Thunderbolt iv timing

[klawton55]

I have a 92 454 with thunderbolt iv ignition. I have recently had the block bored and all new internals. I fired it up today and it sounds goog. I was trying to time it to 8 degrees bdc, but if I go any lower than 16 it starts to miss and backfires out the exhaust. What could cause this? I also cannot get it to fully engage in reverse, forward and neutral seem good but it grinds when put in reverse. If i put some tension on the shift "dog" it will stay engaged. I think that the cable needs adjustment put I have ever done this. Can anyone point me in the right direction?

 

[Bt Doctur]

your using the wrong cylinder to time it or the cam and crank dots were not lined up correctly

 

[achris]

Or the outer hub of the balancer has slipped..

 

[klawton55]

Is there some way to tell other than removing the cover? I would have to remove the engine, or at least lift it up to pull the front cover.

 

[NHGuy]

Did they put on a new front harmonic damper? Or a different one? The Magnum damper and the regular Bravo damper have different part #s. They are either balanced differently or timed at a different angle to the crank. Or both!
You might be best to find top dead center using a piston stop and then time it from there.
Go to youtube and search finding TDC or top dead center. There are lots of demo's.

 

[Bt Doctur]

remove #1 plug, verify piston at TDC compression and look at the timing pointer and check the harmonic balancers mark

 

[achris]

Remove #1 spark plug (I remove all of them as it's easier to turn the engine over) and put a screw driver or something similar in the hole. Slowly (by hand) turn the engine until the indicator you're using in the plug hole is no longer moving up or down. This is very close to TDC. Look at the pulley and see how the timing marks look. If they look a long way off, replace the balancer. If they look close, turn the engine until the you just feel the indicator starting to move. Note the reading on the timing marks. Turn the engine the other way and again note the point you feel the indicator just start to move. The 2 readings should be very close to the same, but one before TDC, the other after TDC.... BTW, it doesn't matter which strokes the engine is on (compression or valve overlap), TDC is TDC, regardless of the position of the camshaft....

Chris....

 

[MikDee]

The 2 readings should be very close to the same, but one before TDC, the other after TDC.... BTW, it doesn't matter which strokes the engine is on (compression or valve overlap), TDC is TDC, regardless of the position of the camshaft....

Chris....

It Does matter which stroke the engines on, but only if you have the Distributor out, or if you moved it! TDC on the crank comes around twice to make 1 complete cycle of the motor, once on Cyl #1, and once on Cyl #6, or vice versa, alternately with each crank revolution.

 

[bruceb58]

It Does matter which stroke the engines on

Achris is describing how to get to TDC to see if the harmonic balancer has shifted. Like he said, it doesn't matter which stroke he is on.

The OP has his distributor stabbed correctly or else it wouldn't run at all.

 

[MikDee]

Achris is describing how to get to TDC to see if the harmonic balancer has shifted. Like he said, it doesn't matter which stroke he is on.

The OP has his distributor stabbed correctly or else it wouldn't run at all.

I got that Bruce, I was just throwing that extra info in there, if maybe only for "shift's & giggles"

 

[klawton55]

The picture shows how it is aligned. It looks good to me according to the dots but the service information shows it going from the tip of the tooth to the tip of the other tooth. Mine is the tip to the v groove. What do you think is it ok or should I move it back the half a tooth? This is double roller instead of single, it's what cam with the parts kit that I bought. http://s105.photobucket.com/user/klawton55/media/imagejpg1_zps7b43e3ed.jpg.html?sort=3&o=0

 

[MikDee]

No Title

The picture shows how it is aligned. It looks good to me according to the dots but the service information shows it going from the tip of the tooth to the tip of the other tooth. Mine is the tip to the v groove. What do you think is it ok or should I move it back the half a tooth? This is double roller instead of single, it's what cam with the parts kit that I bought. http://s105.photobucket.com/user/kla...tml?sort=3&o=0

That alignment is fine, But, I believe that picture you posted with one dot on top of the other is for lining up Cyl #6 to fire. If you give the crank one more turn, to where both dots are at 12 o'clock, then it would be set to fire on Cyl #1. At least that is how it is for the smallblock Chevy, I'm guessing it's the same for the big block Chevy too!

See attached photo:

 

[klawton55]

So do I want to move the cam so the dot is at 12 o'clock? Would it even run where it is set now if that is the case. It ran good I just couldn't get the timing below 16 degrees without missing and backfiring. It also would miss and backfire if the idle dropped down to where it should be. This is what made me think that the timing was off.

 

[bruceb58]

So do I want to move the cam so the dot is at 12 o'clock?

Looks fine to me.

 

[klawton55]

So what do you think could have caused it to backfire when I was trying to adjust the timing down to 8 degrees?

 

[MikDee]

So do I want to move the cam so the dot is at 12 o'clock? Would it even run where it is set now if that is the case. It ran good I just couldn't get the timing below 16 degrees without missing and backfiring. It also would miss and backfire if the idle dropped down to where it should be. This is what made me think that the timing was off.

If your engine was already running, then you took off the front cover to look at the timing chain, & gears, but haven't touched the Distributor? Then don't worry the timing marks are lined up fine, But what you probably didn't realize, is that although the Crank was at TDC, presently it is set to fire on Cyl #6 this revolution. If you take the Dist cap off, you'd see the rotor should be facing Cyl #6. If you were to turn the Crank over one more turn to TDC again, then you would have both marks at 12 o'clock, directly in a vertical line (theoretically), and the engine would be set to fire on Cyl #1, and if you took the Dist. cap off then, the rotor should be facing Cyl #1.
You could do this to check yourself.

 

[MikDee]

Maybe a lean sneeze! Hows your fuel delivery, are all lines, & filters clean?

 

[klawton55]

Yes fuel is good, new filter and line from tank. Plenty of fuel in the carb. Just to make sure that I've done this correctly, when I was using the timing light I had it connected to #1 cylinder. Is that correct?

 

[achris]

Yes, and #1 is the front port side cylinder...

 

[klawton55]

That's what I used, just wanted to make sure. So if the timing is correct and I was using the right cylinder, what should I look at next that could cause my issue?