BR18 and Hi-Lo Idle

[Paul Ahnell]

My '60 Normal idle doesn't quickly return to the 650-700 rpm range to which I set it after a La Dow bottom-to-top tune (a procedure which I have used for years with only perfect results). Fine return to idle in the garage while simply goosing it in situ, but drive a half mile and stop, and the idle will ride in the 1K range and then sloooooowly come down to ~ 700. This has gone on for a couple of months now. Linkage is squared away, ball joints etc. are nicely greased, dwell is 50* and static advance is 5*.

I thought maybe the BR18 advance is too slow coming back into battery after I let off the gas when stopping. I can tweak the rotor CCW a few degrees after releasing it from a CW twist i.e. it doesn't snap back to a hard CCW full stop. Maybe vibration causes it to slowly rotate back those last few degrees to a hard stop. Or is that last few CCW degrees of slack normal? I think it is but I'd like some confirmation so I can throw that out as a possible cause of slow return to normal idle.

Thanks in advance for any advice or solutions.

[Tim Berardelli]

Paul,

Old, rusty advance weight springs that have been heat cycled thousands of times and a brittle , scored sliding surface that the weights ride on can cause the issues you are seeing.

[John Brooks]

Paul

I have seen that three time in the last year. 2 X 912s and a S90. Idle fine after starting but after 10 minutes idle goes up to 1100-1800. I sent the distributors to Bruce Smith at CFI for overhaul. I keep a spare 18 and 21 on the shelf to quick fix one when it comes through, but I have taken them apart and cleaned them with some success. But trying to check the advance with a timing light is hard, you can get static and full but a few degree creep is hard to see. But the true fix is call Bruce.

Web site is
http://www.sparkingplugs.com
Bruce Smith email as bruce@cfi-auto.com and phone number 585-750-1300

[Paul Ahnell]

I don't think the springs are the issue since Bruce did a tune up on the distributor over the past winter, replacing incorrect springs installed by someone in the past with the correct springs. He even installed new points gratis. Printout from his Sun machine showed the unit was spot on when he finished. I'm wondering if that extra few degrees to a CCW hard stop is normal. It seems I remember noting it in the past. The memory banks ain't what they used to be.

[Eric Wills]

Paul,

Maybe try to set the timing all in at 33 degrees while the engine is warm after driving for a bit. Then adjust your idle speed. I like close to 900-1000 RPM at idle to keep the generator warning light off.

[Neil Bardsley]

Paul,

Maybe try to set the timing all in at 33 degrees while the engine is warm after driving for a bit. Then adjust your idle speed. I like close to 900-1000 RPM at idle to keep the generator warning light off.

What Eric said. Surely it's better to have the idle above 900 so that you are charging the battery?

My only suggestion about the idle not dropping back is that maybe the you are a little too lean? I think not returning to idle is a sign of running a little lean?

[David Nicholls]

Hello Paul

Have you been putting a drop or two of oil occasionally, on the felt pad in the Distributor ?

All the Best
David

[Paul Ahnell]

Hi Guys: Thanks for the great responses and suggestions.

Eric: I remember Bruce Smith had an article in the Registry mag explaining the procedure you mentioned i.e. start with setting the timing at high RPM first. I tried it but found my Normal seemed to prefer sitting IAW the book with the static at 5* first and then check at higher RPM. I tried various settings as Bruce suggested but finally went back to the spec. Maybe I'll Bruce's procedure again try it again.

Neil: Yes, the gen light glows a little at 600 rpm idle but I think the time is trivial compared to the time >700 rpm where the light is off so I haven't been too concerned about it. I adjust the carbs using Ron La Dow's procedure which has always worked well for me. When I check the plugs they always look like the "this is a good plug" picture in the plug brochures, but they may be a tad lean. I'll give the carbs another check now that I've put ~2K on them.

David: Excellent point. I always lube the pad in the Spring when I tune and usually change the points, and then again usually in mid Summer. Now that I think of it, Bruce installed new points. Don't know if he lubed the pad and can't remember if I did in April because the new points were already installed. That will be done this a.m. Thanks for the reminder.

[C J Murray]

If the rotor can be moved at all without returning securely to its resting place fully retarded then your idle will be slow to come down. Put a timing light on the car after you return from a drive, rev it to 2000 and let go and watch the timing to see what it is while it is doing the high idle. That is where the weights are close to equilibrium with your weak springs and once the weights slow down they are overcome by the springs and if you have points they drag on the cam a bit and help the cam return to idle.

[Eric Wills]

To add to what Cliff said:

Most newer point sets have thinner springs than in the past. This can cause the points to float causing misfires at high RPM. I would agree the added drag from a stronger spring might help to slow things quicker. The stronger spring also causes more wear on the block that contacts the distributor cam. Just a guess, but I think the manufacturers (Bosch, Beru) were trying to do us a favor by lightening the spring so that the points didn't have to be adjusted quite as often. I have found the timing off by 3-5 degrees in as little as 2000 miles in the past......Yes, even with Bosch grease where it needs to be. If the distributor is in perfect condition it can be used with electronic/mag trigger pickup. They make no contact, and seem to work fine with a good distributor. But, if they fail, its a hassle to change them on the road.

I do NOT rebuild distributors, but I do have a working Sun distributor test machine. I have tested how different sets of points behave first hand. I will say that John Jenkins has been very helpful with advice to me over the years and I send him any 356 and early 911 distributor I need to have rebuilt.

[Mike Horton]

Hello Paul

Have you been putting a drop or two of oil occasionally, on the felt pad in the Distributor ?

All the Best
David

Try a little MMO, 3-in- one, or other light oil on the pad. The point cam rides on a shaft from the drive shaft, and friction in this interface, especially when cold, can aggravate this issue. These lighter oils can flush old dried, or gummy heavier oil from that juncture. Often, a lighter oil, can flow down through the felt pad, and help to keep the motion more free, it's worth a try. If the rotor return test is slow, manipulate it several time after using the lighter oil, to see if it helps. Some have used the dirty oil from the tip of the dipstick, but the cleanliness of that thicker oil varies...

[Paul Ahnell]

Thanks Cliff, Eric and Mike. More info and notes to add to my workshop manual. I'll try the machine oil next time around. I'm told the springs were replaced by a weaker version. Looking at the "before" Sun printout, it appears that the stronger springs were keeping the advance below the spec range out to ~1100 rpm. I'm guessing that that's why the idle would return to the 6-700 rpm range more quickly than it does now.

Thanks all for helping me think this through.

[Wes Bender]

That sounds as if attempting to cure one problem (possibly improperly), caused another problem.
These distributors work fine when they have been properly repaired. I would contact John Jenkins, either directly or through 356 Carburetor Rescue, send the distributor to him and it will be fixed properly.

If you need his contact info, e-mail me and I'll send it to you.

Cheers
Wes

[Paul Ahnell]

Wes: I have it. Thanks.

[Dick Weiss]

Felt pad on (OEM?) regular distributor points? Never seen that except on 4-cam distributors; Then again--?