The Stovebolt Site Forums The Shop Area Engine Shop "small block" I6 to "big block" I6

My 67 C10 has a 250 in it now. I like the power OK, and it'll haul anything I throw at it, but it's very lethargic when trying to tow my big honkin' boat, and I wouldn't even try to tow my delta with it. I want to put a 292 in there for some better low end torque, as I will be putting in highway gears in the rearend (3.08's or 3.23's) and I don't want to sacrifice the low-end that I have now with the 250 and 3.73's. As it is now, it's a bit hard to start off if the bed is full of stuff, and I couldn't imagine with the 3.08's what it will be like. What needs to be done to convert engines?

The basic diference is the right engine mount.
It sets back farther on the 292. You can use a
bracket for the 292 or fabricate something.
You need to use pulleys & bracketsfrom the292.

The basic diference is the right engine mount.
It sets back farther on the 292. You can use a
bracket for the 292 or fabricate something.
You need to use pulleys & bracketsfrom the292. It
is taller so you have to extend the exhaust.
The bell housing fits but you need a 292 flywheel.
I,d rather have a v-8

Matt McD,

I did a similar swap in my '66 c10, swapping a strong, good running stock 230 for a stronger mildly built 292. Easy swap and they both look about the same under the hood - the 292 is a tad bit taller.

Like you I had the 3.73 gears. Suck like crazy on the interstate, topping out at 60-65 max cruising. But with the new 292 I swapped in a 4 speed transmission, with 4th gear having a .73 ratio overdrive. My net final ratio is 2.72, which is even better than those you're seeking. The 3.08 or 3.23 will do you great also. Either will be much better than the engine killing 3.73 top gear ratio you're running now.

If you go with a higher (numerically lower) geared rear end then I recommend you going with a 2 groove input shaft Saginaw 4 speed. This transmission (in factory settings) will give you a 3.11 first gear, which will still give your 292 great low end torque with the 3.08 rear end.

I have a mild cam, headers with a nice deep sounding two chamber Flowmaster and a 500 cfm 4 barrel on my 292. The muffler has single in and dual outlets, so I have dual pipes out the back. This combo makes really good torque and power up through about 4000 rpms. I have no problems whatsoever merging with even the fastest traffic on Atlanta interstate entrace ramps. I accelerate almost effortlessly to 70-75 mph in 3rd gear and shift to 4th for easy lower rpm cruising.

I don't see a big personal advantage in going with the v8, though it would have been cheaper to build a similarly powered small block. For my needs this 292 supplies more than enough. Keep in mind that these 292s were used in some huge, heavy C50 & C60 series trucks that not only weighed 8-10,000 lbs, but on top of that were used to haul heavy loads! And thats a 292 in a restrictive monojet 1 bbl/stock single manifold, low compression piston, small cam form. Power only improves when proper enhancements are made in these areas.

-ftyler

Thanks for teh input. I want to keep this truck looking and driving as stock as possible (with the gearing upgrade to get me better cruising), so that means the 3 on the tree stays.

I understand. My only concern is that with the stock 3 speed and a 3.08 rear end then you might find yourself running into some driveability issues during in-city driving. Because of the high geared rear end, having only three gears you'll possibly find yourself lugging the engine in 3rd or revving it in 2nd to maintain 45 mph.

Gear-to-gear acceleration will suffer some for sure if you go to the higher geared rear end. The 292s strong low end torque may make this minimally noticeable.

-ftyler

Lugging in high gear at 45 mph will not be an issue. I have an 84 K10 with SM 465(high is direct) and 2.73(yes 2.73 not 3.73)axle ratio. Motor is a 305 bent 8 with almost 200k miles on it. This motor pulls just fine in high at 45mph and it doesn't have near the low end torque that the 292 does.

I find this very interesting I have my 66 c30 292 sm420 all stock towed my trailer 31 foot two times this summer on the highway not to bad as long as I kept the speed up but on country roads where I could not get the runny might go up a hill at 20 to 25 mph couldn't even imagine doing this with a three speed trailer does weigh 6000lbs empty I am thinking of headers manifold and cam maybe even roller rockers sounds like it might help overall though it is fun to tow after i got the hang of it.

Anyway good luck
Dave

"I LOVE THE SMELL OF BURNED CLUTCH IN THE MORNING"

You said, that you do a lot of towing and hauling. In the real world, you never back into or pull out of a spot that is level when you have a load.
Either forget the 3.08's or forget the 3spd. 3.23 or 3.08 would be fine with a truck 4 spd such as a '68 up SM465.
That means you are changing engine, trans and rear. You could keep the 3.73's, use a 4spd OverDrive like ftyler and truckedup are using or go to a T5 like mugsy is getting ready to do. That way you only have two things to change.

There is another option. If you want to stay with the 3 speed then you need to locate one of the 3 speed overdrives that were options in these years. I ran across a guy at a swap meet from Oklahoma who had a trailer lined with 10 or 15 of these for sale. His name and number are at home. If you will send me an email asking for that informaiton, I'll send it to you when I get home.

3 speed on the column and cruising can be done...if that is what you want...

You can tow very heavy loads with a small engine and the right gearing, but you won't be towing very fast.292's were put in trucks with 22,000 lbs gross weights, they pulled ok,but no good for fast road work.Low speed torque is meangless on the highway, ya need a cubic inches, like a V-8 if you need to go fast.
I have two 261 powered trucks, one with a 3 spd OD the other with the 4spd OD Richard and Ftyler mentioned. Both trucks have 3.40 rear gears,in OD,that's like a 2.50 rear end gear.Both will tow a 1200 lbs travel trailer in OD at 70 mph on the highway, and it's no problem at slower speeds for occasional use.Unloaded, the trucks will chug along just fine in OD at 45 mph on level ground.
I think for regular pulling of heavy loads, the 3.73's are good, gotta keep the engine spinning at 2500 plus rpm.The OD is nice when cruising along empty.
A 350 V-8 makes more power than a 292 6 at all rpm's and costs less to find and or rebuild.But if ya like inlines, a 292 will do the job nicely.