I'm trying to plan out an LS swap option for an '84 Berlinetta with LG4 & 700R4. I'm trying to make a somewhat high perf budget swap. My plan currently includes:

- LQ4/9 pull complete with PCM/harness/accessories
- L92 heads (with offset rockers)
- LS3 intake
- Appropriate cam
- T-56 trans

Questions that I have:

1. Should I pull the PCM/harness with the engine or go with something like this https://sdparts.com/details/chevrole...mance/12590123 and find a separate harness/PCM from an F-body? It's not clear to me if the truck PCM can be happy with a manual trans.

2. Since I have the digital Berlinetta dash will the mileage still be correct on the dash? Is this something that is now controlled by the PCM that I'll need to have flashed with the correct VIN?

3. Would a general tear down of the short block be necessary or well advised? I'm thinking that piston rings, crank and rod bearings are a good 'might as well' job with the head and cam swap.

4. Cam suggestions? I'm looking more for great street drivability with occasional canyon driving that all out HP, as this will be one of two daily drivers.

5. Are there any pitfalls here that I'm missing, or variations to make this a better overall swap?

Thanks in advance for all the feedback!

 

If you're considering a truck engine, skip the complete pullouts that bring a premium. Instead shop for long blocks or shortblocks since you plan to swap the heads out from the start. This way you're not paying extra for stuff you wont use

Read every harness thread you can find
If you want low cost or DIY, I wrote several threads on the process of taking ANY LSx harness and tailoring it to the specific car
Any stand alone harness will skip alot of the work, but you still need to connect power and gauges, I wrote a thread about that too
If you want plug and play, PM me. I build brand new harnesses to suit

Most PCMs are fine with the manual, really the only control is in the reverse lock solenoid which is easy to defeat even without a PCM. The bigger question is if the PCM is compatible with the TB you want to run?

Your dash is not affected by the conversion. It accepts analog inputs from most of the sensors and common GM signals for the rest, which the LSx PCM is capable of providing

If there isnt anything wrong with the engine from the start, then dont bother with an overhaul. Price out a rebuild of a LSx, the days of $300 overhaul like SBCs had are gone. Couple that with modern engines lasting alot longer than older engines. 200k+ is not uncommon and most still come apart still bearing original crosshatching and minimal wear. The most I do is an oil pump on used engines which is GP for any engine swap unless there is a known problem

Cam choice is up in the air. Mild cams with big splits work great in rect port heads. Keep the lift under .600" and the valve springs will least years instead of seasons. Keep in mind LS3 topped 6.0's commonly put down 420-480RWHP through a stick, be sure the rest of the car, and driver can handle it

Pitfalls are in mods and "might as well" situations. Those turn a project into a money pit. Decide what you want from the start and stick to it. Break down the conversion into subsections and troubleshoot each before starting. Research, research, research!
Avoid parts that arent any better than stock, bandwagon sales etc. ARP rod bolts, head studs, double roller timing chains, fancy coil packs, catch cans, fancy plug wires etc

 

Pocket, thank you for spending the time for a very well-written response. I've gone through many of your wiring threads, and need to start saving off and categorizing them due to my mind getting info confused between them all. Some high points off the top of my head are:

If I want to stay with DBC then I need an LS1/2/6 TB with the red & blue 0411 PCM, correct? And it doesn't matter where said PCM comes from as It'll need to be flashed regardless and all will be made right then (if I understand that correctly).

Is there a preferred method on how to wire the AC? I'm not sure if there are benefits to having the compressor directly wired to the dash or go through the PCM, if I'm understanding that correctly. I'm amenable to either method, just looking for the most OEM like setup. This seems to fall into the 'decide what you want to do' category for me at this time but I don't fully understand the ramifications to either method. I'll be keeping mine since I live in AZ, but haven't researched/decided if sticking with the 3rd Gen stuff is easier or the 4th gen compressor would be better. My car has already had the refrigerant conversion done.

When you say that my dash is not affected, I'm assuming you're referring to my odometer question. Is that display controlled by a module in the dash that integrates the speedometer input and not resident in the PCM? I ask as I know some cars hold the mileage data in their respective ECM/PCM boxes.

Again thank you very much for the sage advice re: better than stock parts in your reply. Going off of the various "How to make a truck engine work in F-body' threads I think I'll be good with all the accessories and whatnot.

My plan was to swap in a 4th gen rear and rebuild/install an LSD. With the expected power of my engine combo are there any other drive train upgrades that 'need' to be done? This car will never see a drag strip, but maybe some autox/drivers events, but other than that I tend to drive (mostly) like a grandma during the week.

Thanks again!

 

No problem

 

If you swear on a stack of bibles to only drive like a grandma, I still wouldn't put a 4th gen rear end in it.

Why?

Zero benefits.

Absolutely zero.

None.

Zilch.

Nada.

Especially if you're going to spend even more money on it...

Instead, get an aftermarket posi (I hate clutch-type posi's, but I drag race - not sure how a Detroit True Trac would behave in autox), 28 spline aftermarket axles, an aluminum support cover (an inexpensive one from Summit is just fine), and weld the tubes (not absolutely necessary, but something you can do without great expense). Of those things, you'd have to do them ALL to the 4th gen rear, and then you'd stick out an extra inch on each side. Why bother? Just build up your 3rd gen 10-bolt.

Unless, of course, you want rear disks. In that case, get a 3rd gen disk brake rear. You can put 4th gen brakes on it. Or convert your '84 rear to disk. That extra inch bothers me enough do anything I need to avoid it.

 

So in doing more research since I first posted this, I don't think a 3rd or 4th gen rear will hold up, at best I'd be at the limit or have very little margin. I currently have rear disks, but originally thought the 4th gen was stronger than the one I have, I mean they came with much more powerful engines, right? Apparently not so.

Only problem is that tough rear ends are so expensive to be reliable at that power level. I'm not really that interested in drag racing, so while I see that as a stressing case (that I won't be using frequently or perhaps at all) I don't want to preclude myself from ever operating there. That said, I'm okay with margin for seldom use, which is different than margin for frequent use. I'm very open to suggestions on ways to go as I have been doing some research but alas have to experience of my own. My goals are to 1) have a reliable rear end assembly for spirited canyon trips, daily driving duties, and (maybe) and occasional hard launch and 2) spend a for what I need and not more.

Right now I'm looking at 12 bolt, 8.8 and 9 rears and utilizing something like Currie's torque arm mount.

That all being said, I'm not sure if your comment about building up the rear I have as you mentioned was as a solution to the motor/trans combo I was planning on using or just as a comp to the 4th gen I had mentioned in previous posts.

Thanks for you input, it is greatly appreciated.

 

Since you mentioned the ARP rod bolts, what is the safe RPM limit for the lq4/9 blocks? There are plenty of builds on this forum last show a lot of motor work for really screaming engines, but what is the limit where this needs to be done? I'm not looking for peak HP as much as a flat, monstrous torque curve.