Cam Rollers

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DWR46
Posts: 621
Joined: Tue Sep 22, 2009 8:23 pm

Re: Cam Rollers

Post by DWR46 »

John: I just had another thought. Make sure the "axles" that the rockers pivot on are installed correctly. If they are "flipped", the oil holes to the rockers are no longer in alignment and the rocker will receive no oil. This can effect the oiling of the rollers also. I can send you photos of this situation, as we discovered it on the TdF engine we are doing now.
John Vardanian
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Location: San Francisco Area

Re: Cam Rollers

Post by John Vardanian »

Dyke, thanks. Funny you mentioned the flipped axles. About 12 years ago when I got this car, the first thing I did is go thru the valves and sure enough found one axle to be flipped. Surprisingly the corresponding roller was okay.

So, Dyke, are you saying that with the bushing completely gone there still should be enough lift to open/close the valve?

john
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DWR46
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Re: Cam Rollers

Post by DWR46 »

John: You would have to check to actually see how much valve lift was left after a roller failure. I was just pointing out a valve does not have to be open very far to make an engine run at a low speed idle. Recall, the very early gasoline engines used "atmospheric" intake valves that were pulled open by the vacuum in the cylinder on the intake stroke.
John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

You're right, good point about vacuum operated valve. Thanks Dyke.

john
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John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

Another question... what should be the lateral slide clearance between the rocker and the aluminum bushing? Thank you.

john
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John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

Has anyone come across this sort of thing? What caused it? What type of valve compressor tools are out there that might be modified to work on this type of springs? I would appreciate any photos of such compressors so I can buy/build one. Thanks.

BTW, this is from the valve with the ruined roller that started this thread. Did the roller cause this or did this cause the roller to go bad?

john

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Colin Angell
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Re: Cam Rollers

Post by Colin Angell »

Hi John

I think lateral clearance should be 0.02mm to 0.05mm, with a specified wear limit of 0.15mm. I have seen examples of at least double that, with the engine still apparently running well, but I guess the you would then have to expect quite a lot of valve stem wear.
Have a good Christmas break

Colin
tim
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Location: sacramento, ca

Re: Cam Rollers

Post by tim »

Greetings… John, that looks very scary. Can't imagine how that came about. I wonder if there is damage to the valve or the collet. Who built the engine. Could it have been put together this way?

Tim
1964 330GT 5769 -the big yellow taxi 61&66 Morgan +4's Daimler SP250 Turner 950S and some other dull stuff plus a brand Mercedes C300 4matic
John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

Hi Colin, thanks. Your numbers jibe with what I heard from another person.

Tim, the motor was rebuilt about 22 years ago (12000 miles). I inspect all these at every valve adjustment which used to be every two years and I would inspect and photograph anything that seemed off. Then I got lazy and let seven years go by (6000 miles) and when I took off the cam covers I found the spent roller and this valve situation. If I get out of the woods the cam covers are coming off every year.

john
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John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

I am used to seeing straight (non-tapered) valve heads that have a groove at the top, then the keepers in turn have a rib that snaps into this groove. When I removed the valve spring with a homemade depressor and found a tapered valve head with non-ribbed keepers. Are tapered valves common in Ferraris?

Another question, what sort of symptoms would worn valve springs display? How would one know if his springs were getting soft? Thanks.

john

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DWR46
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Re: Cam Rollers

Post by DWR46 »

John: Merry Christmas to you and your family! You have a standard inside plug/hairpin spring valve. That is the way the keepers are shaped on those engines. As for the springs, I have never seen a weak one. The problem with the springs is wear in the area where the upper retainer "hooks" over the spring wire. This will eventually began to wear on the spring wire and reduce the cross section of the wire. However, these springs can withstand quite a bit of wear in that area before they become subject to failure, but not from losing tension. Actually the hairpin spring is a very good, though complex design. It does what a coil spring cannot do, in that it applies constant tension to the valve over the entire valve travel as it is opened and closed. Coils have varying levels of tension as they open and close. Also, hairpins allow for shorter and thus lighter valves. An interesting bit of trivia, is that Phil Hill was responsible for Ferrari adopting coil springs. Ferrari had not been able to source good quality coil springs, so they stuck with the more complex but reliable hairpins. However, Hill contacted his friend Art Sparks at Forgedtrue Piston Company (they also made valve springs) and brought a set of Forgedtrue springs back to Italy with him. They solved the problems. A number of Ferrari's built in the mid and late 1960s used Forgedtrue springs (you find them fairly often on Build Sheets in this era).
John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

Thanks Dyke, and a Merry Christmas to you and Sue as well. As I write this, I am stuffed to the gills and will be glad when the eating season is over.

Dyke, here's why I asked the question about the spring tension. Notwithstanding this particular valve, the remaining valve keepers can be driven downward by 1-2 millimeters with a punch and hammer to presumably their proper place. This made me think that the springs floated and the keepers got separated from the valve heads and scooted upward. But, maybe this is the nature of the beast. I think I will drive the car for 500 miles or so then remove the cam covers to see if the keepers crept upward again.

john

PS. thanks, interesting story about Phil Hill and his role in Ferrari's valve evolution.
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John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

These rollers are but $60-$70, but I thought I would follow Colin's lead and try my hand at this. The 3/4" bar stock is bearing grade bronze. Not sure if it was the right thing to do, but I used heat for a tighter fit.

john

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John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

Posting this picture for Colin. Thanks, Colin, for the tip. The cup trick works, even on a crappy lathe like mine.

john

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John Vardanian
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Re: Cam Rollers

Post by John Vardanian »

A question about the needle bearing type rollers... do these tend to be noisier than the bronze type? I understand the race motors had them, why, what was the advantage? Thanks.

john
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