Strait cut timing gear

[Dave_EH]

Hi,
 I'm getting a new cam, lifters and head put on my 179 next month and also have a new set of strait cut timing gear that could be installed.

I've had a chat to the engine shop and they tend to think the strait cuts will drive me crazy with the sound!  

Is it really that bad and does anyone have an opinion whether they are necessary?

cheers
Dave

[TorqueFC]

yes they are noisy, but they wont drive you crazy, the question is what will you be doing with the motor, and how fast will you be goin?

[Dave_EH]

I just like to do things properly the first time.  The stronger everything is the better, that way I can drive it whichever way I choose...  now or in the future.

The driveline and rear end will eventually be toughened up over the next few years so I may as well start with a strong motor.

As long as it doesn't wake the dead or embarrass my girlfriend too much to the stage where i need to get the windows tinted I'd like to use them.  Any other opinions?

Dave

[Glenn 'Stinky' Stankevicius]

I have straight cuts in the 202 that's in the FE, the motor was previously in an LJ Torrie daily driver. I love the sound and spent most of my driving with windows open. When I had enough I cranked up the stereo.

If you hate the sound of straight cuts, gear drives or blown motors, then yes it will drive you crazy.

If you don't mind the sound, you'll get used to it after a while.

If you love the sound, you'll think it's not loud enough  

[NO NAME]

I was talked out of going a lot wilder with my motor when I built it by parts suppliers, I later regreted it pretty bad, this time I will ignore all that crap.
I had a mate who fitted straight cuts to his EK and wasn't happy so he also fitted a gilmer drive wich kept slipping off.
the lower resistance is pretty small and they aren't much use unless you are chasing every half a horse you can get, main purpose is for noise.
remember, if it's too loud your to old.

[TorqueFC]

yes straight cut gears main purpose is noise, also with the gilmor belt drives they are awsome, the old ones were shit but the new ones look and sound great, hasnt slipped off once and thats on a 350!!!

cheers
torque

[Revhead_Fc]

Ive had staight cut timing gears on both 6's and 8's and loved it but remember you also have to put the same gear on the crank which you need a hydraulic puller to remove the old one if you are doing it in the car this may be very difficult but if you are rebuilding the motor any machine shop should be able to do this for you

Hope this helps

Ben

[Dave_EH]

thanks ben,

The machine shop said it would't be any worrries to do it in the car - removing radiator and grille and jacking up engine.  You would assume it would be difficult with the engine in the car though?

If they can do it I may as well put the gear in as I already have it, if not its not the end of the world.

Cheers
Dave

[surferboy]

It will be cheaper to just stick a cat under your bonnet and stick its tail in the fan belt !!!

[NO NAME]

straight cut timing gears are crap as the engine shop said, let me save you finding out yourself, ill give you $90 for them if they are new.

[Dave_EH]

Hey Leon,

I'm not quite sure what you mean?  I was just told they were noisy, and thats what everone one else said too, although some like the noise and some don't.

I think I paid about $130 new, why are you after them if they are crap?

I'm not having a go at you, I just wonder why you think they are "crap"?  Aren't they used on race cars?

Cheers
Dave

[colt]

My understanding of these gears is that they reduce power losses compared to the normal gears. This is why they are used on race cars, not because they sound good. This is why gears on production cars are not straight cut, because they are noisy.
Colin

[4hammers]

Hi.
I think they are also a lot stronger. Being cut straight, they are less likely to have a weak spot & most of the face makes complete contact (If you get my drift?). The standard gears, tend to have areas where not all of the opposing gear actually makes contact, putting more stress on that spot.
Have you ever heard of the "GM Muncie Rock-crusher" 4 speed? Mega, MEGA strong gearbox built for the BIG block Corvettes. LS7 motors (427 Cube, high octane fuel, 500+ Factory HP). They used all straight cut gears internally. They were as noisy as hell & thus earned the nickname "Rock crushers".  These things were STRONG!!

Dr. Terry, help us out here, Mate. Is this correct?

Rob J

[Dave_EH]

Thanks Rob and Colin, thats what I would have assumed too.  The standard timing gear for a red six is only about $30 or $40 dollars I think, and I've heard a couple of old cars with strait cuts and don't mind the whine... sounds a bit trick!

Would like to hear Dr Terry's opinion too... have heard about the Muncie "rock crusher" - I've heard it referred to as an M22 - is that possible?

Cheers
Dave

[Dr_Terry]

Hi Guys.

What we have to do here is to discard the myth & discuss why they make straight cut gears.

When gears drives of any type were first invented, they were all straight cut. The available machining techniques were primitive & that was the best there was. The gear tooth was designed in various styles, involute & stub involute etc, but they were all straight cut. But of course, they all were noisy.

The helical cut was developed over time, its main advantage was low noise, in most cases almost silent, people used to pay extra for this. Most factory gear sets, wether they be transmision , timing or diff gears are helically cut because they are quiet & long wearing. The only problem with with helically cut gearing is that it is more expensive & is slightly weaker in outright strength, only becuase when you cut the gear on the angle, the tooth profile the is slightly narrower.

Ever noticed, how, with manual transmissions they are quiet in the forward gear but noisy, but noisy in reverse. Reverse is usually straught cut, because of cost & it isn't used very often. The Muncie 'Rock Crusher" is so named because its gears are very big, very strong & all straight cut, homologated performance use only, too noisy for normal street use. (Yes Chev use M20/M21/M22 etc as sales option numbers for their manual transmissions as well).

Getting back the straight cut timing gears, AFAIK the main reason there available for street engines on the performance market is because they are sh*t cheap to manufacture, & they use the straight cut bit as a strength/performance marketing angle.

When was the last time anybody saw a metal timing gear gear break because it was too weak ?. Sure the fibre ones die of old age or when overstressed or overevved, but not a helical metal set.

For my money steer clear of so called performance straight cut timing gear sets & spend your hard earned cash on something that will give you more performance or more reliability, not because the noise is cool.

Dr Terry.

[4hammers]

Thanks for that, Doc!
Man, you learn something everyday on this forum .
Regards,
Rob J

[NO NAME]

I thought straight cut gears would have less rolling resistance, I always assumed they would wear faster and the noise was the teeth meshing and grinding together wich sometimes made me wonder if they really could be rolling more freely.
I am not to worried about the wear as I pretty much replace everything when I pull the motor apart.
does any one know if straight cut gears roll more freely?

[RET]

Here's a piece of trivia for you - the Citroen logo represents a double-helical gear, the manufacture of which (in steel, anyway) was invented by Andre Citroen. Here's a rather large pair.

cheers
RET

[normd]

WOW      RET

  Would like to see the "motor"   THEY came out of  
       

Norm  

[NO NAME]

I wonder what the advantage is of the double helical gear, my guess is that it is to reduce the pushing out pressure of helical cut gears wich is were I think you loose energy.
I wouldn't really doubt much of what Dr Terry says as he seems to be pretty much the most clued up on this forum when it comes to mechanical stuff.
but I think there would have to be a advantage with the straight geras as the helicals even at 2:1 would be quite loaded once we fit double valve springs wich I think would make them want to push apart under load.
when you are chasing all the hp you can I still think straight cut gears are a advantage other than just strength.
has anyone tested this?
anyway, do you want to sell them?