Autom. advance spark timing

[alexiskai]

Yeah, setting the Nu-Rex's baseline to somewhere ATDC is a decent workaround and won't hurt the car (unless you idle for a really long time). It's just odd to me that a stock engine wouldn't take 28° advance, particularly if you're using high-octane petrol. Something else must be going on, although we may never know what.

 

[SonicRaT]

A lot of stuff can cause detonation at "normal" advance numbers, not only compression. For example, the plugs might be too hot, or there might be too much carbon build-up. Another possibility is that the owner makes a mistake with initial timing, so the actual total timing is higher than he thinks. I asked about octane because it's a test that would yield some information without requiring engine surgery.

Yeah, setting the Nu-Rex's baseline to somewhere ATDC is a decent workaround and won't hurt the car (unless you idle for a really long time). It's just odd to me that a stock engine wouldn't take 28° advance, particularly if you're using high-octane petrol. Something else must be going on, although we may never know what.

That's exactly right. I had picked up a few different sets of plugs when I installed the unit along with the 6:1 head, as I was expecting the possibility of some trouble. I also have my ignition system quite well sorted, so all proper gaps, new points, condenser, and plate wiring. It had Champion C-16C in it when I acquired it, and I've left those in for now and they've run quite well. I have the NuRex locked in at TDC and no pinging, on either the stock cam or a 340 grind. It is definitely possible to run it that way on pump fuel.


ETA: I love your YT vids too!

 

[jack backer]

FSI recommends idle timing at 0 degrees as well. Combustion chamber turbulence has an effect on timing as well, the Flathead chamber has been studied for decades, Briggs and Stratton has a great design, Jim Brierleys Silberstein design incorporates a stepped chamber that effective too. I run an original Winfield 7 to 1 and an NOS late B high lift cam and still need to control timing to avoid detonation.

 

[alexiskai]

I have the NuRex locked in at TDC and no pinging, on either the stock cam or a 340 grind. It is definitely possible to run it that way on pump fuel.


ETA: I love your YT vids too!

Thanks, I really am going to complete the Nu-Rex series as soon as I can. Just have a lot going on now. I really want to get the B distributor into a video, I think a lot of people don't quite understand how it differs from the A.

 

[JimZ]

My grandfather installed a B distributor on my (inherited in 1990) ‘31 coupe in 1951. In ‘73 when we started the restoration my dad told me it ran great with the B distributor so we left it on. We always set timing to 5 deg. advance at 500 rpm with timing light. Since then, after about 3,000 miles it still runs good but now I’m wondering how much better it might run with an A distributor. Just picked up an A distributor, cable and spark rod at Pate so can’t wait to try it out.

 

[jack backer]

Like anything else, with proper maintenance you will get good results with the B distributor. It does suffer from lack of lubrication so it’s a good idea to disassemble it and lube the flyweight pins and inner shaft. If the engine “rattles” under load back off the idle timing, you can be at 0 degrees at 500 rpm, if you detonate at high rpm under load.

The A distributor is foolproof, other than the timing is fixed where it’s set, you don’t get automatic spark control based on rpm..