[pggto]

There is a 72 455 HO engine for sale on facebook, as I was looking through the pictures and I noticed this picture that appears to have an under cut or bad casting between the intake ports. I'm no HO head specialist but this doesn't seem right? Is this just a bad casting, or is it supposed to be like this? I would think it would leak between the cylinders.

[Formulas]

Standard feature with 7F6 heads some deeper than others

[MescaBug]

What he said.

[Jay S]

Interesting, I did not know they did that. Same engineer that thought that was a good idea must have been around yet for the 301s.

[MescaBug]

A good read:

http://forums.maxperformanceinc.com/...d.php?t=536449

[pggto]

Originally Posted by MescaBug

A good read:

http://forums.maxperformanceinc.com/...d.php?t=536449

Thanks, very interesting. The date code on the heads in question in this post are I241

[dmac]

Would this help with some issues I've seen mentioned about airflow to certain cylinders being uneven due to intake manifold design?

[Jay S]

Originally Posted by dmac

Would this help with some issues I've seen mentioned about airflow to certain cylinders being uneven due to intake manifold design?

My hunch would be Post #6 on the link to the earlier thread had a fair explanation for why Pontiac experimented with this. They were probably trying to knock the combustion temperature down some at idle to reduce some of the NOX emissions. Idea being it would cause a little reversion and drop the combustion temp down some so they could leave more timing in to retain engine performance. Hard to say for sure, but the booster change later on was then likely more of an effort to get some of the engines performance back the they we loosing through dealing with the emissions. Rocky Rotella had a good article about the emissions efforts of 73. A good read to understand what the OEM’s were up against. I would not be surprised if this same theory was used on the 301 combined port either. Was not for performance, it likely was for mounting problems fighting emissions.

https://www.hotrod.com/articles/pon-...ntrol-systems/

[Bruce Meyer]

I think maybe some of you are reading too much into this. I would bet its a mistake at the foundry. I doubt there is enough recess in those ports to affect anything. The uncompressed part of the intake gasket would take up half that space. Just my 2 cents.

[Jay S]

The thought of what it might or might not do and if it was on purpose, what was the reasoning? That is what is interesting to me. Could have been a foundry error for all we know. Very interesting it was found just in early 72 and not any other year though, and also found on more heads in 72 than the 7f6. Interesting little bit of Pontiac history anyway.

[jamaca85]

I put some on a 455 runs great..love the low comp but there cut to 101cc. No issues running them .. with 91 octane gas