BB Swap Using Squarebody Crossmember/Mounts

[BASE]

I read a bit about using the later model crossmember and mounts in the 67-72 trucks here. A couple of build threads where they were used and some scans of an old magazine article that describe it.

http://67-72chevytrucks.com/vboard/s...d.php?t=663541

http://67-72chevytrucks.com/vboard/s...79#post6705979

And FirstC10's awesome build thread where he used it to install an LS.

Just curious if anyone around here currently has done the mod with an older big block install. I had always planned on moving the engine to the fwd set of holes in the frame to try and avoid interference with the firewall. I haven't seen anyone mention moving the mounts forward when using the later model crossmember though. Both mounts look to be more or less centering the engine mounts on the frame holes, so I'm curious how it wouldn't have the same interference issues. Sits lower maybe?

I guess there isn't going to be any way to get around trial fitting this thing at least once but I'd like to minimize smashing and bashing of all my pretty new parts if I can. I'm thinking I'll temp install the mounts where I think they should be and carefully try and maneuver the engine/tranny/xfer case into place and see how it all looks with the headers and stuff.

Pics of the transplant project:

[72gmguy]

Pretty pile of parts you’ve got to get you started! I won’t be any help but I’m in to watch. Good luck. Looks like it will turn out awesome.

[A.Delaney]

I’ll be watching this also as I am planning on doing a 4x4 conversion with a BBC.

[Dieselwrencher]

I've heard guys ask about doing this same swap but I have never done it. I have 1 I've been hanging on to but haven't had the time to mess with it.

[BASE]

I will try and document everything the best I can, either here or in a build thread. This one has been moving really slow so far. I started it over 5yrs ago and then had some medical issues, then it kinda got re-prioritized while I kept the wife happy with a fairly large "home improvement" project. The pile of parts pictured above is the result of almost 2 years of work, a lot of learning and a lot of paychecks.

The crossmember doesn't appear to be as simple of a bolt in as the linked article makes it out to be. I'm going to have to cut down the mounts about 1/2", just like FirstC10 did. The hole spacing in the newer mounts is different than the original (and frame) holes, so that's probably just as well. I can drill them where they need to be once I weld new pieces on top.

I finished pulling the old drivetrain out Sunday evening. The old rear crossmember was more of a pain than I would have thought, had to cut the riveted on "ears" off. I think I'm going to reuse that one vs the new one I have just because it has those ears on it though. I want to reuse that original cast iron bellhousing vs the newer aluminum one I have, so I need to clean those parts up and get them painted. One thing I noticed is that the old tranny/xfer case adapter mounts the transmission about 2" further aft than the new one. That may help, or may be just close enough to cause me issues. I'm now thinking I'll try and bolt the whole engine/tranny/xfer case together and put it into the original rear crossmemeber location, and see where that puts everything up front. I'm hoping that puts it really close the forward (2WD) frame holes, and leaves plenty of clearance at the firewall. Also seems to make for a longer package altogether, so maybe I can get by with a one-piece replacement rear driveshaft. Lots of hoping going on there. I will find out before too long I guess.

One thing I meant to do, but forgot about, was taking a vertical measurement from the top of the frame rails to the crank centerline on the old engine. Would have been a nice reference to have. I may end up welding plate to the new mounts to space the engine up a little if it needs it. I hope to get the headers in there without cutting the frame up if I can.

We are supposed to have some nice weather here for the next few days so I'm going to get busy with the wire wheels and get stuff cleaned up the best I can.

[BASE]

I haven't gotten too far with this one yet. I've been a bit distracted with some rust/bodywork issues, but still moving forward, slowly.

I have the mounts cut down ~1/2" and sitting in the frame. They fit very well if I line them up with the original k-series holes in the frame. The rails get narrower and have that curvature or arch, and the fit gets much worse as you move them forward. In the picture below I have a red line at the approx centerline of the original engine mounts, and the black one corresponds to where I think a factory big block c-series would sit.

I'm hesitant to drill the hole in the frame. I'm going to try and pin the back in using the original holes & crossmember and see where that puts things up front. I'm kinda hoping I can reuse the holes in the back as the upper frame rail might be a pain to drill with the cab on. I have some 1/4" and 1/2" steel pads cut in case I want to raise the engine up a bit. Trial fitting the thing in there should hopefully answer most of my questions. Hoping to give that a shot later today.

[BASE]

So as it worked out the old 221 transfer case crossmember with the 205 adapter mounted on it, pushed the engine forward about an inch. I really didn't think that would be enough room but it looks like it will work fine. The squarebody mounts are not quite a bolt in deal (they are too tall and the bolt spacing is different), but not too bad I guess. I'm also not sure it would work if it weren't moved forward a bit.

I could just barely get the distributor in and out, and there is about a 1/4" clearance from the headers to the passenger side frame rail. The headers are hooker 2463's. I should probably mention the mounts are hooker engine swap mounts too. I clamped the snot out of everything and put some tack welds here and there and pulled it all back out again. The only thing left for me to figure out is how I'm going to rework the clutch rod,cranks & z-bar.

[Yukon Jack]

Looks like a nice fit! Good job.

[Dieselwrencher]

Very nice work! Can you make a bracket for the Z bar stud to mount off the bell housing instead of the side of the block where it does stock? I have a 72 with a 454 in it and it doesn't have the hole provision for the ball stud like the 396s and 402s do. I'm just going to make a bracket and attach the ball stud to it and bolt it on the bell housing and maybe catch a bolt hole on the side of the block as well. This way you might be able to retain your factory z bar and clutch rods.

[BASE]

Originally Posted by Dieselwrencher

Very nice work! Can you make a bracket for the Z bar stud to mount off the bell housing instead of the side of the block where it does stock? I have a 72 with a 454 in it and it doesn't have the hole provision for the ball stud like the 396s and 402s do. I'm just going to make a bracket and attach the ball stud to it and bolt it on the bell housing and maybe catch a bolt hole on the side of the block as well. This way you might be able to retain your factory z bar and clutch rods.

Yeah I kinda got caught off guard with that part. I didn't realize until I went to retrieve the ball stud off of the old engine that it was actually mounted in the fwd hole. I kinda forgot the SB's even had a 2nd hole there for the stud. I seem to remember seeing pictures of a bar/bracket spanning the holes and the stud mounted somewhere in between.

In any case, the stud mounting boss on my old mk IV block is still too far aft, by a couple of inches, to line up with the bracket on the frame. So even though I scooted it forward, it's still too far aft and I didn't see that one coming. I've either got to figure out how to mount the ball farther forward, or move the z-bar back. If I move the z-bar I have to modify the pushrods too so figuring out how to move the ball would probably be easiest.

I tried to take some pictures with a scale but z-bar was not cooperating (needed at least 3 hands). I think you can get the idea from these.

[notsolo]

This is probably from 6 cylinder mid 60's don't remember if it fits Sbc..

[BASE]

That is exactly what I was thinking of but can’t remember where I saw it. I was thinking of making something like that. There is a hole further forward that I think would work for bolting it to.

Problem is that now I’m looking at the pictures I took Sunday, I’m not sure the rear header tube won’t be in the way. You would think that I would have made a note of that. I pranced around admiring my work, taking pictures and measuring stuff for about an hour. I will get it in there one way or another. There isn’t much that can’t be accomplished with a welder and total lack of common sense.

[Dieselwrencher]

My Camaro has a slightly offset Z Bar and I thought about using one on a truck if possible. I was searching these on this project I was talking about earlier. I even thought about cutting a Z bar and butting a bend in the middle to get where I needed to be. I try to keep the Z Bar geometry same as stock because once you go changing rod angles and stuff, it can really be a pain to get working correctly from my experiences.