AMC Eagle Den Forum

The Shop => Altered Eagles => Topic started by: The Dark Side of Will on December 23, 2017, 10:36:57 PM

Title: Small block Chevy into Eagle
Post by: The Dark Side of Will on December 23, 2017, 10:36:57 PM
My dad bought an SX/4 into which some incompetent moron had swapped a 304. He found out after purchase that the list of problems with the swap was long.

He decided to swap in a small block Chevy. He had a '90's LT1 in the shed, so out it came.
He's using the Eagle TF 998 trans.
The adapter plate is laser cut from 1/2" steel plate and had some subsequent machining operations. It's used with the 0.090 thick AMC transmission shim. He drilled the AMC converter pattern into a Chevy flex plate. He made a concentricity collar to fit the outside of the Chevy flexplate pilot journal and accept the AMC converter pilot to properly locate the converter.

Here is engine weight on motor mounts with only the second revision of the engine mount plates.

(https://i.imgur.com/JqaQEjs.jpg?1)

(https://i.imgur.com/kBb6dUa.jpg?1)

(https://i.imgur.com/y2oRM8a.jpg?1)

(https://i.imgur.com/42cos4t.jpg?1)

The crossmember will not be modified.

The engine is centered between the frame rails. The crossmember mounts are offset to the right, so we have to offset the engine back to the left. That is accomplished via the spacers you see between the right mount plate and the block. The pan rails are 9/32" higher than the 258 pan rails and will have to be raised more via thicker mount plates in order to allow room for the third bolt into the block on each side. With these developmental parts, the engine mount interferes with the forward upper bolt into the block. I ignored this for the first two versions, but will have to incorporate it into the next one.

The diff mounts will be incorporated into future revisions of the engine mount brackets. They're just a little more complicated.
Title: Re: Small block Chevy into Eagle
Post by: amcfool1 on December 24, 2017, 01:57:05 AM
hey, you guys go! at latest, this being 2017, still, there cannot be more than 5, 6 maybe eight, Eagle V8 conversions out there. A gentleman from Finland actually being the most successful up to this point. A V8 into an Eagle, while keeping it an Eagle, is fiendishly difficult. The TV show Eagle with the Ford V8 doesn't count, since they took out the front diff, it's now a  2 wheel drive station wagon, cool, but not an Eagle. Hey, even getting the original 258 back into an Eagle is an adventure and a half! good luck, gz
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on December 26, 2017, 11:55:49 PM
(https://i.imgur.com/C7bTP0u.jpg?1)

What a pain in my @$$...

Modeling for the left side diff mount done. Will get the drawings ready and send to the laser cutter tomorrow.
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on February 20, 2018, 10:22:10 PM
Got the prototypes of the next revision back; I screwed up the right side plate, so I need to fix it and have it made again. However, I was able to check the spacer pucks that get the mounts off the bolt-heads on which they overlap.

(https://i.imgur.com/nKpsQeB.jpg?1)

(https://i.imgur.com/Juxw8WU.jpg?1)

(https://i.imgur.com/gjRLH76.jpg?1)

(https://i.imgur.com/4FHMVK1.jpg?1)

(https://i.imgur.com/JKif2jn.jpg?1)
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on February 25, 2018, 09:11:43 PM
With a hiccup or two, my dad and I got the mock-up diff jacked into place and the two main (ie, vertical) bolts installed.
There's so little room above the inboard bolt that we had to cut a piece of threaded rod *just* right to make a stud which we tightened into the diff housing and aimed to slip through the hole in the bracket as we raised the diff on the jack. We had to put the nut in place first and raise the stud into it because there's a boss on the block that's *right* above the nut. We were able to get it fairly snug, though.

There's a bolt boss above the oil filter that my dad wants to use to help support the snout bracket. With a couple of other bolt bosses on the side of the block, we may end up building one somewhat elaborate bracket to grab all of them.

My dad wants to do a second Chevy swap and I've talked him into using the TPI 400 that came out of his old Jaguar. That engine will have plenty of torque to motivate the car even with 2.35 gears. However, based on inspection of an old 400 bare block we have on the shelf, the intermediate bosses aren't there and the boss above the oil filter is present, but neither drilled nor tapped. I think the combined bracket will have to bridge all the way from the engine mount bolt pattern to the bolt above the oil filter.

Bottom line from today is that relative to where it's shown below, the entire diff needs to move to the left about half an inch in order for both the right side mount and snout bracket to slip into position.
Moving the diff to the left will also help immensely in terms of clearance to the block and make it a LOT easier to tighten that nut up.


(https://i.imgur.com/AiCMlXn.jpg?1)

(https://i.imgur.com/FSDfyzj.jpg?1)

(https://i.imgur.com/5g4kw20.jpg?1)
Title: Re: Small block Chevy into Eagle
Post by: eaglefreek on February 26, 2018, 05:15:28 PM
 :occasion14:
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on March 20, 2018, 07:59:08 PM
Fitted the second rev of the design last weekend. It moved the diff 1/2" to the left. It doesn't look much different in pics, so I didn't snap any.

The right side and diff snout mounts now clear the locating fixture, so the diff can be bolted flat on the flange and both fasteners tightened up all the way.

From looking at the fixture, it needs to move another 1/2" to the left and 1/2" up. I made a new rev of the drawings which moves the diff 1/2" to the left, but skipped moving it up, as that would make packaging the diff against the side of the engine + the axle tube vs. the windage tray and oil pan that much more difficult. As it is, there will be significant pan mods.

The drawings are with the laser team to cut.

Either with the current rev or the next rev or both, we'll measure where the output flanges are relative to the lower control arm pickup points on the crossmember to verify that the diff is in the right position left to right relative to the crossmember.
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on March 26, 2018, 09:12:52 PM
we'll measure where the output flanges are relative to the lower control arm pickup points on the crossmember to verify that the diff is in the right position left to right relative to the crossmember.

My dad took some rough measurements over the weekend. The diff is actually already 3/16 to 1/4" to the LEFT of centered between the lower control arm pivots. I canceled production of the next rev of the diff mount, since the diff does not need to move further to the left.

This conflicts with the mount fixture that my dad made from a TF998 case on my 4.0. What we're seeing with the disagreement between the mount fixture and the measurements to the control arm pickup points could be explained if the 258 is offset slightly to the right in the Eagle engine bay.

The mount towers on the crossmember are DEFINITELY offset to the right. I *thought* that the 258 crankshaft centerline was in the center of the engine bay, and the mount towers were only offset to accommodate the bulge on the side of the 258 block where the distributor drive and oil pump are located.
Apparently the truth is somewhere in between. I'll need to take some careful measurements of the Eagle mount brackets on my 4.0 to verify.

Our mount design centers the Chevy crankshaft in the engine bay.

Title: Re: Small block Chevy into Eagle
Post by: amarshall on March 26, 2018, 10:51:31 PM
My Eagle is in storage so I can't measure, but I'm 99% sure that the 258 is not centered in the chassis.  I believe it is slightly offset to the passenger side.  I think I've read here on the forum about that also, in one of the suspension threads about front coil springs.  Something about the factory from coils springs being mismatched to account for the different weights from side to side?
Title: Re: Small block Chevy into Eagle
Post by: vangremlin on March 27, 2018, 02:28:08 PM
My Eagle is in storage so I can't measure, but I'm 99% sure that the 258 is not centered in the chassis.  I believe it is slightly offset to the passenger side.  I think I've read here on the forum about that also, in one of the suspension threads about front coil springs.  Something about the factory from coils springs being mismatched to account for the different weights from side to side?

This is my understanding also.  We must have both read the same threads  ;D
Title: Re: Small block Chevy into Eagle
Post by: amarshall on March 27, 2018, 05:57:12 PM
I've no idea what the source of this shot is, but it is about the best straight shot of an Eagle we're likely to find.  My eyes tell me the oil pan is slightly offset to the passenger side, no more that 1" maximum.

The manifolds hang off the driver's side, and they take up space and add weight.  I can easily imagine how the engineers would slide the whole engine sideways to allow for this.  Center of mass may be on the centerline of the chassis, regardless of the engine block.

Whatever the case, I would try to center your Chevy engine in the bay.
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on March 27, 2018, 09:40:02 PM
Any leads on 3.07 ratio front differential

There are a couple on www.car-parts.com
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on April 08, 2018, 11:44:03 AM
Making progress. This is the right side mount assembly. The gold and dark blue parts are for the disco housing and the "large" non-disco housing. They'd be 1" longer for the small non-disco housing.
Once this is made and fit checked I'll be able to start on the snout bracket.

(https://i.imgur.com/6tXpvxL.jpg?1)
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on April 24, 2018, 07:41:43 PM
The right mount plate AND drop needed a little tweaking. I revised the drawings; the updated parts may be cut this week.
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on June 08, 2018, 09:13:21 PM
And here's the latest on the Chevy Eagle for my dad.

(https://i.imgur.com/FZJaiK7.jpg?1)


On revision 7, I think I have the right side mount plate figured out. I think I have 1-2 more revisions of the drop plates to tune up, but I'll get there.
My goal is to have a design that can be welded on the bench and still fit *PERFECTLY*.
Title: Re: Small block Chevy into Eagle
Post by: eaglefreek on June 09, 2018, 01:45:39 PM
Cool. Then when your done with that, make some for a LSX swap. :)
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on June 10, 2018, 07:59:44 PM
The thought has crossed my mind.

We need to see how the LT1 fits first. The LS engines have the rear face of the cylinder head much closer to the bellhousing face than a traditional Chevy. In some bodies, installing an LS with the bellhousing in the same place as a Chevy means that the LS heads hit the firewall.

So we'll need to get the Chevy installed in order to see how much further forward, if any, the LS would have to sit.
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on June 16, 2018, 09:08:54 AM
Here's one where you can see the weird angle at which AMC mounted the diff:

(https://i.imgur.com/mPc1sO7.jpg?1)
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on September 02, 2018, 08:35:35 PM
I'm still on this. I'm up to Revision 9 on the mount plate on this side. I've been making subtle tweaks that don't show up in photos, but I've finally nailed it. The slots for both drops are in exactly the right places and when the drops are clamped in place as shown above, I can run all four mount bolts in and out with my fingers, so all the important dimensions are NAILED.

The rear drop still needs some work, but I think the next update will get it. The rear drop shown above doesn't meet the mount plate correctly, but does accommodate the 15/32 transfer punch required to locate it correctly on the disco housing. I "fixed" it where it met the mount plate, but then it wouldn't match the hole in the disco housing. I updated it to correct the hole location and got close enough that I can get a 27/64 transfer punch through (barely). That gives me the exact amount I need to move it and a careful photo gets me the direction I need to move it, so I can, if not nail it exactly, get it really really close on the next rev.

I took a stab at a very rough snout bracket for the other side of the engine, and I should be able to get those parts cut this week. However, I will be on Navy duty for the next three weeks, so I won't be able to come back to it until the end of September.
Title: Re: Small block Chevy into Eagle
Post by: The Dark Side of Will on September 16, 2018, 05:58:35 PM
Got to play with the first guess diff snout bracket and drop today.

The snout drop in place. Yes, as shown it interferes with the oil filter. I've fixed that for the follow-up revision.

(https://i.imgur.com/cU2udee.jpg?1)


Some detail on the surgery required on my SWAG dimensions in order to get it to bolt down:

(https://i.imgur.com/NE2MvH3.jpg?1)


Both brackets in place, along with the transfer punch to mark how they overlap. You can see the chunk I had to take out of the upper one because my eyeball wasn't calibrated well enough when I was using a scale to lay it out in the air.

(https://i.imgur.com/WPj72KW.jpg?1)


I updated the CAD with the results of today's test fit.

(https://i.imgur.com/qUnPTG7.jpg?1)
Title: Re: Small block Chevy into Eagle
Post by: mick on May 22, 2020, 03:58:01 PM
This is great write up. i hope you are still at it. Any updates?
Title: Re: Small block Chevy into Eagle
Post by: Run-AMC on December 13, 2020, 03:52:11 PM
I’m going to bump this thread for updates as well as to request a set of the final product for my own project.

Thanks a bunch! I hope the project is running smoothly!