Greetings all, Well got the new crane cam in the mail, went to the local parts store and picked up a set of metal timing gears, now I know there are lots of opinions as to which one is better. I decided to go metal to get rid of the fear factor and once I saw what the new fiber gears look like it sold me. Anyway, there is a noticable increase in gear weight with the metal gear. My question is will the extra weight have any adverse affect, I am not to worried about the minimal lose of any HP, just want to make sure all the roundy round stuff doesnt go flat. Well any reply and advice is greatly appreciated.
Joe

 

I still have a 240 & a 300 with the original gears, but I plan on putting in metal gears when I have them apart. My knowledge is second-hand on this subject, but I'll help get this thread moving. (Somebody is bound to post just to set me straight . . .)

o I believe there is a pair of gears available with a steel crank gear, but an aluminum cam gear. With good oiling, wear should not be an issue and you would have less weight.

o The cam gear turns at half crankshaft speed, so has half the inertial effect for a given weight. The additional weight is at an average radius of something like three inches, so it would be a lot less than the same weight on the flywheel. The additional inertia would slow the wide-open throttle acceleration, slightly, but I doubt you would be able to notice it in a truck.

If you had an aluminum clutch & flywheel in a 2,500-pound race-car, aluminum wheels, etc., then I would recommend the aluminum gear - in a truck you should be fine to go with the steel gear.

 

Aluminum is VERY soft. I wouldn't even consider it.
Since I've got 175,000 miles (and God only knows how many rotations of the cam gear) on my original phenolic gear, that's good enough for me.
Besides, I hear the metal gears are noisy.

 

I will use iron gears when I replace mine - I also understand that there are fine-pitch versions that are the quietest solution to eliminating the potential for sudden failure of the phenolic gears. (Good oil maintenance should let the phenolic gears go a long way.)

Most of the cases of noisy gears reported in these forums seemed to come from using the existing crank gear and only replacing the phenolic gear with a metal one that was not a matched gear. The best combination seems to be the fine-pitched iron gears that are a matched set from a brand-name manufacturer.

P.S.: Aluminum is not as hard as iron, but most iron gears are a power-metallurgy product that are made by pressing iron powder in a die and then sintering it to create a solid gear that needs little machining. This is not quite the equivalent of an alloy steel gear that is carefully hardened and tempered, but remember the size of the gears is large compared to their loading because it was originally designed for phenolic gears. I think aluminum should hold up fine. I mention this not to start an argument - I still agree that the iron gears are the best, but in my opinion anyone who has an aluminum cam gear should not be anxious about it. (From what I hear, a fair number of people have been "bitten" by failed phenolic gears.)

P.P.S.: 175,000 miles should be in the neighborhood of 200 million turns of the cam gear. (Double that if it was mostly around town.)

 

Sorry for the delay in getting back to you guys, weekend at the beech kinda thing. Well Acheda I was hoping to get your opinion. I am not to woried about the noise, I would much rather have peace of mind then worrying about whats gonna fail. The original phenolic gear is a stout gear, however, I looked at a few gears hear around town and it looks as if the newer aftermarket gears are bonding an outer tooth ring for lack of a better word with a substanderd material which in turn is bonded to the center hub. True, cam speed is half the speed of crank speed due to the gearing, I figured since the gears are not spur, the noise will be minimal, helical and or herringbone are designed for thrust and noise reduction if memory serves me right. You formula/theroy about inertia and spacing got me thinking and you got it right there should be a minimal drag on things just due to the physics.
Now for another issue. I read in a post that the nose of the cam should actually protrude from the gear flange some where in the vicinity of .050? have you heard anything like this, the other point would be since there is a thrust plate and washer, would the washer be the stopping point or does it get pressed on flush? Well gotta go unload things, thanks for the help
Joe

 

The added weight of a steel gear vs. aluminum or even plastic is of no concern whatsoever. The added mass might even be worth a few ponies if it dampens the cam harmonics a little better.

As long as the gears are made and installed properly they will be quiet regardless of what they are made of. On the other hand, they will be noisy regardless of what they are made of if they are made or installed wrong. Maybe not as noisy as two steel gears that don't mate properly, but noisy anyway.

Aluminum is softer than steel, but it is still plenty hard enough to take the loads needed to drive the valvetrain and oil pump. It is possible for aluminum to be pretty hard. A piece of 7075 can be so hard that it breaks when you bend it.

 

My Ford shop manual does not mention the nose of the cam protruding .050". (It does mention that the front cam bearing is to be installed .020"-.035" deeper than the front surface of the block - this is not the same thing at all, but it might have been confused by someone.) The thrust plate must have some small (unspecified) clearance. I have not had a 240/300 apart yet, but I assumed that the clearance was determined by a step in the cam snout because the manual did not specify it separately. (Obviously, the cam must turn freely, but with a minimum of backlash.)

I just checked my "other" Ford shop manual and it specifically states that the cam gear is to be "tight against the shoulder on the camshaft".

Regarding aftermarket gear sets, I do not know what is currently available, but I do not think I would go for the multi-piece gear you are describing if I could buy a one-piece steel cam gear (with fine teeth) that was in the same box with a new matching crank gear. Does anyone know what is currently available? Brand names & sources (mail-order)?

P.S.: The HD 300 never had the phenolic gear, so perhaps that is the application that should be used to find the better gears.

 

Well, as for aftermarket gears I have already purchased a set of iron gears. The are a pretty stout set and the MFG is Sealed power. The are a bit pricey, I live in a small town and got them from the local parts store (not a franchise) for $67.00. When I did the Auto zone and Oreillys trip they didnt have them nor did they seem to know what I was talking about I have the cam and everything else ready to go, I will press it on the cam at work then start the install on tuesday. Had the manifolds resurfaced and got a Rebuilt head. I will press the gerar down to the ring that sits against the shoulder of the first cam journal, Ive heard them called a cam button from the racers, however, this ring will allow the gear to be pressed only so far. It is on the stock cam so I will re use it, it looks good and doesnt show any abnormal wear patterns.

 

When you have the gear pressed against the shoulder of the cam, the retainer (with two bolt holes) should turn freely, but not have very much play. Check it while you are pressing - if it comes in a little tight, you can press it back a little.

Let us know how the Sealed Power gears work - they are an old-time name in the business. (Are the teeth the same size as your old gears?)

P.S.: In my experience a cam button is a thrust system that places a button in the timing cover against the front of the cam to control its position. In this system there is no retainer. I never put together an engine that used one, so I cannot tell you much more.

 

A cam button is what Chevy guys use to keep their cams from walking forward when they run a roller cam. With a flat tappet the lobe taper keeps the cam pushed rearward. With a roller it is free to slide forward as it spins. They put the button between the front of the cam and the timing cover to keep that from happening. The guys at Ford were smarter than that. The hold the cam in place with a retainer.

 

Now that you mention it they are racing I think a Monte Carlo or some thing like that, it figures they always have one problem after another. As for the gears, the sealed power gear is a bit wider and much thicker. I would have to borrow a term and almost put it in the bullet proof catagory. The machineing on the drive gear and driven gear looks good, I wouldnt say its up to NASA standards but it will pass, When I do the back lash on the new gears I will post the reading to see how they measure to the stock spec. which I think is .004-.008 I would be curious to see how the tooth contact would look after some blueing.

 

My Ford manual states .002" to .004" backlash. Non-hypoid gears have a more pure "rolling" contact without sliding, so they do not "print" as clearly as hypoid, but all contact should be in the between the tip & root of the tooth and even along the length of the tooth.

 

Its nice having the shop manual. I should get around to getting one with this truck, for now all I have found is the chiltons, not a lot of option out here where I live, every thing is 35 miles away. Good point on the tooth mesh, I believe 80% contact is what we used to see as optimal back in my old life (USN). But we were doing very large slow turning gears. Thanks for the .002"-.004" info.