Engine mount adapter options

[glock35ipsc]

Please keep this thread specific to options available for engine mounting.

I'll start off by posting measurements and diagrams for the least expensive option: adapter plates. These plates will bolt to the LS block, and allow you to use the factory mounts that were on your SBC/BBC block, and bolt them up to the LS block.

The first diagram is a comparison of the mounting boss location on both the SBC/BBC and the LS blocks. RED is the LS mounting pattern, BLUE is the SBC/BBC pattern.

The measurements are taken from the machined bellhousing flange on the back of the block, where the transmission bolts to. From there, we measure forward to:

1] The rear bolt holes on the LS pattern, and
2] The center, or lower bolt hole of the SBC/BBC pattern.



Of the following three adapter plates in the drawing, numbers 2 and 3 are the most common.

The plates run from around $25 for 1/4" steel, up to $160 for polished aluminum. If you have access to some scrap 5/16" x 4.25" flat bar or 5/16" plate and you have a drill and a a tap & die set, they are very simple to make.

Here are the dimensions for each of the mounting configurations:



(As viewed on the drivers side of the block)


From MY experience, #2 worked best for the 73-87/91. Let me describe my original setup:

1985 GMC 1/2 ton SWB 2wd. 305/TH350C. The TH350 had a 9" tailhousing.

By using the #2 plate, all I had to do to mount the transmission (a 4L60E) was slide the trans crossmember about 2" and drill a couple holes on each side. Easy stuff.

These plates put everything in a position to where the shifter linkage was in the proper place, and the driveshaft installed without modification. I am using a mechanical clutch fan, and it sits centered front to rear, as well as up and down, within the fan shroud.

The one issue with using the #2 plates comes when you are going to use the LS's AC compressor in it's original low location. Here is the problem I ran into:



Basically, the forward ear of the adapter plate interfered with the compressor bracket. The green triangle is where the clam shell mount from the old SBC was supposed to go. I determined that moving it to the location of the red triangle would solve the problem. Then cut the excess off at the white line. Essentially, I would be modifying the #2 type plate to be just like a #3 plate.





Now everything will fit:



Then I added an extension to the engine stand so that the rubber mount would have something to bolt to:





Another option would be to add a bracket to the crossmember, and move the engine stand back about 2". Member menace121978 did this with his. He welded a piece to the crossmember. You might be able to do this with a piece of angle iron that is bolted to the crossmember as well:









Here are a few guides to use if you plan on making your own adapter plates:







Comparing the right side plate for use with and without the LS AC compressor:



Car Shop, $45.95
http://carshop.carshopinc.com/produc...id/86959/LS1GM



Swaptech multi-position plates, $99.95
http://tpiparts.net/inc/sdetail/16936



Trans Dapt through Year One, $65.95
http://www.yearone.com/serverfiles/f...hid=613AA79244



Pacific Fabrication, 4x4 crossmembers/mounts. No other info on them other than these pics: