valve adjustment screws

[mark]

Hey you guys. Any preferred vendor for adjustment screws? I've heard of shoddy merchandise being supplied, and of course Jimmy is witness to that.
I would like to avoid a repeat of his experience.

Thanks in advance.

Mark

[TOMKIZER]

Over the years, I used the ball-tip type because I had a batch of bad production types once. I was dissatisfied and wanted to go back to production type but with good quality. I expressed that concern to Geoff Ohland at Partsource. He assured me he had never had a complaint about his production type screws. I bought them and they looked to be good quality but who really knows, so I installed them before Cavallino 2010. I drove 2,500 miles with them, followed by another 1,000 miles since and have noticed no change in valve train noise, so they are probably ok. I'll know soon because I plan to check them in a couple of weeks.
Tom Kizer

[mark]

Thanks Tom:

I've heard of folks using the Porsche version of the screw, or is that just a myth. I like the fact that the Porsche version has more surface area than the oem, but I must say, I am a bit of a purist when it comes to parts.

On another subject, have you tried the needle bearing upgrade on the rollers? My local Mechanic friend says it's great.

[TOMKIZER]

I don't know anything about a Porsche version of the screw. My engine is back to as Gioacchino Colombo, or at least as originally produced from his designs.

I've heard of the needle bearing modification, but don't know enough about the actual materials and pieces to be confident that it would work forever. Hydrodynamic bearings are hard to beat for durability and load carrying capability if they are properly lubricated. Needle bearings have low friction, but normally work at higher hertz stress levels if I'm not mistaken, since they have a smaller load bearing surface area in a "hydrodynamic bearing" replacement environment.

I would have to defer to someone with design or development experience with these "solutions". I've been known to say in the past, "If it ain't broke, don't fix it." Not original but usually appropriate.

Tom Kizer

[mark]

Thanks Tom:

I am of the same persuasion "If it aint broke...", which annoys my friends. Just thought I would ask. I hear about this stuff from time to time, but rarely meet a real person that can authenticate, well except for the needle bearing thing, but I still remain skeptical.

[DWR46]

OK, here goes. In the 1980s there were a number of batches of bad valve adjusting screws. Almost all the various vendors had some bad screws in the inventoy at one time or another, so nobody was immume from buying bad screws. I do not recall if the bad screws came from the factory, or from an outside vendor. The stellite hardening was defective, and the screws wore through the hard surface and failed quickly. I have not heard of these failures lately, and I am sure that all the bad screws were out of inventories years ago. Every valve adjustment, you should pull the rocker stands and visually inspect the screws. "Smearing" is normal and nothing to worry about. Change them when they wear through the stellite or begin to "flake".

As to the Ball Adjuster screws, we use them exclusively in our race engines, as they do work more consistently under hard usage conditions. However, the valve tip must be perfectly flat for them to work correctly. If your valve tips are dished from wear of the old style screws, you should not use the Ball Adjusting Screws. After a valve job, when the tips have been faced off, the Ball Screws are fine. One problem with the Ball Adjusters is that if the engine is overreved and a valve is floated, the ball can "flip over" and hang the valve open , so you have to keep an eye on them if you have a driver who uses lots of revs, especially on downshifts where rev limiters will not protect the engine. We just took an engine apart that bent a valve after it flipped the ball over in the adjuster.

Needle Bearing Rocker Arms: Originally used by the factory in the competition engines (Hot Rod SWB, TR, GTO, GTB/C, LM), they work well, but are noisier than the bushing style rockers. Much harder to assemble, lots of rollers to load in each rocker ( memory is about 25 or so per roller). For street usage and light track work, I see no advantage to the needle set up (nor did Ferrari). Again , we do use them in our race engines, but not in the street engines. If the oil system is good, and the oil kept clean, the bushings will last a LONG time.

[mark]

That settles that, thanks DWR46.. I will be ordering oem screws.

[John Vardanian]

DWR, thanks for the insight. I am rebuilding my Type 168 and am especially interested in anything engine. One question I have with regard to engines that are well run in. How much out-of-roundness is to be tolerated when it comes to the rollers?

Funny, I was thumbing thru an old Cavallino magazine from the 1980's recently and in the back part saw an add where someone (I think it was an SF resident, if I remember right) was asking people who'd had engine failure due to faulty valve adjustment screws to contact him. It seemed much like the prep for a class action. It sounds funny now, but I guess it wasn't too funny, if you had just spent a whole $15,000 on a professional engine rebuild.

john

[tyang]

The other problem is how long it can take for this problem to show up in some engines. Some Vintage Ferrari engines just don't get driven enough to see these parts fail for many years, and often in the hands of a subsequent owner. Whenever we get a new customer with an unknown engine, we highly recommend a valve adjustment with a thorough inspection of the valve train. This establishes a baseline so regular inspections will hopefully catch inordinate wear.

I've also heard the same stories with bad camshafts, and let's not forget about the head gaskets!

Tom

[DWR46]

As to roller out-of-roundness, I have found it normal to see .001-.002". I used to many years ago, when I was young and full of energy, carefully set the valve clearance with the rollers in the "tightest" position. Now, I am lazy and just pick a spot and set the clearances.

As to cam wear, I have personally never seen a "factory" cam go bad unless something else was the cause. Four Cams and Dinos excepted, as they can wear out cams due to incompatibility in hardness between the cam and valve pad materials.

[John Vardanian]

The other problem is how long it can take for this problem to show up in some engines. Some Vintage Ferrari engines just don't get driven enough to see these parts fail for many years, and often in the hands of a subsequent owner. Whenever we get a new customer with an unknown engine, we highly recommend a valve adjustment with a thorough inspection of the valve train. This establishes a baseline so regular inspections will hopefully catch inordinate wear.

I've also heard the same stories with bad camshafts, and let's not forget about the head gaskets!

Tom

Agree. The first time I did an adjustment on I found that the bronze insert in one of the rollers was nearly all gone, lucky it was on the intake side.

john

[tyang]

As to roller out-of-roundness, I have found it normal to see .001-.002". I used to many years ago, when I was young and full of energy, carefully set the valve clearance with the rollers in the "tightest" position. Now, I am lazy and just pick a spot and set the clearances.

As to cam wear, I have personally never seen a "factory" cam go bad unless something else was the cause. Four Cams and Dinos excepted, as they can wear out cams due to incompatibility in hardness between the cam and valve pad materials.

Hi Dyke,

These are aftermarket cams that were bad.

Tom

[Jimmy Chen Shiba]

Remember me ? If I may chime in (since someone mentioned my name). Well, as for my 275GTB outcome, this iswhat happened. I searched, pondered, and took advice of my broker friend (who I trust). We decided to custom fabricate the screws from scratch at this racing car shop that my friend trust. The first set was made, tried, but was too soft still. The second set was made, tried, but was too hard and broke. Finally, the third set made and worked fine. So that is what happened to the car. I have driven few times since and indeed the engine is "quiter", more "smooth", revving seems "lighter" and all the good things to go along with.

The other option I considered seriously (which I ruled out for this time) was this shop called Roelofs Engineering BV. (I believe it is in Germany) http://www.roelofsparts.com/rp
They sell their own custom kit that is claimed to work super well. You might wish to look into this option.
w/ smiles Jimmy

[250GT]

Jimmy, saving some money on one side can be very expansive,
I believe Roelofs take about 1650 euro for this full upgrading.
and is tested on racingcars over more than 10 years without problems.
I drive them since 1997/8.
2 or 4 new cams plus 24 valve is a bitt more I think..... cyl.heads off etc
Trust is nice. but no garantee,
I like to have a more confience and lower heartbeat at 7000 -8000 rpm.
But I must admit, you must have a lot of GUTS.
We would like to know how the next 10000 km functioned.
neverthless good luck, you will need it.

Cornelis

[Jimmy Chen Shiba]

I hear you loud and clear and I am sure your way is the wiser choice. It really wasn't the cost per say for my decision. Things just turned out that way. As you say, we shall see and pay close attention as things go along. Nevertheless, thanx for your sage advice, Cornelis. w/ smiles Jimmy