My 454 Rebuild

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Piratehunter

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just in case, have a new melonized dIzzy gear on hand when you pull the distributor this weekend.
 

ralmo94

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The GM replacement ones are typically NTK which are made by NGK. AC Delco does not really make anything of their own really and has not for years. Some are also Bosch.
I have seen parts store ones target different afrs, on a wideband. That's the reason I ask
 

Spareparts

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I'm putting a new dizzy in it. The current gear was a new melanized gear when engine was rebuilt. so should be good still if the new one is not.
My cmp if it starts at dead 0 at 1.2k rpm it will be near or over +4 when hot and i did see it at +7 also
The o2 sensors are new and are reading pretty much the same as the 20yo ones i took out. I can't remember the brand but maybe Walker? They are not the problem.
 

Piratehunter

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Have a pack of nylon dizzy shims (.030, .060, .100) handy too. let me know if the dizzy gear is knife edged when you pull it out. I know you put a new one on there prior. I’ll explain my experience if it is.
 

Spareparts

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I got the .bin using PcmHammer. I believe i can change it with Tuner Pro RT or Universal Patcher then reload it into the 0411.
Problem is i just dont know enough about tuning anything to be brave enough to do it.
 

Spareparts

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Got the distributor changed and injectors tested.
All the injectors are working and flow the same according to pressure readings. They all start at 58 PSI and drop to 46 psi. None are leaking.
The distributor change, changed nothing.
I'm beginning to think i have a problem with the heads, something with the valves?
A compression check shows even compression across all cylinders. When cranking all appears good but when running maybe it has weak valve springs or sticky valves?
The heads were checked out by the machine shop but did not need any new parts as they were rebuilt not long before i got them so they should be good i would think.
With cranking compression between 155 and 160 i just can't imagine anything internal being bad. All cylinders passed a leak down test performed at 100psi.
I'm now out of ideas. There is nothing else i can change. I have changed every sensor on the engine. Everything is new. Looking down the intake runners i can not see any evidence of a manifold leak. It does not build vacuum with the PVC and breather plugged checking at the oil fill tube. Timing light shows all plugs firing rhythmically as you would expect to see.
I'm now at the point of putting the black box ecu back in it and taking it to the one respected shop in town and telling them to fix it because i'm apparently not smart enough to do it my self.
 

Mangonesailor

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Well, maybe it's a lifter that's not pumping up? Not enough o2, too much fuel to o2 sensors, running rich condition, pulls fuel.

Or what about a rocker?

Cause as far as the fire triangle goes, we've got fuel, we've got ignition, your wires aren't crossed for the injectors (as far as we know).

Maybe you need to pull the valve covers and roll the engine and see what you see?
 

letitsnow

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Most of the guys responding here know much, much more about the tuning of these trucks that I do.

Keeping it simple - why is your tune so rich, being as it was an in person tune at BB? Has your intake or exhaust set up changed? I would think that if nothing has changed, even a fairly incompetent tuner could get it closer than -15-25 on the fuel trims.
 
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