timing

[Burkhalter]

I think I have a timing issue. At about half throttle and under any kind of load I loose most of my power and get a lot of after fire. I'm going to look at my timing when I get home, but I'm curious where it should be at. My book at home says 8 degrees. But I keep seeing 15 degrees on here. Should I split the difference?
I have a 361 with a RV2 cam and HEI ignition.

[hatzie]

What does the spec sheet for your cam say?
If it doesn't say anything then what does the emissions label under the hood say?

[Burkhalter]

That's part of the problem. My dad and grandfather installed the cam in the early 90s and everything emissions related including labels were removed a year after he bought the truck new in 86.

[hatzie]

That's part of the problem. My dad and grandfather installed the cam in the early 90s and everything emissions related including labels were removed a year after he bought the truck new in 86.

The GM service manuals are linked in my signature.  8 degrees doesn't sound wildly incorrect.
If you could find enough info on the cam the manufacturer likely can dig up their info and tell you if it differs from stock.

My Droid from orbit

[rich weyand]

Sounds like your distributor isn't clamped down tight and it drifted retarded.  That's exactly how it would act.

Read the sticky thread on timing at the top of this sub-forum page.

[Burkhalter]

This is kinda weird. I was at about 46 degrees when I first put the light on it. So I moved it to about 20 degrees. Wouldn't start. Went back to 46 degrees it ran. Advanced it a little more to about 50 degrees and it runs great and power like it should. Could they have put the cam gear in wrong? Or could it be multiple things like worn lifters, worn cam and a stretched timing chain?  The motor does have 385k on it.

[rich weyand]

There are three timing tab locations.  Sounds like you have a balancer and a timing tab that don't match.

Where is your timing tab?  Right on top, off to the drivers side,...?

[Burkhalter]

Driver's side

[rich weyand]

One timing mark location on the balancer is 40* CCW from the keyway in the crank (timing tab on top of the engine), one is 10* CCW, and one is 2* CCW.  So if your tab is in the driver side location, and you have the wrong balancer on, you will read 30 or 38 degrees more advanced than you really are.

So you are probably reading 38 degrees more advance than you really have.  50 would then be 12, which should perform nicely.

You can check this by noting the location of the key on the crankshaft and comparing that to where the timing mark on the balancer is, per the above: 40, 10, or 2 degrees ccw from the keyway?

[Burkhalter]

Just looked at it. The mark is 40* ccw. Thanks that helped a lot.

[Fairlane514]

Was your vacuum advanced plugged in to full manifold when you were checking the timing?

[rich weyand]

Just looked at it. The mark is 40* ccw. Thanks that helped a lot.

I put one of these one mine.  http://www.jegs.com/i/Proform/778/66518BKC/10002/-1

[Burkhalter]

Normally yes, but it was D/C and plugged while checking the timing.

[Burkhalter]

That's a nifty little piece. But I would be concerned that you wouldn't be able to read the numbers with the timing light.

[rich weyand]

That's a nifty little piece. But I would be concerned that you wouldn't be able to read the numbers with the timing light.

Nah.  Works great.