4.3L OMC 1989 Dwell and gap dilema

[Stanp1]

Guys,

the manual calls for .19 gap and a dwell angle of 39 at 600RPM.

I got the .19 gap, the 600RPM but the dwell is 33. I tried knocking down the gap to .18 and it didn't change the dwell much at all 33.2.

Points look good. The cam is a bit loose. When you turn the dist. the cam has .30 play in the "lash" (for lack of a better term) Is this normal?

I don't want to mess with the gap, so I put it back to .19. The points are adjustable only with a flathead screwdriver, there is no external adjustment screw.

Am I ok with 33 as the dwell angle?

 

[bruceb58]

Re: 4.3L OMC 1989 Dwell and gap dilema

I am sure you mean 0.019 gap. Do you also mean 0.030 lash for the distributor and not 0.30? Even at 0.030, that sounds like a lot.

With your dwell meter on, measure the dwell at various RPMs. It should remain constant. If it doesn't, you need to rebuild the distributor.

The dwell angle measured by the meter is what you need to go by. 33 is probably ok but why not set it to spec.

You do know you need to set your timing AFTER you set the dwell right? Dwell affects timing.

 

[lynnboy021]

Re: 4.3L OMC 1989 Dwell and gap dilema

what is a dwell meter and where you hook it up? i never got to know how to set dwell

 

[bruceb58]

Re: 4.3L OMC 1989 Dwell and gap dilema

http://www.amazon.com/Actron-CP7605...YUUS/ref=sr_1_1?ie=UTF8&qid=1303191872&sr=8-1

 

[Stanp1]

Re: 4.3L OMC 1989 Dwell and gap dilema

I am sure you mean 0.019 gap. Do you also mean 0.030 lash for the distributor and not 0.30? Even at 0.030, that sounds like a lot.

With your dwell meter on, measure the dwell at various RPMs. It should remain constant. If it doesn't, you need to rebuild the distributor.

The dwell angle measured by the meter is what you need to go by. 33 is probably ok but why not set it to spec.

You do know you need to set your timing AFTER you set the dwell right? Dwell affects timing.

Bruce,

You are correct, .019 gap and .030 lash. My mistake. The dwell angle does remain constant thru about 2000 rpm. I have not checked beyond that rpm. I will today just to make sure.

So, reduce the gap to increase the Dwell angle from 33 to 39+/-2. Then check the timing which calls for 6 degrees BTDC.

Does the play in the cam indicate that I may need to rebuild anyway?

What might cause the Gap and dwell to be so different? does it really matter? Is there any damage to the engine from long term running at a 33 dwell angle vs 39?

 

[bruceb58]

Re: 4.3L OMC 1989 Dwell and gap dilema

Does the play in the cam indicate that I may need to rebuild anyway?

What might cause the Gap and dwell to be so different? does it really matter? Is there any damage to the engine from long term running at a 33 dwell angle vs 39?

If you have that much lash, then who knows what is happening once the distributor is turning. That is why things aren't making sense. Personally, I would get the distributor fixed.

You are using new points right?

As far as the dwell being off, if the points aren't closed long enough, there is a possibility that the coil does not saturate and your spark would be weaker than it should be.

 

[Stanp1]

Re: 4.3L OMC 1989 Dwell and gap dilema

Bruce

I set the dwell to 37 (minimum spec). I did set the timing to 6 BTDC at 600rpm. The gap had to be set a .014 to get the 37 dwell angle. The points are a year old. They were set with a gap tool last year at .019.

I ran the rpms up. There is minor (plus .2) increase in the dwell meter reading. It seems that the play in the cam is in the Dist. shaft at the gear. I will order a new distributor from ebay. Saw one for $225.00, new. It's easier than rebuilding the old one.

 

[bruceb58]

Re: 4.3L OMC 1989 Dwell and gap dilema

When you say play, you mean side to side or up and down? Side to side is what you need to worry about.

 

[jefro]

Re: 4.3L OMC 1989 Dwell and gap dilema

Just remember that "gap" only gets you in the ballpark. Dwell is what you should worry about.
I hate points as they start wearing as soon as you install them. I have always replaced them with electronic ignitions whenever I could. There are several aftermarket ones to be had for cheap. Engines always run better and are more reliable with them. Here is just one:
http://www.google.com/products/catalog?hl=en&sugexp=ldymls&xhr=t&q=electronic+ignition&cp=13&rlz=1R2GGLJ_enUS348&bav=on.2,or.r_gc.r_pw.&wrapid=tljp1303261845343020&um=1&ie=UTF-8&cid=10210215250304639665&sa=X&ei=NzKuTYHUDoz6swOzsdCSAw&sqi=2&ved=0CEYQ8wIwAg#

Good luck.

 

[Stanp1]

Re: 4.3L OMC 1989 Dwell and gap dilema

When you say play, you mean side to side or up and down? Side to side is what you need to worry about.

Side to side, there is some play. I can twist clockwise & counter clockwise. It doesn't register much of a difference on the dwell meter when I rev the rpm's up. But it does move the dwell from 37 to 37.2 when I increase the rpm's.

Worn distributor? I am planning on buying a new one.

 

[bruceb58]

Re: 4.3L OMC 1989 Dwell and gap dilema

I probably wouldn't if the dwell doesn't vary anymore than that.

Next thing you should check is the total advance at 3500 RPM.

 

[Stanp1]

Re: 4.3L OMC 1989 Dwell and gap dilema

I probably wouldn't if the dwell doesn't vary anymore than that.

Next thing you should check is the total advance at 3500 RPM.

How do you check that? where should the timing be at 3500?

 

[bruceb58]

Re: 4.3L OMC 1989 Dwell and gap dilema

Run the engine up to 3500 and see what the timing goes to. In order to measure that you either need to use an "advance" timing light or use timing tape on the harmonic balancer. You can buy that at the autoparts store.

You will have to look up what the total advance is supposed to be in a manual. I believe it is going to be an extra 12? from your starting point for a total of 18?. Thats much less than the V8 models. You may be able to measure that out and put a mark on the harmonic balancer. Just measure what 5? is supposed to be from your timing tab and put 5? increments on your balancer from TDC.