View Full Version : six cylinder to V8 switch

10-31-2006, 10:44 PM
Hi, I'm new to boards so, I'm not sure if this is in the right place but my situation is me and my dad are restoring a 73 Javelin for me and we purchased two for $1200 and the one is a six cylinder and the other is a 360 and since the six cylinder is a rust free body we want to use it but with the 360 from the other carcass so, we were wondering how much, if any, of the front suspension needs changed to accomadate the V8 into the sixcylinder car?
thanks for any help you can give,
Danny R.

Big Bad AMX
11-07-2006, 08:37 PM
I believe you'll need to swap the front springs, get new V-8 shocks, swap the sway bar and V-8 front cross member. Also the rear end and driveshaft, maybe the tranny crossmember too.


11-07-2006, 09:55 PM
Thanks, I was beginning to think noone would answer.... :o ...is there a place where I can get the driveshaft? I have one but it's in absolutely horrid condition?

Big Bad AMX
11-07-2006, 10:10 PM
I think I'd look into having one made. It may be easier than trying to locate and ship one. At least that's another option. But if you want a used/original one for some reason you might want to contact American Parts Depot. If I remember right they are in Ohio.


11-08-2006, 04:23 PM
yeah we're trying to get by as cheap as we can, like, get the basic components to have the car running and look good then mabey later upgrade some stuff like, I don't have a posi unit and probably won't until well and after I have been driving the car for awhile...a used one would probably be cheaper right?...

11-08-2006, 06:31 PM
Yes if you find it local. Like BBA said shipping and cost of used one prolly cost more than having one made. IMHO

11-09-2006, 10:29 AM
If the Javelin with the 360 is an SST it should have a Dana posi in it. It would probably have a 2:87 stock rear gear with a 140 mph speedo, right? I'm sure about a 71 but not about the 73.

11-09-2006, 07:55 PM
...it has the ralley pack gauges, the 360 and 2.87 gears but I don't think it's a posi?... it doesn't have any trim that says SST?

Big Bad AMX
11-10-2006, 11:22 PM
Just an FYI: The SST package was an interior upgrade, there weren't any mechanical or performance upgrades included in the SST option.

The reason for swapping out the rear-ends is simply because the V-8 rear-end is bigger and stronger than the 6-cylinder rear-end. It doesn't matter if both are open rear-ends or if the V-8 unit is a posi or not.

The ratios would be 2.87 or 3.31 in 6-cylinder, 2.87 or 3.15 in V-8 automatic or a 3.54 with a 4-speed.


11-11-2006, 10:40 AM
The following things for a swap out is needed for the a swap from a 6 to a V-8.
You will need to replace the cross member for the V-8. Along with this you will have to change the springs and other front end coponents. The reason for this is because AMC used different spring rates for the 6 in comparision to the V-8. Since the motor (V-8) weighs more you will need the stronger rate springs, upper and lower control arms, etc.
The rear end will need to changed also to the Model 20 rear. The 6 rearend is too small to handle the torque of the 8. Along with this, you will need to change the rear springs. I believe that the 6 springs are a 4 leaf variety and the 8 are 5 leaf. If you are using a used set of rear springs, have them check to make sure that they still have the proper arc to them. After 30 years, the springs will sag and become inverted.
The SST option was done away with in 72 or 73. AMC put the so called SST package on all of the cars starting with 72 or 73 model cars. So the basic model Javelin was the SST package of previous years. This was done to cut costs for AMC and the trim level went from 3 down to 2.
As far as rearends again are concerned- All Javelins from 68-74 came with various ratios open rearends. The posi was an option that ran extra. Most Javelins had open rearends including all trim levels and again this was standard issue for the cars. The buyer could optioned for the close rearends in differing rearends ratios with the 3:54-1 being the more popular choice.

12-26-2006, 12:28 PM
the SST became the base in 73,