The Stovebolt Site Forums The Shop Area Engine Shop Chevy 292 Vs. GMC 302

I plan on doing an engine swap sometime in the future on my 47 2 ton and was wondering if anyone knew of some of the advantages or disadvantages of either engine. Which one was tougher or torquier. I know where I can get a Military GMC 302 rebuildable long block for 800. I've heard you can bore the 302 out to 4.125 with sbc pistons and stroke it out to 4.250 with mopar rods making it into a 341. I haven't heard much about boring or stroking a 292. If anyone has any information i would greatly appreciate it. Perhaps any ball park horsepower and torque figures or even dyno tests. I'm mainly looking for low-mid grunt and I don't want a v8.

I don't have direct answers to the specific questions you ask, but I do have a couple of thoughts regarding the two motors.

First is that a GMC 302 is going to swap into your truck with very little modification since the configuration is the same as was used in the GMC versions of these trucks.

On the other hand, the 292 is a more recent design and likely easier and cheaper to buy parts for.

Comparing performance of modified motors is a bit more difficult and I don't feel qualified to do that...

The main downside of the 302 will be the fact it was a fairly limited production engine when it was new, and parts availability hasn't improved over the years. On the plus side, it's going to look more original, and it will be close to a bolt-in swap.

The 292 is rugged, recent-manufacture, and at least some parts will interchange with the smallblock V-8 line, making repair parts much more affordable. You'll have to do a lot more adapting to make it fit your chassis, however.
Jerry

Nothing exchanges with V8 except lifters, valves and valve springs.

You should ask Tony #107 your questions. He built a warmed up 302 for his '37. He doesn't post here that often anymore. You can probably find him hanging out with the other strictly GMC guys.
Old GMC Trucks
Look in their Discussion boards. Those guys would have an idea of what is available and where.

The 292 shares the bellhousing and flywheel with V-8's. You would probably have to find a crossmember from a TF/60's truck to match with the bellhousing.
Fred

''The 292 is rugged, recent-manufacture, and at least some parts''

ANYWAY you cut the mustard
it's ALL EXPENSIVE....................................

As far as the ''COOL FACTOR''
.....................IT's ALL COOL

FIRST buy leo santucci's book on powering L6 motors. read it
learn to do a search on this bolt page about 292 vs 302's as there is LOTS of that info out here.
the search button is in the upper right corner.
http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=2;t=009843#000000

the 302 is longer than any other L6, where as 194-292 are the same length.
more parts are avail for 292's. intake, exh manifolds, valve covers & tin-work, pistons /cams are more affordable
it all depends on what you want or how much time you want to spend sourcing vs driving.
there are lots of very good engines out there. at one time when and shortly after i got our little 3104, i knew we needed a new engine. re-building a 235 was 3-4 times the expense vs. what i was lucky enough to find my 292 completely rebuilt and ready to install. so that's a no brainer. the 292 won my vote. 250's rev a little higher than 292's and are a little faster. 292's have torque, you have a 2ton so consider a 292. there are many trade offs to building a reliable bolt.
it's your choice. differences are also made w/ a modern tranny and rear end gearing.
good hunting and luck.
my.02

I just measured a GMC engine and a 292 Chevy that are sitting side by side in my garage, they are both almost exactly the same length from the back of the block to the end of the water pump shaft, both are 33" long. My 292 is stock bore but if you choose to bore it .060 it will be a 302. The 292 has 7 main bearings and the 302 GMC has 4 mains, so the lower end is stronger in the 292, the head of the 302 has nice ports and valves so it breathes good, but the 292 head can be easily modified to breathe better than the 302. Unless you get a 12 port head (read expensive and rare) for the GMC, the 292 with a little work will make a good bit more Horsepower than the 302. There is no substitute for cubic inches, so the 292 will always make more horses than a 250. My mildly modified 292 with head work, cam and headers with 3 Weber sidedraft carbs makes about 350 Horses, and is a great street engine. Destry, good luck with the '47, I know you will enjoy it whatever engine you use.

I'd go with the 302 just for the "cool" factor. These are the engines that were blowing flathead Fords and 265 Chevies out of the water back in the day.

There are some mods that the military 302 will need. There is a great article on this at the OldGMCtrucks.com forums.

Destry,

Is your truck a chebby or a Jimmy? If it is a chebby I'd go with the 292. If it's a Jimmy I'd think about the 302 since it would be a bolt in swap. 302s are a little bit more spendy than a 292, but they definitely have the wow factor. Very few people outside this forum and others like it would even notice the difference between a 216, 235, 261, 228, 248, 270, 302, or a 292.

Hello Richard!Come on over to the "other site"Chevys are welcome,lol. Yeah,I put a modified GMC 302 in my 37 Chevy pu to replace the modifed 261.It bolts in after you move the radiator foward and fab up a spacer for the front motor mount.
GMC's are somewhat expensive to modify,but not that much more than a 292 Chevy perhaps,which is a more pricey than a common V-8 unless ya shop carefully for bargins.
A modified GMC 302 that's streetable,headers,cam,forged higher compression pistons,more carb,makes about 240-260 HP and 340 lbs ft of torque with a mildly reworked head.The Chevy 292 is probably capable of more power for the same money spent as mentioned above.For instance, bearing sets for the GMC are expensive,specially for better bearings like the discontinued Clevite 77's or GM Morriane 400 bearing sets.

Impress the public? most don't know what there're looking at anyways.I've had guys look at the 302 in my 37,ya see headers,Holley 4 bbl,extra crankcase breathers and they ask "is that the stock flathead 6?
Anyways,the 302 looks old school under the hood and I like it..

Thanks a lot for all the replies. Right now I'm sort of leaning towards a 292, if it's cheaper it's a bit more realistic for me right now. As i'm 16 working a part time job. As far as the rear end & transmission I'm keeping them stock unless a really cheap heavy duty 5 speed transmission rolls my way or a higher geared rear axle. But I am thinking of an auxillary transmission for the over drive factor. I want to be able to go the speed limit without pushing 3000-3500 rpms.

As far as the 292 goes, can you stroke it out a little more? Like weld and grind the crank and use either shorter pistons or shorter rods? I really don't know much about the 292, or the 302 for that matter. I'm wondering what all the specs are as far as rod length, deck height, piston height, etc. goes. I'm a sucker for tri power carb setups and am wondering if anyone here has done that and what would be better? 3 big 1 bbl carbs or 3 small 2bbls, or do the progressive linkage with a big center one and two small outer ones, or vice versa. I also want to learn about what other people here have tried with their Sixes and see what works. I'm not looking entirely for power, I do want reliability and I want something different... with a bit of torque.
-Destry

This book is where you need to start. It will answer many of your tech. questions about the 292 and will probably persuade you to go the 292 route. These days, I think anything besides a SBC is an automatic cool factor. It is expensive any way you cut it but all that money won't do us any good when we're dead, so spend it I say!

I will have to purchase this book. Actually Today I saw a 292 for sale, but the guy wanted way too much. I'll just have to look around, call some junk yards.

I have seen websites that sell rebuilt 292's for about $1400 as a crate motor. Sure, it won't be hotrodded, but it's pretty similar to some of the ridiculous prices for 292 builder cores that I have seen out there.

If you can find one of these big sixes, that's definitely cool. I got discouraged. Oh, I could find 235's all day long, but one of the biggest irritations of mine was not being able to keep up with traffic. That's why a lot of us jump to the "belly button" V8's. They do offer serious bang for the buck.

But they will never be more cool than an old-school straight six. I once won a trophy at a car show just because mine was the only one with a straight six. It was a little beat up, and daily driven, but it won the people's choice because it was the only one without the shiny chromed-out V8.

Who knows, maybe someday I'll go back to a big inch 292 like you, if I ever find a good deal on one. Drive on, sounds like a cool truck!

Hey Tony, did you stick with the original solid axle front end?

I guess you don't realize you are asking a question about a 9 year old post to a guy who hasn't been here in 8 years. I wouldn't expect him to answer.

Hey Tony, did you stick with the original solid axle front end?

If you're considering the 292, get Leo Santucci's book Chevrolet Inline Six-Cylinder Power Manual.