Cam Rollers

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John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Cam Rollers

Post by John Vardanian »

Over the course of the last 14 years, I have come across completely spent bushings in these rollers three times, once in one car and twice in the other. In all three instances the spent roller was on the intake side. What would have happen if it had been on the exhaust side?

This last incident was on my PF coupe. The last lime I adjusted valves on this car was 6000 miles ago. My adjustment routine includes removing the rocker saddles and inspecting the moving pieces up close under good light. What can one do to not get these nasty surprises? Remove valve covers every year? What a pain that would be.

john
PF Coupe
Colin Angell
Posts: 49
Joined: Tue Apr 13, 2004 1:11 pm
Location: Worcestershire, England
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Re: Cam Rollers

Post by Colin Angell »

Hi John

This is a really high wear area and I would be in there every year, if you are driving the car. The rollers themselves seem very hard wearing, but the bronze bushes inside them are subject to a lot of wear and I would expect to check each one as a matter of course every time you adjust the valve timing. There are wear limits indicated in the works manual, both for the bushes and also for the bronze spacing washers which control any lateral movement of the rocker arms, but with a bit of experience you can judge the wear by feel. Sometimes you will find the steel pivot pins wear as well and that is usually signalled by a louder than usual tick tick tick from under the cam covers!


Spares are available and you can fit new pins and rollers very easily, although I have found the spacing washers difficult to find. If you have the time and some decent equipment it is not difficult to press new bushes into place, which saves the expense of replacing the rollers. They are supplied with an undersize hole and have to be bored through after installation, but must be perfectly concentric with the outside of the roller. I do that by turning a simple cup chuck in the lathe and make the rollers a light push fit into the end, so the roller is dead true to the lathe and can then be accurately bored. You can buy spare bushes from usual suppliers, but I have in the past turned my own from Colphos 90, which has good wearing properties. I wonder if anyone has the specification for the bronze alloy actually used by the factory?

Good luck

Colin
John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Re: Cam Rollers

Post by John Vardanian »

Thanks Collin. It is baffling to me that a roller can go from good to completely spent, while the remaining 23 that looked and felt the same will continue on. I have to learn to gauge the health of the rollers.
Regarding the lateral space washers, I understood that they were still available for the coil spring heads, I got some many years ago from the UK. But for the hairpin spring heads you have to machine a new aluminum spacer to replace the old one. This is the hairpin type. I addressed a couple of deficiencies with aluminum shims instead a number of years ago and they are still holding up.

Can you explain to me that “simple cup chuck”? Instead, can you just chuck the old roller in the lathe, shave out the old bushing, press fit in a rod from that “Colphos 90” and then bore a hole for the pin? When you press fit the two what should be the ID/OD difference of the two material? Thanks again.

john
PF Coupe
330Jim
Posts: 85
Joined: Thu Oct 21, 2004 3:24 pm

Re: Cam Rollers

Post by 330Jim »

The press fit between the roller and the bushing for something like this should be 0.0015 to 0.0020 inches of interference. There should be 0.0008 to 0.0012 inches of clearance between the bushing and the pin.

Cheers Jim
John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Re: Cam Rollers

Post by John Vardanian »

Happy Thanksgiving to all of you... especially those who are screwing off in the garage while the spouse toils in the kitchen.

Here you'll see a few destroyed rollers, the one on the right is the subject of this thread. You can see that this one has completely lost its bearing while the other two from past have managed to retain some evidence of it. I found the oiling hole of the clevis completely jammed and had to force a 0.022" welding wire into it to unplug it. Now it's a question of chicken or egg. Did the hole get plugged and cause the bearing to self-destruct, or did the bearing melt away and a piece of it got jammed in the oiling hole?

john
PS. Jim, thanks for the clearances.

Image
PF Coupe
250GT
Posts: 968
Joined: Wed Oct 15, 2008 7:41 am
Location: germany/holland

Re: Cam Rollers

Post by 250GT »

John, if you are considering the ultimate solution you must buy the Piet Roelofs this convert ion,
I use this on two engines since 1999/2000
one problem less for a lifetime.

C.

Notes
Improved valve adjustment bolt kit for 250 and 275 type engines.

Advantages of the new valve adjustment bolt with smaller camfollower roll and needle bearings:






The system needs more clearance between the valvestem and the rocker. Therefore smaller rollers on needle bearings, as developed by RE, are used. The advantage of the smaller rollers is the smaller angle between adjustmentbolt and valvestem when the valve is fully opened. This reduces the sideward load on the valvestem.


The force on the valvetip, exercised by the adjustmentbolt, is now spreaded over almost the entire area of the valvetip. The advantage is that the valvestem will not get hollowed anymore and in that way the sideward load on the valvestem will be minimised. This means much less wear on the valveguides.


It is no longer necessary to harden the valvetip, so the elasticity of the material will be maintained.


This whole set-up will reduce friction in the valvetrain. The result is a gain of engine output.


This system can be installed in all 250, 275 and 330 engine types, provided the valvetip is perfectly flat and doesn't show any signs of wear. The advantages mentioned in points 1-4 make the system almost indispensable for racing engines with racing camshafts.
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John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Re: Cam Rollers

Post by John Vardanian »

Hi Cornelis, thanks. I have actually considered this option, but at the time of a rebuild, which for this car is about 3-4 years away. I have read the comment about the tip of the valve needing to be perfectly flat, does that imply a new valve? What would happen if one installs these on an older engine with moderate valve tip wear?

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

Re: Cam Rollers

Post by DWR46 »

John: We have used these "elephant's foot" adjusting screws, and the tip of the valve has to be pretty flat for them to work satisfactorily. We have also used a lot of the " Ball tip" screws with the ball with the flat side. They also require a fairly flat valve tip, and can flip the ball over if the engine is severely over-reved and the valves floated.
250GT
Posts: 968
Joined: Wed Oct 15, 2008 7:41 am
Location: germany/holland

Re: Cam Rollers

Post by 250GT »

John in my case it was not need to use new valves.
In the 90th i did use very often an Maserati 3500gt next to 250gt cars.
i was always impressed how good was the M. driving in normal traffic
it feels like it has much better torque and this was only a SIX cyl with 500cc more.
that is missing with our 12 cyl imo.
you must rev up to 5000rpm to feel something in an F-car to see some torque
so if standard V12 is instalated you must go up.

I do understand that some people don't like to rev them as they worry about wearing them out etc, but these engines were actually designed to be used up to the red line or even over for a short time. It's called maximum permitted, and everything below that is allowed by the design. Of course this means you need to maintain your engine-which you are doing- I would advice to make an other management -if you like to drive-
I did change this by other cams, carb jetting, timing etc now the torque peak is at approx 4000rpm.
which make it so much better to overtake cars in front of you, a real joy.
especially in the US with speed control at 60 mph this make so much more fun( roadrallyes) I think.

could send an torque /HP diagram.
but writing this sitting in a boring Orthodontic professional schooling this morning.
( Richard P. Mc Laughlin (Interarch Class 3 treatment mechanics.)

C.
John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Re: Cam Rollers

Post by John Vardanian »

Thanks Cornelis and Dyke. Yes, maintenance must be religion with these cars. It is surprising how much malfunction can go unnoticed with these smooth revving, tight-angled V12's-- my perished roller is a great example of that.
Why is it important that the head of the valve be like new? What happens otherwise? Thanks.
john
PF Coupe
Colin Angell
Posts: 49
Joined: Tue Apr 13, 2004 1:11 pm
Location: Worcestershire, England
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Re: Cam Rollers

Post by Colin Angell »

Hi John

Sorry for the delay in replying, but I have been away for a few days. The problem with most lathe chucks is that they "run out" to some degree and you would normally have to take a very light skim off the outside of a round bar to true it up. So if you hold your roller in a normal lathe chuck and bore a hole through the middle then the inner and outer surfaces won't be perfectly concentric. To overcome that problem I hold an oversize piece of steel in the chuck and face off the end before turning out a shallow recess, about 5mm deep and a light interference fit with the outside of a roller. Then you just have to push a roller into the recess (I call it a cup, hence my description of a cup chuck) and bore out the middle which will obviously now be truly concentric with the outside.

There are a couple of things to bare in mind. Firstly the set up will only be any good once, so it is best to work on a batch of rollers together, because once you take the cup chuck out of the lathe you won't be able to get it back in exactly the right position again. Secondly you have to be able to get the rollers out after you have finished them. I do that by drilling or milling a slot across the bar first, so I can get a small lever under the roller to push it back out of the recess.

It may sound crude, but it works!

Colin
John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Re: Cam Rollers

Post by John Vardanian »

Thanks Colin, got it.

john
PF Coupe
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treue
Posts: 141
Joined: Mon Sep 16, 2002 8:49 am
Location: Oklahoma

Re: Cam Rollers

Post by treue »

John,

When I was overhauling the engine in 9129, I liked the concept behind the Roelof rocker arm mods, so I bought a set. They cost €1625 in March of ’06 plus international electronic funds transfer fees.

I heard no complaints about the installation (done by Vintage Connection) of the Roelof mods, although getting all those needle bearings in place just had to include utterance of a few wirty dords. After about 900 miles and one valve adjustment, things look good under the cam covers and the engine runs OK. I think the mods would need several thousand miles and another valve adjust for a comprehensive evaluation, but as of now, mine seem to be fine.

The OEM valve adjuster screw is a simple, one-piece threaded rod with wrench flats on one end and a hemispherical ball tip on the other. This ball end tends to make a dimple in the top end of the valve, that is if the adjuster doesn’t wear down to a nub first. The Roelof adjuster has a second part, a swivel end (see Cornelis’ picture of the Roelof parts, above) that is crimped on the ball end of the screw part. The end of the Roelof adjuster screw is closer to a full sphere, allowing the swivel end to do its swiveling. The bottom end of the Roelof swivel is flat, always staying in area-contact (instead of point-contact) with the flat top of the valve.

The engine in 9129 had stopped, pre-2002, due to a dropped valve, so I decided to replace all the valves with one-piece stainless steel Manley valves. A file stroke showed the Manleys to be very hard but that was immaterial due to the much-less-aggressive contact of the Roelof adjuster-swivels.

If you wanted to keep the old valves (although I would have to ask why; my set of Manley custom valves were $508 in 2002), you could have the ends dressed flat if they weren’t too badly worn.

Tom
Tom Treue
67 330GT 2+2, No. 9129 (former owner)
John Vardanian
Posts: 1906
Joined: Wed Sep 04, 2002 12:13 am
Location: San Francisco Area

Re: Cam Rollers

Post by John Vardanian »

Hi Tom, thanks. There is no doubt that the Roelof system will eliminate this concern and at the time of an overhaul Roelof's rollers would be only an incremental additional cost and well worth it. But, I am not prepared to go thru my engine at this time.

My concern right now is to stay ahead of the game and not have one of these rollers go bad without knowing it. One way to do this is to take off the cam covers once a year and at the least finger spin each roller in place. The other day I thought of another trick that just might work. What about taking temp readings at the exhaust manifold at the heads with a laser thermometer? I'd imagine you might get a much colder reading if the roller is gone. Thoughts?

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

Re: Cam Rollers

Post by DWR46 »

John: Your thought about measuring exhaust temps is good, but at idle, the difference due to a roller failure would be minor, as an engine needs very little valve lift to idle well. The factory used the needle rollers in the comp engines, but stayed with the bushings in the street motors for noise considerations. They are louder. We use the needles in the race motors, but I have run many race engines on bushings with no problems. I am not sure why you have experienced the failures, but I wonder if your bushings are NOT original, and but were replaced with non-original bushings at sometime in the past.
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