I wonder why it stresses the clutch when it is a high-revving motor. Should have less torque than a stock A15.

Fit a new set of plugs. Run it round the track, shut off during acceleration (coast to a stop) then use a magnifying glass to look at the base of the insulator, to see if it is sooty. It may be that it is only sooting up during low rpm which is common with high-duration cams. In which case you can lean out the idle mixture screw and live with a rough idle loping.

It definately has more power, but I am still sorting the Weber carbs. It is running very rich, plugs are sooted, tailpipe is black and sooty.
We broke the engine in, on track, with no real run in period. We ran it for 30 hours, under race conditions with no problems other than a set of soot fouled plugs and an exploded alternator( could not take the revs).I will change from BP6ES back to BP5ES plugs and rejet the carbs. More jets arrive this week.
It saw 8K on every lap, burned 105 gals of race fuel, and did not use any oil at all.
looking for jetting suggestions.
A15, 280 cam,GX head with 37mm valves, weber 40 DCOE carbs(33 mm venturies)

So it's like most Datsun B210 clutches. Other than having a clutch shop fit a stronger spring, not sure what you can do.


How did your engine turn out otherwise? Does the engine have torque now, or just revs higher?

It doesn't use springs, It uses a single Belleville Washer.

i'd put a washer under each apring, but a thin washer to raise pressure from 728 lbs to 1000 lbs.

Tried a new clutch...no change.
I have searched and called all over for alternate spring but can not locate one. Ideas?
Aggressive disc?

Sounds like you need a new clutch, not necessarily a stiffer one.

Or at least use a thinner washer, keep it to 1000 lbs similar to the Nissan clutches.

What was your solution? would a more aggressive disc help? It only seems to slip when shifting. It eventually locks up (3-5 secs)
We ran a 24hr road race with it, and it was about the same at the end as it was when we started.
Hi Gary, we have met several times. Last time was at the ORP track day.

I would not recommend stacking the clutch springs in the 310. We had built a dune buggy back in the '80s around the 310 drive train. The built A-15 with GX head and Volvo SU carbs needed more clutch. Tried stacking the belleville springs as a quick solution. The only quick thing to happen was the destruction of the center main bearing thrust face.

Thanks for the reply dd. I was thinking the same way. The stock clutch is rated at 728 lbs at full load. The revised clutch would be rated at about 1450 lbs, plus the increase caused by friction between between the springs.
My thought was that for racing use it will be ok, but you don't want to keep the pedal depressed for long periods of time.(when stopped, place car in neutral!)