• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

5 speed conversion using the Datsun clutch assembly

Share this page

Rut

Rut

Obi Wan
Country flag
Offline
I'm gathering info on the various 5 speed conversions and I prefer the Datsun clutch assembly. That said, how do you ballance the clutch, flywheel, and crank as an assembly? I have a local machine shop that can machine the flywheel for the Datsun clutch, but this ballance issue has me concerned.
Rut
 
Rut said:
That said, how do you ballance the clutch, flywheel, and crank as an assembly?
Rut
Click to expand...

By dismantling the engine!

But unless you are dealing with a crank that uses external counter balance weights this shouldn't be needed unless you are after the ultimate in sub gram balance precision. If you are worried have the balance of the removed flywheel checked. If it is way off of balance as a discrete unit then you may have a problem. Swapping flywheels is a common activity and rarely causes a problem with balance in the real world.

If the original flywheel for some reason is way out of balance the technician doing the work may be able to duplicate the same imbalance in the new flywheel. Proper indexing would then be critical on reassembly.
 
I've not talked with the machine shop about the balance issue yet and everything will be apart when I take it to them, crankshaft, flywheel, clutch assembly. My 1275 was rebuilt, but some things need to be addressed. The compression ratio is 12:1, the rear scroll needs to be adjusted/line bored, cylinder walls need a little Scotch Brite, tolerances need to be checked, etc. The engine runs great, but I'm not too sure it's street able in its current configuration.
Rut
 
Rut, good luck on gas for a 12 to 1 engine now day's! If you have ethanol blender pump's you can probably make it work.

Kurt.
 
Kurt,
once I know how the PO got the compression up to 12:1 I'll know how to solve the issue. If he shaved the head I have a replacement from another 73 that's virgin, if it's the block I'll have to replace that as well. Looking for 10:1 max!
Thanks, Rut
 
Rut, Just talk to Gerard and be done with your research. He'll take care of the flywheel as well. It fits into a Large Post office Flat Rate box and for 12.95 it ends up in San Diego at Gerard's Shop where he give it to a guy who has done many of these already and you don't have someone experimenting on your one and only flywheel. His clutch slave adapter bracket allows you to use a standard Spridget Slave and you won't need to do any special engineering. It's a bolt on and you are done.
 
Bill, Gerard is in San Francisco.
 
Rut,
Not knowing what your CR can and will cause issues. Never go on hearsay or assumptions. But it’s quite easy to know all the answers by doing the math. Simple way is have you a deck height bridge https://www.benchmarkarizona.com/Deck_Bridge__Magnetic__standard_3_hole-8-126-193.html. Take this measurement and record it. Second you need to have the head sitting level at both axes placing a ¼ “Plexiglas with two ¼” holes in it. I like to use colored denatured alcohol so you can see clearly. Pick up a graduated cylinder at CVS that’s Milliliters or CC’s, either one will work if ML you can use a conversion chart. I like this CR calculator best, https://www.rbracing-rsr.com/compstaticcalc.html. Grease the outside of combustion chamber and set Plexiglas tight to head and fill one hole up to bottom of other hole. Plug all the rest of the information in and you will have your answer. You can use your deck gauge in helping to dial in your CR after you CC head by dropping the tip down to fluid which will tell you how much you need to mill head.

Clutch, flywheel pressure plate; these are personal issue to weather your looking for performance or standard leisure driving. The heavier the flywheel the longer it takes to spin up. Heavy flywheels are better for starts but not coming off corners and such. If you want a light flywheel 7.5 lbs Fidanza is a very nice set up and you will not have to balance it because it comes ready to install, pressure plates are already factory balanced. If the 1275 clutch doesn’t hold up to your style of driving you can move into the Tilton clutch. Remember a smaller mass diameter will provide a quicker gyroscopic rotation.
 
one milliliter = one cubic centimeter
 
That would make some great possibilities.
party.gif
 
Back
Top