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Nov 27, 2012 - 11:34AM

Valve timing (not M20 but still from Brum!)

Anyone got ideas about valve timing?
I found a pair of 62-2450 cams in an engine and want to use them in a 400cc B31 project. As far as I can ascertain the 2450 is a Goldstar exhaust cam used in combination with 65-2448 or 65-2454 inlet cams for touring or scrambles use.
If I use one as an inlet then the valve timing doesn’t correspond to any of the normal inlet values so it will be a compromise and it’s a case of deciding what the best option is and making sure the valves don’t get intimate. (I measured peak lift for inlet use with a disk but it may be a degree or 2 out)
I’ve made a diagram of the 2 possible scenarios with comparison to the standard cam combinations (GS). I think it is self explanatory with the 2 options on the outside
The outermost settings appear to be the closest match to the 350 and 500cc scrambles combinations but with the inlet closing a bit early. However the other option has the inlet opening rather late (although not as late as standard 65-2420’s).
As you can probably tell, I have no idea what I’m on about… as usual. So, if anyone has any advice I’d be very grateful! – yeah I know I should get the correct cam but Christmas is coming and I have to pay for a turkey!

Cheers
Pete

email (option): petercomley@web.de

Ian Wright

Nov 27, 2012 - 9:49PM

Re: Valve timing (not M20 but still from Brum!)

Hi Pete, Hard to tell what will work and what won't with cams used in the wrong place in a given engine. There is a 350 exhaust cam for instance, that works exceptionally well in the 500s. The thing to do is 'suck it and see'...At least with the BSA engine it is fairly simple and quick to change a cam if you need to. In fact the camshaft 'guru' who developed most of the Goldie profiles used to change them between sections on the trials, to give him the chartacteristics he wanted for the conditions..He must have known his 'stuff'.!
Overall lift is not that important, lift at and around TDC is the thing you have to watch, when one cam is 'following' the other. This is particularly the case in the smaller head of the 350. On late DB 350 engines the timing of the exhaust cam was altered to help this..After Christmas when your birthday comes round get the missus to buy you a pair of 2446s!..Ian

email (option): ian@wright52.plus.com

Pete C

Nov 28, 2012 - 7:45AM

Re: Valve timing (not M20 but still from Brum!)

Thanks Ian
If you hear some awful banging and popping noises it will be me experimenting.
Cheers
Pete

email (option): petercomley@web.de