LSX mounts to C2-C3

00fxd

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For anyone thats interested I have decided that pretty much all suppliers of of adaptor plate are copying each other, wrongly. Every adapting mount that I see advertised places the engine about 1.5 inches too far ahead. Including the Scoggins Dickey super fancy billet adaptors I bought. Th Scoggins Dickey mounts were even lasered "left" and "right" incorrectly. :mad: Once I got that figured out my engine wont work with the Scoggins Dickey clutch cross shaft bracket that is supposed to work with it. My engine fan will now be too far ahead and my driveshaft yoke is not in as deep as I like. So I look at on the net and all the common mounts have the same design. Has any one else noticed this? I have found a solution, if anyone has interest in this we can discuss it further...
Frank
 
00fxd,
I'm casually interested right now, and will be very interested in about two months. I'll be putting in an LS6 and Tremec TKO 600 in my '65 after the holidays. Right now I'm in the process of rounding up the required parts.
I have a buddy that owns a full machine shop, so if you have a drawing I could probably get the parts made for free in exchange for the drawing.

Rick
 
For anyone thats interested I have decided that pretty much all suppliers of of adaptor plate are copying each other, wrongly. Every adapting mount that I see advertised places the engine about 1.5 inches too far ahead. Including the Scoggins Dickey super fancy billet adaptors I bought. Th Scoggins Dickey mounts were even lasered "left" and "right" incorrectly. :mad: Once I got that figured out my engine wont work with the Scoggins Dickey clutch cross shaft bracket that is supposed to work with it. My engine fan will now be too far ahead and my driveshaft yoke is not in as deep as I like. So I look at on the net and all the common mounts have the same design. Has any one else noticed this? I have found a solution, if anyone has interest in this we can discuss it further...
Frank

I am all ears, an LS swap is in the near future for my 80
 
I tried 2 sets in order to find a comprimise between spacing at the front, back, and yoke position.
I would probably get these if I had to do it over again.
http://dirtydingo.com/store/America...II/IV-GM-Muscle-Car/c1_206_305_306/index.html

Hi Gary, yeh I'm still workin' on this thing. I just discovered those mounts. They were the solution I mentioned. Looks like a brand new item - just added to their website. I would prefer to not use solid mount but those would sure solve a lot of problems.
I think these trans dapt plates would also do the trick:
http://www.tdperformance.com/images/?id=5805&rsku=0
Edlebrock also makes a couple of set back choices:
http://www.summitracing.com/parts/EDL-6701/?image=large
http://www.summitracing.com/parts/EDL-6706/?image=large
I still don't understand why they say the usual plates place the engine in the stock position when they don't.
 
The 1" setback reslted in the bell housing touching the tunnel and the ROD yoke was only about 1/4" from binding. The mounts that share the center bolt from the SBC mount put the C5 exhaust manifold a little too close to the idler arm. That new mount would have allowd a comprimise.
 
The 1" set back plates will place the engine where the bell housing will mount the trans in the original location resulting in the driveshaft yoke sitting in the same spot on the trans output shaft. If the drive shaft yoke is where it was before on the trans output that means the bellhousing is in the same spot. Why the heck would it now contact the tunnel when it didn't before? I must be missing something here but I can't imagine what.
 
I went from a SBC 158 tooth housing to a BBC 621, 163 tooth housing. The setback plates seemed to put the LS engine farter back than I think the SBC was. It was impossible to reach the trans housing bolts with the setback plates.
You can see the black allen head housing bolts are flush with the firewall in this pic.
So it looks like the setback plates may set the back of the motor slightly farther than stock. In addition, I think the crank centerline may be a bit higher with respect to the mounts on the LS motors.
12clearance.jpg
 
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I went from a SBC 158 tooth housing to a BBC 621, 163 tooth housing. The setback plates seemed to put the LS engine farter back than I think the SBC was. It was impossible to reach the trans housing bolts with the setback plates.
You can see the black allen head housing bolts are flush with the firewall in this pic.
So it looks like the setback plates may set the back of the motor slightly farther than stock. In addition, I think the crank centerline may be a bit higher with respect to the mounts on the LS motors.
12clearance.jpg

Hey Gary. You probably know this stuff already but just to re-cap. In my 30 odd years of fooling with these things it has always been very easy to swap a Big Block to Small Block and vis a versa. Same frame engine mount stands, same rubber mounts. Even the same distributor. In the old days when I was an auto partsman I noticed that even the exhaust Y-pipe was the same on some applications even tho the entire engine and exhaust manifolds were different BB to SB. I know that we are dealing with a modification here but it has never mattered if swapping from a 153 tooth flywheel to a 168t with the larger bell housing the trans ALWAYS ends up on the same mounts. And the engine. The last time I had this car all apart to install the sb400 I used a 168t so I could use a larger clutch and all I could find for a bellhousing was an old 60's truck cast iron thing. Worked fine.
So if these engine mount plates are putting the engine in the orig position it seems to me that the trans should land on the same mount.
I did already consider what you speculate that the crank centerline may be higher on the LS engines but it would be easy to make the plates mount the engine lower. If not that would play havoc with the driveline alignment-trans tail shaft pointing down. I imagine some are thinking that I'm making a big deal out of this but somethings not adding up. All I see right now is all the mounting plates are wrong for some reason. :cussing:
 
I have plates that supposedly move the bellhousing mounting flange to the (near) stock location. Haven't dropped the engine in yet, I'm waiting on my damn xmember plates to be made up. They're Speedhound plates. I should be dropping the engine in early next spring and I'll let you know how things turn out.
 
I'm pretty sure most mounts raise the crank centerline. My drivelide angle at the trans yoke went from 0 degrees to about 2-3 degrees down in back. I've heard this from others too. Raising the trans any significant amount was not an option with the ROD since the shifter mechanism is really tight as is. It was easier to trim the front differential rubber bushing to raise the diff angle up about 2 degrees.
It came out less than 1 degree of opposite angles. Probably better than some stock installations and I dont have any vibration.
 
Hi Greg, looking at those speedhound plates, now that I know what to look for, I have a feeling that they will work. The incorrect plates utilise one of the 4 block mount bolts for the rubber mount bolts. The speed hound plates have 3 dedicated holes for the rubber engine mounts moving the engine back where it belongs. I assume then that the speedhound z bar mount will actually work with mount adaptors. That will be nice.
Now we need to see if you will experience the same thing as Gary with his engine being tight to the firewall. My situation will be different in that my car is a '65.
I had considered the speedhound plates as well but for convenience I had some other stuff ordered at ScogDick so I just got it all there.

Gary, good info, I planned to take good measurements on my driveline angles as well. I don't want any bad vibes either.
Frank
 
The only problem with them that I know about is you need to modify the motor mount backing plate thru holes. The reason as Trey (Speedhound) explained to me is he used a generic SBC motor mount for mock up that apparently didn't line up with other motor mounts in terms of the backing plate. I didn't see this as a huge problem, so I modified my energy suspension backing plates to work. You basically slot the thru holes. It's not noticeable and still give support to the mount. Some even question if the back plate is needed because the adapter acts like a backing plate on its own. I do have pictures on my home machine or I can take a few for you if you'd like to see. After fiddling with it, I believe the reason why the holes don't line up on the backing plate is because of the rib that is rolled into it. Trey had the plate cut to clear this, but it probably differed on the one he used for mock up. I never would have thought mounts would vary much either.

Also, in reflection of the driveline angle discussion, I never thought that the plates would raise the axle CL, but I do believe that to be true. It adds a percentage of the thickness of the plate (good ol' trig strikes again) depending on the underside angle of the mounting plane. I don't believe it is too significant (it can't be or else more people would complain of driveline problems), but should be noted and checked.
How does one check the driveline angles? I know the physical approach using an angle finder on the yoke or output/input shaft, but how do you compare them? Anyone have a good source? I've done some googling and searching, but what I found really only confused me more.
 
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I made kind of a study of C3 driveline angles a while back and have never measured an engine angle less that 3 degrees. Most are 4 degrees. Also, I don't know how cutting the rubber isolator on the diff will rotate the nose up. Cutting the rubber actually rotates the nose down.
 
I guess I wouldn't doubt your OEM engine mount angle. I only measured the driveshaft before removing it, and the diff at reinstall. I'm guessing we're striving for better geometry than the factory.
There's a rubber isolator between the front diff mount "tongue" and the frame. Cutting that down will rotate the front of the diff up. Just trying to get it as close as possible.
Someone else ran into the same problem on a conversion and rotated the diff by wallowing out the rear of the 2 horizontal front diff mount bolt holes. This allowed the diff to rotate up around the front horizontal bolt. I'll see if I can find the post tomorrow, I remember he posted pics too.
 
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Awesome. Thanks Gary. That actually made some sense for my thick skull. When you measured your angles, were you still concerned with weight on the vehicle? I assume we don't need to be concerned with that since our diff is fixed as apposed to a live axle. One more thing, did you check your horizontal angle? As in, the angle between the yoke and say, the transmission crossmember? I would assume that would effect the vibration as well.
 
It doesnt really matter if the weight is on the wheels with the fixed diff. I did try to keep the frame supported at all 4 corners and level. That way any bending in the frame would be similar to on the wheels.
No on the horizontal alignment. It's my understanding that the engine is offset to the passenger side. Just keep the trans mount in the same relative location to keep that alignment the same.
 
I agree that keeping the engine favored to one side more than the other, but I think this is more of a rotation about the axis along the crank and trans CL. I've been told, haven't seen it myself though, that the crank CL actually intersects one side of the frame, not parallel. Basically if you had the car on the lift or had the body off and were looking down, the engine/trans wouldn't be parallel to the frame. If this is true, an angle would form in the horizontal plane.

If there is an angle there from the factory, I'm sure they set up the diff to balance it. However, if the transmission is longer (or just the trans yoke is closer to the rear) this will effect the angle. Most likely increasing said angle.

I hope I'm just overthinking this, because I honestly don't have a solution.
 
I agree that keeping the engine favored to one side more than the other, but I think this is more of a rotation about the axis along the crank and trans CL. I've been told, haven't seen it myself though, that the crank CL actually intersects one side of the frame, not parallel. Basically if you had the car on the lift or had the body off and were looking down, the engine/trans wouldn't be parallel to the frame. If this is true, an angle would form in the horizontal plane.

If there is an angle there from the factory, I'm sure they set up the diff to balance it. However, if the transmission is longer (or just the trans yoke is closer to the rear) this will effect the angle. Most likely increasing said angle.

I hope I'm just overthinking this, because I honestly don't have a solution.

Years ago in another universe a fellow named Norval did a bunch of measures and stuff on all this horizontal and vertical drive angle stuff......I not so sure I understood it, really.....I just notice that any tranny seems to want to go off 'center on the cross support, but recently replacing the engine mount on the driver's side, it slipped right in place no sweat....

the car was a Munice car when I got it, and so first change was a 700....all I did was set both trannies up on the bell housings in the kitchen (not married at the time)...and measure offsets with my carpenter's framing square....and a tape....lowered the mount in back and had done with it....

going to the 200 tranny later on, I noted that it sat on the cross support like it was made there, just elongate the holes to the rear about 3/4 inch and centering was fine....height was 'same' as the 700, so I left it alone....

I do wonder about vibration though...
 
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