JK's v6 book

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Micke
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Re: JK's v6 book

Post by Micke » Wed Oct 12, 2011 11:35 am

Richard Jameson (from the other forum) got good results using standard, but I imagined modified 12v manifolds; limitations due to class of competition he was competing in?
I'd be really careful about his stuff. His cams killed a friends engine.
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Re: JK's v6 book

Post by Zagato » Wed Oct 12, 2011 2:45 pm

Can you elaborate a little on that?
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Re: JK's v6 book

Post by Zamani » Wed Oct 12, 2011 6:42 pm

I have his cams. How did the cams kill the engine? Was it the aggressive ramp? Broke some springs?
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Re: JK's v6 book

Post by Micke » Wed Oct 12, 2011 10:45 pm

The exhaust lobes were too aggressive/big to fit on the followers.
So it chewed the exhaust followers in a couple of hours.
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Re: JK's v6 book

Post by Jim K » Wed Oct 12, 2011 11:25 pm

Alfa used 22mm exhaust followers for all 12v V6’s up to the introduction of fwd models, where they cleverly changed to ~25mm (I don’t have one here to measure) greatly reducing lobe/follower wear which was unfortunately very frequent with 22mm followers. Point loads are lower with the new design but retrofitting requires serious machine work to enlarge the bores. The original small followers precluded use of wilder profiles, limiting acceleration and lift possibilities.
I don't know how deep most of you have dealt with cams, but I assure you a good and reliable design is not easy to generate! Making power is of course what we're after, but no engine component wear is of paramount importance! There's a limit to ramp acceleration, dictated by max rpm and weight (=inertia) of associated moving parts like followers, shims, retainers, valves, part of the springs. If you want to design a new profile, there's also a more practical approach imo: check out the profile of an F3 cam for a similar architecture engine (...Novamotor TS maybe?) and consider that as the limit to acceleration! Someone else has done the work for you there so you can safely stay a few % under its particular acceleration. Those profiles had ~13.5-14mm lift, a duration of ~280* -for 8v engines- and max rpm ~6200, considering the 24mm restrictor. There, you have your 'outer' envelope! If you then use a pure cosine curve, you can carefully add the desired ramp characteristic, usually following a parabolic design. Using and properly combining these mathematical shapes, you can ensure a lobe design with the minimum acceleration and loading (= no wear) on associated parts since the sine/cosine curve is the result of pure harmonic motion. This is how my JK303, 292, 320 and V6 profiles came about. The 303 and 292 in particular have seen ~15-20yrs of service in some cars (some are even used as daily drivers) and still no wear. Since I have no specialized software for all this, I use good old trig functions and calculate values every 2*. I then cut a master lobe on the milling machine with a good no-slop dividing head and voila, I have my prototype lobe. The 2* steps are visible at this point; minimal polishing takes care of that. Next step is lobe profile verification. You then take this to a cam grinder, who uses it to make a larger master lobe is made for production purposes. Notice that the above work will give us the simplest possible cam profile which is considered outdated for a long time now, preference being given to so-called polydyne or multi-curve profiles with different opening/closing ramps and flanks. However, anything other than harmonic motion is bound to increase component loading and careful spring pressure adjustment is a must.
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Re: JK's v6 book

Post by Murray » Thu Oct 13, 2011 1:44 am

Greetings from Canada Jim .You appear to know what you're talking about ,maybe you should consider writing a book :lol:
Haven't received mine yet ,but it should arrive in time for some winter reading.probably being held at the border by government censors :)
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Re: JK's v6 book

Post by Zamani » Thu Oct 13, 2011 11:06 pm

Jim,

Can you elaborate on the ramp? From what I know, it's not the peak lift and total duration that kills the lifter/lobe. It's the lobe acceleration which kills. The trick is to accelerate the lobe as fast as possible without wrecking the lifters and the lobes. This is the mystery. What is the peak rate of acceleration for the lobe? 0.3mm/ cam degree? I have no idea. To see the limits set by the novamotor, one would need the lobe data lift/degree, I guess the peak values are useful, but can't really tell you the whole story.
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Re: JK's v6 book

Post by Jim K » Fri Oct 14, 2011 3:55 am

I have measured the Alfa-Novamotor F3 cams a long, long time ago and I don't have the specs handy.
However, the first concern with an unknown profile is the max velocity value, which occurs somewhere very near the edge of the follower. For 35mm Alfa tappets the max is ~0.012"/* and for 22mm followers its down to just ~0.007"/* !! Very interesting how this limits profile choice! Exceed these values and you start breaking things, irrespective of rpm. As a matter of fact, follower diameter dictates max velocity!
Acceleration on the other hand has to do with rpm and valvetrain component mass, being expressed in thousandths/*/* (Acceleration is the mathematical derivative of velocity?)
Max positive acceleration value occurs where the ramp meets the flank; like I said, a clean parabolic design is best for lowest/no wear. on the other hand, minimum acceleration occurs near the max lift point, where valve motion slows and momentarily stops before reversing.
I place great importance on the design of the point where the cam actually contacts the follower after the clearance is used up that is. I try to design for the 'softest' possible contact which in turn is an excellent recipe to avoid wear. Most -if not all- Alfa performance cams (past and present) make for aggressive contact; I will never understand this since there is every reason to do otherwise. Its this violent cam/follower contact that generates the 'hi-perf' cam noise.
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Re: JK's v6 book

Post by WhizzMan » Sat Oct 15, 2011 4:07 am

darryl longley wrote:ebay has loads
got mine shrink wrapped for£20.00 inc postage

Thanks for the pointer. Just bought one, now camping under the mail box.
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Re: JK's v6 book

Post by Micke » Sat Oct 15, 2011 7:07 am

However, the first concern with an unknown profile is the max velocity value, which occurs somewhere very near the edge of the follower. For 35mm Alfa tappets the max is ~0.012"/* and for 22mm followers its down to just ~0.007"/* !! Very interesting how this limits profile choice! Exceed these values and you start breaking things, irrespective of rpm. As a matter of fact, follower diameter dictates max velocity!
Exactly the problem here. It was an old style head and cam too.
In search for max velocity the cam went outside the follower and killed it in no time.

(the last communication i saw from RJ was that you should check this when you buy a cam and followers from him. How many ever did that?)
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Re: JK's v6 book

Post by Jim K » Sat Oct 15, 2011 9:15 am

The customer is expected to check profile suitability??? :shock: That's nice...passing R&D to the public... :roll:
I would think the cam manufacturer is responsible for testing his product before releasing it for sale!! That's what every self respecting firm does, it goes without saying!!!
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Re: JK's v6 book

Post by 75evo » Sat Oct 15, 2011 9:23 am

That was one of thing I was concerned with. I chose one with a lower velocity from him.

Here's the problem. Nobody I knew ever gave definitive values for the velocity, until JimK.

Also in the US it's more and more difficult to get the proper oil for flat tappets.

In Europe it seems 10w60 can easily be purchased. Although oil may not have anything to do with lobe velocity, it's important for these close-to-the-limit applications.

Thinking of Lubro Moly 10w60 GT1. Only other 10w60 easily found is Castrol 10w60 TWS sold through BMW because their S54 E46 M3 engines blew up using 5w30 (originally factory recommended).

Any recommendations for 10w60?
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Re: JK's v6 book

Post by Micke » Sat Oct 15, 2011 11:57 am

Remember 60 is only the value for hot viscosity. Doesn't say anything more or anything less.

Personally I never used that thick oil on the street or racing.

As for oil recommendations I find as many as people asked. Can't help there.
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Re: JK's v6 book

Post by MR2 Zig » Sat Oct 15, 2011 1:29 pm

In other discussions I've read the missing piece of the oil puzzle for our type of cams and followers is one that has a high level of ZDDP or just zinc for short. It is an anti-wear additive that while good for our cams is bad for catalytic converters. In the USA there is a API symbol showing the service standard that oil is made to. If that API symbol shows that the oil is "energy conserving" it means that there is NOT much (or enough) zinc to protect our cams and followers. I understand that the 'magic' number is 1200ppm of zinc. I also understand that oils aimed at the diesel market have the right amount of zinc and the right weight spread.

hth,
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Re: JK's v6 book

Post by la_strega_nera » Sat Oct 15, 2011 7:10 pm

JimGreek wrote:The customer is expected to check profile suitability??? :shock: That's nice...passing R&D to the public... :roll:
I would think the cam manufacturer is responsible for testing his product before releasing it for sale!! That's what every self respecting firm does, it goes without saying!!!
Jim K.
Rich Jemison always talks about using the later 164 heads - big follower, stronger rockers - so naturally his cams are designed to work with them... While I understand the frustrations of a grenaded motor, surely if you're putting together a hotty you'd eyeball this stuff during assembly?
He's well and truly tested his cams and worked out where the limits in velocity are for the exhaust rockers on the 12valves in a race environment...
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