Primary and Drops gears

[Jono]

I have a techie query. I am building a 1300GT based motor - 1293, 276 cam, ported head, light flywheel etc. It will being running on a straight cut rod change box, ST ratios, with 3.4 diff.

I need to obtain a primary and drop gear to progress the build (engine man needs the primary to balance the bottom end assembly). Two questions:

1 Which gears do I need/are best for this set up - I understand there are different tooth counts and that pre A+ may be different?
2 Presumably I can use helical gears with the sc box - I imagine this might be quieter than using sc primary and drop as well?

If the answer to 2 is yes, does anyone have a set of the appropriate helical gears for sale?

Cheers

Jon

[Smiffy]

I have a techie query. I am building a 1300GT based motor - 1293, 276 cam, ported head, light flywheel etc. It will being running on a straight cut rod change box, ST ratios, with 3.4 diff.

I need to obtain a primary and drop gear to progress the build (engine man needs the primary to balance the bottom end assembly).

If thats what he told you, take it somewhere else !

Two questions: 1 Which gears do I need/are best for this set up - I understand there are different tooth counts and that pre A+ may be different?
2 Presumably I can use helical gears with the sc box - I imagine this might be quieter than using sc primary and drop as well?

If the answer to 2 is yes, does anyone have a set of the appropriate helical gears for sale?

Cheers

Jon

Imho You want the 'S/GT gear set with your set up, straight cuts are not needed.
Yes you can use helical drop gears with a straight cut gearbox.

[minimans]

Noise from the straight cut drop gears won't be an issue if your using a straight cut gearbox! you won't hear them above the box anyway..................

Swift tune has all the stuff you will need for Pre A+ and A+ I'd go with 1:1 gears....

[minimans]

I have a techie query. I am building a 1300GT based motor - 1293, 276 cam, ported head, light flywheel etc. It will being running on a straight cut rod change box, ST ratios, with 3.4 diff.

I need to obtain a primary and drop gear to progress the build (engine man needs the primary to balance the bottom end assembly).

If thats what he told you, take it somewhere else !

Really? my guy likes to bolt everything up to do a final check with the full clutch attached to the flywheel so you'd need the primary in place.

[Spider]

The eariler 24 tooth helical cut gears would probably be the go, they are a bit stronger than the later 29 tooth types, though they are what I run in many of our cars without any additional issue over the eariler type.

While on the subject of Transfer Gear Sets does anyone know is Helical Cut types in a ratio of around 1:0.9 (ie, slowing down from the crank to the Gearbox Input gear) are available? Something around 28-29 tooth Primary Gear and a 31-32 tooth Input Gear? I have seen them in straight cuts but I was after helicals.

[almondgreen]

Noise from the straight cut drop gears won't be an issue if your using a straight cut gearbox! you won't hear them above the box anyway..................

I do not think so, the drop gears make more noise than the gearbox.....

[Vegard]

I have a techie query. I am building a 1300GT based motor - 1293, 276 cam, ported head, light flywheel etc. It will being running on a straight cut rod change box, ST ratios, with 3.4 diff.

I need to obtain a primary and drop gear to progress the build (engine man needs the primary to balance the bottom end assembly).

If thats what he told you, take it somewhere else !

Really? my guy likes to bolt everything up to do a final check with the full clutch attached to the flywheel so you'd need the primary in place.

I agree. How on earth are you going to balance the flywheel assy without the spacer (clutch plate) between the backplate and flywheel?
Yes, balancing a Mini clutch is almost impossible, but doing it without the primary gear and clutch plate cannot give you the correct result.

[Jono]

...well he was with MED for 2 years and then ran QED's engine workshop so I think he knows what he's doing


so...has anyone got a set of helical drops they would like to sell to me?

[Smiffy]

LOL you balance the crank, then you fit the correctly assembled flywheel and balance that. You DONT need the primary gear to do this.

[Vegard]

LOL you balance the crank, then you fit the correctly assembled flywheel and balance that. You DONT need the primary gear to do this.

You're wrong Smiffy. Don't you balance the back plate? Flywheel only? What about the clutch diaphragm?

[Smiffy]

LOL you balance the crank, then you fit the correctly assembled flywheel and balance that. You DONT need the primary gear to do this.

You're wrong Smiffy. Don't you balance the back plate? Flywheel only? What about the clutch diaphragm?

You balance the whole rotating assembly, the crank is put in the machine first, this is balanced. Then anything that is fitted to the crank that is out of balance, shows up when the machine is spun. They do the whole clutch flywheel assembly, rather than the flywheel then the backplate.
As the flywheel/backplate always goes back in the same place, this is how it's done.

[Earwax]

exactly how different shops balance the flywheel/clutch... is a good question.... i don't know and i am not sure if either of the methods from Vegard and smithy would produce different results..... they both present as sound methods to me.... but as i said, i actually have no clue

[Vegard]

LOL you balance the crank, then you fit the correctly assembled flywheel and balance that. You DONT need the primary gear to do this.

You're wrong Smiffy. Don't you balance the back plate? Flywheel only? What about the clutch diaphragm?

You balance the whole rotating assembly, the crank is put in the machine first, this is balanced. Then anything that is fitted to the crank that is out of balance, shows up when the machine is spun. They do the whole clutch flywheel assembly, rather than the flywheel then the backplate.
As the flywheel/backplate always goes back in the same place, this is how it's done.

This is how it CAN BE done.

Doing it this way, the spacing between the flywheel and back plate is wrong. Due to the clutch diaphragm, the backplate will be closer to the flywheel than it will be when everything is bolted up.

Are you saying this will not affect the balance of the assembly? If it doesn't, then I'd like you to prove it.

This is just like when ACDODD balanced his rods measuring the cap and "rod themselves . If all caps and all "rods" where the same weight, then they surely must have been in balance

[mk1]

This is just like when ACDODD balanced his rods measuring the cap and "rod themselves . If all caps and all "rods" where the same weight, then they surely must have been in balance.

CLASSIC!

For what its worth, I have always had my engines balanced as follows, Crank first then add the water pump pulley, flywheel & associated bolts, then add the primary gear, back plate, clutch plate & pressure plate in a lump. Seems the sensible way to do it to me.

BTW. Whatever happened to A C DODD the self acclaimed A Series Engine Expert?

Expert
Ex = Has Been
Spurt = A drip under pressure

[Spider]

You're wrong Smiffy.

No. He just does it different to everyone else.

Gotta say, I do end up with balancing the lot, including the primary gear and plate. When I do balance them up, it's pretty clear one the primary gear, plate and diaphragm are added that it would be a lesser result if they were not.

[Smiffy]

Cant any of you read what I actually said, the whole clutch assembly, this is how all engineering firms do it. If you pay more you can have each part individually balanced, but whats the point when the clutch plate and primary gear are in a different location every time the clutch is used.

[251 ENG]

When I balance engine bits , I do them in this order

Zero balance crank ( that means the out of balance on machine reads zero , NOT just do it till it is near )

Assembly flywheel , clutch and backplate to get everything in correct place ( spacers , straps etc )

Take clutch / backplate / cover off but leave straps / spacers on flywheel

Zero balance flywheel

Fit primary gear assembly

Re-assembly flywheel / clutch / backplate / cover and fit to crank

Balance assembly by drilling backplate

Generally cranks are out , late mpi one,s are very close , flywheels also out but backplate are normally good .

Although this is the procedure we follow , we actually have a selection of scrap cranks that have been zero balanced and use them to balance flywheel assembly,s and front pulleys.

Also different types of machine,s use various ways to spin crank and you will get slight variation in results.

[Vegard]

Cant any of you read what I actually said, the whole clutch assembly, this is how all engineering firms do it. If you pay more you can have each part individually balanced, but whats the point when the clutch plate and primary gear are in a different location every time the clutch is used.

Come to think of it, you're right. And they never are when the engine is up and running either. Static!



Seriously. I balance the way you do, but then I follow up by fitting the clutch plate. I guess you could make a spacer/washer the thickness of the clutch plate to get the backplate at the correct position compared to the crank mains.

I'm not too worried about how what in your book "all" engineering firms do it. They are rarely A-series specialists, and we must not forget that the clutch on the Mini, albeit ingenuitive, is plain rubbish

[ianh1968]

!

[JohnA]

Where did all that come from ?