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4.8, 5.3, 6.0 vs gen 6 l29 454...

For a L29 to work right with the 0411 pcm you should change out the L21 454 24x reluctor wheel.

For those that don’t know the L21 was the big block sibling that bridges the gap between the L29 and the L18 8.1. It’s basically a L29 with coil near plug ignition like a LS engine or 8.1. It uses no distributor but has a cam sensor in its place.

L21’s were medium duty only, no light duty trucks got them.

Funny thing is the L21 valve covers look identical to an 8.1 cover but they are different. The sealing surface on the 454 head for the valve cover is lower than an 8.1. The 8.1 valve cover sealing surface is higher to the cover is shallower. Bolt pattern is identical. One could use a L21 cover on a 8.1 to clear larger than stock rockers but you can’t go the other way.

L21 parts are scarce but the only one you really need is that reluctor which several have in the aftermarket.

My buddy with the 8.1 CUCV blazer is building a L29/21 hybrid for his K20. I was still able to source the L21 valve covers last year for him. I doubt they are available now.
 
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sweetk30 said:
Love my 8.1L nv4500 combo .
Click to expand...

Try it in a truck that weighs a couple thousand pounds less and half the wheelbase. You’d love mine.

Then again I’ve driven 8.1/Allison equipped class A motorhomes up highway passes in the mountains at the speed limit or better. Passing semi trucks and most other rvs on the road. Most of those were geared way deeper than any gm truck with the same combo of engine/trans.

The best was the back to back runs comparing a v10 ford chassis with a 8.1 workhorse. That made believers out of even the most non technical, non-car folks. A v10 goes up a 5% grade revved up to 5500 or more rpm. Same size coach with an 8.1 wouldn’t go over 3500 and still maintaining better speed. That combo alone is how workhorse outsold ford in the gas class a market within a year of the debut and all the way up to the demise of workhorse itself. Gm had not outsold ford on gas class a side for many many years.

Driving the v10 had folks afraid the pistons would come through the floor between the front seats when it was at full boil.

Still came down to big block grunt at a low engine speed.
 
Nice.....
If I'm ever your way I'll take you up on it!
 
CnP has more consistent timing with the crank trigger, and hotter spark than a regular inductive ignition without a CDI box. You also don't have to worry about rotor phasing limits or wear in the distributor and rotor, as their are no moving wear parts in a DIS ignition.

But that engine would still use a dummy gear to drive the oil pump from the camshaft like the 8100.

You can put DIS w/ CnP on an older big block, its very easy on any Gen VI though, including the L29.
 
I have 3 L29s, have access to another, but have access to 2 L21s. I plan on building at least one.....
 
I think the BB would be fun on the street, sand, and mud. I’m not sure I could justify the move from SB to BB for rock crawling. I would rather save the weight gain and just keep a healthy SB in place. (Cooling system and trail fuel economy another point)

I’m in for a BB to tow my SB K5 but at the moment I’ve got a 6.0 to wind out :)
 
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