Gen 6 454 Questions

[someotherguy]

For the 2nd time no, the GenV block does not accept the factory GenVI roller rockers or cam. The heads and intake will bolt right up, but you may need a special head gasket to make that happen.

Roller rockers in a gen VI? I think you mean roller lifters/cam, right? They're still regular ol' stamped rockers, non-roller, at least in the ones I worked on. ... and non-adjustable Comp Cams has that hardware kit to make them adjustable.

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Richard

 

[454cid]

Greetings 00CrewCab,

I've got a little different take on your situation. If you compartmentalize this temporary swap
the right way, and play your cards right, you may well be able to get a free ride out of a
'less desirable' Gen V motor while your Gen VI motor it out for repairs.

Thumbnail sketch:

1) Source the most promising yet affordable Gen V motor.

2) Pull your Gen VI engine out. Remove the intake manifold, sensors, etc.

3) Remove the intake manifold from the Gen V motor. (Bag the Gen V
intake & stash it for temporary safe keeping.) Swap YOUR Gen VI
intake onto the Gen V engine. Stuff this Gen V/VI hybrid into your truck,
hook it all back up, drive it.

How's it going to run right with peanut port heads, and a lower compression ratio on a stock L29 tune?

 

[Schurkey]

That's why I suggested swapping the heads along with the intake. But that--potentially--causes head-gasket issues.

The "peanut" ports won't make much difference at low to moderate engine speed. Lower compression will act like a semi-worn-out (or high-altitude) L29.

The burn characteristics of the older head might be of some concern...if this wasn't intended as a "temporary" engine.

 

[b454rat]

Too bad weren’t closer, I have an L29 for a parts truck. Didn’t really get to drive it but ran decent. Local yard had 2 (last I checked) L21’s I thought about getting. But theres another project I can’t do right now….

 

[Road Trip]

How's it going to run right with peanut port heads, and a lower compression ratio on a stock L29 tune?

Back in the Mark IV era, there were people who were forced by circumstance to mismatch
oval and rectangular ports between heads & intake manifolds. And they would run better
than one would think:

https://www.yenko.net/forum/showthread.php?t=87614

As for the compression, the key point is that this is a temporary substitution, not a
permanent downgrade. And since we're not starting with a 305, what is going to be
lost while driving at street rpm won't make that much of a difference, short-term.

Besides, if it runs too good then the Gen VI motor may never make it back into the
engine bay. Just thinking about getting all the power back could be a motivator
for the OP to see the project through to completion, sooner rather than later.

I know it sounds kinda funky, but a suboptimal big block is still plenty OK for
a workaround like this. I wouldn't hesitate to drive something like this for a short while...

 

[Supercharged111]

Roller rockers in a gen VI? I think you mean roller lifters/cam, right? They're still regular ol' stamped rockers, non-roller, at least in the ones I worked on. ... and non-adjustable Comp Cams has that hardware kit to make them adjustable.

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Richard

Yup, you got me. Words are hard.

 

[someotherguy]

Yup, you got me. Words are hard.

It's what y'all get for ******* out my Gen V. edit - really? d0gg1ng is censored.. wow. I thought that was only a dirty word on the other side of the pond.

Richard

 

[Supercharged111]

It's what y'all get for ******* out my Gen V. edit - really? d0gg1ng is censored.. wow. I thought that was only a dirty word on the other side of the pond.

Richard

I kinda have one in my Monte. GenV heads but thank God for the GenVI bottom end.

 

[454cid]

I mean, I'd rather have a Gen5 than a small block

I'd love to have an early 3500 with a 454. I'd prefer the Mk4, but I'd take the Gen5 if the rest of the truck was inline. It would just be a cruiser for me.... maybe haul bulky items once in a while.

 

[00CrewCab]

Here you go. Finding one of these in the treasure yard would be akin to finding a unicorn at a rodeo,
but stranger things have happened:

When my GMT400 isn't enough...

Tow rating isn't a function of engine power, but more of a balance of braking, stability and handling. Remember, those semi trucks from the 50s & 60s hauled 40k lbs with less power than today's diesel pickup trucks. I'm sure the 800's bumped towing rating came from 4 wheel disc brakes and...

www.gmt400.com

Note: Tip of the hat to @someotherguy for the above. :0)

Read through it, pointed to some other great articles, my only concern most of these 8.1 swap include quite a bit of fabrication or custom work, which I’m not apposed to, but I’d like to keep it as oem as possible. If I could just find a vin to order the 01-02 3500HD “classic” oem harnesses, computers, and related accessories, I’ve found loads of complete 8.1’s near me for about the same price as a good GenVI short block. But I work at a GM dealership so maybe I could talk to some of the parts guys and see what they can work up on the computers.