Im switching my 68 mustang I6 to a 390 and was wondering if any c6 yoke would work? The drive shaft still works as the engine with transmission are the same length but eventually im gonna switch driveshafts just not right now. Also i have questions on the fuel line and throttle cable. Can i just get a regular v8 throttle cable for a 68 mustang even if its a small block v8? And the engine is from a 65 thunderbird so will a fuel line from the fuel pump to carb be the same as a 68s? I didnt know if i would have to order it for a 65 390 or if it even mattered.

 

Are you connecting a 390/C6 to the 7" rear? Can I watch? The 9" rear used with the 390 requires a significantly shorter driveshaft than the 200/7".

68 Mustangs did not use a throttle cable. They used a bellcrank and pushrod system. The one for manual trans and 289/302 auto is available, but not the 390/C6 throttle. You'd have to get the 289/auto throttle and relocate the kickdown arm to the spot the 390 requires, for clearance. The rest is available ready-to-use.

The stock V8 fuel line will work for you, but you'll have to use headers, the stock manifolds for a Mustang cannot be attached to the Thunderbird heads. JBA has a real nice set of Tri-Y's for the Mustang, and they will fit the Thunderbird heads. Pricey, but they actually fit.

 

i have the stock exhaust manifolds that were on it on the engine now. I have the engine sitting in the car i was waiting on mounts and finally got them. So i couldnt get the yoke from the tbird car and switch it onto my i6 driveshaft?

 

Your Thunderbird manifolds don't hit anything? Interesting. Hooking pipes to them will be interesting.

I doubt the six cylinder u joints are compatible with the Thunderbird C6 yoke. You'll need the yoke from the T'bird, and likely the driveshaft, too. You may even have to have a shaft made. Not the end of the world.

 

Its snug but no they dont hit anything. I just kept them on until i found some headers that were reasonable and held up with the motor. I think i found some long tubes but idk. How much for someone to make a driveshaft approx?

 

LOL

anyway, even if you get that hooked up, the 7" rear end will say good bye and blow to smithereens once you put the accellerator on the floor. I speak from experience with a 289 and I can only fathom what a 390 will do to it.
I hate to bear the bad news, but you'll destroy that thing.

 

I don't care to watch the hooking up of the driveshaft, but I DO want to watch the first time he nails the throttle of that 390 so I can see what breaks first, the driveshaft or the rear axle.

If you still insist on connecting the driveshaft to the C6 yoke and the driveshaft is indeed the right length, there are many assymetrical universal joint crosses available. Do some research once you find the dimensions of each cross and you can find a cross that has the C6 dimensions AND the smaller cross dimensisons. You will need the distance across the cross with the caps in place and the diameter of the caps.

If you want the driveshaft and rear axle to hold up, put an egg between your foot and the gas pedal. As long as you never mash hard enough or quickly enough on the gas pedal to break the egg, then you probably won't break the rear axle. It will be some very dull driving though.

 

Oh, you should get the yoke, but I doubt it'll fit the I6 driveshaft. Once you get the rear axle squared away, have a shaft shop make you a proper shaft. IIRC, the 67 I6 had the same size shaft as the V8, but the u-joint part will require some careful planning. A new shaft will cost $200-$300. Don't pay extra for aluminum, you don't need it.

 

Is the driveshaft the correct length or not?

 

Ok look i know that the driveshaft and the i6 rear end will be weak and im gonna change them out when i get the money to do so. I just wanted to get the driveshaft done so i can drive it for a little while. The driveshaft is the correct length just have to get a different yoke or find a driveshaft for the motor. I wouldnt get on it too hard right now anyways i would get into too much trouble around where i live and i know its not gonna be fun driving without being able to do that i just want to be able to drive the car right now.