Unless it's your daily driver you are going to drive a lot, you will never recoup the cost of any modern engine conversion in gas savings. Besides, as others said, The V8 is a defining feature of the Corvette. There's nothing like the sound of an old school cammed up V8 shaking away with a big throaty exhaust on it. I can't tell you how many people came up to me and asked what was in my 80 Corvette just from the sound. Besides, with careful tuning and an overdrive tranny you can easily get these cars in the 20's for mileage. My 406 with the 700R4 got 22 mpg on the highway in the 80. It probably won't be that good with the 4.11 gears in the 75 Vert.

 

Go with a 5 or 6 speed ,it would be perfect for you.I put one in my car and it made a huge differents in gas mileage.

 

funny that you mention that - I'm planning on putting a diesel in my DD.... of course, My DD is a Hummer H3 that has gotten as bad as 12 mpg - so doubling or even better the mpg is possible with the 4BT that I'm planning to put in it.

 

The way I see it a Corvette is just a big model kit to play with in the garage.. all you really need is a late model parts car like this...

 

Mariobro,

I have a C3 (1981) and have the very issues with no power and a gas sucker. In fact is worse with the original TH350 auto transmission.
I have been trying get info, research etc into the 3.6L v6 also. The newer 2016-2018 3.6L are putting out about 342hp and yes get 30mpg hwy with a heavier vehicle.
I will try to get back with you with any information that I can dig up. And I’d appreciate you doing the same.

Thanks

 

I can’t answer for mariobro but I looked at LS1 (97-02 Camaro/Trans Am) swaps first. But a good engine with less than 100k miles goes for $6400-7000 with a T56 transmission. It’s and $1500 less with the 4 speed auto. That puts them out of my league. You can find the newer 3.6’s for $1300-3000. That was my main interest in the 6 vs 8.

 

I wonder if he ever did the v6 swap. That was
6 years ago. 🤔

 

Not a bad thread to resurrect ...

When I look at my warmed over L82 that might eek out 300 HP on a good day (while getting 12 MPG), I can't help but be tempted by these 320+ HP pullouts that can be had for < 2k.

 

I was half way through this thread before I realized how old it is! LOL!
Scott

 

Same here! I didn’t even look at the dates. Sorry guys.
But I’m still in the same position.
I have a 1981corvette. I’ve redone the interior, exterior and put in a sweet stereo with kickr. The original engine and transmission still sits there purring nicely. Numbers matching. The transmission is starting to slip just a bit into 3rd when I’m pushing it hard trying to keep that 1.5L turbo in sight. And I’m thinking, this just ain’t right! This is an American icon...... so I’m just waving at those kids in their Ford Focus and Honda Civics until I can add some muscle and make us vette folks proud when I whip a 4 banger!

 

How much did you have to pay for the parts car if you don’t mind me asking?

 

blasphemy

 

Wild idea! (I know this is an old thread...but wild ideas never die)

I also have a LLT 3.6 with an aisin 6 speed manual in my CTS. I love it, but I would never consider putting it an old school corvette. It will get 30mpg in a 4000 lb car, but only at 60 mph and 2000 rpm And it will barely pull the car in 6th gear at that speed. It quickly drops to 25-24mpg at 70-75mph cruising speeds. It's just not enough torque. Even an LS6 will get similar mpg at those speeds. I have seen many of them get 26-28mpg babying it. And don't think I get much better around town, 19 for my 3.6, 16 for my friends LS6. My car is just begging for more torque, or dropping 600 lbs would certainly make that little engine run better.

But it would be just as much trouble, and maybe just as costly as doing a LS1 or LS6. A stock LS1 with 6 speed can get you 30 mpg, or near it, and have way more torque.

Then you have the exhaust sound issue. I had to change the exhaust in my Caddy 'cause it was too quiet, (dead silent). Haven't heard too many 3.6 Camaros that I liked the sound of, whatever exhaust they had. With the right exhaust on it it can sound mean, but then it sounds like a Porsche 911 with the sport exhaust, and that was way too loud. After too much experimentation I got mine to purr nicely, but it is just not a Corvette type of sound, in any of the variations I have heard.

The LS6 is such a sweet LS motor even the twin turbo 3.6 can hardly beat it on hp or mpg. (Now that would really be a complicated install !)
I have given serious thought and planning on what it would take to put an LS6 in my CTS, it's very do-able, but I decided the $10k just ain't worth it for my daily driver.

OTOH I just dropped plenty on a 454 LS6 for my Vette. I know of 2 guys getting 18 hwy with a motor like that, (Mine won't but they have F.I and 6 speed.)

Torque rules!
My CTS has a 4:15 1st gear and a 3.42 in the rear. About double the 2.20 1st gear / 3.23 rear in my Vette!

I'll just have to dream about what the 454 would run like with a deep 1st gear of a 6 speed and a 3.70 in the back!!!. Aren't they like 3.5?

 

Do any of us ever recoup the money we put in to our cars.

 

No, we don’t. But that’s love right? You put more in that you get out.

3.6L and it’s sound..... now that’s something I hadn’t thought of. And yes, an American muscle icon simply MUST sound as bad as folks think it should. Imagine me, pulling up at that traffic light next to that turbo 4 banger, I’m ready for it this time cause I’ve got that bad a$$ 3.6L with that single turbo (don’t think double turbo would fit) only to have the young guys next to me laughing their bones off listening to my bad boy sounding like a singer sewing machine!

So...... it’s back to the LS1 and either an auto or that sweet t56 6 speed transmission. And I know those can sound like Simba chasing off those hyenas!

Thanks guys for putting me back in the straight and narrow. Not sure what that ever really meant but that’s what my dad would say before he shredded skin with that big leather strap.

 

Plan B:
(81s have airplane gearing don't they? my friends 82 does) Dump the restrictive crossfire, add some decent heads, decent cam, more compression, 5 or 6 speed and some 3.70 gears. It'll run real well and get over 20 mpg. Probably low 13's too. 350-380 Hp is all you need. And some pipes for that rumble! F.I. conversion if you just must. Waaay less than an LS conversion.

 

Hey leigh1322,

I’ve thought of this as well. My brother is a master mechanic who has gone into sales. So he’s working 10-12 hour days. He told me exactly what heads, cam and headers etc that I’d need. And he said the same that I could expect to double the stock 190hp. My 81 didn’t have the crossfire injection, that’s the 82. But yeah I’d want a Fitech efi for the easy starting, smooth starts and better mpg. Do the later model C3’s have a 4 bolt main?

But you make a great point and I need to get $ numbers from my vette mechanic on just what you say. And to get a T56 6 speed would be fantastic.

Thanks for your input

 

Why not get a 5.3? They are cheap. Seen some crazy HP out of them when boosted.

 

I got 26mpg on a road trip in my 07 Z06. 505HP car getting 26mpg. Who would have thunk it....

 

The posts you are answering are 6 years old.

Might be time to start a new thread.