1968 GT Fastback -390 install

Chinoz71 · Apr 23, 2018

Hello All,
Just joined the site. Glad to be here. Just bought a 1968 GT fastback J code.

I have a question about installing a 390 in my new 68 GT. The car came with no engine or trans but was originally equipped with a 302 4 speed. I bought a 4 speed top loader trans and i have a newly rebuilt 1970 390 truck motor with adjustable rockers and Edelbrock 2106 cam kit, Edelbrock 2105 intake and Edelbrock 1406 Carb that was going in a 1973 pickup that I sold.
My question is, what is needed to make this engine work in the 68 mustang other than the obvious motor mounts. I know that in 68 some GT's had 390's but is this engine in its current state a good match for this car? Ideas? Recommendations? Video link below.

Thanks!

View: https://youtu.be/JJQimRlOI5w

WORTH · Apr 24, 2018

In stock form, you can boil the tires off a 68 Mustang with a 200 six. Now add a couple hundred HP and a few hundred pounds to the nose and it will melt tires by breathing on the pedal. So it all depends on what you are after. Ideally that car should have a built 289-351 windsor, for FUN the 390 is more insane.

that being said I'd do it in a heartbeat. But if you've never done it before they'll be a learning curve on the road.

Just curious, how old are you and what do you intend to do with this car?

Chinoz71 · Apr 24, 2018

Hi Worth. Thanks for the reply. Im in my mid 40's and I remember a time when you could actually see a fastback daily driver on the street. I've always loved the styling of 67-68 fastbacks more so than any other year. My car was originally Highlland Green. I would like to go back to stock form with a little more oomph!

WORTH · Apr 25, 2018

It will definitely be fun with the 390. I had a '69 Mach with the 428, had a blast with it, just could never get it to hook up good off the line. But it was damn right nasty once you got it going 30. Oh, and you couldn't breath on the throttle in the rain or she'd turn around and head home.

Neuron · Apr 28, 2018

Had a '67 390 GTA, real torquey(mostly stock) but down on HP. In a hard corner you could actually make the front tires smoke(Boss 429 did the same thing).396 Camaro's would blow my doors off, should had a 427/429. My '70 Cleveland 4-bbl. was actually slightly faster and handled much better. I will never forget trying to change the spark plugs on the 390 with air tubes blocking you and the Cleveland wasn't much better.

Chinoz71 · Apr 28, 2018

Neuron said:
Had a '67 390 GTA, real torquey(mostly stock) but down on HP. In a hard corner you could actually make the front tires smoke(Boss 429 did the same thing).396 Camaro's would blow my doors off, should had a 427/429. My '70 Cleveland 4-bbl. was actually slightly faster and handled much better. I will never forget trying to change the spark plugs on the 390 with air tubes blocking you and the Cleveland wasn't much better.

Nice! Ive been hearing exactly what you are saying from others as well. It almost seems like the ideal engines for these older mustangs are actually the small blocks. Maybe i should go back to the 302 or even 351 windsor. My car is a GT and it is supposed to have heavy duty suspension. I have yet to figure out what is different from the standard suspension. Maybe the HD suspension helps with the 390? Thanks for your reply!

GOvert · May 15, 2018

The truck engines may have the exhaust manifolds that are shaped like rectangles. The 1967 Mustang manifolds are uniquely shaped and mount on a diagonal bolt pattern

horse sence · May 15, 2018

You need the mustang /cougar exhaust manifolds ,truck manifolds will not work . You also need the GT heads because they have a different bolt pattern than the truck or standard 390. A different intake manifold ,a good cam like a comp cams 280 H and a set of hooker headers and that 390 will roast the tires . The down side is ,fuel milage ,front end weight,and fitting that 390 in ,the headers will make it even more fun

scaraj · May 23, 2018

There are other little issues you may run into. The front sway bar may need to be changed (or at least spacers added behind the brackets) so it doesn't rub against the oil filter. Front coil springs rated for the extra weight of the FE. And generally, big block Mustangs
had reinforced shock towers to handle the extra weight.

zookeeper · Jun 9, 2018

WORTH said:
In stock form, you can boil the tires off a 68 Mustang with a 200 six. Now add a couple hundred HP and a few hundred pounds to the nose and it will melt tires by breathing on the pedal. So it all depends on what you are after. Ideally that car should have a built 289-351 windsor, for FUN the 390 is more insane.

that being said I'd do it in a heartbeat. But if you've never done it before they'll be a learning curve on the road.

Just curious, how old are you and what do you intend to do with this car?

You can? I'm going to have to throw the BS flag on that. Even with the worst bias-ply tires, I doubt even a decent one-legged burnout is possible with a stock 200 six in an early Mustang. I've driven more than a few, so maybe I'm wrong. In fact, even with a stock 289/2bbl, my '68 wouldn't boil the tires. Chirp, yes. Spin, no. In fact it ran 17.76 @ 77mph in the 1/4. Not exactly face-melting acceleration. Same with the 390, time has moved on and there are MUCH better choices than an FE big block for an early Mustang. Ask anyone who's ever attempted to change plugs how they like it. Not to mention the fact they were (and still are) dogs in the power department. I hate to be the bearer of such bad news, but trust me when I say you'll be MUCH happier with a big-inch Windsor. 400+ ci Windsors are cheap, fit nicely and make a whole lot more power and torque than the 390 ever dreamed of. Don't say I didn't warn you...

horse sence · Jun 13, 2018

I ran a 390 in my 78 f150 prerunner for a couple of years ,10 to 1 compression ,edlebrok intake ,650 holley ,and a 280 h comp cam , i ported the heads ,it would roast the tires dirt or pavement . I pulled it and replaced that with a fuel injected 5.0 and put the 390 in a 67 fairlane ,it would also roast tne tires . I sold the fairlane to a guy that drag raced it for years ,dont under estimate a 390 with a few bolt ons and a little porting. With all this said ,i would go with a small block ,weight to horse power ,and handling is way better

GOvert · Jun 18, 2018

If you could just lighten it up a bit. The 4 bbl cast iron intake was 80 + pounds on the stock 390's and relocate the battery to the trunk would be a start. I don't recall the heads being too heavy, but aluminum would be nice.

WORTH · Jun 22, 2018

zookeeper said:
You can? I'm going to have to throw the BS flag on that. Even with the worst bias-ply tires, I doubt even a decent one-legged burnout is possible with a stock 200 six in an early Mustang. I've driven more than a few, so maybe I'm wrong. In fact, even with a stock 289/2bbl, my '68 wouldn't boil the tires. Chirp, yes. Spin, no. In fact it ran 17.76 @ 77mph in the 1/4. Not exactly face-melting acceleration. Same with the 390, time has moved on and there are MUCH better choices than an FE big block for an early Mustang. Ask anyone who's ever attempted to change plugs how they like it. Not to mention the fact they were (and still are) dogs in the power department. I hate to be the bearer of such bad news, but trust me when I say you'll be MUCH happier with a big-inch Windsor. 400+ ci Windsors are cheap, fit nicely and make a whole lot more power and torque than the 390 ever dreamed of. Don't say I didn't warn you...

Slight exaggeration, but was easy to spin tire in my '65 6cyl vert on a wet road, or starting on a turn. My point was they are too light for a big block if you are just out to have fun. You can make these things fun to drive with a 289-351 windsor, cheap and easy. IF you're just trying to boil tires put a big block in it. I had a '69 428 that was a POS as a daily driver. Had way more fun in my small blocks. And if you keep your foot out of it, they get pretty good mileage.

WORTH · Jun 22, 2018

GOvert said:
If you could just lighten it up a bit. The 4 bbl cast iron intake was 80 + pounds on the stock 390's and relocate the battery to the trunk would be a start. I don't recall the heads being too heavy, but aluminum would be nice.

I have a 390 in my '66 F100 project, weight isn't an issue there.

ricky50 · Sep 7, 2020

I was wondering if fuel injection is that much better than having the old carburetor as I am still years from starting my project.

Neuron · Sep 8, 2020

ricky50 said:
I was wondering if fuel injection is that much better than having the old carburetor as I am still years from starting my project.

I loved my carb's in the day, but that day is long gone.Driveability, economy, ease of tuning, and easy to install. A bit more cost though from what I see. For a show car/garage queen carb OK for me anyway.

1968 GT Fastback -390 install

Chinoz71

Member

WORTH

Chinoz71

Member

WORTH

Neuron

Chinoz71

Member

GOvert

horse sence

scaraj

Member

zookeeper

horse sence

GOvert

WORTH

WORTH

ricky50

Neuron

Similar threads

1968 GT Fastback -390 install

Member

Member

Member

Member

Similar threads

Privacy & Transparency

Privacy & Transparency