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454 vortec timing gear question (updated)

Magikal

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7.4l vortec. Started popping and backfiring, barely keep it running. Was thinking timing chain is stretching and ready to go. It will run like this for undetermined amount of time and then suddenly will purr and run great.

Anything other then timing would make it backfire? Sounds like an old 350 with the timing off a tooth....
 

ZooMad75

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Two things possibly. The ignition control module is getting hot and cutting out or the harness under the plenum is shorting out. Seen both.

The ign module is located on the back of the upper intake plenum and can be impacted by exposure to heat over time.

Does the problem get worse as it gets up to temp and runs better cold after it was first started?
 

Magikal

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This seems like too much slack to me.....

No, it has progressively been getting worse. Used to only be after it warmed up, now it's all the time. Barely can move it around the yard.

Obviously not now as i tore into the motor...lol
 

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bigblock72

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This seems like too much slack to me.....

No, it has progressively been getting worse. Used to only be after it warmed up, now it's all the time. Barely can move it around the yard.

Obviously not now as i tore into the motor...lol

Timing chain is a little on the loose side but not bad enough to cause any issues. I'll bet it's the distributor cap, these like to arc through the plastic and send spark where it's not wanted. Use ONLY a Delphi cap as the parts stores ones will only last a few months before they do it again.
 

Wes Harden

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Yes the small gm distributor is horrible. The flat cap is the worst.
Keep spare cap and rotor at all times.
 

Magikal

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Yes, i have new tune up stuff for it, all ACDELCO. I know the vortec motors are picky about brands of parts.
 

Magikal

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What's involved in removing the reluctor wheel for the crank sensor?
 

Magikal

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So i ordered a timing set and after recieving it i discovered that the bolt pattern diameter for the camshaft is larger then what i have. I'm 100% certain i ordered the correct year and model from rockauto. After inspecting the options in there some more i don't see any difference mentioned. As far as i know the motor is all stock so no aftermarket cam or such.

Can anyone shed some insight into this? Perhaps a correct part number?

20210830_170449.jpg

20210830_170500.jpg
 

Wes Harden

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some of rockauto stuff is old inventory from parts stores and warehouses. Some of it has been sold then returned, then resold on rockauto. Don't take for fact they sent you an unopened box or even a miss boxed part.
Can't help with big block bolt circle sorry.
 

bigblock72

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So i ordered a timing set and after recieving it i discovered that the bolt pattern diameter for the camshaft is larger then what i have. I'm 100% certain i ordered the correct year and model from rockauto. After inspecting the options in there some more i don't see any difference mentioned. As far as i know the motor is all stock so no aftermarket cam or such.

Can anyone shed some insight into this? Perhaps a correct part number?

View attachment 388164

View attachment 388165

You need a Cloyes C3213 timing set.
The 1996-2000 gen VI engines use a roller cam with a reduced bolt circle to make room for the cam retainer plate. A lot of catalogs don't differentiate between the early Mark IV/Gen V large pattern and the later gen VI small pattern.
 

Magikal

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Prior to reading the last message i did more homework and ordered another timing set. Turns out it was a cloyes c3213. Got it bolted on and almost back together. Sadly, i finally picked up a 32 spline sm465 so the blazer is gonna get tore apart more before i get to run it. Replacing the 4l80e. I'm so over automatic trannies. I seem to go through about one a year. Lol.
 
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