Setting timing on a 4.3

[big zeke]

I've got a 1998 4.3 4 bbl. I have just finished changing plugs and will soon be changing cap, rotor and wires. I was taking a closer look at the engine and there are no timing marks near the harmonic balancer and no timing mark on the balancer. I've set base timing tons of time on autos but without timing marks, I have no clue how to set them on this engine. Since I'll be tinkering with the cap and rotor, I'll definately want to be checking the timing. This engine was rebuilt once and there is a good chance any decal with the marks is long gone.

Any guidance is appreciated, I really don't want to own a scope just for this rare useage.
Zeke

 

[Don S]

Re: Setting timing on a 4.3

Being a carbed engine, the base timing is 10? BTDC

Here is the procedure for setting the timing on the Thunderbolt V ignition.

 

[big zeke]

Re: Setting timing on a 4.3

Thanks for the post Don, but the problem is that this engine has no timing tab on the timing cover. I did find the mark on the balancer but I am 100% sure there is no timing tab on the timing cover. The only thing I can think is that this cover came from an engine that had a crank position sensor (EFI model) and thus didn't need timing marks.

Back to square 1 I think...

 

[achris]

Re: Setting timing on a 4.3

I've got a 1998 4.3 4 bbl. I have just finished changing plugs and will soon be changing cap, rotor and wires. I was taking a closer look at the engine and there are no timing marks near the harmonic balancer and no timing mark on the balancer. I've set base timing tons of time on autos but without timing marks, I have no clue how to set them on this engine. Since I'll be tinkering with the cap and rotor, I'll definately want to be checking the timing. This engine was rebuilt once and there is a good chance any decal with the marks is long gone.

Any guidance is appreciated, I really don't want to own a scope just for this rare useage.
Zeke

Correct, no timing marks that you will be familiar with. All that's there is a single line on the balancer and notch on the timing cover. You need an Advance Timing light to do the job (or as a rough estimate, just mark off the balancer)....

Chris.......

 

[achris]

Re: Setting timing on a 4.3

Thanks for the post Don, but the problem is that this engine has no timing tab on the timing cover. I did find the mark on the balancer but I am 100% sure there is no timing tab on the timing cover. The only thing I can think is that this cover came from an engine that had a crank position sensor (EFI model) and thus didn't need timing marks.

Back to square 1 I think...

Nope, MPI/EFI models still have the mark. I'll take a photo of mine and post it for you...

Chris.....

 

[big zeke]

Re: Setting timing on a 4.3

Thanks Chris, I think I'm getting somewhere...

So all I need to put in the required timing (10' per the reply from Don) but how do I know what the mark on the balancer should line up with ....there is literally nothing on the timing cover.

BTW, are these things typically rentable...I can foreseee me using it annually, maybe less.
Zeke

 

[Don S]

Re: Setting timing on a 4.3

If you set your advance timing light at 10?, all you need to do is when the engine is running is line up the mark on the timing cover and the balancer. Your timing light adjusts it for 10?.

 

[big zeke]

Re: Setting timing on a 4.3

Ok, I hear you Don...I still cannot find the marks on the cover...any mark anywhere in it...I must be blind.

Zeke

 

[achris]

Re: Setting timing on a 4.3

Thanks Chris, I think I'm getting somewhere...

So all I need to put in the required timing (10' per the reply from Don) but how do I know what the mark on the balancer should line up with ....there is literally nothing on the timing cover.

BTW, are these things typically rentable...I can foreseee me using it annually, maybe less.
Zeke

Far far less. My previous engine had TB-IV, I checked the timing on that recently (now in a friend's boat) and it still hasn't moved, and that's 18 years on!!! Even if you change the cap and rotor, as long as the body of the dissy isn't moved in relation to the engine, then the timing will not change.

Here's that photo... (the mark on the cover is a bit hard to see, but it's just left of top vertical, just behind the balancer) Hope it helps.

Chris.......

EDIT: Just remembered I have a spare timing cover under the bench, so here's a photo of it... That timing mark is on the right as you look at it (left hand side of the engine)

 

[Don S]

Re: Setting timing on a 4.3

The mark is actually cast in the plastic timing chain cover.

 

[big zeke]

Re: Setting timing on a 4.3

I think I've zeroed in on the issue...the obvious mark located at about 2:00 relative to the crank opening on the second pic from Chris does not exist on my engine. The cover is totally smooth all around the balancer (both to the left and the right of the balancer) and all the way up to the water pump pulley. If I can ever figure out how to post pics I'll gladly show you. Any other suggestions?

 

[Don S]

Re: Setting timing on a 4.3

How to Post Pictures - The Basics - Page 1 - 468676

 

[achris]

Re: Setting timing on a 4.3

.... Any other suggestions?

New timing cover? If you do go that route, DO NOT buy the overpriced unit from Mercury, buy it from a GM engine parts supplier, it's the same thing, and about 1/3 the price!

I use Buy GM Parts Worldwide * Genuine Replacement * GM Parts Accessories

Is you cover metal or composite (plastic)?

Chris........

 

[big zeke]

Re: Setting timing on a 4.3



The cover is metal, I would dearly love to avoid replacing it, even ona stand it would take a fair bit of time. I just got to believe there has to be an easier way....HELP!!!

 

[achris]

Re: Setting timing on a 4.3

I've got a 1998 4.3 4 bbl. ...

I seriously doubt that now! What's the engine serial number? By '97 all the covers were composite. That one in the photo is tin, and some moron has neglected to install the timing tab. :facepalm: (Makes me wonder how the guy who supplied the engine managed to time it initially.) The good news is you can buy the timing tab... The part number is -75435A1, it's $13 from any Merc dealer (or on-line Merc shop).

And you'll likely have Thunderbolt IV, not V, so the timing procedure above (in one of Don's posts) is not for your engine.... Just time it the way you would any 'normal' engine... nothing special needed.

Chris.....

 

[big zeke]

Re: Setting timing on a 4.3

Amazing, this is so helpful you have no idea. The TB IV must have been assumed, I don't think I ever posted it as a TB V. Nonetheless, the new part is on order and I'll be able to install it when it arrives.

Thanks a bunch
Zeke

 

[Don S]

Re: Setting timing on a 4.3

Amazing, this is so helpful you have no idea. The TB IV must have been assumed, I don't think I ever posted it as a TB V. Nonetheless, the new part is on order and I'll be able to install it when it arrives.

Thanks a bunch
Zeke

TB V came in 96 and replaced the TB-IV. Since you said you had a 98, it was just assumed it had the TB-V ignition.

 

[achris]

Re: Setting timing on a 4.3

TB V came in 96 and replaced the TB-IV. Since you said you had a 98, it was just assumed it had the TB-V ignition.

I guess we need to be more insistent about engine serial numbers, ah?

Amazing, this is so helpful you have no idea. The TB IV must have been assumed, I don't think I ever posted it as a TB V. Nonetheless, the new part is on order and I'll be able to install it when it arrives.

Thanks a bunch
Zeke

Zeke, post up your engine serial number and we'll be able to give you a more accurate year of that engine, because 1998 it is not...

Chris......
EDIT: And your timing is 8 degrees BTDC, not 10...

 

[big zeke]

Re: Setting timing on a 4.3

So I dropped by a local engine rebuilder, he smiled once I described the problem. Apparently this is not a rare problem. So very common that Mr Gasket makes a set of bolt-on timing marks that sit under 2 of the bolts on the timing cover. The one he had is for a SBC with a 7" damper, fits like a glove as the 4.3 is essentially a SBC minus 2 cylinders. About 5 mins to install and it looks like it always was there. When I asked him how the previous installer could have set the timing without it, he said he must have done it by ear, then he smiled and said "We get a lot of business like that".

Thanks for the help guys.
Zeke

 

[achris]

Re: Setting timing on a 4.3

So I dropped by a local engine rebuilder, he smiled once I described the problem. Apparently this is not a rare problem. So very common that Mr Gasket makes a set of bolt-on timing marks that sit under 2 of the bolts on the timing cover. The one he had is for a SBC with a 7" damper, fits like a glove as the 4.3 is essentially a SBC minus 2 cylinders. About 5 mins to install and it looks like it always was there. When I asked him how the previous installer could have set the timing without it, he said he must have done it by ear, then he smiled and said "We get a lot of business like that".

Thanks for the help guys.
Zeke

Just like the original.... and your serial number?