Nick's 308 to 4.0 conversion

Examination of used bearings and the bearing bosses indicate that bearing failure is the result of radial loading. Both of the blocks that are being used as prototypes show radial wear of .002 of an inch within the inner bearing boss. It is our belief that the fundamental problem is the resistance to radial loads. The proposed bearings are several times stronger than the bearings spec’d by Ferrari without materially altering the axial load capacity. Your concerns are theoretical and fail to address the reason for current bearing failure. Further, the proposed bearings have a much longer projected service life than the bearings Ferrari used for these engines.

Multiple circlips are already used to secure the bearings in the bores.

Ferrari has used several bearing and seal combination for the cam drive bearing setup for the 308 and they are not interchangeable. Your question regarding the use 355 bearings implies that they universally interchangeable and superior.

Ferrari has not demonstrated the ability to adequately engineer the cam drive bearings for the entire production run of the 308 and 328 despite a number attempts.

Thanks for your concern,

Mark Lewis

 

The following pictures illustrate the process of machining the drive bearings bosses. It also shows both of the prototype blocks.

Thanks,

Mark Lewis
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Mark, you're missing the point, or ignoring it.

The inner bearing is located in the block. It cannot be pushed in any deeper as it bottoms out.... Hence perfect axial loads capability. However, the shaft then just pushes into it, and can of course pull out again. The only thing stopping it being pulled out is the outer bearing, which is now your roller type, which is NOT designed to carry an axial load, even though it probably can accept a light one.

Now, your blinkered response is getting rude. I'll certainly not respond any more on a technical level to this thread. I've said my bit and was/am trying to be helpful. I've nothing more to offer you.

I think your design changes are flawed, but are very easily fixable with use of an external double ball bearing. Would it really hurt your pride so much to admit an oversight...especially one which is so easy to correct.

I wish you, but more importantly your customers luck.

 

Ferrarifixer does make a good point. The shaft is semi press fir into the block bearing. You can have all the c-clips you want securing the bearings in there bores..but what about the shaft movement itself?

 

Your response is not technical; it is antidotal. Regrettably, you have not quantified the axial loads; you have guessed. You have been given a formula to make such a calculation and have chosen to shoot from the hip. You have don’t know what bearings are being spec’d because that information has not been released. You don’t even know the radial or axial load carrying capabilities of the subject bearings. You champion a five-dollar bearing in favor of one that costs over ten times more.

Further, you have not proven that axial loading is a problem. The axial movement is resisted because the bearings are secured by a common shaft that is retained in the boss by clips. The physical attributes of the bearing and the installation of clips limit movement is both directions. A good gauge of axial loading is the construction of this retaining mechanism. The clips are flimsy, the grooves are about a couple thousands deep and cut into aluminum. In addition, there is no physical evidence at the bottom of the inner boss that this is resisting axial movement. Point of fact, there is not much axial loading! The problem is and has been radial.

I have not tried to be rude; I simply disagree with the substance of your argument. Inherent with taking a position such as yours, is the responsibility to support your case. I believe that you have failed that test.

Mark Lewis

 

There is an interface fit between the shaft and the inner ring of the bearings. If the bearings were sliding or spinning on the shaft there would be a wear pattern on the shaft and the inner ring of the bearings housing. I don’t see that pattern. If the floor of the inner boss was used to resist axial movement there would be a wear pattern here as well. Little or none has been observed.

If I thought that there was a problem with the proposed solution, I would freely admit it.

Thank you,

Mark Lewis

 

This front cover came off a 1981 model year engine. It serves to better show the weakness of the retainer groove external support. Just how much axial loading can there be with so little material supporting a narrow steel snap ring?

Quote by Steve Demirjian

“Make sure to mention that we will most likely eventually make a billet front cover sans oil pump for our 4 liter engine. My plan would be to make the cover deeper where the drive bearings go which would allow a double ball bearing width bearing to be fitted on the outside. Probably use a larger outside diameter bearing as well. There is just no material in the stock cover to allow a thicker bearing to be fitted.”

“Guys are already *****ing about the price - wonder how many would pay for a billet cover. The roller bearing I have come up with is a cost effective replacement for the stock single row ball bearing. There is no other bearing available in this size - no max type bearings incorporating a greater number of balls for instance.”

Thanks,

Mark Lewis
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That front cover sounds like a great upgrade! This would be a good opition to have as a single piece available for any 308 even if they didn't want to go with the entire engine. I'd imagine it would be a little more difficult to incorperate the stock put set up in the cover..but if what you say is true regarding the bearing upgrade (which I know for a fact are a problem) then this would be a good upgrade in itself.

But the one question I have...These 308's are getting quite old. Many of these cars are still running around on there factory supplied timing drive bearings. Is the design really as bad as you say..or is it the fact that the cars are just getting older and these things are starting to creep up because of that. Just look at the number of 308's on here and even some 328's that are now experiancing corwn gear bolt issues. Obvioulsy the car lasted 15 years without a problem..so is the design of these bearings as they were from the factory really all that bad? 20 plus years on some of these cars for bearing life..really isn't that bad..

I would like to find a Ferrari tech that was working on these 308's when they cam out..to find out how much an issue these bearings really were or if this is just an issuse of age.

But I must say again..the workmanship in the project seems to be top notch. The question I ask is more of a general nature. I'm not slamming the project. In fact I'm quite interested in this because I thought of doing somthing similar about 5 years ago..but never got around to doing it unfortunatly.

 

I received the following response from Steve Demirjian on the drive bearing topic and thought that it was wise to share it with you.

The camshaft is always putting a load on the drive gear assembly whether the engine is accelerating or decelerating. It makes no difference. The camshaft has no means of putting a driving torque on the gear during deceleration. The camshaft is not driven by the wheels on the car!

“The gear and integral shaft are a slight press fit in the stock bearing - will be the same in the roller upgrade. The amount of press is not significant regarding the bearing not spinning on the shaft. It is impossible for it to spin because the inner race of the bearing is solidly clamped between the gear face and the outer belt drive pulley when the nut is tightened. The bearing is trapped between two clips so it can not move for and aft in the timing cover. So the outer bearing takes whatever thrust load there is. The inner bearing does nothing in terms of thrust load. It is merely solidly supporting the shaft to keep the gears in proper alignment.

I don't understand what the heck this guy was talking about when he mentioned cutting a snap ring groove in the shaft itself. The shaft is solidly clamped to the bearing by the external nut holding the drive belt pulley on - the inner bearing race is trapped between the gear and outer pulley as I explained above and is clearly shown in the photos.”

Thank you,

Mark Lewis
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The issue on the cam drive bearing is not the years (20 plus years on some of these cars for bearing life..really isn't that bad..") most of these 20 year old cars have less then 30,000 miles and the I personally have seen the bearing failures on several, including twice on mine (now with 71,000 miles on it).

The bearing design was a problem and Ferrari in 1983 in the middle of the production year changed the bearing size to what would be used in the 328 (my 308 QV is an early 83 and has the smaller bearing. This change seem to limit the failure but then again with the average late 308 QV's and 328's on average having less then 30,000 miles on them who really knows if the design fix was a marked improvement.

 

I'll help him out with this one. The helix angle look like 30 degrees, so axial load= belt tension x sin30. It is there and very real. So you state, not knowing what bearing you have selected, I cannot comment on whether or not is appropriate other than to say that for this application you can not simple replace both ball bearings with straight roller bearing…but that may not may not be you plan anyway. Everything look very well thought out, I’m sure you’ve thought about this too.

 

and as for shooting from the hip.....I'll have all the 360/550 type outer bearings you can get me at $5 each thanks........

and if you're charging over $50 each for those roller types...you're making a sizable margin too.

Good on ya, I hope you retire early enough to avoid the warranty claims.

 

As a point of clarification:

1. The bearings that we have removed from various 308’s were of lower quality with a replacement cost in today’s market of around $5.00 per bearing.

2. The 4-liter bearings are a substantial upgrade in both radial loading and service life as compared with that of the stock 308 bearings.

3. The jobber cost of the upgraded bearing is approaching 10 times that of stock replacement bearing.

4. There have been no representations by me regarding the retail cost of 360 or 550 drive bearings. Those bearings carry different parts numbers than those for the 308.

5. Ferrari does not manufacture the drive bearings. It is very strongly believed that all bearings that have been referenced in this thread are available through the same bearing manufacturer.

6. In the event that the upgraded bearings are not the ultimate solution, they will never be marketed to the public. A more expensive alternative has already been mentioned.

7. The comment about “shooting from the hip” was in reference to axial loading theories that have been thoroughly addressed by Steve Demirjian and myself.

Thanks for the interest on this subject,

Mark Lewis

 

I thought that I would share with you some additional photographs of the upgraded balancer assemble. We are really pleased with workmanship and beauty of these pieces.

The theory is that crankshaft is simply a big tuning fork and if those harmonic influences can be dampened then things like bearing life and the accuracy of cam timing would improve. We believe that these are real issues in light of Ferrari’s flat crank design. The vast majority of V8 cranks have 90 degree crank throws. This is done for the smooth operation of engine and better crank harmonics.

Our balancer is lighter. It uses a clutch pack to cancel vibrations, which we believe is better. A balancer is required even if the crank assembly is internally balanced.

Thanks,

Mark Lewis
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Crank harmonics fascinates me, as I've seen all sorts of vibration issues over the years.

Can you shed any light on the possible reasons Ferrari have removed the balancers from the 360 engines....

Their biggest capacity V8 engine (until 430), has no vibration damper.....weird, or do they know something ??

 

The reasons that we have decided to replace the stock balancer are as follows:

1. The new crank is lighter than the stock crank. Less rotating mass allows the engine to rev more freely. It is purported that each 1 lb. of mass taken off the crankshaft is equivalent to approximately a 2.7HP gain.

2. The 4-liter engine has a longer stroke than the stock crank, 71 mm vs. 79 mm. The amount of torque per cylinder is also greater. The net effect is that each 4-liter piston is transmitting greater torsional loads that are leveraged by a longer stroke. Each engine pulse literally attempts to twist the crankshaft. The complex harmonic vibrations can destroy a crank and alter cam timing. The firing of each cylinder is like ringing a bell. In this analogy, the crank is the bell. By using a high quality balancer the tone generated by the engine is actually altered. In some engines the dampening effect is perceptible by the human ear.

3. A billet crank will twist more that a cast steel crank or a forged crank.

4. The design of the stock dampener, rubber sandwiched between an inertia ring and the hub, is designed for low rpm service. The 308 is a high revving engine so the stock dampener does little to mitigate vibration problems at higher rpms. The upgraded crank balancer is designed to work throughout the targeted rpm range. The spring setup in our balancer also provides for more immediate and effective dampening than the stock unit.

5. The rubber between the inertia ring and the hub is a spring that allows the inertia ring to oscillate with engine pulses. The effectiveness of this spring is directly tied to the physical condition of the rubber. After more than 20 years of heat and exposure to the elements, the rubber rings in the stock balancer have significantly deteriorated. The replacement of the stock balancer is expensive and is only marginal when in good condition.

6. The stock balancer is limited in size to about six inches by the protrusion from the oil pump in the front cover. Given the design type of the balancer and its limited size, the stock balancer is largely ineffective. The bottom line is that the stock balancer would be more effective if it was larger. In the interest of reliability, we have attempted to upgrade the balancer.

7. A proper functioning balancer will extend bearing life, improve cam timing and protect the crank from catastrophic failure. Modest horsepower gains are achievable over both the stock balancer and a no balancer setup. I find it interesting that NASCAR balancers are individually tuned for each engine and can result in as much as an additional 5 to 10 horsepower.

The question was posed, why did Ferrari eliminate the balancer altogether for the 360 and 550 models. I really don’t have a good answer for that question, however the theoretical merits of doing so is discussed in the following article. http://www.atiperformanceproducts.com/products/dampers/damper_dinan.htm

Thank you,

Mark Lewis

 

Mk e,
I agree. However, the design's inner bearing is a double row ball bearing, not a roller bearing.

While they haven't said, I assume that the inner bearings are similar to those used inside the belt tensioners which can handle axial loads. (Altho why the belt tensioners need to handle any significant axial loads is something that hasn't penetrated my thick skull tho.)

I agree with your helix angle analysis, the axial force from the gears is going to be there. If the outer bearing is a roller bearing, then it can't handle any axial force, which leaves the inner bearing to handle it. A quick analysis of the two axial force possible directions is:

CASE 1: INWARD AXIAL FORCE - PROBABLY NOT A PROBLEM
If the axial force is inward, the outer balls & race race of a double row bearing will transfer the axial force from the inner race into the block.

CASE2: OUTWARD AXIAL FORCE - ????
However, if the axial force is outward, I don't see how the inner bearing could handle an outward axial force, unless it's so firmly pressed into the block that it can transfer the outward axial force by the friction fit between the outer race & the block. (Am I missing something?)


A key question to understanding the system's ability to handle this axial force is the force's direction when the engine is operating.

AXIAL FORCE IS UNI-DIRECTIONAL:
Whether accelerating or decelerating, the engine only rotates in one direction, and the force on the cams from turning the valves is in one direction, so the resultant axial force resulting from driving the belt will also be in one direction.

AXIAL FORCE DIRECTION:
A quick examination of the cam drive gear image in MTLewis's 10-JAN, 03:54 AM post reveals that driving the gear counter-clockwise will produce in an INWARD AXIAL FORCE. So, at the risk of going out on a limb, there's NOT an axial force problem if the inner bearing can handle axial forces.

 

When trying to sort out the problem we had w/JWise's service, we had the opportunity to ask this question of a tech who worked for the MA Ferrari dealership from '77 until the late '80s. During the entire time he was there, the dealership never had to replace a set of timing drive bearings. In fact, he didn't remember them doing any engine work beyond the normal belt, valve adj, etc. PMs. Of course most of the cars never accumulated more than 5,000 or 7,000 miles during the entire period.

Presumably Ferrari did see some level of problems, because they did redesign to use larger bearings. However, IMHO, we're seeing the recent problems because the grease in the bearings is drying up after 20 or so years. Most likely replacing the outer bearings every scheduled 15K service/10 years would prevent any failures.

 

Just so I don't have to go back and read everything over again, we're talking about the cam drive bearings in the lower portion of the block, yes??

 

I think you’re right, the force looks like it’s in… most of the time. There are points in the cam revolution where 1 valve is closing and nothing is opening so the spring is driving the cam and the force will reverse….but I don’t know how much it matters since friction always acts against it and the belt has some spring which both act to minimize it, and except during cranking the pulse is for a very short time.

What troubles me is that the OEM setup bolts the shaft into the outer bearing then clips the bearing into the cover making me think the design is for the outer bearing to handle the thrust. I’ve never measure the clearance to the rear bearing, it may be touching or nearly touching that bearing too…but it might not.

 

I guess I am going to try axial load thing one more time. By the time we are done we will have beat this horse to a pulp. I have the distinct advantage in knowing what new drive bearings are being used.

Plus I want to make the point that if the drive bearings and the timing belts are of a better design then there nothing to stop us from increasing the timing belt replacement intervals. This would be a serious costs savings, not to mention a hassle that could be differed a while longer.

I suggest that we look at the following:

1. The angle of the helical gear is not very great.

2. The amount of press fit surface area on the new inner bearing is twice that of the stock bearings. The radial load capacity of the new inner bearing is two to three times greater that the stock bearing. The new larger inner bearing is rated as good by the manufacture for axial loads, similar to the stock bearing.

3. The drive bearings are secured in both directions. The two snap rings and the bearing press fit controls outward movement. The press fit of the bearings also limits inward axial motion. As the nuts tightens on shaft, the lower drive pulley and outer drive bearing are sandwiched together between the front housing. This not only limits out outward motion, but inward motion cannot occur unless you pull the drive pulley through the front cover.

4. The cylindrical roller bearing moves in a channel with flanges and does resist axial loads, all be it, not to the same degree as a ball bearing.

Thanks,

Mark Lewis

 

mk e,
The SKF specs for the OEM bearing confirm your thinking. The outer bearing is a fairly tight tolerence bearing, while the inner bearing has additional tolerence as recommended by SKF for a bearing application on a shaft with the other end fixed. Also, the outer bearing is a snug press fit in the housing, (yes, it's c-clipped also). The inner bearing is a loose press fit in the block, & the shaft is also a loose press fit.

There's definitely a gap O(2-3 mm)between the shaft & inner bearing's inner race. Found that out the hard way once when I installed a timing cover, hadn't snugged the pulley onto the one of the shafts, and the end of the shaft was about that much further inward than the other shaft. When I tightened the ring nut, it pulled the shaft out. That's when I decided I'd better pull the cover out & reseat the inner bearing in the block.

However, all of this is the original design. These guys have changed enough things that only they know how the dimensions work out.

 

Ok, so why NOT use a new spec double ball outer bearing that resists both radial loads to a higher degree and ALSO axial loads to a higher degree too.

Why stick with rollers when a simple swap to double ball will do BOTH jobs better.????

What's so great about these rollers anyway.

A point about axial loads too...it's not so much the specific effort to drive the valve train that is the problem If the drive gears were straight cut it would have no axial load, but be noisy and have more backlash.

The axial loads are applied at all times when engine speed is running. The inertia of the valve gear pulls it the opposite way on overrun, and friction and loads push it the other way when just driving constantly or accelerating.

For me, I'd specify bearings designed for axial and radial loads...just like your car wheel bearings.....

But I'm just a spanner turner, what would I know