7M5 heads
 

I have a 1973 455 I'm going to rebuild eventually. I disassembled it and found it did in fact have 4X heads with press in rocker studs. THere is a guy in a local shop I was talking to and he said he had access to a set of 7M5 heads that a customer never picked up.

Is it worth upgrading to 7M5's from 4X's? I'm not going to have too serious of a build. What are 7M5 heads worth as cores or needing rebuilt? Thanks.

They're far too similiar to offer any real performance benefit. About the only difference is the 7M5s larger exhaust valve. I'd suggest small-chamber 4Xs (ie 4X-7), or 5C or 6X heads for a compression boost.

There okay if you're building a turbo engine (huge chambers). They are also missing the end bolt bosses for the exhaust flange so your prone to leaks unless you have some material to tap new holes. What are they worth? Well I asked $50 for a set of cores and everyone laughed.

Well, I'm a little new to the Pontiac scene. I'd figure that 7M5's use screw in studs. In stock form, they should flow a little better than later heads. Is this correct?

Thinking about it, the guy at the shop may have been hinting they'd already been rebuilt. I probably won't go through with the deal unless it's a really good one.

They don't flow any better, and as mentioned are missing the end exhaust bolt bosses, which makes header installation a pain. Stock manifolds are fine though.

I don't think the 7M5s have screw in studs, either. Only heads with the big intake valves (2.11" intake) got screw-in studs prior to mid year '73. After mid year '73 all heads got screw-in studs.

I'd do as Rocky suggests. The head castings he mentioned will have the big intake valves, screw in studs, smaller combustion chambers, and all of the necessary bolt holes. They're not too hard to find, either.

Will's right, 7M5 heads do not have threaded rocker arm studs.

I think I'll steer clear of them if they don't have screw in rockers. I'll probably steer clear of them either way though. Just thought maybe they would be good for a mild build and if I could get them cheap.

7M5's didn't come with 2.11 intakes? What about my 4X's? Just curious about this.

I owned a set of 7M5s and had the screw-in stud KEEN-SERTs installed. Nicely done & affordable.

Drill &Tap the EXH Flange end-holes (4 places) gets the 7M5s to Ram Air III casting parameters (aside from compression). Mine were the 2.11/1.77 combo. Good blower head.

HIS...could you provide more info on KEEN-SERTS ??

Is there any difference in the valve seats. Thought the 6xs were more forgiving than the earlier heads with unleaded gas.

FWIW:
 

There are studs made with 1/2" X 7/16" to fit the press in style heads without using heli coils.

I have a set of the 7M5 heads for sale. Take offs of a 455. Hav the big valves with press in studs. No outer exhaust bolt holes.

7M5 Heads
 

I have a set of 7M5 Heads also.
Anyone can have them for the shipping cost

Asked Jeeves, for http://www.newmantools.com/kee.htm

and it looks like the right item. Cheaper & more righeteous fit to the pressed-holes, than Heli-coil parameters.

Or, as P-dude says, just pull the pressed studs, tap the resulting hole for 1/2-13 threads and use the ARP studs with 1/2-13 bases and 7/16" tops. Easier, faster, cheaper.

Might want to re-consider.................


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