for that era ! The engine bay that is .. LOL


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