Unusual cylinder head mod!

General Chat with an emphasis on BMC Minis & Other iconic cars of the 1960's. Includes information on MK1 Action days.
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Re: Unusual cylinder head mod!

Post by spoon.450 »

Quite a common mod....sometimes necessary to reduce the diameter of the push rod ( cam end ) to pass through the sleeve.
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Re: Unusual cylinder head mod!

Post by cpr1 »

If not wrong, in David Vizard a series tuning book shows why and how this should be done.
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Re: Unusual cylinder head mod!

Post by 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
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Re: Unusual cylinder head mod!

Post by 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.
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Re: Unusual cylinder head mod!

Post by 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.
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Re: Unusual cylinder head mod!

Post by 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.
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Re: Unusual cylinder head mod!

Post by wantafaster1 »

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.
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