Cosworth Mk 16 engine & Modern Counterpart

PostPost by: SJ Lambert » Sat Jan 21, 2017 2:13 am

Oh, and a smidgeon of anaerobic thread sealant too!
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PostPost by: 2cams70 » Sat Jan 21, 2017 3:57 am

Now - Is that a BSP or an NPT thread? (sorry, had to slip that one in!)
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PostPost by: SJ Lambert » Sat Jan 21, 2017 5:35 am

It's M6 amongst a nest of imperial threads!
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PostPost by: SJ Lambert » Mon Mar 13, 2017 2:14 am

rgh0 wrote:Yeah the nomaal L1 cam clearance setting was 10 thou. If you have a cam you want to get checked to confrim its profile you can take it to Clive Stenlake at Clive Cams and he can measure it up on his cam measuing machine to give you a detailed profile ( for a price )

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I've got a pair of high performance cams running in a motor and one of them, the exhaust one, is drilled for oil feed to the followers at the base of each exhaust lobe.

The problem I have is that even before I see engine temperature on the gauge, oil pressure drops 30 lbs and absolutely hoses out the exhaust side without moving the original reddened puddle of cam lube stained oil out of the number 4 inlet pool around the follower.

I'd like to run a camshaft without base drillings and just rely on bearing overflow follower feed. I'll give Clive a call as to whether he can either supply one or even reliably plug the holes in my existing one.
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PostPost by: rgh0 » Mon Mar 13, 2017 5:46 am

With those drillings I would be worried that the rear cam bearings would not be getting sufficient oil. I don't see any reason to drill the back of the cam lobes as their is plenty of oil in the head to lubricate the can to follower interface without it.

I am sure if you could plug the holes with a suitable (small ) tap and tapered plug that is recessed fully. But maybe easier to just get a new cam made.

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PostPost by: SJ Lambert » Mon Mar 13, 2017 6:02 am

The manufacturer tells me it's for additional exhaust side oil cooling - & that my cool oil pressure drop is due to aeration. He may well be onto something re the aeration frothy oil at tank baffles means I ought to lower oil level to let the baffle system work?
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PostPost by: rgh0 » Mon Mar 13, 2017 7:04 am

I do not believe additional exhaust side cooling is needed and I doubt that oil flow will achieve much cooling in any case even if it was needed. There are plenty of water jackets around the exhaust valve and port if you look at the head cross section, oil on the top of the follower will not do much

The return oil from the scavenge pump should go into the tank part way up and just above the oil level in the tank. This way the aerated oil when it returns to the tank sits on top of the non aerated oil and can disengage the air over minimal distance to the oil free top section of the tank. If the whole tank is becoming full of aerated oil when the oil is cold then you need to look at how it is all arranged to get better de-aeration or change the oil being used or change the scavenge to pressure pump size ratio to reduce the amount of air being sucked in. I dont build dry sump twin cams but I would have thought all this would have been sorted pretty well as lots of people build them for open wheelers like yours.

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PostPost by: SJ Lambert » Tue Mar 14, 2017 2:16 am

p1140122.jpg and


p1140124.jpg and



Prepping to heat and remove plug and then sleeve with aluminium tube drilled for journal feed only
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PostPost by: SJ Lambert » Tue Mar 14, 2017 2:04 pm

[quote name="SJ Lambert" post="7866422" timestamp="1489498776"][img=https://s24.postimg.org/5y7agiomt/P1140122.jpg]
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[img=https://s27.postimg.org/zed5xd5ar/P1140128.jpg]
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[img=https://s13.postimg.org/prp1ud2qv/P1140133.jpg]
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[img=https://s13.postimg.org/c85yhqumv/P1140140.jpg]
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Not sure whether this lot should be captioned "Desperate Times" or "Take one look at that bonded in 15mm diameter plug and 'Poof', it's gone"!!![/quote]
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PostPost by: SJ Lambert » Wed Mar 15, 2017 9:52 am

image.jpeg and


A sketch of the hollow blanking sleeve
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PostPost by: SJ Lambert » Thu Mar 16, 2017 3:45 am

We've abandoned the idea of using seals for fear of creating sliced rubber fragments that could lead to a gallery blockage - so will use the hollow sleeve as a restrictor without looking to totally block the cam base holes.
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PostPost by: 2cams70 » Thu Mar 16, 2017 11:41 am

Some discussion on another forum about this topic:

http://www.ferrarichat.com/forum/vintag ... lling.html

I'd be a little wary of blocking them off completely without knowing why they are there. You don't know the metallurgy of the camshaft. Odd too that the inlet doesn't have the same drillings. Are both inlet and exhaust camshafts from the same supplier? I'd be quizzing the supplier further about any failures leading up to the need to drill them.

The pump should be able to maintain pressure regardless provided it has enough flow capacity.
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PostPost by: rgh0 » Thu Mar 16, 2017 12:13 pm

I would ditch the cam ( or sell it on Ebay as a "special" racing cam at a high price :lol: ) - whoever made it did not know what they were doing with twin cams IMHO.

I suspect they had excessive lobe wear at some point due to using too high nose loads or poor metallurgy or poor running in for cams or followers and were trying to compensate for that by adding extra lubrication to the follower rather than fixing the root cause problem.

The cam in the photo does not appear to have been running properly on the follower judging by the oil film marks so perhaps the lobe or follower has not been ground correctly?

There is no properly built twin cam engine I have come across that needs lubrication to the followers through the cam lobe --- no matter how "hot" or how "special"

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PostPost by: rgh0 » Thu Mar 16, 2017 12:17 pm

The flow to the cams is metered by the cutouts on the jackshaft. Putting extra holes in the cams will lead to lack of oil at the rear end of the cams. Especially if you have long bolts installed for the cam sprockets which you need in a high lift cam. The drilling in the long bolts restricts flow to the cams to some degree and you dont need the extra leakage out .

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PostPost by: SJ Lambert » Tue Mar 28, 2017 2:58 am

p1140176.jpg and


Blanking/restricting tube drilled for bearing feed, but not for cam lobe hole feed going in as a test measure.....
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