Looks like isoran might have been a subsidiary of Pirelli which may now be defunct. Cant find a lot of info. How good are gates timing belts? Maybe we should do a poll of people and see if we can nail down which belts are breaking/ratcheting?
What ever happened to this? I alomst bought the last one Ed had but missed it. The followinf quote is from anotherF-Chater. -------------------------------------------------------------------------- When I first joined FChat a couple of years ago there was an FChatter, Herbert Edward Gault frpm Gaffney, SC (since left), selling a belt upgrade kit to a thicker, heavier rounded tooth belt that came with belt and sprockets, much like the long life Honda system. The idea was a MUCH longer change interval (100K miles) and less distortion. He was not able to generate enough initial paying interest for a 4valve engine, and kits were only made for the 2 valve before he left.
interesting, from what i can see the pullies and layout look to be the same between the 2v & 4v. wonder where the difference is?
another idea that creeped into my head is to design a chain driven timing system, using a roller chain and sprockets. much like you'll find on the chain drive of a motorcyle, no oil bath needed. haven't a clue as to what stresses or speeds are permitable for some of those chains. but an idea...
I could certainly be reading this stuff wrong, but I think Ferrari used the trapezoidal type belt because of the average high engine speed and small diameter pulleys. I also am not sure if the curvilinear toothed belt would be the best choice going around such a small diameter drive pulley. Gaults setup may have worked, but who wants to be the test mule? I either want OEM new quality stuff, or something where there is absolutely no question it would exceed that quality or endurance. Right now we know what we have and its approximate TBO. If we change something drastically we will no longer have a baseline. I like these new pulleys, they look rather sharp.
i guess the one question is, how many people are interested in these pullies? i'll be doing a set for myself. when those are done i'll know the final cost, the machine time is the unknown right now.
more than you probably wanted to know but hey it's learning http://www.mitcalc.com/doc/tbelts/help/en/tbeltstxt.htm
Yeah, thats a lot to read, and more to try to figure out. The simplest and safest, and in your case easiest to absorb, is stick with the design we have. I dont believe a different belt design would provide any greater endurance and it could be worse! I think our main goal should be to find the best and strongest belt on the market, and perhaps re-engineer the idler to accept a larger pulley. I like you new pulley. I have a long ways to go toward getting my car back on the road, so it would be a while until I would spring, but I would probably do so, if for no other reason that to move away from the fiber ones. The ability to move the timing events is just icing. I think we need a decent pointer to go along with those pulleys as well. I would assume, the indications would be degrees in one revolution, so one line on the pulley would in actuallity be two degrees crankshaft, yes??
Can anyone elaborate on the advantages. I always thought changing the cam timing would just shift the powerband up or down.
Because our engines are twin cams, we have the ability to move either cam independently of the other. You could advance your intake, and simultaneously retard your exhaust cam. Or, you could simply advance or retard one alone, leaving the other in its place. Also, when you shift the power band up, as you say, you also increase its power up on top, while giving away some low end power and driveability. On a CSI car, for example, you "could" dial the cams into thier stock timing positions, and with these new pulleys, install the pulleys with them already advanced or retarded, say, 5 degrees indicated on thier registers. Now once its all together, you would have the ability to advance the intake, for example, almost 30 degrees of crankshaft rotation, without disturbing the belts, or opening up the engine, and later on put it back again. This is assuming the indications on the pulleys are 1/360 of a circle, camshaft rotation?
There are differences in the timing system parts, but I've never been able determine their significance. Most(but not all-see below) 4V engines have iron gears, & the 2V engines had the plastic gears. Now the 2V & 4V have the same replacement cam gears. Also, the 4V cam belt & cam drive gears are a different from the 2V Ferrari part numbers. I can understand the 4V cam drive gears being different, the larger cam drive bearings require a larger shaft, so I suspect that shaft diameter is the major difference between the 2V & 4V drive gears. (See detailed p/n comparisons below) I have no idea why the belt p/ns are different tho. Have sent eMAIL to Malcolm @Ferrari.uk to see if he can tell us. While most QVs have iron cam gears, I have an early QV (built in Oct. '82) & it has the same plastic cam gears as the 2V engines (go figure). I bought Ed Gault's old plastic cam gears on eBAY & have verified that they're identical to my car's cam gears, down to the mold markings. It wasn't until after the auction & I got the invoice that I found out I'd bought them from Ed. He hadn't connected the eBAY Verell with the Fchat Verell! We had a good laugh over it. I have always believed that I would have been able to use Ed's cam belt system on my car if I just bored out the holes & recut the keyways in his cam drive gears. Just couldn't come up with the $1K he wanted at the time. However, some of the data presented below makes me wonder how reliable his system is with the small drive gear diameter. Funny thing is that no one has every come forward & said that they have one of his systems. There are 10 of them out there somewhere! Wonder if none of them ever got installed other than the system on his car. Here are the Ferrari Part numbers for the Cam belt & drive gears,cam belt, & tensioner. 308 GT4, 308 Carb'd 2V, 308 Injected 2V ---------------------------------------- CAM GEAR [11] #113097 C/SPROCKET (INNER BELT GUIDE) Unit price: £77.20 Quantity required: 2 This part supersedes: 102586, 108033, 110994 [12] #113098 C/SPROCKET (OUTER BELT GUIDE) Unit price: £77.20 Quantity required: 2 This part supersedes: 102587, 108034, 110995 TENSIONER [25] #105206 SEALED BEARING CAM BELT TENSION Unit price: £90.80 Quantity required: 2 This part supersedes: 126720 CAM DRIVE GEAR [28] #104914 PULLEY (CAMBELT) Unit price: £156.80 Quantity required: 2 CAM BELT [10] #107833 CAM BELT INJ&CARB ENGINE Unit price: £10.70 Quantity required: 2 This part supersedes: 102877 ------------------------------ 308 QV CAM GEAR Same as 2V! TENSIONER Same as 2V CAM DRIVE GEAR [33] #121273 PULLEY Unit price: £126.80 Quantity required: 2 CAM BELT [15] #111334 CAM BELT QV ENGINE Unit price: £8.50 Quantity required: 2 ------------------------------ 328 4V CAM GEAR [16] #126569 CAM BELT GEAR Unit price: £151.00 Quantity required: 2 [17] #126568 CAM BELT GEAR Unit price: £151.00 Quantity required: 2 TENSIONER Same as 2V CAM DRIVE GEAR [33] #121273 PULLEY Unit price: £126.80 Quantity required: 2 CAM BELT [15] #111334 CAM BELT QV ENGINE Unit price: £8.50 Quantity required: 2
Here's a couple of data points: 1) The 246 Dino used a chain system that's essentially laid out like the 308's belt system. Given the overall similarity between the 246 & 308 engine designs, It at least is proof of the feasibility of a chain system in this class of engine. 2) Many of the motorcycle engines with chain drives have redlines almost 2x that of the 3x8 engines, & have horsepower that's close to half of the 3x8 engine. So I'd say the chain technology could handle the much slower 3x8 timing system speeds.
The 4v heads are shorter and IIRC the valve angle is different so the cams are closer together making the belt shorter.
here is the list of ferrari's that use the same belt; http://catalog.markivauto.biz/CatalogoWeb/Login.do?language=EN&area=OTH&origin=http://62.110.184.188/dayco/en/ the far right tab pull down and scroll to 94095
you bring up an interesting point, the cam turns at 1/2 speed of the crank so 1* crank is 1/2* cam. now for the pin placement on the factory pulley they are spaced out in degrees relitive to the cam. first pin placement is 3* cam but 6* crank. the marks i have are cam based to match the flexibility of the factory pulley, which means the 10* full advance is 20* crank. i double checked the cam, pulley and the WSM to make sure that's how ferrari designed it. edited.. got it backwords at first. cold medicine and scotch make for some interesting numbers..
Of, course, I knew that from my cam lock work. DUH: just didn't add 2 & 2, have always ordered the belts by Ferrari p/n & never thought to lay both tupes of belts side by side. Malcolm west just told me the same thing:
alrighty then, seems that to satisfy the issue of having a bolt wiggle loose and your timing is thrown off. i needed to find a way to pin the disks together. enter the shoulder pined adjustable pulley. it seems i can never leave anything well enough alone. now this may be a moot point but this will keep the cam degreed even if the locking bolts loosen up. a vote to what everybody thinks, overkill? the first is fine or is dead nuts accurate is the way to go? Image Unavailable, Please Login
this is too much a step backwards to the original design for my taste. Why not securing the bolts ? Maybe by using hexagon bolts with a lock tab. Similar to the principle how the central cam pulley bolt is secured ? And I think that 3 bolts would be sufficient. A weak spot are the slots, because there's always the problem of increased surface pressure under the bolt head compared with normal drillings. Best Regards from Germany Martin
Perhaps use studs, well attached, then on the outside, hardened washers to distribute the load. ESNA (nyloks) nuts could easily be used and if they are replaced with each use, should retain without fail. IMO, the earlier design is the best route, as it offers adjustability, without having to go thru the usual hassle. I can foresee a real benefit in being able to tune the cams quickly and easily when @ the track. No doubt there are times when more midrange and low RPM power may offer the edge, just as on different tracks more high RPM output may be the ticket. Advancing or retarding the cams will give this area a tunability never before available. For the hardened track runner, a set of belt covers with access holes would make cam adjustments a job that could be performed in minutes. JMO
for clarification, the pin is an M3 hexhead bolt. screw-in screw-out, same adjustability as the first one, just added the bolt to retain the degree. the rendering makes it look thinner than it is, the flange thickness is over a 1/4" with a 1/2" plate on the cam side. also just finished the tool, thin enough to fit on the pullies with the belt. .2" thick with an M8 bolt t ohold it together. Image Unavailable, Please Login
sorry, but this tool will probably not work, because the teeth of the pulley would have to be in the exact same position as those on the tool, what they probably never are. Except you turn the pulley into the correct position, but I assume that is not what you aim for. Best Regards from Germany Martin
accutually the teeth will always line up becouse the belt holds the two in sinc with each other. now you may need to rotate the engine a tooth to line up the tool. but this is for changing the belts not adjusting the timing. think of them as gears, two pullies and the belt. they are fixed to ewch other so the layout is always known.
In the first design, it seems very simular to the type available to the jap car crowd. If it works okay on a Toyota, it should work in this application. Keep it simple, things work better that way. I tend to like Kermits idea, to use studs threaded into the back peice. Highest grade available, aircraft quality. You could probably use an 8mm stud, and a shouldered nut, if there is enough room. You could even use castleated nuts and we could safety wire them. Additionaly, it may be a good idea to have the front section retained to the rear with a snap ring? What about making these parts of steel? I know its heavier, but it may prove to be more durable? As far as liability, I'll take the Mark Donahue stance. Its a race car, its 30 years old, and some of the new replacement parts are race car parts. Those of us here should all be smart enough to know if this thing will work, and if we are also knowledgeable about monkeying with valve timing, we don't need no stinking liability. I bought my car used, anything on it could break. No one is standing behind any of the rest of the parts on it, why this part?
