SE5A Valve to piston clearance

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SE5A Valve to piston clearance

Post by Jpwill7675 » Sun Jun 16, 2019 12:48 pm

I have recently reinstalled the engine and road tested the car. The engine ran roughly and was noisy. I have removed the heads and can see witness marks where the pistons have made slight contact with the valves. It is not dramatic but the the evidence is visible.

I rebuild the engine because an exhaust valve seat had dropped out. I sourced two cylinder heads and had the valve seats recut and lapped in. The company also skimmed the head by 18 thousands of an inch. By comparison to the old heads, I can see the valves are much closer to the surface of the combustion chamber but not actually proud of it. The pistons are powermax and the cam is a Kent mild road cam. I have not changed anything ( timing gears etc) except the cylinder heads.

Can I resolve this problem by getting the valve seats recut to the "correct depth"? Is there are specification for valves seats i.e. to what depth should they be cut into the head?

Appreciate your thoughts and comments.

Regards, Jim

SE5a Rolling restoration, MX5 daily driver, Cannondale Synapse fitness

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Old and Slow
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SE5A Valve to piston clearance

Post by Old and Slow » Sun Jun 16, 2019 9:26 pm

Setting the valve seats deeper into the heads will improve the clearance you are looking for, I hope none of the valve stems ended up bent though.

Philip Needham
Ashley-bodied TR3; '54 Ford Consul; '55 AC 2-Litre Saloon;'65 850 Mini; '70 Ford Zodiac MkIV; XR3i
'81 911SC Targa, '64 Sabre Six

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Dennis Nicholas
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SE5A Valve to piston clearance

Post by Dennis Nicholas » Mon Jun 17, 2019 10:49 pm

I once made a solid copper gasket for my BRISTOL 405 engine after having to have head skimmed to remove a badly burned groove between two cylinders after a gasket blew and I stupidly continued home with it. Bristol senior engineer advised me to just make the copper gasket the same thickness as standard + whatever was skimmed off. Had no further troubles.

Dennis Nicholas(RSSOC)
1980 GTC Trafalgar Blue, 2010 basic Skoda Yeti (petrol), Austin 7s, Rileys.

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