Crossflow Tappet Adjustment

[Gavin]

cam is listed as Caterham BCD. You refer to it as a Kent cams 234 which, if I'm not mistaken and I'm setting myself up here, is a completely different cam.

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BCD - cryptic for 234. It is the same camshaft.

[BrianHorn]

Thanks to all for your comments.

 

I spoke to the engine builder yesterday who tells me that he races cars with rattly tappets week in & week out and that it is MUCH better that way than too tight!

Apparently the head on Kent engines 'grows' when hot (and it gets hot!) therefore taking a bit of play out of the valve clearances. If adjusted to be quiet at tickover and lower revs for example then the play will disappear when it gets hot, perhaps enough to cause the valves not to close properly therefore burning the edges. Obviously not the ideal scenario.

 

I'm going to have to run with this explanation as I've sold the car now and it's being collected tomorrow.

 

Brian

 

Common sense is in spite of, not the result of, education.

 

--Victor Hugo

 

[Roger King]

The Supersprint cam is the Kent 234 whatever other names it may be given. Official clearances are .022" inlet and .024" exhaust although I always preferred to run both figures .002" tighter. In reality, with pushrods, rockers, rocker posts, etc, all bending and flexing, there is so much error that the figure is far more approximate than you find on an engine with direct acting bucket tappets.

 

The standard Ford cam figures are .014" inlet and .021" exhaust, although there are plenty of books and spec sheets that quote variations on these figures.

[BrianHorn]

Hi Roger,

 

So a few rattly tappets are better than nice quiet ones working on the premise that quiet = tight = burnt valves?

 

Thanks for your, as always, valued input