swappin a 292 for a 350

[ya it is a classic]

hey guys i found a 1972 gmc 1/2 ton 2wd pickup at the neighbors and it has a overhauled 350 with 13000 miles. my friend is going to buy it for 200 (its rough) but before i said anything about my friend looking for a pickup the neighbor said i could swap the 350 for my 292 with 80k on it for free. so my 67 gmc is a 1/2 ton 2wd with a 4speed manual and the 72 has a 4speed manual too. im going to swap the motor 2maro what will that entail? this is my first motor swap. the 72 has power brakes so will the brake booster thing work with the 292. also the 292 is a 1970. it was swapped before i got the pickup. can i just swap the motor mounts around or will need the welder? and does the 72 have an electric fuel pump? will the transmission bolt up? on the 67 reverse is left than down and the 72 its right than down(i think). and do i have to pull the transmission or will it be easier to leave it in the truck?

[Shyguy]

Don't pull the transmission, it will work just fine.

The transmission in the '67 is supposed to be a real sturdy transmission.

My '67 has the same transmission and I like it. My '71 has the newer version with the reverse down and to the right. I like both transmissions myself.

The '67 has a I-250 and the '71 has a 454.

You may have to go with a small air filter with the 292 because of the brake booster.

Good luck with your swap.

Danny

[RichardJ]

The '67 is a SM420 and the '72 should be a SM465. The SM465 has a larger bearing retainer and will not in the smaller hole of the '67 bellhousing.
I put a SM465 in my '67, but I was replacing a 3 spd.
I had to make a new driveshaft. I had to cut open the floor for a tall, bolt-in hump. The hump I found, had the hole too far forward and I had to relocate it. I don't know what the hump came out of, but I think it had a V8.

[ya it is a classic]

Originally Posted by RichardJ

The '67 is a SM420 and the '72 should be a SM465. The SM465 has a larger bearing retainer and will not in the smaller hole of the '67 bellhousing.
I put a SM465 in my '67, but I was replacing a 3 spd.
I had to make a new driveshaft. I had to cut open the floor for a tall, bolt-in hump. The hump I found, had the hole too far forward and I had to relocate it. I don't know what the hump came out of, but I think it had a V8.

ok im not really seeing what ur getting at but i want to leave the transmissions the same but swap the motors. will i have to change the flywheel around on the motors and will the brake pump fit on the 292 or will i have to rig something up?

['68OrangeSunshine]

So you want to keep the SM420, drop in a 292 L6 and add a power brake booster in a '67 C/20?
It should all drop in fine. That stuff was all optionable when the truck was new. If you're keeping the stock Rochester Monojet 1-Bbl, there should be no air cleaner issue. If you get fancy with a Holley 2-Bbl or any 4-Bbl on a Clifford or Offy intake, then you may need to get creative with aftermarket air cleaners.
I don't have power brakes on my '68 C/10 w/292, but I have a 12" diameter Moroso round air cleaner with a 3" tall K&N filter element. Carb is an Edelbrock 1404, 500 CFM 4-Bbl on an Offenhauser intake with Clifford headers. Transmission is SM465, straight one- piece propshaft and 3.73 Corp 12-bolt rear end with Eaton Posi.

[ya it is a classic]

Originally Posted by '68OrangeSunshine

So you want to keep the SM420, drop in a 292 L6 and add a power brake booster in a '67 C/20?
It should all drop in fine. That stuff was all optionable when the truck was new. If you're keeping the stock Rochester Monojet 1-Bbl, there should be no air cleaner issue. If you get fancy with a Holley 2-Bbl or any 4-Bbl on a Clifford or Offy intake, then you may need to get creative with aftermarket air cleaners.
I don't have power brakes on my '68 C/10 w/292, but I have a 12" diameter Moroso round air cleaner with a 3" tall K&N filter element. Carb is an Edelbrock 1404, 500 CFM 4-Bbl on an Offenhauser intake with Clifford headers. Transmission is SM465, straight one- piece propshaft and 3.73 Corp 12-bolt rear end with Eaton Posi.

well we went and started the pickup and it ran fine. but MY 67 gmc has the 292 with the SM420 and NO power brakes. the 72 gmc has the 350 WITH power brakes and what ever the transmission was. i hope that clears up the confusion.

[raycow]

If you want to keep the 67 transmission in the 67 truck, put the 67 bellhousing on the 350. The 72 bellhousing goes on the 292. Keep the flywheel and clutch on the engines they came on.

On both trucks pull the transmission off the bellhousing before you pull the engine, then pull the engine and bellhousing together. The heads of the bottom two transmission bolts are INSIDE the bellhousing. Swap bellhousings with the engines out of the truck, then install the engine and bellhousing together. Install the transmission after the engine is sitting on the mounts.

While the engines are out, get the right side (only) engine mount frame bracket off the 72 and install it in the rear set of holes on the 67 frame. The 67 right side bracket goes on the 72 frame in the front set of holes. The left side mounts are the same on both trucks, so you don't have to do anything to those.

The 292 intake manifold should have a port (with a plug in it) that you can connect the power brake hose to. You will need to plug the PB port on the 350 so you don't have a vacuum leak.

Ray

[Jacfourteen]

I could be wrong but aren't the bellhousing crossmembers in different locations, v8 crossmember sits about 3" forward of the location for the 6 cyl. My truck came with a v6/4 speed originally and I swapped to a 350 and now my engine sits about 3" farther back than a stock equipped small block would. To get my engine mounted up I left the bellhousing crossmember where it was and I got some engine stands off of a 250 I6. So if you swap for the v8 in your truck you will be fine, you just need some 250 I6 stands and have to either get a 4x4 fan shroud or convert to electric fan. For the other truck though It will make the engine sit about 3" forward of where it should, which may cause radiator interference and I'm not sure what you would do about motor stands. Here is a picture of how my 350 sits in my engine bay, you can tell its further back because of the big gap between the water pump and the rad and also how close the dizzy is to the firewall.




Hope this helps.

['68OrangeSunshine]

The 292 uses a different, 292-only motor mount on the passenger side.

[Shyguy]

I am not an expert, but I have heard that the V-6 and the I-6 are different as to how they set in the engine compartment and have different mounts.

Danny

[Jacfourteen]

Originally Posted by Shyguy

I am not an expert, but I have heard that the V-6 and the I-6 are different as to how they set in the engine compartment and have different mounts.

Danny

That is true the v6 and I6 have different motor mounts and towers, but they both sit have the tranny in the same spot which is farther back than the 350. This is because the I6 and v6 have a longer overall length so they have to move the tranny back to avoid radiator interference. I know it sounds funny that the v6 is longer than the v8, but the v6 is a huge monster! It is also true that the 292 has motor towers that sit offset from each other, so one is the same as a 250 and the other is unique to the 292.

[raycow]

I can't speak for GMC, but on Chevy trucks with manual transmissions the V-8 and 6 cyl bellhousing crossmembers are all in the same location. On my truck a PO did a 6 cyl to V-8 swap and the crossmember was not moved.

Some rodders doing V-8 swaps like to put the front mounts in the forward set of holes on the front crossmember to gain more room for the distributor or valve covers. All of the swaps that I have seen like this were either automatic or had hydraulic clutch linkage. If GM had allowed for the stock clutch linkage to work with the engine in the forward position, I am sure at least some of these swaps would have used it.

The forward set of holes is used the right side only with the 292 because on that engine the locations of the mounting holes (on the block) and the fuel pump were reversed when compared to the 230 and 250 engines.

Ray

[Jacfourteen]

Originally Posted by raycow

I can't speak for GMC, but on Chevy trucks with manual transmissions the V-8 and 6 cyl bellhousing crossmembers are all in the same location. On my truck a PO did a 6 cyl to V-8 swap and the crossmember was not moved.

Some rodders doing V-8 swaps like to put the front mounts in the forward set of holes on the front crossmember to gain more room for the distributor or valve covers. All of the swaps that I have seen like this were either automatic or had hydraulic clutch linkage. If GM had allowed for the stock clutch linkage to work with the engine in the forward position, I am sure at least some of these swaps would have used it.

The forward set of holes is used the right side only with the 292 because on that engine the locations of the mounting holes (on the block) and the fuel pump were reversed when compared to the 230 and 250 engines.

Ray

So are you saying the four speeds all sat back? it was my understanding that all of the v8 (except 4x4) sat in the forward holes. If so it wouldn't be the first time I've been wrong...just ask my wife

The only reason I didn't change to the front holes is because I didn't want to have to get a longer driveline. I didn't even think about the clutch linkage, as a matter a fact I had to modify it to work in my current setup.

[raycow]

Originally Posted by Jacfourteen

So are you saying the four speeds all sat back?

Sorry, I wrote that badly. I should have said "on all the factory installs that I have seen". However, you did bring up a good way of finding out. If anyone here has access to a parts manual, it should certainly tell if the 6 cyl and V-8 driveshafts are the same length.

Just out of curiosity, why did you have to mod your clutch linkage if you installed your engine in the stock location? Was it needed to clear headers?

Ray

['68OrangeSunshine]

The L6 and V8 clutch Z-bars [bellcranks] are different too. I believe the L6 Z-bar is shorter because there is a bracket that bolts to the block and holds the pivot ball out to meet it. On the V8s, it screws into the side of the block directly.
[On 4x4s at least.]

My guess on why the 292 has the passenger side positions for fuel pump and motor mount reversed is that maybe the forward mount gives better resistance to torque wanting to pull the higher block over to one side. Just a guess.

[RichardJ]

292 has 4 1/8" stroke and crank almost hits cam. Fuel pump eccentric had to be moved or the crank and big end of rod would hit it. The 250 has a much shorter stroke and the crank clears the cam.

[Jacfourteen]

Originally Posted by raycow

Just out of curiosity, why did you have to mod your clutch linkage if you installed your engine in the stock location?
Ray

Now that I'm thinking about it I didn't have to modify it, it just doesn't sit straight. When you are looking at it from front of the truck with the hood open bellcrank isn't square with the engine. IIRC the ball on the engine sits farther back than the notch in the frame bracket, making it crooked. I was gonna modify or move the frame bracket, but have had bigger bugs to work out first (like hooking up the E-fan, you can see the dangling plug in the picture a few posts back). Sorry for the confusion. It seems like when most people do a v8 swap they throw in an auto, so not to many are sure about how to make the 4 speed work. I know I did alot of research when I was swapping mine and the info is hard to come by.

['68OrangeSunshine]

Originally Posted by RichardJ

292 has 4 1/8" stroke and crank almost hits cam. Fuel pump eccentric had to be moved or the crank and big end of rod would hit it. The 250 has a much shorter stroke and the crank clears the cam.

OK. I'll buy that.

[Shyguy]

When we took the 350 out of my truck and put the 454 in the bell crank ended up being a little crooked because of how we placed the 454.

We did not bolt the 454 in any pre-drilled holes because we did not want to move the 4 speed transmission and mess with the drive-shaft.

Like you someday I will work that out, but for now it works fine.

Danny

[Kas68c10]

Hi! I am lookin to do the same swap, the 350 in my jimmy wore out, want to put in a 292, how did your swap go? Just needed passenger engine tower and motor mount? Any cross member/clearance issues?

[ya it is a classic]

Originally Posted by Kas68c10

Hi! I am lookin to do the same swap, the 350 in my jimmy wore out, want to put in a 292, how did your swap go? Just needed passenger engine tower and motor mount? Any cross member/clearance issues?

hi. i didnt have to swap the motor i just bought the pickup. if i was you i would put another 350 in cause the 292 gets like 10mpg. although the power is bout the same. my .02

[68lwb292]

Originally Posted by RichardJ

292 has 4 1/8" stroke and crank almost hits cam. Fuel pump eccentric had to be moved or the crank and big end of rod would hit it. The 250 has a much shorter stroke and the crank clears the cam.

You know Stacy David did a straight 6 on his show Gearz and they claimed it was a 292. I went round and round with his people on his forum about how I thought it was a 250 because it had the mounts centered on both sides but they finally got mad enough to kick me off their forum. They claimed they checked the numbers and everything else but I still claim its not a 292.

[raycow]

Numbers or not, there is no way you can BS anyone about a 292. The difference will be obvious as soon as you look at the right side of the engine. That other forum sounds like it must be populated by idiots.

Ray

[Shaky]

Originally Posted by 68lwb292

You know Stacy David did a straight 6 on his show Gearz and they claimed it was a 292. I went round and round with his people on his forum about how I thought it was a 250 because it had the mounts centered on both sides but they finally got mad enough to kick me off their forum. They claimed they checked the numbers and everything else but I still claim its not a 292.

It's easy - tell him to order up some 292 lifter valley cover gaskets and install them. When there's an extra coupla feet of gasket hanging out it'll be obvious...

[Jacfourteen]

Originally Posted by Shaky

It's easy - tell him to order up some 292 lifter valley cover gaskets and install them. When there's an extra coupla feet of gasket hanging out it'll be obvious...

They probably knew that they were wrong, they just didn't want to sound bad when they had to explain it on their show.