L29 rebuild - give me ideas

[TexasAggie]

Find some headers for that thing! I've been doing some shallow research and from what I have read, the Vortecs respond really well to a quality exhaust. Headers for certain models are hard come by though (I've got a K2500 Suburban and don't know if anyone makes them anymore).

 

[Supercharged111]

All Vortecs have super weak factory tunes.

 

[Philip Parker]

Find some headers for that thing! I've been doing some shallow research and from what I have read, the Vortecs respond really well to a quality exhaust. Headers for certain models are hard come by though (I've got a K2500 Suburban and don't know if anyone makes them anymore).

I have heard this as well. I've had two sets of headers on two cars and they both cracked, probably because they were cheap. I think gibson makes a set for this truck .

 

[Supercharged111]

I have heard this as well. I've had two sets of headers on two cars and they both cracked, probably because they were cheap. I think gibson makes a set for this truck .

I've had headers on over a half dozen applications and never cracked one.

 

[Christian Steffen]

Thanks so much for the advice. The truck is a 99. I talked to a well known engine builder here in Colorado on Monday. His suggestions were similar to what some folks here have mentioned. One thing he was adamant about was that for my uses stroking the motor was not something he would do. As mentioned before you're looking at lots of extra expense like high flow heads and if you want to run EFI some very spendy aftermarket kit. We mostly covered long block ideas during our conversation.

He suggested the following:

1. Keep compression as close to stock as possible, maybe a quarter point bump to keep the efi happy. I need to research the 99 EFI system to see what sort of tuning it can do. Info is a little hard to come by. He's a carb exclusive builder so I need to do some additional research on this.

2. Take the long block to the best shop around with the best machines. Have it blueprinted and put together really well with new long skirt pistons. He mentioned how much power you can pick up by simply reducing friction. Use at least a 1.5-1.5-3mm ring set.

3. Install CHE bronze valve guides and stainless valves. Have the seats recut. Clean up the heads as much as possible and flowed to see where they're at. I've seen some numbers for L29s that isnt bad. He also suggested investing in adjustable roller rockers.

4. He said the stock cam numbers aren't that bad. He's never built an L29 but knew about the 6 degree retard against the crank. The machine shop that will be doing the long block is a COMP dealer and will help me spec something out. This seems like the zone where there is some potential, and something I've read countless times on the web about L29s.


In general is seems like this thing has a super weak tune from the factory. Is that kind of the consensus? I will definitely be adding the stepped up injectors to the parts list.

I suppose the goal at this point is a nicely built, easy running L29 with gobs of low end torque that isn't going to throw a fit if it gets a tank of questionable 87 from some middle of no where gas station.

Just to Summarize where I'm leaning:

Bore & deck block minimally.
Deck head minimally
Flow the head
Bronze guides
stainless valves
Adjustable roller rockers/PR
long skirt pistons (need to spec)
all bearings
Crank polish
Injectors
Stock Manifolds (?)
New cats
4l80E rebuild
ECM Tune

Anything I'm missing?

Just curious, but what does he have against stokers? I'd say you're on a pretty good track though, good cam and a little more compression will still make a nice amount of torque. Tuning will definitely make a difference, stock tune blows.

Is your 4l80e hurt? Because if not i wouldn't mess with it, they're stout stock. A transgo HD2 is the most that i would do.

Just as a header aside, I have JBA headers on mine and they've been good.

 

[Philip Parker]

Just curious, but what does he have against stokers? I'd say you're on a pretty good track though, good cam and a little more compression will still make a nice amount of torque. Tuning will definitely make a difference, stock tune blows.

Is your 4l80e hurt? Because if not i wouldn't mess with it, they're stout stock. A transgo HD2 is the most that i would do.

Just as a header aside, I have JBA headers on mine and they've been good.

I'm not sure about the stroker thing. I think he's able to make big power without stroking - he's a meticulous machinist apparently. There are some longevity concerns with an under square which I get. I think his point was "reduce as much of the stresses on the assembly as you can for reliability and longevity" which is totally my goal.

The 4L80E has been doing some weird things for the past year or so. It is taking an abnormal amount of time to build pressure and start turning when in drive. We have an exceptional transmission/speed shop in town that did a TH350 for my dad's Jeep J-3800. I'm an opportunist so if I can get it sorted out while I have easy access to it I'll likely do it. It is also leaking profusely from the tail.

I've seen those JBAs. Not a bad price for some stainless kit!

 

[Supercharged111]

I think the torque converter is to blame when it takes a while to get moving out of park.

https://www.performancetrucks.net/forums/gm-drivetrain-suspension-22/4l80e-trouble-425006/

 

[Bu327]

502 short block

 

[Schurkey]

It is taking an abnormal amount of time to build pressure and start turning when in drive.

The 4L60E in my Trailblazer did that in reverse, when cold.

New filter and fluid flush fixed it. How old is your trans filter?

 

[TexasAggie]

What are the best crate motor options for the Vortec 7.4? I’ll be in the market sooner or later and like the crate motor option as it means the truck is down the shortest amount of time.