rabinaba

Alright, so I have a 1981 4 speed that I’m doing a resto-mod on, which includes an LS swap. I’ve never done an engine swap before, and we’re going to try to tackle it ourselves, if we can. At least the install. Tuning and such we’ll send it out for.

I’ve sourced an LS1 out of a 2004 Pontiac GTO, mated to a T56. It seems to come with all the sensors, harnesses, and ECM from what I can tell. However, it doesn’t come with the exhaust manifold…which is fine because I planned on getting headers and doing a full exhaust anyway.

What else do I need to know here? I imagine I’ll have to do some massaging to the transmission tunnel, no? Can I expect the shifter to be in the same spot/height, or will that have to be modified? Obviously, I’ll have to get engine mounts, not sure if there’s any modification I’ll need there. In terms of electrical and fuel infection, I’m not sure what I’ll need to consider there. And then lastly, I’m unsure if the hood will need to be modified/if the LS will sit higher.

This is at least what I can think of at the moment, I’m sure more things will come up as we jump into it. But if you can think of anything that I’m missing here, I’d love the help!

78vette5.3

I did a 5.3 in my 78 on the cheap but used a 700r4 instead of a manual. LS will sit lower than the stock SBS with a car plastic intake on it. Your GTO comes with a LS1 intake I believe. Engine mounts are easy, you can do solid or poly and get the SBC mounts then get LS setback adapters so you can play with position. The motor mount adapters are less than $40 don't think you need to go expensive and will bolt right in. If your going 6psd you gotta figure out the crossmember but thats it on getting the engine/tranny in. You will need a new driveshaft (I always use Dennys). Upgrade your radiator to a Champion 2 row core with 1" cores and plumb it to the LS. Heater hose will need to be blocked off or new holes drilled to get you different outlet position. On the tuning I don't mess with the stock stuff anymore and prefer the Holley Term X as you can get it running good with the handheld or laptop and most tuners know the holley stuff. The Holley will output the right signal for your Tach, get a LS1 3 wire coolant temp sensor and you can keep the stock temp gauge in the console. Throw a Cam in it Stage 1 or 2 from summit to wake it up and add easy power if you feel comfortable opening up the engine. Depending on mileage on the motor you might want to do a new oil pump Melling 295 or 296 for reliability. My LS1 oil pump died on me while driving and have a tendency to fail. I don't know anything about the manual trans side of things but at Carsile they had swap kits so I'm sure you can find what your looking for.

gearheadib

First of all you need to be mechanically inclined with a very good understanding of the way All Systems work. Yes I know my build is a twin turbo Auto build but maybe it will help.

https://www.corvetteforum.com/forums...car-build.html

ignatz

Yes and no. The centerline of the driveshaft sits higher and may create driveline vibrations with unequal angles on the universals. Something to watch out for and correct early.

78vette5.3

I was just referring to his question about the hood needing to be modified.

corvette74

Your GTO LS1 has a front sump oil pan so you are going to need to change that. Also look at the alternator mine had to be moved up to the top for clearance(06 GTO LS2).
Dale

Tranz Zam

The heater hose outlets on the LS waterpump run right into the upper control arm mount. So I blocked the factory hose outlets with a 5/8 and 3/4 freeze plug, and drilled and tapped two barbed fittings on the top of the water pump.

Other than that, they install pretty easy. Get an F-body oil pan, or one ever shallower. The clearance for the power steering is slim to none.

ignatz

Just FYI, there was a long running LS install thread here

https://www.corvetteforum.com/forums...directory.html

cagotzmann

Here is my 1978 GM LS3 swap. For you starting with a 4 speed car, the transmission cross member is not removeable, this makes transmission swaps more difficult.

1978 LS3 Swap Completed. - CorvetteForum - Chevrolet Corvette Forum Discussion

My T56 swap from auto.

T56 Magnum Install 78 Corvette. - CorvetteForum - Chevrolet Corvette Forum Discussion

427Hotrod

It'll cost you twice what you think it will usually...


JIM

4-vettes

In general, when working on old cars the above is "Sorta" Correct. It'll generally cost you at LEAST double what you originally estimated for what you knew you where doing.
THEN, It's all the collateral damage that you never foreseen. That will be another 4 times above and beyond your original estimate.
I've been in the old car hobby all my life. I am now considered old. I speak with experience.
And I wouldn't want to even begin adding up receipts for all I have done on my car! And still I have the original block! (And one really nice old car).
Best of luck to you.

Bikespace

It'd not going to cost twice what you think, unless you farm out the work. You already have the expensive bits. There are some great builds linked above.

Silver Sport Transmission can sell you clutch parts, a driveshaft, and other bits. Do you have a hydraulic clutch? That might be one complication. Or you could keep your manual clutch, if you pick an exhaust that clears the Z-bar.

This site has some useful info. I went with -03 (truck) spacing for both swaps, with some parts from ICT Billet.
https://www.ictbillet.com/swap-guide/ls-swap-guide.html

rabinaba

Oh interesting, so how am I supposed to change the crossmember? My existing one was already cut by a previous owner to allow straight pipes to pass through, so regardless I need to replace it.

rabinaba

Ahh damn I didn’t even think about the clutch. How do I determine if mine is hydraulic?

Bikespace

All 80-82 crossmembers are removeable. No issues there. Get an aftermarket one with wide notches, instead of the stock narrow holes (79 and earlier).

Do you have a functional Z-bar under the brake booster? That's a manual clutch. Go take a look.

Billy Boat headers should work with the Z-bar, but you'll have to figure out the engine-side mount for the Z-bar yourself

rabinaba

I was gonna say! I see bolts, there should be no reason I can’t remove it 😂

Got it, I’ll have to take a look when I get home. My gut tells me it’s manual, but I’ll have to confirm. Let’s hope it is, it’ll be one less thing to worry about.

Bikespace

I wouldn't say that. Have you priced headers? LS manifolds and a hydraulic clutch might be cheaper. I have the same LS7 manifolds @cagotzmann used for his swap for my 79.

rabinaba

Got it, I was actually just able to confirm I have a Z bar, so looks to be a manual clutch. I haven’t priced out heads yet, but they do seem to be expensive (those Billy Boats are like $1500). I’ll have to do some more digging to see what will and won’t work there, but this is a start at least.

TommyFox

Do yo have a budget set?

rabinaba

You mean the budget I blew passed when I decided to buy an engine and tranny? 😂

But in all seriousness, yes and no. I’m currently trying to price everything out to see what it’s all going to cost, roughly. From there I’m going to decide where I can “cut corners” and where the money absolutely needs to be spent. $1500 headers aren’t out of the question, but at the same time I feel like there should be less expensive options out there. If I’m wrong, $1500 it is.