454 (7.4L) swap / repair options - 1999 Suburban K2500

[Supercharged111]

Be advised that a K2500 at 2500 RPM in OD and 4:10 rear is traveling about 80 MPH.
3500 offers 103 MPH.
Pulling at 55-65 MPH you'll range 1700 to 2200 and this is where you want, at the least, be well into the cam torque curve.
In no way would you aim at a "2500 to 3500" torque peak. Operating in that high RPM range would require 3rd gear on every knoll when operating at normal speeds

FWIW:
Input Parameters Are the Following:

Differential Gear = 4.00 to 1

Transmission Gear = 0.75 to 1

Tire Diameter (Inches) = 31.00

Vechicle MPH = 60

Computation Results:

Computed Engine RPM is 1952

Critical thinking will save time and material, and prevent disappointing outcomes.

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I was alluding to a downshift into 3rd rather than steady state pulling at that RPM. If 3rd gear can't get it done then you're coming up short (automatic).

 

[Bu327]

What about the GM HT502? Direct replacement with new injectors, better exhaust parts, and a tune should wake up the truck. I don’t know if the vortec manifold bolts to those heads. If it doesn’t, get just the short block and have your heads freshened up.

 

[Gibson]

For towing you need low RPM torque.
In most states, when you're towing the speed limit is only about 55 or so anyway.
To be able to stay in OD with a locked converter you want an engine with a torque curve that will let you cruise along at 55>60 with RPMs around 2>2.3K,, assuming 4:10 gears and stock sized tires.
No reason for a stick-shift, especially trying to start-out from a dead stop on an up-hill grade.
Chevy has almost always had higher tow ratings for automatics.
If you're moving/towing heavy loads their is nothing that will beat cubic inches.
Chevy did make a SB for medium-duty trucks that did pull well, the 366, a tall deck, small bore/long stroke engine.
But they do not like to rev.

 

[L29Sub]

Not to get too far off...but a bit of history if you will.
I once had a Chebby gas 401 V6 that was quite respectable in those days. A smaller version was sold in Suburbans.
401 was bullet proof if used as designed. Seem to remember less than 3k recline? 5 speed/2 spd and it worked.
They made a siamese V12 and a diesel in the same layout.
These were very high torque for their displacement.

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[badco]

So only skimming the topic i can say ported heads help torque if done correctly and yes that includes vortec big and small blocks. That means a radius cut valve job, slight roll of short side radius, and a bowl blend. Port match to intake isnt a bad ideal as long as its matched and lined up as it would be on the engine. now as far as holding rpms on a bbc its mostly in piston weight and pin clearance that kills them. Make sure to get correct hone job to match what ring says specs are. A decent aftermarket rod and floating lighter weight or at least match vortec weight piston but use a small dome or a different compression height on piston to bump from 8.8 to at least 9.5 or 9.8 so still could run cheap gas and balance it to take care of bottom end. Cam needs to be between [email protected] ground on a 110-114 and degree in at 106ish* a limited travel hyd roller lifter ensures under a hard pull it wont lose power in the hyd part as bad, use good upgrade springs from what cam recommends, in comp book it will list one spring and have a optinal one in red numbers that is a pacoly spring that will last longer than engine. Also use a como chromoly 3/8 pushrod like the older bbcs had. That's not the "budget" built way but it would make a ton of tq and of ever reved up it wont die. And with any cam change you need to tune pcm. Just my opinion on a vortec bbc and making it pull and last.

 

[badco]

Not to get too far off...but a bit of history if you will.
I once had a Chebby gas 401 V6 that was quite respectable in those days. A smaller version was sold in Suburbans.
401 was bullet proof if used as designed. Seem to remember less than 3k recline? 5 speed/2 spd and it worked.
They made a siamese V12 and a diesel in the same layout.
These were very high torque for their displacement.

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They make a ton of tq because the rotating assembly was heavier than a whole 350! They was heavier than the old 366 pistons. That why no rpm or the rods came out to say hello. They didnt have any valve spring pressure so they wouldnt rev up. They were monsters for pulling thats for sure

 

[L29Sub]

They make a ton of tq because the rotating assembly was heavier than a whole 350! They was heavier than the old 366 pistons. That why no rpm or the rods came out to say hello. They didnt have any valve spring pressure so they wouldnt rev up. They were monsters for pulling thats for sure

Wonder if a 401 V6 would fit into a 1999 'Burb? And the Spicer 5 spd and...WTH, the 2 speed? The engine was offered in 3/4 ton pickups and 'Burbs.


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[454cid]

....Chevy did make a SB for medium-duty trucks that did pull well, the 366, a tall deck, small bore/long stroke engine.
But they do not like to rev.

The 366 is a big block, not a small block. I've wanted to get one, but I have no idea what I'd do with it.

 

[Gibson]

The 366 is a big block, not a small block. I've wanted to get one, but I have no idea what I'd do with it.

Yeah, my bad, you're right.
Kind of a "small" BB.
Their are some YouTube vids of guys running 366s.
This one sounds good;

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[HotWheelsBurban]

Yeah, my bad, you're right.
Kind of a "small" BB.
Their are some YouTube vids of guys running 366s.
This one sounds good;

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The 366 was a "small" big block designed for medium duty trucks. They wouldn't be revving a lot in normal use,that's what they have lots of gears for.
Money no object, I'd go with the 502. The old saying about: no replacement for displacement " and all that.....otherwise just build a 454 to do what you want. Towing requires low end torque, so whatever is necessary for that. Then if your transmission, rear axle, brakes and frame are up to the task, you're good.
What type of terrain you tow on makes big difference too. I can tow all day with my stock 99 5.7 vortec on flat ground. Get into hills like around Austin or further west, and loaded trailer wants to push me around.