update on L31 (99 burb) 4L60E swap into 71

[Tim240Z]

Well I got the engine and trans mounted today.
It ended up being a very disappointing afternoon.
1st:
The mount plates which I had moved rearward to the 6cyl mount holes had to be moved back to their original spot as the tunnel was just too tight to allow the A4 to get anywhere near X-member. I would have has to beat the hell out of the tunnel which I didn't want to do. The silver lining (if looking for one) was that the chassis had factory holes for the tranny X-member, so it was a bolt in affair.

2nd:
The stock L31 (5.7 Vortec) exhaust manifolds hung so low that the manifolds were resting on the chassis (actually the engine mount brackets) about 1 inch up from where the mounts would sit in their cradle (1" gap between the engine mount brackets on the chassis to the rubber mounts on the engine).
I wanted to keep the factory manifolds so that if I was caught by a roadside emissions checkpoint (CHP and BAR are doing this again!!) I would be OK....Another kicker is that I had the PCM programmed to delete other sensors but not the EGR!!) grrrrr.
Well, it was either fabricate some new mounts, or put the headers from the exitting engine on....I chose the latter.

OK...so the engine is mounted. I am taking the drive shaft in tomorrow to be shortened, overhauled and balanced. I also pulled the fuel tank as I need to weld in another line for the return from the injectors (actually I will use the OEM feed as the return and install a new feed line at the bottom of the tank to gravity feed the high pressure in-line pump).

I should have the PCM back tomorrow (according to UPS tracking), so I can start the wiring. I also need to get an engine oil cooler (off to the JY in the morning).
I should have it done (at least running by Sunday)......

I did all the work so far completely alone, so my body is rebelling with aches and pains!!! Time for a beer!!

Tim

[shifty]

Just curious, why'd you choose the 5.7 instead of the 4.8 or 5.3?

[Tim240Z]

Originally Posted by shifty

Just curious, why'd you choose the 5.7 instead of the 4.8 or 5.3?

In hindsight I wish I had gone with the 5.3 or 6.0, but I thought the L31 would be a bit more straightforward...
One of the major factors which pushed me to the L31 was that my Company truck is a 97 2500 with 170k miles (hard miles) and it is still 100% reliable, uses no oil and drives great. 3 of the guys at work (pipeliners) have the same drivetrain with 200k+ miles with zero issues (one guy has gone through a couple of alternators and one belt tensioner)....I am very impressed with these stats......

[shifty]

I've been reading a lot about using a newer model engine...Looks like you're screwed no matter which route you take. If you don't hafta fab a new tranny x-member, you gotta fab out some new engine mounts. I really wish there was a bolt-in solution to move to the newer fuel injected engines. I can only imagine what kind of wicked gas mileage I would get from one of the Vortec engines...especially know my shortstep weights almost half of what a newer 1500 extra cab or crew cab does.

[Tim240Z]

Apart from the exhaust manifold and the driveshaft length, the L31 is as drop in as you can get....
Tim

[shifty]

Couldn't you just drop some shorties headers on that thing and get by OK? I mean, stock manifolds blow nads anyway....

You didn't hafta do any fabrication for the tranny?!

Is it auto or manual? hmmm....wonder what gas mileage is like and what kinda tranny you can slap on that bad boy...

[Tim240Z]

I used the headers that I had on my 350 that I took out of there. like I said above I wanted to keep the OEM manifolds to keep all the EGR stuff, but 'Oh Well'!
No problem with the auto 4 speed (4L60E), but there just wasn't enough tunnel 'hump' to push it back like I had hoped.....I'm hoping for 18-20 mpg.

The only thing I had to do to mount the tranny was drill a hole in the X-member for the tranny mount (TH350 has 2 bolts, the 4L60E only has one stud that connects it to the X-member.)

[shifty]

You got a tall hump or short hump? (sorry for all the ?'s)

[Tim240Z]

Originally Posted by shifty

You got a tall hump or short hump? (sorry for all the ?'s)

Ahhhh....dunno, please explain?

[shifty]

your transmisson hump in your truck, is it one of the short ones or a tall one? or do you know?

[Tim240Z]

http://67-72chevytrucks.com/vboard/s....php3?t=148092

[stickshift_or_walk]

Tim,

That's a low hump cab. If it doesn't bolt in, and is essentially part of the cab floor, it's a low-hump.

If it bolts in, it's a high-hump, which was used by GM to clear larger drivetrain components. There are several different varieties - one round hole forward for 4spd, no hole for BB/Turbo400, dual holes for tranny and transfer case levers, one hole rearward for transfer case lever on auto trannys, etc.

Randy's thread here shows several pics of the most common high-hump, the one for a 4spd manual:



This would probably give you more than enough room. Just cut the floor out using the new hump for a template and bolt it in. I used silicone to seal it up. You will need a different floormat/carpet, tho.

SSOW