just bought sears timing light w/advance and thought Id try it out. I checked initial advance 14 degrees w/vacum advance can disconnected. at roughly 700rpm. Checked timing at 2000rpm and read 42 degrees total advance. Reved engine to 3000rpm, still held at 42 degrees total advance. Hooked vacume advance back up and read 20 degrees at idle and 60 degrees at 2000 rpm. 60 degrees to me sounds like way to much. reved engine again to 3000 rpm and timing stayed at 60 degrees total. Was planning on HEI conversion in VERY near future anyways, but are these readings way off??

 

couple of things to check/verify.
make sure the ring on the balances has not slipped, bring #1 to TDC and the timong mark should line up on 0. Have heard of a lot of them slipping on old motors.
Get Lars paper on timing

 

If you are using the stock dist it is worn out. It allows the advance to go beyond the normal amount. The slot or the pin with a bushing on it that limits the advance it worn out. If you plan on keeping the original head to someone with a dist amchine and have them set it up. It sounds pretty close to mine before I had it recurved. It runs much better after I had it setup.

 

your 42* w/o vacuum advance and 60* with vacuum advance is way too high and you will get major detonation that can destroy your pistons.

your distributor is bringing in too much mechanical advance and as Gordon mentioned it's probably because the slot on the cam plate is worn allowing too much movement and therefore too much advance.
Those old cam plates are no longer available so you have basically two choices - find a good cam plate from another distributor and replace it or have the slot reduced which is done by welding some metal in at the worn end of the slot to limit the excess travel.

You don't want to exceed 36* total timing w/o vacuum advance connected and 50*-52* with the vacuum can hooked up.

Also, having your total timing all in at 2,000rpm's sounds a bit low to me. You may want to change out to some slightly stiffer springs so it comes in at around 2,500 - 2,800rpm's.

As mentioned already, finding someone with a Sun Distributor machine would help greatly after replacing or repairing the cam plate to get your distributor and curve set up correctly but it's not always easy to find one anymore. NO ONE local to me has one but I was finally able to find someone on the NCRS board with one that was willing to do mine and the performance of the car was significantly improved afterwards once it was set up correctly.

 

Thanks for the input. I thought 60 degrees all in by 2000rpm was too much. Thanks for the sugestions on how to repair it, but I think I'm going to swap in a new a HEI distibutor as I had planned.

 

Even with the new HEI I would check out the advance curve and total timing. Just because it is new does not mean it is right.

 

Here's a simple followup question. I have a '69 350/350 and the owner's manual says the initial timing should be 4 degrees BTDC. So should I also be expecting 20 degrees of mechanical advance, and thus around 24* total advance (w/o vacuum advance)? And then vacuum advance added should give me another 14-16* to put me at around 38-40* total?

I'm confused because I've read threads saying all 350 SB engines like to run at around 36* total advance w/o vacuum. If that's true, does that mean they all have different recommended settings at idle and thus different amounts of mechanical advance to get them all up to 36 total?

Thanks for anyone that can clarify this for me-
Andy

 

Andy,
Your owner's manual is giving you the factory "detuned" setting. To be able to achieve full 36 degrees by 2,500-2,800 RPM requires having your distributor "recurved" by changing different weights and or springs. This is typically done on a Sun distributor machine but you can do it in the car too, it just takes more time and not as easy as on a machine.

 

So should I be looking to curve my distributor such that I keep the idle advance at 4*, and then tweak the weights to get the mechanical advance to 32* to get a 36* total? And then play with the springs to adjust when the advance starts to come in?

Or for starters should I just set my engine for 36 total, let the idle fall where it may, and then do a test drive? And if the 11:1 compression starts to ping on my 93 octane gas-- start backing it off 2 degrees at a time?

Also is 14-16* vacuum advance pretty much standard? I just got an advance timing light, so I'm eager to try it out.

Thanks

 

You simply set it to come in between the 34-36 degrees at 2,800 +/-RPM and let idle be where it ends up.