8 replies to this topic

[jime17]

998 auto - standard. 1990. D59 distributor. Powerspark hall effect points replacement.

Hi.
Just had mot... emissions passed easily but I'm wondering if it's too lean.

Reading was 1.501 CO..... 495 PPM HC.

I've got the timing set to 30 degrees at 3500 rpm which is about 16 degrees at idle with the vac disconnected and plugged....


It runs well but I'm worried I'm going to melt the piston in the longer term...

Any thoughts?

Thanks
Jim.

[Bat]

Hi,

16 at idle sounds a bit too much?

What's the manual say?

Exhaust gas readings and timing are interconnected.

Cheers 

[jime17]

Book says 8 but it doesn't want to run well at that.

My aim was to set it to 32 at max advance and 16. is what it ends up as at idle.


Edit. I'm questioning myself now. Maybe it ended up at 16 with the vac advance. I'll have to go and check later if it ever stops raining.

Edited by jime17, 14 October 2018 - 10:07 AM.

[Bat]

Hi,

It maybe the dizzy is partially siezed if you can't get the full range of advance.

Vac advance should be doing nothing at idle if the carb is set right.

Set the timing to 8 then get it running right with that.

Cheers 

[jime17]

I need to double check what I've done I think. Can you check the free range of advance by turning the distributor base plate against the pull of the springs?

From rest to full advance the plate should turn at least 32 degrees of the circumference of the distributor body?

Ie. Just over a 12th of the total?

Or am I over simplifying it?

Edit..Actually it won't be max 32 will it as you start off at 8 so it only needs to turn through 24 degrees to get to max?

Edited by jime17, 14 October 2018 - 02:22 PM.

[cal844]

1.5% CO is too lean, turn that up to 3.0% the timing also needs looked at but alter the fuelling first so you know what made the change

[mcduff2]

I need to double check what I've done I think. Can you check the free range of advance by turning the distributor base plate against the pull of the springs?

From rest to full advance the plate should turn at least 32 degrees of the circumference of the distributor body?

Ie. Just over a 12th of the total?

Or am I over simplifying it?

Edit..Actually it won't be max 32 will it as you start off at 8 so it only needs to turn through 24 degrees to get to max?

Remember 24 distributor degrees is equal to 48 crankshaft degrees as it turns at half the engine speed.

[jime17]

The advance plate seems free. I can feel it's definite stop points at both ends of its travel and it seems free enough.

I've set it to 8 with vac blocked off at 1000 rpm. It hits about 32 at 4000 rpm but that's hard to be totally accurate about as I've added a paint Mark 12 degrees before the tdc Mark. It seems to idle better at 10 degrees at the no but I guess that's because it's too lean.

When I go for the retest on Tuesday I'll ask them to put it on the analyser and I'll tweak the mixture up. I'm guessing I'll be able to retard the timing back to book spec then.

Mcduff yes i forgot that. So the plate should only move through 12 degrees of circumference from 0 to 24 degrees max advance at the crankshaft?

Think I was confusing myself before as to how I'd set it and to what.

Edited by jime17, 14 October 2018 - 04:41 PM.

[cal844]

Set it at 10, then adjust the fuel to 3.0%CO