question on steering boxes and leaf springs

[Ed Dorey]

I have a 78 aspen v8 and a 80 volare /6. Are the steering boxes and leaf springs the same. And will the power steering pump be the same. Just wondering what I need to switch when I swap in the v8 and the 8 1/4 into the /6 car

 

[Oldiron440]

Unless you have swap motor mounts you will need to change the K frame and use the V8 K frame.

 

[BudW]

This part of the P/S pump is the same.
The pulley (diameter and offset), the can, as well as the brackets will be different.

Some year /6 P/S pumps create less pump pressure (lighter car, less HP engine) – but I don’t recall the year frames. The reason I bring this up is some people prefer to have less power assist, and swap in a /6 pump for their V8. It doesn’t bother me, either way.

Once the pump is off car, the brackets can be swapped over. With brackets removed, there is a large nut (for pressure hose), that can be unscrewed. Once that is done, the can slides off. I would replace the can seals (large O-ring) for any P/S pump that has been removed from the car – for that is a very likely source of a P/S leak (or potential leak).


The steering gear are the same regardless of engine size. The /6 gears are fairly easy to change. V8’s with 3 cats – not so much.


The rear leaf springs will all interchange between all (’76-89) FMJ body’s – but there is a bunch of different spring rates. To make it easier, I use 4-leaf and 5-leaf springs (but there are variations between each type). 5-leaf springs are used in station wagons, police and vehicles with towing package – but not true in all cases.

The 8¼” will swap in place of most 7¼” - as long as you also have the shorter propeller shaft to go along with it (going by memory, but I “believe the 8¼” uses a 1.6” shorter propeller shaft).

The first couple of year 7¼” differentials used 2½” diameter tubes (instead of 3”) and the ISO-Clamps have different U-bolt spacing to accommodate the tube size difference. A huge majority of FMJ 7¼” differentials use the large tube (3” diameter) – so shock plates/ISO-clamps will interchange.

IF you glance at the differential tubes – where they are pressed into/welded into the carrier housing, the large tube 7¼” neck down, noticeably. Matter of fact, if you find any Chrysler differential that tubes neck down before they go into the carrier – it will be a 7¼” differential.


Personally: if you are going to have the differential out of the car – I highly recommend tossing the ISO-clamp system and either use an older Chrysler shock plate or use a kit from FFI. The car will feel and handle so much better. Also, the ISO-clamp is a weak link – that when it breaks – you will have to get car towed (tire touching rear inner fender and leaf spring will be touching the ground.
BudW

 

[BudW]

Unless you have swap motor mounts you will need to change the K frame and use the V8 K frame.

Yep, the V8 and /6 K-frames are different.

I might recommend you remove K-frame with engine/transmission still attached – and transfer it over as an assembly. It might even make the swap faster.

There is a company who makes V8 to /6 conversion engine mounts – but if you already have everything, I think it be faster, better and cheaper to use what you already have.


One other thing, the propeller shaft lengths are different between 2-doors and 4-door/wagon cars.
BudW

 

[Ed Dorey]

Thanks so much. I planned on rebuilding the k member from the v8 car before I put it into the /6 one. That way all steering and suspension will be fresh. The 318 is currently on a stand waiting for a stroker conversion from SCAT. I have people wanting some of the extras parts left over and wasn't sure exactly what ones I would need to keep.

 

[BudW]

My goal (once I get more parts located), is to drop a big block into my ’86 Fifth Ave (for fun, not for racing). I have a spare loaded V8 K-frame and my plan is to rebuild and paint the K-frame/suspension, drop engine/transmission onto it. Raise body up, roll the old 318/K-frame out from under the body. Roll other engine/K-frame over and drop body down on top of it.
Makes for a fairly easy swap – well, maybe “fairly easy” might be tad too kind, in my case - but a lot better if doing the work solo.
In my case, the front end work needs done, as well - so mul


If you are going to be racing it, or driving it hard like I’ll be doing – I highly recommend to get old K-frame welded up really well and check for cracks, before painting.
BudW

 

[Oldiron440]

Bud W,
The C body oil pan and pickup are needed for the swap.
If you're using HP manifolds or headers I would plan on doing test fit's before painting engine compartment.

 

[Ed Dorey]

this may be a silly question but do I need to undo the upper control arms before I drop the k member or does it all come out as a unit

 

[DCAspen]

Unbolt the upper ball joint

 

[BudW]

do I need to undo the upper control arms before I drop the k member or does it all come out as a unit?

A person will need to unbolt both upper control arm bolts (by frame rail) as well as the two brackets the upper control arm and shocks attach to. The bracket sits over the top of frame rail about ½” (on each side).
If a person could unbolt the bracket(s) from K-frame with upper control arm still attached (but shocks removed) – that would be great – but the extra labor to do so, and frustration on trying to reach those bracket bolts do not make it a worthwhile method.

I can take some pictures of what I mean, if I can get home from work while it is still light out (fingers crossed).

So to answer your question, the K-frame can be removed as an assembly – with exception of upper control arm bolts and upper K-frame brackets.
Once dropped down, a person can reattach both brackets, install some large bolts (in place of the upper control arm adjustment bolts) and then you can wheel your K-frame with engine still attached (if applicable) around in your shop (or outside, or whatever) using existing tires/wheels.

My spare K-frame is currently outside in that condition, outside, with a pair of snowflake wheels and bald tires.

The C body oil pan and pickup are needed for the swap.
If you're using HP manifolds or headers I would plan on doing test fit's

The C-body oil pan/pickup is needed for a big block A-body install. I happen to have an extra one (187) for my ”V”-code ‘70 300/H (if needed).
An FMJ will use a normal big block oil pan and I’m almost certain (but not 100%) that the larger 6 quart B/E-body pan will fit, as well.

In my case, I will be making a mock-up for that, for exhaust and a lot of other things, before making the swap. I even have a corner of my garage there full of different year and body big block HP manifolds, pans and other things to try out.
I even have a pair of repop Max Wedge exhaust manifolds to try – but I just don’t think those will fit.
BudW

 

[Oldiron440]

Thats the oil pan I used, C body.

 

[Duke5A]

Lots of good information in this thread. Only things I could add that haven't been mentioned in regards to swapping a big block are: test fit the block with the oil pump and filter in place and modify the tunnel sheet metal.

I had my motor in and out at least a dozen times trimming the K for oil pump/filter clearance. Once it's in, spin the filter on and off too.

The tunnel where it meets the firewall there is a considerable lip that will interfere with bell housing bolt access. Slice it in three or four areas and hammer flush with the firewall.