Unusual cylinder head mod!

[spoon.450]

Quite a common mod....sometimes necessary to reduce the diameter of the push rod ( cam end ) to pass through the sleeve.

[cpr1]

If not wrong, in David Vizard a series tuning book shows why and how this should be done.

[ivor badger 3]

The Longman trick was to drill out and sleeve the push rod. Knowing how thick the tube was, you then used it as a guide to open the inlet tract. When you hit the tube, you stopped grinding

[MiNiKiN]

I reckon it doesn't affect 'airflow' adversely. In my opinion so-called airflow is actually less flow, more like compression (or pulse-) waves. These are affected and dampened by sharp corners and edges, rather than short cross sectional constrictions.
Just my2p and believe.

[MrNoo]

All my Slark race heads were sleeved, thought it common practice although I did have one Mini 7 head that had much smaller ports than any Slark heads I had, guess this speeded up inlet port and exhaust port gas velocity, whatever it certainly was an exceptional head. I sold it in the end when I gave up racing and it ended up on another 7 engine which gave the most hp of any 7 engine on Pitstop's rollers. This head wasnt sleeved.

[Vegard]

You can say that you knew what they were doing, but then again they didn't. Have a look at modern heads, which produce more oomph than 70ies ones, and none are as big in the inlet port as the "old ones". It's just because that's not where the limitation of flow is.

If you grind a head so much that you break into the pushrod hole, you've done something wrong. End of.

[wantafaster1]

Vegard
I'm not sure about things being better now than back then. I'd love to see the data that would support this. For example, changing a good Longman head for swiftune and gaining 10bhp?

I don't think so.