engine timing mystery

[jdheff1982]

I had my uncle check my timing for me. The timing indicator is proper, but when he set his light to 0, the mark was at the ten o'clock position. This is with vacuum advance disconnected.

Any ideas?
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[78 Chevyrado]

What engine?

it's very common for the outer ring of the harmonic balancer to slip on the inner ring, making the timing marks wrong. all that seperates the inner and outs ring is a bonded rubber layer. the rubber layer loses its "bond" and slips sometimes, leading to bad readings on the timing light.

only way to know for sure is to find TDC and mark the balancer whiles its set to TDC at the 0 mark on the timing tab.

[y5mgisi]

I think you are going to need to give a little more info then that. Your question is a little bit confusing. My idea would be that your timing is retarded(after top dead center).

[jdheff1982]

If you follow the link in my Sig, you will find my truck specs.

The truck runs fine as is. The first reply sounds legitimate. Thanks.
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[piecesparts]

Since the engine is in a 85 truck, does it have the original timing marker tab on the timing chain cover behind the water pump? If so, is that where you checked the timing? You have to look down from the top of the engine by the front end of the intake manifold to get it aligned. If your timing is off, then you could have the balancer slippage as noted, or you could have the wrong balancer with the keyway groove cut in the inproper place, or finally you have the timng set wrong on the dizzy. I see by your info on the other webpage, that the eninge has been reworked, so many possibilities exist.

[jdheff1982]

Ya, the tab is where it is supposed to be. We were looking where you indicated, but found the mark to be way left of the tab. My uncle claims that if the timing was that far off, the truck would be shootin fireballs out of the carb.

[piecesparts]

Looks like it is time to pull #1 plug and find TDC. When done, then look at the tab and the dizzy pointer. Replace parts as necessary to get the stuff right. The balancers are different for where your tab should be and if the balancer has slipped, then get a new balancer and make it right.

[78 Chevyrado]

what year is the engine in your truck? if its INTERNALLY balanced, the balancer slipping wont hurt anything but the timing accuracy. if its EXTERNALLY balanced, the more it slips the more your engine balance will be off, which is not good.

[TJBrown]

We ran into this problem once. The way we figured it out was to use the same set up we use to degree our cams in our race cars engines.

You can purchase a piston stop from Summit or Jegs that screws into the spark plug hole on number 1. Remove all Spark Plugs as this will make it easier to turn over. There is a pin inside the insert that screws into the spark plug hole. Adjust this down so it is stops the piston on the way up like 10 degrees or sofrom top. With Number one at just before or after TDC turn over the engine by hand with a ratchet and touch the stop and mark this with a white grease pen. Then turn it the opposite way and touch the stop again and mark with a white grease pen. We use a degree wheel to get within a 1/4 of a degree but for this type of stiff, a white grease pen or even liguid paper will work fine. With Both stop marks marked on the balancer, measure and split the difference. This is true TDC by the Piston position. If the outer ring has moved, you can replace the balancer (recommeneded) or by a balancer tape and apply it at the correct TDC.

[jdheff1982]

Originally Posted by TJBrown

We ran into this problem once. The way we figured it out was to use the same set up we use to degree our cams in our race cars engines.

You can purchase a piston stop from Summit or Jegs that screws into the spark plug hole on number 1. Remove all Spark Plugs as this will make it easier to turn over. There is a pin inside the insert that screws into the spark plug hole. Adjust this down so it is stops the piston on the way up like 10 degrees or sofrom top. With Number one at just before or after TDC turn over the engine by hand with a ratchet and touch the stop and mark this with a white grease pen. Then turn it the opposite way and touch the stop again and mark with a white grease pen. We use a degree wheel to get within a 1/4 of a degree but for this type of stiff, a white grease pen or even liguid paper will work fine. With Both stop marks marked on the balancer, measure and split the difference. This is true TDC by the Piston position. If the outer ring has moved, you can replace the balancer (recommeneded) or by a balancer tape and apply it at the correct TDC.

It's ok to reverse engine rotation? I had always thought that was bad?

[y5mgisi]

As long as you dont just sit there and spin it backwards forever its ok. The trouble with it is it spins the oil pump backward and therefore spits the oil out of it. But to rotate it around once or twice backwards certainly shouldn't hurt anything.

[jdheff1982]

My Uncle gave me another clue to this mystery. He said that h.balancers from the 70's were timed from the passenger side of the engine. Possibly, I have a 70's balancer with the indexer on the wrong side.

[406 Q-ship]

Originally Posted by jdheff1982

My Uncle gave me another clue to this mystery. He said that h.balancers from the 70's were timed from the passenger side of the engine. Possibly, I have a 70's balancer with the indexer on the wrong side.

Not the SBC I worked on .......always on the drivers side......always. Around 1978 did Chevys have the timing tab directly under the water pump.

I have never seen any Chevy V8 with a timing mark on the right side (passenger side). I have seen the tab on the left, top and bottom (Big Block motorhome).

[71swb4x4]

Never heard of them be timed from the passenger side, but I was barely even alive in the 70's.

Start with the basics and find TDC as mentioned above. After that it should be a walk in the park.

[piecesparts]

Dang, I must be older than I thought.

[jdheff1982]

I guess in my case, the outer ring has moved. If I were to remark the balancer by finding TDC, where on the engine do I need to turn? Or would I be better off in replacing it?

Thanks.

[hatzie]

Originally Posted by jdheff1982

I guess in my case, the outer ring has moved. If I were to remark the balancer by finding TDC, where on the engine do I need to turn? Or would I be better off in replacing it?

Thanks.

If the balancer damping ring has moved replace it with new. When the ring moves on the 6.2l & 6.5l diesels the crankshafts break because the vibrations it's supposed to be damping are being amplified instead. Gas engines don't have the vibrations of a diesel but it can't be good for a gas engine either.

Summit has OEM type balancers with degree marks for around $50.

[sumran]

Originally Posted by jdheff1982

I guess in my case, the outer ring has moved. If I were to remark the balancer by finding TDC, where on the engine do I need to turn? Or would I be better off in replacing it?

Thanks.

Your engine is internally balanced. The harmonic damper does not need to be replaced to keep the engine balanced. If the timing mark is off, you can address it as noted above, although having the mark in the right place makes life easier.

However, replacing it would be the best thing to do. The function of the damper is to lessen vibration caused by the rotation of the crank. The active part of the damper is the rubber between the inner and outer ring. They get old and dry. If yours has moved the rubber isn't functioning properly.

Is it a big deal to keep using it? Probably not. But a new one would be better and it would look good when you opened the hood. If you get a racing damper it may even go faster.

[jrcaprai]

What Kind of Timing Light, is it a fixed, or is it an adjustable ?

[jdheff1982]

Originally Posted by jrcaprai

What Kind of Timing Light, is it a fixed, or is it an adjustable ?

It was adjustable. When he set the light to 0 and left the vacuum advance unplugged, the mark was clear over on the passenger side of the truck. He had to advance his light to 100 before it would get to the indexer.

When he left the advance plugged in, the mark would register under the indexer. I think he said something along the lines of 28 degrees total advance between idle and accel.

He didn't want to mess with the timing until I get the carb fixed / replaced. Hopefully, next payday, I'll have an E-Performer 750 in my hands.

The truck runs fine, it does misfire depending on the rpm range, not bad tho. If I get on the throttle, engine doesn't miss a beat.

[jdheff1982]

I am curious, if the engine is timed to the cam, would the timing be off according to what the indexer would show?