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  • October 16, 2018, 11:51:50 PM

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Author Topic: Small block Chevy into Eagle  (Read 1660 times)

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Offline The Dark Side of Will

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Small block Chevy into Eagle
« 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.









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.
« Last Edit: December 23, 2017, 10:38:00 PM by The Dark Side of Will »

Online amcfool1

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Re: Small block Chevy into Eagle
« Reply #1 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

Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #2 on: December 26, 2017, 11:55:49 PM »


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.

Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #3 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.










Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #4 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.






« Last Edit: February 25, 2018, 09:16:54 PM by The Dark Side of Will »

Offline eaglefreek

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Re: Small block Chevy into Eagle
« Reply #5 on: February 26, 2018, 05:15:28 PM »
 :occasion14:
1986 AMC Eagle Wagon 4.2L/4.0L head, AW4,NP242, Chrysler 8.25" rear.
1981 AMC Eagle Wagon As Seen On TV  Lost In Transmission


 

"I know he'd be a poorer man, if he never saw an eagle fly,
Rocky mountain high"  John Denver
Click for Fayetteville,TN Forecast" border="0" height="100" width="150

Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #6 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.

Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #7 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.


Offline amarshall

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Re: Small block Chevy into Eagle
« Reply #8 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?
Wanted:  More time to work on my Eagle!

1988 Eagle Wagon - Overlander Build
http://forums.amceaglesden.com/index.php?topic=45852.0

Online vangremlin

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Re: Small block Chevy into Eagle
« Reply #9 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
1981 Kammback 258 - "Pepe"
1980 Coupe 258 - "Ginger
1972 Gremlin X 304
1978 Gremlin 4 cyl 121 - sold
1964 TBird 390 - sold

Offline amarshall

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Re: Small block Chevy into Eagle
« Reply #10 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.
Wanted:  More time to work on my Eagle!

1988 Eagle Wagon - Overlander Build
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Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #11 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

Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #12 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.


Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #13 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.

Offline The Dark Side of Will

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Re: Small block Chevy into Eagle
« Reply #14 on: June 08, 2018, 09:13:21 PM »
And here's the latest on the Chevy Eagle for my dad.




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*.