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

[oifla]

good morning all,

the 454 (7.4L) in my 1999 Suburban (K2500) model needs to be rebuilt. it has 150,000 and several looming issues (likely head gasket, leaking injectors, and early signs of rod trouble).

i'm considering several options:

1) rebuild the 454 with minor mods

2) rebuild the 454 with minor mods, delete the fuel injection, and and switch to a carburetor

3) instead of rebuilding it, i'm considering pulling it out and swapping something else in. 8.1L would be an obvious choice but i'm not sure how easy it will be to find a good one (and how much $!) so open to other ideas (i'd like to keep it as a gasser)

any other swap options i should consider? direct bolt in to the frame would be a huge plus, hence the 8.1L.

the 4l80e will not be an issue because i have an NV4500 ready to install.

thanks!

O.

 

[oifla]

important note: this is a family mover / tow vehicle. we don't put a lot of miles on it (it only has 150K and MPG is obviously not a top priority).

 

[454cid]

#2 is a very poor choice for a family/tow vehicle in my mind. It would be a better choice for something like a mud/race truck.

After being certain that the original engine is going bad, I'd probably opt for another 454, either a crate engine, a rebuild of the existing, or possibly a used engine if a deal can be had.

What makes you think the head gaskets and rods are going bad?

 

[LC2NLS6]

Think of it as a racecar project, pick a budget, and see what you can do with that as a starting parameter. You can get a shortblock ready to go for 2200. Have the heads rebuilt and put them back on, L29 are I think 102cc chambers and with this https://www.jegs.com/i/ATK-Engines/059/SP06-HP/10002/-1 would be low 9's to 1 comp ratio? You can get a +22 but might be too much compression for pump 87 gas. Throw the stock cam back in or a mild comp 206/212 https://www.compcams.com/94-801-10.html
Headers are gonna cause trouble, at least on my 93 with rear heat and rear a/c the lines are in the way. Could do what I'm doing, cam, intake and holley sniper efi. Let the stock computer control the 4L80E by hooking the sensors back up like stock.

 

[oifla]

#2 is a very poor choice for a family/tow vehicle in my mind. It would be a better choice for something like a mud/race truck.

because the carb setup is not reliable?

After being certain that the original engine is going bad, I'd probably opt for another 454, either a crate engine, a rebuild of the existing, or possibly a used engine if a deal can be had.

What makes you think the head gaskets and rods are going bad?

exhaust is getting that sweet coolant smell. definitely have a broken valve spring / rocker scenario. not sure if the rod (and/or cam) is also toast. need to look further.

 

[oifla]

Think of it as a racecar project, pick a budget, and see what you can do with that as a starting parameter. You can get a shortblock ready to go for 2200. Have the heads rebuilt and put them back on, L29 are I think 102cc chambers and with this https://www.jegs.com/i/ATK-Engines/059/SP06-HP/10002/-1 would be low 9's to 1 comp ratio? You can get a +22 but might be too much compression for pump 87 gas. Throw the stock cam back in or a mild comp 206/212 https://www.compcams.com/94-801-10.html
Headers are gonna cause trouble, at least on my 93 with rear heat and rear a/c the lines are in the way. Could do what I'm doing, cam, intake and holley sniper efi. Let the stock computer control the 4L80E by hooking the sensors back up like stock.

thanks, will look into the Holley option

the trans stuff is not an issue because i'm going to swap in a 5-speed

 

[PolarBear]

For the money? I'd just throw a 6.0 LS engine in it and call it a day. The 96-00 Fullsize OBS trucks are basically a bolt in swap and the easiest vehicle to swap.

 

[b454rat]

No ****** way would I swap a 6.0 in place of a 454. More power n torque than a 6.0 liter with the same or better mileage. Rebuild the 454, maybe bump compression, mild cam, rebuild heads with roller rockers, tune it and enjoy it. Depending on state, can’t run carb cause of emissions. But being it’s a heavy duty might not have any. But going with a car over today’s technology is taking a step back. Can get just as much power with today’s EFI over a carb, and better drivability.

 

[andy396]

Can you provide budget to help narrow in the suggestions?

 

[stutaeng]

No advice to OP, but just a general question since topic is 7.4:

Does anybody have any experience with the L21? It sounds pretty cool with forged internals and coil-on-plug ignition. Never seen one in person. Looks like only the Kodiak/Topkick had them? Not sure what HP/TQ those made. An why did they make less power than L29? Seems it would make more? Maybe it was vehicle-specific factory tune?