Strait cut timing gear

[Dr_Terry]

Hi Guys.

The more the angle of the gear cut, then the longer the tooth & then more side loading is put onto the thrust plates of the gears. This is where any frictional losses would occur.

The slight angle difference between a genuine Holden timing gear set & a straight cut gear set is so small you would be measuring the loss difference in milli ergs not hp.

Gears sets of any type will have slight losses. In drag racing, I've seen comparisons done on V8s (with very heavy valve springs) between the standard timing chain set-up, straight cut gearsets  (Pete Jackson style), Helical cut gearsets,  & notched belt drives (Gilmer style). The only one shown to have any advantage was the notched belt drive.

This is in Pro-Stock racing, where they spends hundreds of dyno hours for minor hp increases.

Supercar V8s also use the notched belt cam drive.


Dr Terry.

[fcfromscratch]

Hi,

The benefit of double helical cut is that it neutralises the thrust or sideways force of a single helical cut gear set that Dr Terry mentions above.......by having equal but opposite thrusts from the two sides of the helical cut teeth.  

So the tendency to create sideways thrust, particularly for large gear sets like the one in RET's link, is all but eliminated....meaning that the thrust bearing duty/wear is very much reduced or possibly eliminated, depending on what other forces are at play in the design of the gears....

Brad

[2door350]

The muncie rock crusher isn't 100% straight cut.  The gears are on an 18 degree angle which is less than the regular muncie.

[NO NAME]

I am now at the stage were I need to purchase timing gears and have had to look into it myself.
while the old alloy helical gear was good it only has one keyway.
after talking to my engine guy this morning he said that there may be helical cut gears that are adjustable but if you get straight cuts they are usually adjustable with extra key ways, without this I cant dial in the cam.
I guess that is something to look at if you are building a hotty.
I went down to robbo's this morning were I knew they had straight cut gears for $99 but when I got there I noticed they didnt have extra keway slots, bugger.
so now I am in the market for a new set of timing gears.
while at robbo's I saw some older holden stuff there that you wouldnt see in auto 1 or supercheap.
It was a tiny shop but there were chromed bits hanging up as eary as FJ, also a nice new chrome grey rocker cover behind the counter and a grey harmonic balancer was in the front window.

[Glenn 'Stinky' Stankevicius]

Diecrest Engineering make (or made) the adjustable straight cuts.

Details are from the Hot Rod Internet site so they may be out of date.

Diecrest Engineering
Bagshaw Street, Harcourt VIC 3453
Ph: 5474 2321 Fax: 03 5474 2536