Timing problem?

[metalmonkey47]

First off, engine is an A15 with gasket match ported and rebuilt head, weber DGV, and MSD CDI multi spark box and low restriction exhaust..

 

Here's my problem:

 

When I setup my MSD box, the timing was WAY off whack and I'm no longer running a vacuum advance.

 

When I check the timing, it was super advanced about 40 degrees and didn't hardly run. I had to rotate the distributor back a tooth to get it to the point that it would even run. FSM shows 10 degrees BTDC and the closest I could even get was 15 degrees. Rotating back another tooth with the timing advanced as far as possible put my timing way below 10 degrees. There is literally no possible way of getting it timed to 10 degrees.

 

 

After looking under the dizzy cap, I noticed that the advance plate wouldn't hardly move and appeared to be stuck in full advance, which could possibly explain why I couldn't get it timed right. Biggest question though, is what should the timing be at full advance?

 

It's currently getting VERY poor gas mileage and very low on power(my car can't be that slow can it?) But still enough to spin tires ;)

 

 

 

I'm driving her daily now back and forth to work, and it's more evident now and I want to get her healthy.

 

Could just 5 degrees of advance cause i noticeable difference in power and fuel economy?

[ggzilla]

what should the timing be at full advance?

32 degrees if factory spec for most Datsun A-series engine. They seem to run well at 35 degrees @ 4400 and higher RPM.

 

 

FSM shows 10 degrees BTDC

Yes, factory service manual specifcation is 7 to 10 degrees BTDC, like most engines. That is mostly for emission control reasons.

 

 

the closest I could even get was 15 degrees...There is literally no possible way of getting it timed to 10 degrees.

 

Sure there is. A-series engine can be timed anywhere you want it, but it will only run correctly within a certain range. Do you mean that you can't rotate the distributor enought to get it to 10 BTDC? That's common, it means you gotta pull the distributor out and re-time it.

[datzenmike]

Take the distributor cap off and suck on the hose to the vacuum advance. You should see the plate rotate and then return when you let go if it's working. If the advance isn't working properly or stuck, get that fixed first.

 

Vacuum advance is important to low speed part throttle economy.

[metalmonkey47]

A-series engine can be timed anywhere you want it, but it will only run correctly within a certain range. Do you mean that you can't rotate the distributor enought to get it to 10 BTDC? That's common, it means you gotta pull the distributor out and re-time it.

That's correct, it cannot be rotated to get 10 degrees. Even rotating it back a tooth doesn't get me close. Timing is about 5 degrees if I recall correctly. Although, I think a stuck advance makes sense at this point.

 

Take the distributor cap off and suck on the hose to the vacuum advance. You should see the plate rotate and then return when you let go if it's working. If the advance isn't working properly or stuck, get that fixed first.

 

Vacuum advance is important to low speed part throttle economy.

 

Done it and saw literally minimal movement. Thats what leads me to believe it's a stuck advance plate. I suppose I'll have to tear it apart. About how far should it rotate?

 

 

If I'm running no advance over the 15 degrees, would that noticeably effect my fuel economy?

Edited February 21, 2011 by metalmonkey47

[ggzilla]

Stuck advance plate will not stop one from setting it to 0 BTDC. It'll only keep the advance from working

 

 

I suppose I'll have to tear it apart.

90% chance you'll find the ball bearing plate has broken and the bearings are loose or lost.

 

 

About how far should it rotate?

about 5/16"

 

But this make it run badly. Yes, it can effect the fuel economy, but remember some 210s don't have any advance except in top gear. A stuck vacuum advance does not cause it to run badly.

 

The mechanical advance works differently and doesn't depend on the plate rotating.

[datzenmike]

90% chance you'll find the ball bearing plate has broken and the bearings are loose or lost.

 

Common problem. This is from a Z motor and there are three BBs under the bulges that it turns on.

 

 

You could try moving it by hand and see if it loosens up.

[ggzilla]

Most of the A-series distributors don't have a metal bearing plate like that. They have plastic ones that break. I built a new bearing plate out of poly, but it takes a bunch of time to do. New bearing plates are available about about $75 from Nissan.

 

Monkey, see Ignition Timing for more details and photos. I have both A14 and (older) A12.

[zed]

 

Done it and saw literally minimal movement.

 

if you read my thread on L18 timing - the vacuum advance was hardly moving the base plate in the distributor when I sucked on the pipe. The spring inside the vacuum advance unit must be too strong. But you can't get in there to modify it...

[ggzilla]

It shouldn't move when you suck on it with your mouth. You need lots of vacuum to move it, at least for the A-series vacuum advance units. But you should be able to move the plate with a screwdriver. It only moves about 1/4".

[metalmonkey47]

I think for the sake of keeping my car driveable, I'm going to leave it alone and order a re-man from rock auto.