The Stovebolt Site Forums The Shop Area The HiPo Shop My '52 GMC has a 350 now.

Well I did it. Over a two week period of time, I pulled the huge 235 and installed a much smaller 350 that makes 3 times as much power.

It wasn't easy. In case anyone is thinking about the swap, here's the issues and how I dealt with them:
1. The bellhousing is first. I had to find a bellhousing that matched both the SM420 tranny AND the 350. They were made by GM up to about 1990 I guess, and not too hard to find. But I had to cut out a space for the 350's starter to fit through and get to the flywheel. Angle grinder with a cutoff wheel will go through iron like butter.

2. The new bellhousing is the same size depth-wise, and mounts to the tranny crossmember if you drill two new holes.

3. The firewall will not quite clear the valve covers. Nor an HEI distributor. It will barely clear low rise valve covers and a conventional distributor. Anything else will require slight modifications to the firewall.

3. The steering box is totally in the way. It either has to be moved over or replaced. I'm gonna try shifting it over first, but eventually would prefer to replace it with a rack and pinion.

4. Speedway Motors sells a universal crossmember to mount the engine to. If you get this, CHECK IT FOR FIT FIRST. I found out the hard way that they welded the mounting tabs about a quarter inch too close together and had to make modifications.
Another point, do NOT weld the crossmember in. Bolt it in. You really need the flexibility when installing the engine with clutch into the transmission's input shaft. I needed to be able to rotate the crossmember to allow the engine to slide back.

5. I used an old Corvette 10.5" flywheel, which required a Corvette clutch. That's 153 tooth. I know that will work, but I'm not sure about a 168 tooth flywheel!

6. Even with a long water pump, I need about a 3" fan extension to get the fan close enough to the radiator.

7. The stock gas pedal can be modified to work with a cable. Unbolt the solid rod and use that to mount the cable too.

But that's it. Looks really good in there. There is so much room above the 350 that you could easily hide a big 8-71 and no one would have a clue. I've still got lots of nitnoid details to attend to, but the worst part's done.

sounds pretty cool dude! now all we need are pic's ????

Congrats! I appreciate your work. I too am heading in that
direction, only a little different. Changed to M11 frontend,
using 98 LS1 with 4L60E. I changed out the firewall, rad support
and inner fenders to "Bitchin Products"
Cheers

350= more yes but also more rod's on the pavment !
I wish you the best of luck. . .
But 350's have been nonthing but bad news for me. . .

Mike

[quote=Hot Rod Dad]

But that's it. Looks really good in there.
Looks good in there you say? There are a bunch of guys here wanting to follow in your tracks and do the same swap. So crank up the camera and send us some pics.

on my swap , it has a turbo 350 behind the 350 small block an the motor mounts were moved forward to Fix the Distributor /valve cover clearance / distance from Radiator Issues .
Yes it did in the same breath make the purchase of a custom length drive shaft a must ...but the cost of the drive shaft outweighed the problems in my opinion.
I have plenty of room behind the motor for a HEI & any valve cover and my fan sets right at 3/4" from the radiator.
Tim

Tim, I wish I could have gone the route you did. However, I needed to use my stock SM420 Muncie, which was already set with an enclosed driveshaft, etc. I will be swapping trannies to an SM465 that I picked up cheap, for slightly better gear ratios and a lot more strength. On that one, I will definitely be getting a custom driveshaft.

On the pics issue, rest assured, I am recording my progress photographically. I will make sure to get some pictures here.

On an unfortunate note, looks like I will be repainting the truck next. I had some stuff slide off the fender and put a few nice gouges in the paint. Oh well, now would be a good time to do a little bodywork.

Oh, one more thing, I took the TPI fuel injection off my IROC-Z Camaro when I removed my 350 (not an original Camaro 350, this one is built up well).

So next year, I plan on putting it back to tuned port injection. Should look great and make even better torque.

I used a 350/350turbo and a 57 pass car drive shaft bolted right in after I changed the 57 course spline for the fine spline.Other times I've just gone to the wreakers and some of them have piles of drive shafts,so I just picked one that was the right length.Usually they just gave it to me as they know me,I have paid as much as cough,cough$10.00 Canadian(that's $5.00 American now)lol
Lothar

That's a good suggestion. For now, I will use the SM420 that came with the truck, and has its own inclosed driveshaft. I do have an SM465 that I will need a new driveshaft for, so I will consider a salvage yard driveshaft once I get the measurements I need. I might just leave the SM420 in place until I convert the truck to 4WD, because then I can get dedicated transfer cases that mate to the back of the SM465.

Looks like exhaust solutions are going to be a challenge. Even with the steering box moved, I have some serious doubts that any headers will clear the frame rails. It's just too tight, and most headers require a good 4 inches on each side to make the bends. Iron manifolds will be tight too, but would fit barely. The tightest thing I've ever seen has to be the Sanderson iron header/manifolds. Someone had a set on their AD truck with V8 conversion, and those babies only require about an inch and a half clearance! But they're about $330 bucks a pair too.
Another option are the TruRam header/manifolds made by Speedway Motors. The iron version is $300 bucks, stainless steel is $350 bucks, and gorgeous polished stainless is $400.
Tough decision.

I do have two header sets I can use. One is a set of shorties from the IROC, but to allow for the AIR tubes makes them require at least 4" if not more, for the turns. They're probably not tight enough. I also have a full length set I could try.

What did you guys do?

Hotrod Dad,glad to hear your swap came out AOK. I too am running a 350 in my 55 2nd Series.Behind it is a built 700R4 overdrive automatic and a stock 3:90 rear.The best of both worlds the 3:90 rear and OD tranny give me good performance and gas mileage,(20 MPG).I got lucky when I installed new side motor mounts,cause later on I installed a large HEI distributor and had just enough room.Although a lot of guys here feel that you should leave everything stock,I enjoy being able to drive at freeway speeds and have plenty of power and good MPG.My other truck a 65 shortbed has a 500 cu. in. Caddy engine,with a 400 Turbo hydramatic,it is also a lot of fun to drive.

The stock versus originality issue is definitely a personal choice. But I do know that originality does not equal streetability in many situations with today's streets and highways. Having 4.56 gears in my 3/4 ton and a 235 straight six that does not like to rev past 3500 rpm, means cruising on the highway at speeds dangerously slower than other traffic. Slowing down climbing mountains to at times, single digit speeds, is another extreme safety issue. So to me, original is nice if you can do it...or want to, but I can't fault ANYBODY for wanting to bring an AD truck up to date.

I admit that with the stovebolt, even without a decent paint job, I took home trophies at car shows that other people with MUCH nicer AD trucks didn't, mainly because people's choice tended to prefer the stovebolt. But none of my truck is original anyway. It's got parts that vary from 1949 to 1954, and had a 1959 stovebolt in it; so exactly what part of my truck is original is a darn good question. It's Frankentruck.
Now, if I had a beautiful original survivor, I might have made more of an effort to keep it that way.

The 350 I've got is one I've built myself, and it's been stone reliable all these years. I first had it in a '68 Corvette, then moved it into an '86 IROC-Z, and now will power my '52 GMC. In every case, it's been a great engine. And the funny thing is, it's picking up parts from each of those applications. It has the flywheel from the Corvette, and will have the tuned port injection from the IROC.

My IROC, by the way, had 3.42 gears with a built 700R4 and that first gear in the tranny was STEEP. I can't imagine how brutally yours must launch with 3.90 gears! Wow.
Sounds really nice.

I also redid my interior with the plush leather back seat out of a Ford Expedition to use as my front seat, and resultingly, it is one of the more comfortable vehicles that I have to cruise in.
No...mine's a driver, and therefore must remain streetable.

Just a "heads up" H.R.D. on the junk yard driveshaft. I finally gave up in my search through the local salvage yards for a usable shaft. I had a new one built to order for a little over $100.00.
It seems all the driveshafts I found had been bent by the forklift they use to pick up the vehicle.

I moved my box over 1 3/4" and found a pair of driver side exhaust manifolds that look almost identicle to the 55-56 pass car 265 manifolds-perfect clearance, paid $5.00 for the pair at an antique car swapmeet.I believe they are both dr side 77 chevelle,not possitive on the year though.
Lothar
PS $100,00 for that shaft is a good score.

Hey Hot Rod Dad sounds like a good swap I have a 56 two ton that I put a big block in not finished yet but have done a lot of research on the subject. You may want to check your transmission alignment before you drive your truck. The bell housings that fit this application changed in 67 for the new SM465 witch has a larger pilot hole at the rear of the bell housing so you 420 will not be properly centered. I believe that Advance Adapters makes a spacer ring to run the 420 in the later housing. If you have used the early housing your 465 will not fit in the smaller hole.
By all means get us some pictures we want to see, if you want to see my 56 just check out my webshots page there's lots of picture of the project to include steering and brake upgrades and yes there are some with the monster big block sitting in its place.

Oh I mite add this BB is a stroker motor and is 496ci and all roller 450hp and 550fpt I can't wait to get her finished.

cool....got any gas?

Naw, we're gonna run it on GE's stumpwater!

Your funny LB but I don't want to blow the heads off her I have been thinking about propane though maybe with a supercharger beings as propane is about 130 octane if I would have built it to run propane from the start it would have had 11:1 pistons in it now it's 9:1.

Hot Rod,
I used the old Rams horn cast GM manifolds .
The drivers side had plenty of room the passengers side i had to notch out a bit of the frame for clearance and welded a 1/4 thick plate around the notch to strengthen the frame back up , and my exhaust has plenty of clearance with those manifolds.
Tim

HevyHauler, I've got the right bellhousing. It mated up to the SM420 perfectly, just like the old one did. I'm sure it's okay.

SW Radial, that's good to know the ramshorns fit. I'd like something the flows a little better than iron manifolds though. If I can modify an old set of headers to fit without mangling them, I will. But if not, I am leaning towards one of the iron header/manifolds I've seen for sale.

We now have 6 inches of snow on the ground and still falling. So until things calm down outside, I won't be crawling under the truck much. I'm glad I got the install done before winter weather finally set in though.

I used a set of block hugger headers they worked out sweet and cleared everything and they sound awesome too !
I think I paid less than $200 for them also,
http://rides.webshots.com/photo/2056977520100410726fpiuWO
http://rides.webshots.com/photo/2980237740100410726cfsjcx
http://rides.webshots.com/photo/2690489320100410726AyCvfD


Good luck Bro & have fun

Todd

I think my headers MIGHT work if I am successful in moving my steering box outboard more. But armed with a welder and some primary tube bends, I'll bet I could modify my headers to work.

I looked at block huggers, but if I can make full length headers work, my torque will probably be slightly better.

Todd,
Your pictures look great. Main reason why you are not having any problems is because you are not using the stock steering box, which is normally right on top of the rail, right where your headers begin their curve downward.

It is possible to relocate the stock steering box more outboard, which is what I'm looking into now. It does move outboard, but only so much before hitting the inner fender. Any more than that would probably require trimming the inner fender for clearance.

I would very much like to modify my truck for rack and pinion steering, and it looks possible, but I would have to make my own modifications. With a welder, the conversion does look fairly simple.

Okay, the Blackjack headers that I had will not work. For one thing, they are not deep enough, so they don't clear the transmission crossmember. Also, surprisingly, even though they're Chevy headers, they don't clear the Chevy mounts. Rather than seriously mangle these headers to work, I think I'll put my money into either a set of Speedway Tru-Ram iron ramshorn headers, or a set of Sanderson QP1000 cast steel headers. The Tru-Ram's require 3.5" of clearance from the heads to the frame rails, and that might still be very tight. But looks like it would breathe better. The primaries are 1 13/16".
The Sanderson's only require 2.25" from the heads to the frame rails, but I'm not sure how well they'll clear the motor mounts. They look like they get awfully close. Primaries on those are 1 1/2" so they won't breathe quite as well, but also don't require a gasket.

I think if they'll fit, I'll get the Tru-Ram's. You can also get them in polished stainless steel, but way too expensive for that. I'll just get iron and ceramic coat them.
If there is any chance of a clearance issue with the frame rails, then I'll get the Sanderson headers.

It's really a bummer that the long-tube headers wouldn't work, but I think they would only work if I welded up my own custom set...so maybe someday, but it's not something I really want to mess with right now.

PICS send pics. We need proof...

Well I am taking pictures along the way. If you want to see the Ramshorn headers, they are really beautiful, especially polished. Believe me, I looked long and hard at those polished ones, but I think I want to just get the iron ones, for $150 bucks less and then ceramic coat them, #1 so they don't rust, and #2 so that they are a little less hot to the touch.

You can see what they look like if you cruise on into www.speedwaymotors.com and type in "tru-ram" and search the site on those.

Hey Hotroddad your SM420 will bolt up fine to the later bell housing but will not locate properly because the later housing has a little bigger pilot hole than the early one for the 420 you can still use it but you will want to use a locater ring that adapts the 4 and 11/16th" SM420 bearing support to the 5 and 1/8th" pilot hole in the housing. Novak Conversions makes one P/N BR4 and it is only $35.00. With out a locater ring in there you risk ruining the transmission or taking out your crank bearings or both. I highly suggest you look in to this with all the great work you put in to it I would hate to see a simple thing like that ruin your day.