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Author Topic: Kent cams valve clearances  (Read 5044 times)
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HFStuart
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« on: March 22, 2013, 02:18:45 PM »

Apologies for the cross post from the Guy Croft forum but:

I've bought a pair of Kent FT10 Cams (blanks not regrinds) for use in my Lancia Beta Spider 1995cc. They are used but after cleaning they look unmarked.

Th Kent website says to use clearance of 0.008" / 0.2mm both inlet and exhaust. This is obviously tighter than the standard 0.42mm & 0.48mm used by Fiat / Lancia.

What should I set the clearances to ?

Many thanks,

Stuart
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HFStuart
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« Reply #1 on: March 22, 2013, 05:57:18 PM »

I've had a reply from Guy so in case anyone is interested:

"The setting of 8thou cld is correct, yes!

I know it seems weird but running clearances do vary according to the design of the cam!

G"
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75coupe
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« Reply #2 on: March 23, 2013, 10:44:06 AM »

Hi Stuart

What is the spec on these cams?
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HFStuart
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« Reply #3 on: March 23, 2013, 11:07:15 PM »

Kent FT10 (from blanks not regrinds)
Cam Lift - 10.54 Clearance 0.2 - valve lift 10.33 (std valve lift c9.5mm)
35/67 67/35 (ie 70 deg overlap)
Duration 282 deg
Lift @ TDC 2.7 IN 2.5EX

Difficult to comapre it directly with the std cams as (so I am told) the lancia timing figures are quoted at 0.8mm clearance rather than the actual but essentially it's a fast road cam. The power band is supposed to be 2-6k
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mangocrazy
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« Reply #4 on: March 24, 2013, 01:17:29 AM »

Sounds excellent - power in the range where you need it. Did you just happen upon these, or were they a premeditated purchase?
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1980 Lancia Beta Spider 2000 (S2FL)
2002 VW Transporter T4
2017 KTM Duke 690R
2008 Aprilia SL1000 Falco
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75coupe
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« Reply #5 on: March 24, 2013, 02:06:20 AM »

Sound just the ticket are you keeping the Std carb or going for twins?

At least you know Kent Cams are good, I bought a pair of GC 3A cams and they were ground by Kent Cams, even came in their boxes......
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HFStuart
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« Reply #6 on: March 24, 2013, 11:02:39 AM »

Serendipity more than anything else.

They were on eBay being sold by a chap who'd had them in his Ritmo/Strada 130TC for a couple of hundred miles before it got rear ended and written off (ouch). They were cheap so I took a punt on them and they turned out better than expected. Almost no wear and the boxes have 'Blank' on them which is a bonus. The journals and the ramps aren't even polished up so I believe the mileage too.

I two days later I stumbled on a pair of kent pulleys 120 the pair and they cam in their original boxes too.

I've had enough cr@p this year that I'm taking the good fortune as karma!

To be fair to Guy I think he does say that Kent grind his cams but to his profiles - that's probably true of the wilder cams I couldn't comment on his fast road ones.

With luck this week I'll have the crank re-ground and I'll know if I can re-use it or not. I'll put another thread up for any that are interested in that. I know grinding the crank is supposed to be a no-no but I think I've found a way to do it.

Edit: Forgot to say I have a pair of Solex ADDHE carbs that I've found 34 and 36mm chokes for. These are nominally 40s but the barrel is simialr in size to a 45 DCOE. I'll get the car running on the standard carb and then play with tose, I have a local rolling road that can jet them. If they don't work then they've cost me no nore that a couple of hours on the road.
« Last Edit: March 24, 2013, 11:09:55 AM by HFStuart » Logged
75coupe
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« Reply #7 on: March 26, 2013, 11:53:22 AM »

Go with the 36mm chokes. I had a pair of 45 dcoe 36 chokes with increased CR and std cams, plenty of mid range torque and far nicer than std carb for drive ability and noise....
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mangocrazy
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« Reply #8 on: March 27, 2013, 11:13:36 PM »

Talk about lightning striking twice etc.... I've just been offered a set of Kent FT10 cams that have apparently only had about 1000 miles of running. I received them today, and the wear (or lack of it) on the lobes would chime with the small amount of mileage. But some of the bearing surfaces appear quite badly scored (easily noticeable with a finger nail) and on some of the bearing surfaces there is what appears to be spots of corrosion/rusting. Can this be normal or acceptable?

I only received them today, so will try and post some pics up when I can get some natural light photos of the cams.
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1980 Lancia Beta Spider 2000 (S2FL)
2002 VW Transporter T4
2017 KTM Duke 690R
2008 Aprilia SL1000 Falco
1992 Ducati 888 SP3
1988 Honda VFR750F
1980 Yamaha RD350LC
Neil-yaj396
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1979 1300 Coupe


« Reply #9 on: March 28, 2013, 08:11:47 AM »

Wouldn't be unknown for someone to bolt down some nice new cams into some nasty old shell bearings!
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HFStuart
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« Reply #10 on: March 28, 2013, 10:54:46 AM »

Or to bed them in at idle.....
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75coupe
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« Reply #11 on: March 28, 2013, 01:15:56 PM »

Scoring of bearing journals is usually down to "dirty" build when assembling. Debris falls into the oil ways in the cam boxes or cylinder head, and once oil pressure builds, forces the debris round the cam bearings......Give the journals a polish up and they will be fine.....If you are worried get them measured, preferably in V blocks and check for run out. The cam boxes come off worse than the cam as they are just soft alloy and will be scored more than the hard steel of the cam.

The cams are usually "parkerised" which is a hardening treatment which gives the black appearance. if that is still present on the lobes then all is well.....

Use new shims when fitting, and lubricate generously with cam lube before start up and run at 2000rpm for 10-20mins to bed them in.

I have successfully used old shims reversed, as the side that faces the bucket does not wear too much, but new is best!

Have fun!
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mangocrazy
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« Reply #12 on: March 28, 2013, 04:42:17 PM »

Thanks for the comments. I've actually posted photos of the cams up on Guy's site, and rather than upload them twice, here is the link:

http://www.guy-croft.com/viewtopic.php?f=13&t=3087

If I'm contravening any forum regs about linking to other forums, please tell me and I'll upload the pics here. I'm hoping that the cams look worse than they actually are, or that I'm just worrying about nothing (it has been known...)
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1980 Lancia Beta Spider 2000 (S2FL)
2002 VW Transporter T4
2017 KTM Duke 690R
2008 Aprilia SL1000 Falco
1992 Ducati 888 SP3
1988 Honda VFR750F
1980 Yamaha RD350LC
HFStuart
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« Reply #13 on: March 28, 2013, 08:26:12 PM »

I've just seen Guy's reply! I suspect I know what the result of that inspection will be.

The lobes look OK. I'd give them both a good clean with jizzer or similar and remove the surface rust with 1200 grade paper. So long as the journals in the carriers are OK and the cam lobes are smooth & free from corrosion I expect they'll be fine.

Stuart
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mangocrazy
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« Reply #14 on: April 01, 2013, 08:02:07 PM »

I've just seen Guy's reply! I suspect I know what the result of that inspection will be.

The lobes look OK. I'd give them both a good clean with jizzer or similar and remove the surface rust with 1200 grade paper. So long as the journals in the carriers are OK and the cam lobes are smooth & free from corrosion I expect they'll be fine.

Stuart
Yes, I think I know what the result of that inspection will be, as well... The seller feels the same way and has asked that I get a 'local' second opinion, so I'll take them into the garage I use for the van and the wife's car. A camshaft is a camshaft, when all's said and done, and they don't have an interest in selling me a replacement...

I think they'll be OK - I was planning on using grey Scotchbrite to clean up any marks - that's the finest, least aggressive grade.
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1980 Lancia Beta Spider 2000 (S2FL)
2002 VW Transporter T4
2017 KTM Duke 690R
2008 Aprilia SL1000 Falco
1992 Ducati 888 SP3
1988 Honda VFR750F
1980 Yamaha RD350LC
rossocorsa
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« Reply #15 on: April 01, 2013, 08:34:14 PM »

GC is far too honest to try to gain sales from condemning people's stuff but he is a perfectionist, conversely many 'mechanics' are happy to use any old junk if it looks vaguely OK. The corrosion on those cams doesn't look too good to me but I'm no expert on these things.
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Neil-yaj396
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« Reply #16 on: April 02, 2013, 10:10:26 AM »

Having looked at the pictures some of that corrosion is pretty deep. I wouldn't be confident getting the surface back to a point where it won't damage the shell bearing. On start up the oil pressure can be pretty low at the top of the engine.
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mangocrazy
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« Reply #17 on: April 02, 2013, 07:11:00 PM »

You'll have to excuse my ignorance; I've never taken the top end of a twin-cam apart. So there are shell bearings between cam and carrier? Similar idea to big-ends, I guess? I'm a little perplexed as to how soft(ish) shell bearings could score the hardened steel of a camshaft journal. And how does corrosion like that take hold in an oily environment?
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1980 Lancia Beta Spider 2000 (S2FL)
2002 VW Transporter T4
2017 KTM Duke 690R
2008 Aprilia SL1000 Falco
1992 Ducati 888 SP3
1988 Honda VFR750F
1980 Yamaha RD350LC
Neil-yaj396
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« Reply #18 on: April 02, 2013, 07:30:31 PM »

Looking at the pitting I think it's more likely down to poor storage. The cams are likely low mileage as stated but might have been left in the damp without any protective oil.

Now you mention it I'm not sure if the cam bearings are shells, but either way they rely on oil under pressure to ensure they run properly, and classically our engines stand around not running with the oil draining down into the sump, or worse out of an old cam box gasket. When the engine fires up it's these surfaces that are the most starved of oil for those first few seconds.

If these cams were used, removed, then stored, some minor scratches could have developed into the pitting now visible.
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HFStuart
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« Reply #19 on: April 03, 2013, 06:46:46 PM »

GC is far too honest to try to gain sales from condemning people's stuff but he is a perfectionist, conversely many 'mechanics' are happy to use any old junk if it looks vaguely OK. The corrosion on those cams doesn't look too good to me but I'm no expert on these things.

Don't get me wrong I don't think Guy would lie to generate business, it's just I know his standards and (like you said) that he's a perfectionist. In my opinion that means his attitude to risk is very conservative. That is probably a good thing in a race engine builder who's reputation depends on the quality  / reliability of his work but it might be OTT for a road car where the owner is happy to take a calculated risk.

Put it another way while there may be an ideal way to build an engine there are other approaches that don't necessarily automatically lead to disaster.

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