The Stovebolt Site Forums The Shop Area Engine Shop Big Six question???

I am picking up a 1948 Chevy coupe in mid-July and am thinking of going with either a 235 or 250 Chevy Six, or perhaps one of the big GMC Sixes, just to be different!

I know the 235 and the 250 are pretty similar across the board, but how do the larger GMC engines compare in physical size to the 235/250 engines? Is engine mounting the same, or different? Would this go in a '48 coupe without major drama? I'm wanting to run a 700R4 O/D transmission. The original 216 is gone, as is the 3-speed transmission, so I have a big, empty engine bay to start with!

I'm going for the "traditional"/rat look - it's going to be low-buck, yet comfy and safe with lots of old-skool flavor. I love the sounds of a big Six with headers and dual exhausts!

Any ideas?

GMC 270 or 302 was the old fix for horsepower back when. THe GMC is only 1 1/2 inches longer than the 216 and bolts up to the old Chev bellhousing, front mount will need to be modified. For the automatic trans and the GMC/Chevy 235s you will need an adaptor, avialable from Langdon's or Buffalo Ent. If you use a 250/292 type motor it bolts right up to the automatic trans but you will have to pick up some side motor mounts also avail. from Langdon's. I have a 47 coupe and it's great although would be nicer with the automatic.

The engine bay in the AD looks bigger than it is, especially without a motor in it. I was given a 292/700R4 for free, bought some mounts from Langdon's, and put it in my 53 3600. I had to cut the firewall to get enough clearance (4.5") between the radiator and water pump pulley. Do not even think you are going to use the mechanical fan, it sits way too low.

The classic hot rod treatment for that coupe would be a warmed-over GMC 302, if you can find one. Back when Dad was building flathead Fords for the dirt tracks around middle Tennessee, there were lots of military-surplus 270 GMC's around, and some of them were pretty competitive. Their biggest problem was too much low-end torque causing excessive wheelspin off the turns, but if one ever got hooked up, it was hard to beat. Most of the well-modified engines around Nashville were running astronomical compression ratios, multiple carbs, and an alcohol/peroxide fuel mix, and the babbit-rod Chevy engines just wouldn't stand the strain. The full-pressure GMC's with insert bearings would take a lot more abuse.
Jerry

I've got a 302 GMC I'm getting ready to replace my 261 with. It has a much larger oil pan (8qt) than the 235/261, and is a bit longer, but at least it has a high mounted water pump. At least with GMC's you can still use your original bellhousing, you can't do that with a 250. The radiator needs to be slid slightly forward for clearance or you need an electric fan. You can't shorten the water pump on a GMC, they already are.

Patrick66
Would your 48 be a "business coupe"? I had one when I was in high school. The old 216 gave out (from my cool driving) and I dropped a 55 Olds in it. Those old coupes can look really nice.

Here's the 48 coupe that I'm rodding. I went typical small block and auto with a Nova front and rear. The only reason I'm building this car is for experience in stubbing a car and to practice my metal fabbing. So far I haven't bought a single patch panel for it. The only parts I'll need to buy will be the rear fenders and the fuel tank. Let me know if you need any pointers when you get started, I'm pretty much through the mock up stage and will be doing body work when I get back to it,
Scott

The car that I am trading for. Pretty solid coupe, minor rust in the floors, a few dings, and a broken door glass. Perfect!

1948 Chevy coupe

It is NOT a business coupe, BTW.

I've tossed around the idea of putting my '69 440 engine in it, just to confound those at car shows where all you see are SBC engines in cars, regardless of the car make! I think the GMC Six would make a pretty good statement, too!

Uuuhmmmm, that aint a '48, looks like a '42 to me.

That is a 1946 grille for sure,guaranteed . 1942 grille trim outer edge came down to the bumper or splash pan area. 1946 has that horizontal bar at the bottom of the grille that covers part of the front fenders.

yer right Waldo, 42 grill, the one Scott linked has the 48 grill

Bill

From the "Old Car Manual Project"

1948 Chevy Brochure http://www.oldcarbrochures.com/main.php?g2_itemId=19258

1947 Chevy Brochure http://www.oldcarbrochures.com/main.php?g2_itemId=19079

1946 Chevy Brochure http://www.oldcarbrochures.com/main.php?g2_itemId=18837

1942 Chevy Brochure http://www.oldcarbrochures.com/main.php?g2_itemId=18628

I think your grille and the Chevy hood emblem says 1947, patrick66.

Just for fun, visit Tom Langdon's site and listen to his GMC 302 (bored to 341) in his 39' Chevy.
http://www.stoveboltengineco.com/tomsride.htm

1942 and 1947 totally different grille look closely at them.It's a 1946 grille.

1946 chevrolet grille

You're right bowtietim, that is a 46' grille. (I even had my glasses on earlier!)

After looking at the 48' brochure closer, the rest of the door and hood trim looks 48', the Stylemaster Series, not 47'. (One of these things doesn't look like the other...LOL)

http://www.oldcarbrochures.com/main.php?g2_itemId=19280

So, a 48' with a 46' grille?

Anyway, put a nice 6 cylinder GM truck engine in it to keep our discussion sufficiently trucklike.

Randy your right on the 1948 stylemaster series,looks to be the club coupe.I zoomed in on the front fenders and can see the old outline and bolt holes of the original 1948 grille.The original color looks to be green.

I would put a 235 or 261 in this jewel.
Nice car patrick66 !!

1948 stylemaster series

I'm looking at either a 261 or a 235, ideally, but will consider a 250. One of you guys within 400 miles or so of me has an engine and transmission for sale that is good, right?

I think it'll make a pretty neat car!

I've got the '55 235 that came out of my 48 and a 250 that came out of the Nova that I robbed the stub from. Interested? Condition of both unknown,
Scott