L31 swap for my 72 K20

[The Blue Pig]

Hello! I finally made up my mind. I was at a local impound auction yesterday and purchased a 99 Suburban (was involved in an armed standoff with local law enforcement a little over a year ago). After I paid my $450, I changed one flat tire, hooked up my jump pack and it fired right up after sitting for 15 months. Anyways, I have an engine in my K20 that runs just fine, quadrajet, 350 trans, NP205. I have no real interest in performance, tire roasting, hill climbing or anything like that. Just one turn of the key, no choke, no 5 MPG, not BS. Just go, and once to speed, go in OD!

I know that this swap is becoming less and less popular, being as it's somewhat old tech and the LS swaps are the big thing now but I bought what was cheap, somewhat straight forward and available. In fact, after searching and searching for weeks, I have found that information on this project is sparse. I know that the 4L60E will necessitate the moving of the T-case back, driveshaft modification, possibly shifter/floor modifications, etc.

What I am not super clear on is:
1) I need to get the ECM flashed? And if so, what items are the items that need to be deleted for this project?
2) How does one get around the loss of a mechanical speedometer input, or can I just expect to have to buy new digital gauges? I'm not really interested in some flashy, ridiculous gauge set. Just as close to factory as possible would be my preference.
3) Everyone "claims" that this project will bolt right in, however, in my current configuration, the manifolds are like, 1/4 inch away from the engine mount bracketry. Will the engine truly fit directly in, or should I plan on putting other manifolds on before I drop it in the cradle?

Anyone who has done this, please, let me know what you experienced! This will all be a learning process but I sure don't want it to take 5 years to get done! Haha!

Thanks guys!

[hugger6933]

Ok I have not done this either but you can drop that motor in a nd bolt up to what you have. You may have to use your rams horns and have the O2 sensor bung welded into the exhaust pipe[as close to the manifold as possible. You probably don't HAVE to have the pcm flashed but you will be so much happier if you do. Any re flashing experience I've had increased both Performance and economy. I would think about LT1 wiring dot com to do the wiring[rework your factory harness] and reflash the pcm. they are one of the original companies to do that sort of thing . Or Speartech he is a great guy and does what he says he will do for the price he quotes and has it done when he says he will[John is a great guy from my dealings with him]. as far as the mounting and stuff it is just a 350 now the oil pan is not the same as the old truck neither is the flywheel if your not aware of those two facts due to the one piece rear seal that GM did us a favor on and stopped the oil leaks that had been plaguing the small block since its birth. Jim

[MARKDTN]

I agree with the above. Bolt it in in the original location with original style mounts and use the original exhaust. I would keep the Vortec serpentine system, but if you don't you can use all your old stuff.

You will want to have the PCM burned to remove VATS and probably EGR. You may want to have it set up to delete the second O2 sensor so you can get rid of the Cat. There is a lot of stuff that is on an OBD2 system that is not needed for an early retrofit.

Now, if you have a K20, what are you doing about the transfer case? A 2wd transmission won't spline to a transfer case. A 4wd 4L60E won't spline to the original case either.

[The Blue Pig]

Thanks for the replies. This is all good stuff. Hugger, those are all good points to consider. If I can get away with using stock manifolds from the burb, that's what I'll do. If not, it may get slightly complex. Concerning what you said about the oil pan and stuff, I have also heard that this swap can possibly cause interference issues with the front drive shaft and the oil pan that either necessitates a new, low profile pan or a lift. Mark, I am definitely aiming towards keeping most of the engine how it is, including the serp. system. Also, I was thinking of deleting the fan from the crank all together and running electric. Right now, after some research, I think maybe I'd like to keep EGR and MAF, get rid of the rest, including the rear O2's, VATS, etc.

As far as the T-case, from what I've read you're exactly right and I'll have to source a different tailshaft and T-case adapter/stand to make this setup work with my 205, as well as move it back, etc.

Honestly, pinning out/creating this standalone harness is what has me the most worried. I contacted Brendan at LT1Swap.com and he seems to have a wealth of knowledge on this stuff and reflashes for $75, keeping or deleting whatever you choose.

[truckster]

Rather than move the transfer case and have to lengthen/shorten drive shafts, you can move the engine forward. That will also give you a little space between the back of the engine and the firewall, and from what I understand it makes the front driveshaft clearance issue a little less of a problem. There are a lot of threads on the site - search for "Vortec swap".

I'm in the beginning stages of my Vortec swap, although I'm going with HEI and a Quadrajet. Things I know are issues: You already know you'll need an adapter to mate the trans to your transfer case, and there are a couple of ways to do that; you need to change the PS pump fittings (you should be able to move your old ones to the new pump); If you're planning on hooking up your temp gauge, the sending unit on the Vortec doesn't work with the 67-72 gauges; there's something about a bypass hose, but it's late at night and I can't remember right now.