The Stovebolt Site Forums The Shop Area Engine Shop 235/SM420 into a '79 GMC

I've a gutted '79 C35 w/v8 mounts & I wanna drop in my '53 235 w/side&front mounts. I need motor mount ideas. I'll can scab together the rest since it's just a barnyard/field rig for now.

It just might be that you are the first person trying to do this swap. Seems kind of backwards installing a motor that is 26 years older than the chassis. Good luck to you.
John

This should be a easy install. There are no side mount kits designed for this and no stock parts combo that can be used, but since both engines are side mounted and the mounts are in about the same place, you should be able to fab up something.
The cable throttle might be the hardest part of it all, but that is doable.

Chuckling to myself, "I'm getting that impression", 40 views and 1 reply. Yes, I know, it is backwards but when the parts are laying around...why not. It's just for a farm truck (to run ~5x/year) off pavement and it's keep the parts off the ground, all together and running. I figure I'll position the engine/trans all hooked up, take measurements then weld-up some 1/4" flatbar to get from the block to the v8 mounts; mod. the 465 mount onto the 420 then the rest is easy. So does a 235 need to sit level or low in the back?
Thanks

Thanks Dave. Yup, I don't even care if I have to use an old choke cable to operate the throttle. Hahaha, easy to teach the kid about stick shifting (pull throttle 1/4 way out, ease off the clutch and away we bounce...) Oh, thanks for the rain. We can use all we can get here on the East side.

Why not?
Keep us informed, including pictures.
Good luck.

I plan to lift the 235 and place it in the bay of the '79 today but I've a quick question for you all.

Where/how is the best way to attach the chain to the complete 235? Along with the rocker cover, carburetor, fuel pump, is there something else I need to pull off to minimize accidental damage?

Pics coming soon. You gotta see the rust in that '79 cab, I think it was a Seattle truck. Oh well, no tears lost when I hack-fit this combo in.

Getting back to the level of the engine, just eye ball the carb base and set it where it level with the ground when you get all the weight on the truck. It doesn't have to be right on, but thats a good place to start. Since its a Field truck, driveline angles should be close enough if the carb is setting pretty level.

When lifting the engine, you might try a couple of heavy nylon straps, they will conform to the surrounding engine parts with out denting them.

Joe

Thanks Joe. I'll give your advice a try.

I plan to put this:[image]http://bluebarnfarm.webs.com/235L%20copy.jpg[/image]

Into this:[image]http://bluebarnfarm.webs.com/79FPass%20copy.jpg[/image]

More to come.

Well, I finally got around to pulling the power-pack from the '53, removed the trans. and am about to pull off the Bell-housing. It looks like there's 4 bolts inside the BH going into the block besides the 2 top ones on it's outside.

Am I right to regret that I have to pull off the pressure-plate, clutch & flywheel just to get to the 4 inside bolts?

Correct!

Thanks Grigg.

Is the flywheel pressed on or will it come off "easy" once the bolts are out?

Edit: Whew, it slid off easy. Project is about 1/2 done now. A '53 car 235, '55 truck bell-housing and a '67 SM420 all fit together nicely
Four more bolts and I can set it into the '79 engine-bay.

Thanks to the Stovebolt forums' knowledge I knew what parts to get for this project.

One more question. What size/length/pitch/grade of bolts hold the SM420 to the bell-housing?

Edit: I figured it out; 1/2x13 by 1&1/4" long w/lock washers.

Kicking myself, now I've got to work in the snow.

Teaser, one step closer.

What a pitr. Took most of the day to get the '79 rad. cradle off; was a good thing I didn't know how hard it would be or I'd a torched it off. No less than 4 different style screw-heads and a couple a metric heads tossed in for good measure as well. All in all not too bad; no cuts, bruises or frostbite.

So, next is to yank the remaining exhaust outta the way and swing the power-pack in place for measurements. If the temp. stays above 0 maybe I can scab some brackets on Friday.

Stay warm.

It's in!
Pics are at http://bluebarnfarm.webs.com/projects.htm

Now for the real work.

I need your input.

1. I thought the 235 engine mounts were the same distance back from the front of the block? They look not to be. Are my glasses crooked?

2. Does anyone know if the 420 came with a 3" longer rear yoke? A longer output yoke would make things easier.

3. Advice? I was thinking it would be easiest to remove the '79s rear support & cut the firewall to slide everything back to the driveline then fabricate bell-housing+engine mounts and make a housing to cover the firewall hole. Anyone try something like this?

Dads53,

Yes, the passenger-side mount is at least a 1/2" further aft. I recently put a 1954 261 in a street roadster and discovered this difference. Should not be a problem as the frame-to-engine mount brackets needs to fabricated anyway.

I don't know about a longer yoke for the 420, but it seems that making a longer driveshaft would be easier than cutting into the firewall.

Hoyt

Oh good, I thought my eyes were going bad.

This truck uses a support bearing and the front shaft is solid. If I push the front shaft forward in the support bearing I don't think there's enough spline left on the back shaft to make the difference. I'll try that tomorrow. What's the acceptable minimum amount of overlap in a slip-joint?

There is about 4" (3 1/2" of spline) of shaft in the barrel of the slip-joint so there might be enough to cheat a couple inches forward and connect to the 420 since it's just that much shorter than to original SM465.

Any advice on how much spline contact in the barrel would be a minimum?

Farmers also did this with 216 dipper engines. Put a 216 dipper in a 1962 pickup.

Perhaps a SM420 specialist like Novac could answer your questions about the yoke with a longer spline engagement. I recall from a machine design course nearly fifty years ago that a self-centering spline should have an engagemrnt length of at least twice the spline diameter, but I cannot verify that.

53moneypit also had some good comments last year on driveshafts and spline engagement driveshafts and spline engagement.

Hoyt

Thanks guys!
Well, I've found yet another "challenge". I was just going to slide the driveshaft forward about 2.25"(through the support bearing leaving about 2" of spline contact) to bolt it to the trans when I noticed that the shaft Dia. is larger under the bearing than from there back to the splines. So, I guess I'll be bolting a plate to the crossmember holes and then bolt the bearing to the plate a couple inches forward. I didn't get to it today, too much to do then hurt my back trying to get it done. Time for an icepack. At least I'll have a little time to "visualize" what I'll be doing next.

Finally, I'm "back" in action; sorry, I couldn't help myself. Back took me down for almost a week this time; "ice is my friend".

Mocked up the transplant today. The BH hits the floor just under the firewall, the support bearing cradle is slid as far forward as x-member allows, the slip-joint has about 2" of spline contact and the motor-mounts almost line up.

Now to get some flat-bar to mount trans to its pad and then use angle or flat-bar or tubing or combo thereof to bolt to the block and weld to the V8 engine plates. Any advice?

New dilemma though. I'm not sure if I have the '79's clutch linkage, just a rod pushing down out of the floor when I push the pedal. Might be a challenge to get the clutch linkage setup.
Any linkage idea's?

New pics are at my site.

I'm learning about 70's chevy mechanical clutch linkages off the net. I might have to work some voodoo to make an engine-side bracket to mount the Zbar. However, my question probably applies to all mechanical clutch linkages.

Does the adjustable rod from the clutch fork to the zbar have to be parallel to the crank/trans shafts or can I get away with it being at an angle?

My 50's chev's linkages pull from behind and they look parallel.

Anyone?

Update...dang snow.
The top shells of v8 mounts are too narrow and hit the oilpan flange on 235 block and trimming the shell might compromise their strength. Latest plan: remove v8 mounts, use flatbar in the 235 cushions and weld squaretube risers down to the crossmember. Rear trans bracket will be similar to one I saw in a "sloppy 2nds" article. I might be able to scab the zbar between the foot starter pivot shaft on the bellhousing and the frame.

Any progress reports?