Datsun Roadster Forum-311s.org

have an R1600 will not rev above 4K , just fall off and seem to loose throttle remains running ..............asking for a friend

Has this problem been around for a while or just recently become evident?
If the engine has recently been rebuilt, I would suggest checking the crank to cam timing

My guess - Fuel Starved due to float/bowl issues, fuel filters, fuel pump, etc?

Look at the spark plugs... they are the first place to look for how the engine is running. I suggest a brand new set, run the engine on the street (not free reving in the garage) especially where it's not working well and shut the motor off quickly after some time spent at that rpm. What do they look like (be sure to pull all 4 and don't let it idle. Might want gloves as the plugs will be hot). Report back.

Likely possibilities if this is a new condition: fuel delivery issues (lean or rich); poor spark (coil or points condenser failing); distributor not advancing (check with timing light).

If just rebuilt: cam timing issues due to being off a tooth or more likely a miss match of metric and SAE timing gears.

Update: Had another couple thoughts while watching the game... valves out of adjustment, or the throttle plate(s) are not opening enough?

Ask if it's bogging, spitting/backfiring through the carbs, missing/stumbling... and under what circumstances.

Check the centrifugal advance Weights for free-ness, is it running on 1 carb, old gas , carb slides free
When it stalls at 4k is the exhaust turning rich ,lean might try it in darkness to see any secondary arcing
Take a cold compression test and or cyl balance test ( pull each plug wire running ...with plug pulling players grounded) air filter off ?
What's the vacuum read ,snap throttle test

We figured it out, broken centrifugal advance spring.

Thanks you everyone

I have new non-smog springs and distributor cams for sale if you need them.
Dave

We when with a 123 ignition, thanks for the offer Dave

That’s great, you will still need to give it a proper curve for your 1600.
Dave