The Stovebolt Site Forums The Shop Area Engine Shop 261 versus 228 swapped success!!!!

The 261 slipped into the 50 gmc ok.The bellhousing is the same and rear mount aligned ok.But the front mount is short a couple of inches just missing the cross member a bit.I thought I'd make an adapter out of a piece of steel plate to extend the cross member to meet the mount.If anyone has a better suggestion for the front mount please let me hear it.thanks to all for all suggestions.

Bob
I found the difference to be in the crossmember.
I went the other way from Chev to Gmc and cut
the rivits from the Gmc crossmember and put it
in the Chev frame. Take a look at the Chev
crossmember where you got the engine,and see
if that is where the difference is ?
Mike

howdy Mike,I was thinking on that line about the chevy cross member mount.I don't know if I want to remove the original gmc mount to put in the chevy mount.I'm not sure if the bolt centers of the two mounts are different or the same will look at it tommorrow.I did'nt notice either if the frame rails are parallel or tapered.I thought I could put a thick piece of steel plate in there to span the space and put large bolts through the steel plate and cross member and then drill holes in the rear side of steel plate for mount to set on.will look at it again tommorrow.thanks

Bob,
About 5 years ago I bought a '52 GMC 1/2 ton with a late model 235 installed. One funny thing that I noticed was that when I drove over bumps on the road, the whole driveline would "bounce" and oftentimes the 4 speed would fall out of gear. I thought that I had a worn out tranny but it was never really that bad so I kept driving it.
A few months back I pulled out the 235 and put back in a GMC 6 cyl engine. As I pulled the 235 out I saw a possible cause of the driveline bounce. As you know the 235 is about two inches shorter than the GMC block and the PO had used a flat piece of 3/8" steel to bridge the gap. Two bolts went through the frame and the other two went through the timing cover and engine mount as usual. He had also put a piece of flat steel of the same thickness underneath each engine mount off the sides of the bellhousing. I think this was so that the engine was raised the same amount in the front and the back.
One thing I noticed was how much the steel plate in the front allowed the front of the engine to flex up and down. This could have been because of worn/loose bolts or bad rubber mount, I'm not sure.
My thought was that when I would go over bumps in the road, the front of the engine was bouncing up and down enough to put a bind on the driveline.
This theory could be bogus but I do know that with the GMC engine sitting on the crossframe like original, I don't have any more problems with the same tranny falling out of gear.
Because of all this I would recommend that whatever method you use to make the 235 fit on the front crossmember, be sure to make it solid and strong enough to support the front of the engine weight.
Hope this helps.

Thanks shop shark,I've been thinking about whether the plate type adapter would be rigid enough.The mounting bolts of the front mount come down just behind the cross member and just above where the crossmember curls back and finishes off.I also thought about a heavy piece of angle welded across the frame but I'm not sure yet.I don't know that I want to remove the cross member from the gmc or from the chevy parts truck to solve this problem.because I may want to sell the chevy frame and or put the 228 back in the jimmie some day.never the less I see your point of the mount being nice and solid and level with rear mounts.thanks and I'll let you know how it works out.