How to shoehorn a 1983 258 into a 1970 Hornet (long)

[Tom Jennings <tomj@xxxxxxx>]

In short, it's not a drop-in. I got it to fit perfectly, but it
requires a bit of care.

I've taken photos, it'll be some weeks probably before I put the
page up, but basically the problem is two-fold: in 70/71 there is
a built-out box in the cowl/firewall for the wiper motor that
lives precisely where the valve cover desires to be.  Two, the
head is either larger or positioned further back on the newer
motor.  Third, I think someone on this list pointed out that the
1981?-up motor is 1/4" taller.  Oops that's three-fold, so sue me.

That's with the motor mounts dropped into the stock location on a
six-cylinder front crossmember. There are two sets of motor-mount
brackets for the six, that position the mounts forward or
backwards; I used the right set (I have both).

The back two head bolts live UNDERNEATH the wiper motor box, and
the rear of the head casting is about 1/4" from the vertical part
of the firewall. It touches the brake lines that happen to run
along the firewall there.  (Ruining my perfectly-formed steel
brake lines in the stock location.)

The cast aluminum (after market) valve cover for the plastic-cover
sixes will NOT fit because of all this. Flat out ain't gonna
happen.  No clearancing of the valve cover short of extraordinary
will make this fit, I'm fairly sure it can't be done. No way I'm
chopping the chassis up.


So I moved the engine forward exactly one inch. It's suprisingly
easy.  I still have nearly an inch clearance between oilpan and
crossmember. Drive shaft is now 1" short but I can deal with that.

I hoisted the motor, took off the front mounts and brackets,
redrilled the x-member pads. Easy!

I had to move the already-modified trans mount forward an inch;
this left it hanging over the "shelf" on the rear x-member, so I
had to add a 3/16" support underneath. Strength is fine.

I haven't put the radiator in yet. I had a clutch-fan installed,
but that will probably run into the fins. In the super-short-term
I'll put a regular crap fan on for checkout if I have to, but I
may just space the radiator forward a matching inch. I want to
eventually go the electric fan route.

Even with the shifted-forward engine, the notch I made in the back
of the valve cover is still required! There's a ton of room
between the trans body and the hump, as you'd expect from shifting
it all forward, but I can just get my fingers between the head and
the firewall. And I am quite certain that the rear mount is at the
right height (jacking the tailshaft up to the sheetmetal does
increase clearance but not to what you'd think) so it's not that.
The brake lines on the firewall now have enough clearance too.

So there is some substantial difference at the back of the block
between 1970 and 1983. I foolishly assumed they were 100%
compatible, but most definitely not. What I've got now is stable,
safe, reliable, etc but it wasn't a "drop-in".

It's a little strange. Working from the rear, the '72 driveshaft
and '72 torqueflite are properly positioned, and have "the usual"
amount of hump clearance (about 1" all around) and the bellhousing
breaks at the right place (more or less flush with the firewall
vertical).  So that's all correct. (However, there is the
discrepancy of the rear trans mount; the ear is too long, I had to
cut and redrill. But I had to do this same mod to the 1975 Gremlin
(304/A998) and that was the original engine/trans/x-member, so I
think this is a red herring, the part is simply the wrong
listing.)

The distance from the rear mount to the front mounts on the 1983
motor + 1972 A904 = 1970's 232 + BW, it's just that it puts the
back of the head up against the firewall. Annoying.  It's what I
get for fooling around I guess.