motor mounting plates pics and questions



500 being bolted into a 4wd 1973gmc jimmy

i remember being told that the motor mounts need to be 5 inches forward from the stock ones and the top hole of the new mount needs to be flush with the frame rail.
in this pic you can see that the new mount is 5 3/4 inches from the stock mounting place

now i could reverse the bolts on the back of the mounting plate to gain another 1/2 inch which would give me 5 1/4 inches, would this be acceptable or not?

any ideas?


Ok...this is why I dont sell headers,engine or transmission kits ...they dont fit everything period

First thing you need to do is mock up your engine and transmission with the oil pan you intend to use on the engine
also put the engine mounts and those plates on as well.

get the engine in the engine bay and bolt the tranny to the tranny crossmember

If you can slide the transmission crossmembe fore and aft.....this is a good thing if you cant its ok but your stuck as far as engine placement goes.

  Chances are one of the bolts that holds those plates is useless as the angle of the bottom part of the cadillac mounts are set at a different angle.

unhook one of the bolts (same on both sides) and set the engine down on the rear plates (make sure the weight of the engine is on the plates.

Center the engine in the frame,make sure it isnt "nose down"

If everything is like you want it tack the front part of the engine adapter kit  "short part with the holes" at the correct angle and tack the back part to the crossmember of the truck

  Remove the engine and mark the plates from the underside with a marker or pencil or whatever then knock the tacks loose and drill them for whatever size you feel comfortable with.

If there is enough meat left in the front part of the engine mount kit you can take a die grinder and oblong the holes so the bolts line up or weld them on solid

lots of checks and rechecks to make sure everything is lined up and you might wanna stick the nose on and mock it up to see if you have enough room for a mechanical fan

  Thats the short version...if you have any questions PM me ive done quite a few swaps and have 2 different kits that I do not advertise however neither of them will work for what your doing.
In the plans tho.....I have a 70 C10 that will have a all forged 472 based powerplant

  Good luck


Active Member
Oct 14, 2004
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Click...thats the sound of flame retardent shorts going on. I have an 85 blazer that will be getting the same swap this summer. In your picture the frame mounts sticking out and the engine mounting crossmember in front of them. If you have the skills and tools think about doing it this way...remove both side mounts and the crossmember and start over. Why? Because it will get you a lot more clearance for exhaust and oil pan room. I don't know if you could run a front sump pan but I think a mid sump pan might clear the front diff ( if your truck has a lift kit in it that will make it even easier to clear the diff). That crossmember is ther to keep the frame rails straight from top to the weight of the engine doesn't twist the bottom of the rail out and away from the engine. It doesn't have to be where its at with the caddy engine but it does need to tie to the motor mounts and bottom of the rail when its installed. In other words you could move the mounts forward and then put a new crossmember in tying the rail flanges together at the bottom. That crossmember isn't a real crossmember because it doesn't tie directly into the frame on both the top and bottom of the frame...its riveted to the bottom flange and bolted to the side of the engine mount, no attachment to the top of the frame. So, in my opinion lose that whole mess and start over.
Good luck.


You are getting some good advice. This is my 2c worth:

When I put the 500 cid into my vintage Dodge 4x4 I got the engine mount bushings I wanted to use (urethane from Summit Racing) bolted them to the engine, bolted on the exhaust manifolds (shorty headers were the only solution for my swap) and then hung the engine in the truck as Torque Inc describes. I found that urethane mounts do not compress like rubber, so when I had the engine where I wanted it, and lowered its full weight onto the new mounts, I retained the placement I wanted.

You will not successfully place the engine correctly using a formula - you must custom fit your engine to your truck. I cannot imagine how anyone could fabricate engine mounts for an engine swap without mocking up the mounts with the engine hanging in the truck and bolted to the trans.  This is especially true with 4x4 swaps because that engine oil pan must clear the front differential housing, taking into account the location of the diff when the suspension is fully compressed on either side. I swung that engine in and out many times before I had eliminated all of the fitment issues. Why? because I would see one problem, take the engine out, fix that problem, swing it back into the new position not allowed by the last problem, and then see that something else had to be changed, and so on.

I made card board (easier to modify than steel) mock up engine mounting brackets and then fabricated the steel brackets from 1/4" plate using the card board models. Think about what forces the engine will exert on that engine mount and frame location. Do you need to gusset an angle on the mounting bracket to support a weld? Does the frame need to be boxed at the location the bracket attaches? Will the crossmember keep the frame rails from twisting when the weight of the engine is on them?  While I am not familiar with your particular swap, judging from the pictures, I tend to agree with smalltruckbigcid that cantilevering off of the stock frame mount location is not the best way to do this, but rather just build from the place on the frame where you need to attach the new mounts. As a general proposition, twisting forces are not good; you want direct loads.

Those are Grade 8 bolts in your picture, right?


thanks guys, i'm going to take all your advice and try and lower the engine in before in install any mounts. I'll take lots of measurements and pictures so i can get it right the first time. Thanks.