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Chris Witor's camshaft


piman

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Hello all,

has anyone used Chris Witor's own design camshaft with higher inlet than exhaust lift, and if so how does the engine run?

I'm starting a re fit of my car and need to replace the camshaft. It has an old SAH cam at the moment (Type 307) and looking for a bit more power if possible?

Alec

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Hello all,

it would seem that Chis' camshaft is not that common, any other favourites that people can recommend? Engine as is has balanced TR5 bottom end, cleaned up cylinder head at 10:1, 6-3-1 exhaust manifold and P.I. of course.

Alec

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Alec,

Are you looking at the CW3021 or the CW3003?  I presume the latter as the former would likely be a detune from your current cam (though I don't know much about that one).

Perhaps depends where in the rev range you would like to have the power and how comfortable you are with tweaking the injection to match?

CW is not the only one to suggest that the Triumph engine works well with asymetric timing and greater lift on the inlet valves.  I did consider the CW3021 for my PI, but ended up putting the standard "132 bhp" cam in because I had a good one to hand.  Some also get the same effect by using roller rockers with higher ratio on the inlets.

Cheers

Nick

PS. Just noticed your 10:1 compression ratio.  You'll need to maintain a reasonable duration (TR5 +) for that I think.  I have about 10.2:1 on mine and that seems to be on the edge with 95 octane even with electronic management.

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Hello Nick,

thanks for the reply, yes the 3003, which also needs longer valves apparently. I would like a fair spread of power and torque, definitely not a top end only cam.

I gather the 307 cam I have is based on the TR5 and has 30/70 timing, lift I do not have the dimension any longer?

I'm quite happy with setting the metering unit, as I had to do quite a bit to get it to run my present configuration.

Perhaps someone else will contribute in due course?

Alec

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Alec,

While CW is probably right about the longer valve stems giving better rocker geometry with higher lift cams, the same would be true with any increased lift cam and most seem to work ok with  standard valve lengths in practice.

The SAH 307 sounds alot like the Newman PH2 which is also a 30-70 / 70-30 though possibly with more lift than the 307 which will tend to make it behave as though it had longer duration - so it might fit your needs.  Newman will also do a hybrid of their PH3 on inlet and PH2 on exhaust giving 40-80 / 70 -30 which would seem quite similar to CW3003 if a little wilder.

Have you tried asking the in 2000 register forum?  I think you mind find more CW cam customers there?

Cheers

Nick

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Hello Nick,

I haven't tried the register forum as there seems to be many more performance orientated drivers here, but no harm in asking?

I don't know if Chris's valve lift is on the top of lifts compared to other cams as he says that there is a chance of the follower coming off the valve tip with standard length valve. Ideally the rocker to valve stem should be at 90 degrees at half lift so differing lifts need different valve lengths in theory but practically I doubt if there would be a discernible difference.

Alec

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Hello Colin,

Thanks for the suggestion.
I certainly wouldn't be able to ask for a cam to my own specification, totally out of my experience. At least GT in his appraisal of after market cams says little derogatory about Newman (He even says they are more reliable than most) He doesn't like Piper cams at all.

Alec

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Really?  He was at Stoneleigh this year and no doubt will be present at other big marque events throught the year. He lives in Estonia but travels a lot.

I get on ok with him, although not everyone does.  He is a very knowledgeable chap but his methods of doing business do not suit all.

If you are considering trading, plenty of people on here have interacted with him. I would suggest talk to them beforehand outside of this public forum to understand what works well with him and what doesn't.

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Hello Mikey,

thanks for the advice, I was going by what I read on his website, however it is an old page so maybe he's changed his mind.(But not his web page).
I did buy his revised tuning book from him but that is all I have bought.

Alec

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