Best performance and economy are achieved when timing is advanced. Advance it as far as you can without it pinging. Step it up about a degree at a time until you hear it start to ping under hard acceleration, then back off a little and recheck. If it still pings, back off some more until you don't hear it anymore.

 

where is the timing chain located on my truck? i just got this truck last year and haven't messed with anything yet. dont have the manual or any manual for it so don't ask.

 

Idle CO readings tend to go up with too much spark advance.

Jim

 

will the co and hc readings go down if I retard the timing say to 8 btdc? instead of 10?

 

Not sure how many miles are on your motor but most timing chains far outlast the motor and self adjust as needed.

 

I agree with EPNCSU2006 about timing advancement on carburated motors but its a different ballgame with computerized motors.

 

Hi guys, I don't want to be the one "who knows it all" but here is roughly the theory regarding timing. :
The ideal point of ignition is TDC. You need to advance the timing because the process of igniting the fuel takes a certain time ,-- from 12dgr. BTDC (or so) to TDC. That is called the Ignition Delay. If you advance the timing too much, the fuel ignites before TDC, called Pre Ignition. That process will cause an decrease in combustion temp and (maybe ) pinging or knocking. A Late Ignition, that means 6degr. (or so) BTDC, will cause an increase in combustion temp. and an uncompleted combustion process (loss of power and overheating)

 

I just replaced my timing chain last weekend. The truck has 130,000 miles on it. The previous owner replaced the chain once before as well, I'm not sure what the mileage was. The chain I replaced was very slack, and allowed about 7 degrees of play in the ignition timing. Think of what advancing the timing 7 degrees does....that's what I was experiencing...well, it was jumping retarded, but still moving around quite a bit.

Edit:
How is timing an EFI motor different than timing a carburetted motor?

 

Its nearly the same, with the exception of pulling the spout connector on a computer controlled, or EFI vehicle, but when I've timed my bronco advanced I lost quite a bit of mileage, about 50 miles per tank. But I also noticed tremendous gains in power. I guess everything has its trade-offs. About your timing chain problems I have many friends with many miles on their motors and none have changed theirs. Of course there will always be those exceptions. But like I said most not all. I apologize no misinterpretation intended.

 

Its nearly the same, with the exception of pulling the spout connector on a computer controlled, or EFI vehicle, but when I've timed my bronco advanced I lost quite a bit of mileage, about 50 miles per tank. But I also noticed tremendous gains in power. I guess everything has its trade-offs. About your timing chain problems I have many friends with many miles on their motors and none have changed theirs. Of course there will always be those exceptions. But like I said most not all. I apologize no misinterpretation intended. I suppose that I should give you some valid examples of actual vehicles mine being the first ones, I have a 1997 Taurus V-6 with 174,000 miles that has been used mostly for bussiness, never had timing chain replaced. My father in-law bought it new. He just sold his 2000 Taurus V-6 to my brother in-law it has 140,000 and has never had a timing chain which was also used for bussiness (by the way my father-in law is a brake Salesman for Carlisle). Of course there is my very own 1991 Bronco it now has 225,000 miles on it, but it has had a timing chain however only because I had it overhauled at 193,000 miles I also have all receipts to prove it. Then there is my very best friend CJ he has a 1993 F-150 with 147,000+ miles. Its also never had a timing chain. Then there was my 86 bronco II 167,000 miles with no new chain while I owned it I put approx. 70,000 of those miles. And last but not least my piece of trash Datsun I think that I replaced virtually everything on that darn thing except the timing chain. I suppose that I could go on all day by asking my other family members but I'll spare you the boredom. I suppose that I could be out in left field, but those are real examples, I promise.

 

Umm, it's common knowlege that timing chains DO stretch over time and mileage. Just because those motors have a lot of miles and are still running, does not mean the timing chain's haven't stretched.

7 Degree's of play in a timing setup causes lotsa probs.

 

My local engine rebiuld shop Schap's automotive says that a good quality timing chain like Cloys should go the life of the engine. But timing belts however do need replacing. Please show me where it says to replace the timing chain @ 30k, 60k,100k. I've never seen these recomendations in any of my maint. guides. Just curious.
Not saying that they don't stretch all chains do but not enough to cause any ill effects to these machines above.

 

Well, 100K on mine and I just replaced the timing chain...it solved my rough idle. It was stretched to 3/4 deflection, which is 1/4" beyond the replacement measure. I guess the don't outlast the engine.

BTW, timing chains don't self adjust...you are thinking about timing belts with tensioners.