The Stovebolt Site Forums The Shop Area Engine Shop Help build a 292 I6 for towing

What I have is a low mileage (28k) 292 that I plan on using to replace a 6.5 diesel. I am trying to get as much low end torque as I can. I hope to use the same torque converter currently in the truck.
I have purchased all new bearings and gaskets, a 4 barrel intake and cast iron headers. I also have a lump port kit, metal timing gears, HEI and I'm sure other stuff I will remember.
I need help with choosing the best camshaft for my needs, and help with buying the right motor mounts.
I am curious as to the worth of roller rockers and lifters in a low rpm engine such as this.
The engine is to go in an 86 K30.with a 4L80E.

The parts you have listed are for building an old school race engine. Those will *not* work well on the street, especially for towing.

Hotrod Lincoln will almost certainly be along soon.

I strongly recommend you take his advice.

The 292 was designed by the engineers at GM to compete with the Ford 300 six. It was almost, but not quite as good. The cylinder head design with the siamesed ports is the sticking point, and lump ports only show an advantage on the dyno at high speeds most street engines seldom, if ever see. Do a good stock rebuild- - - -you'll have far more low end torque than your hotrod engine will ever be able to make, since the R&D department at General Motors has already optimized the engine for medium truck use. They had far deeper pockets and more toys to play with than any aftermarket engine builder. DO NOT overcarburete the thing- - - -Use a Quadrajet calibrated for a Chevy 305 V8 or an Olds 307 if you insist on running a 4 barrel. Doing race engine stuff on any street machine is stupid squared- - - -particularly in a K30 intended for trailer towing.
Jerry

Motor mounts are the standard 350sb mounts

A 4L80E is a good transmission. As you no doubt know GM put it behind the 454 and with the 5 pinion overdrive, behind the 496. You will not stress it with a 292. The problem with this setup is not enough gears -- only 4 and 1st is higher than the 4L60 making the gears a bit closer together in the interest of trans longevity. Even so, the engine you build will need a broad, flat torque curve like the 454 has or the stock 292 has.

I am on a road trip at the moment with an AD pickup loaded with a camper and grossing about 9,000 lbs. The 261 does just fine even though it's a bit peaky with ~254 degree cam, about 220 at 0.050 lift. The only reason this works on the road is that I'm running what amounts to a 10 speed plus 3 ranges of compound low. There is about 400 RPM between gears. From Bakersfield to Barstow I only had to drop to 3rd and over because I got caught behind a slow motor home on the Tahachapi grade. The rest of the time I just work the top three gears. When I'm gearing down for a grade the fire pretty much goes out below 2500 RPM so shift early. Torque peak seems to be about 2900 and the horsepower comes on above that. I turn it up to about 3300 to make the next gear on the way up if I'm pressed by traffic.

l hope this road tale tells you a little about what to expect when pulling hard. If you're limited to a straight 4-speed you need a very broad, flat power band and the "RV cam" I use won't do it for you. You need good intake velocity at 1800 and power up to 2800 RPM. You're going to see about 1,000 RPM between gears with the 4L80. I have one behind a 454 that I tow a 15,000 gross rig. That's a 98 Vortec 7.4 and I keep wishing I had at least a 6L80 trans even with that big engine.

I would guess that the 4L80 and stock torque converter for that 86 K30/6.5 would be pretty good with the 292. The 6.5 turbo Detroit was not an extremely high RPM motor, it made really good torque in the low RPM range so the TC should be fine. The K30 would have 4.10 axles as stock or an option was 4.56'S. If I were putting that engine together, I would call Comp Cams and speak with an advisor, give them the specs and expectations, they will advise the cam grind.

I've got the bits and pieces to build a tow rig from a retired fire truck that was given to me a few years ago. It's an American LaFrance pumper on a 61 GMC pugnose rig, with a 401 V6 and a direct drive Clark 5 speed transmission. I'll be removing the driveshaft mounted fire pump and replacing it with a 3 speed Brownie- - - -under, direct and overdrive in the Brownie, which will give me 15 forward gears and 3 in reverse. I'll remove the fire bed and add a commercial 5th. wheel and a gooseneck hitch. That one should tow anything I can hook up to, and pass anything but a gas station! If the engine doesn't work out well, I've got a couple of 454s stashed away to upgrade the power train, and a 500 cubic inch Cadillac with a Turbo 400.
Jerry

Check out 12bolt.com for a roller cam option. I looked at the web site & he seems to have some well thought out options.

I'm really curious what you're running here; a T5 with deep under Browning?

I'm pretty sure he's got a real transmission- - - -some sort of an under/direct/over box in front of a SM 420. A T5 couldn't handle that kind of load down a steep hill with a tailwind.

Maybe a bit late on the reply on this:

No, a T5 would not carry the load. I'm thinking I should put a temperature gauge on the main box as when it gets hot the 3rd and 4th syncros bark if I shift to fast. This is since I put a Novak overhaul kit in it and switched to mineral oil rather than GL4. Never did that before but now it got a hot 261 in front of it.

As Jerry said, the main box is real truck transmission, an SM420 and the brownie is a progressive 3-speed, not a deep under, -- 24% under and 17% over plus direct. Says Spicer-Brown Lipe 6231A on the tag.

After 7 hours of running down the CA central valley at 63MPH, 2600RPM, the brownie creeps up to about 200 degrees. That's at 65deg ambient. It doesn't get that hot on a hard pull in under drive for whatever reason, probably because the output shaft is turning 2/3 as fast. Input shaft speed is still about 26-2800 RPM. With the previous engine, a similarly tuned 235, I would have to pull in 3rd and overdrive for short periods, maybe 5-6 minutes, over the Siskiyou Mtns. and over Tehapachi out of Bakersfield for longer periods. I worried about main box temperature but no gauge. With the 261 I can pull both in 4th under. If I put a gauge on the rear drive axle then I could worry about that too. I ran the 5.13 axle for decades at similar speeds, maybe 3 MPH slower, and it never complained. I used to get paid to do this sort of thing back when trucks had 2 sticks and 335 horsepower if you had seniority, 220 if you were a newbie.

I have used this rig to tow an 8,000 lb. travel trailer home from North Central Montana to North Central Washington. It wasn't fast but it kept ahead of the log trucks.

Back in the late 1970s I drove a Freightliner with a 270 cat and a 15 speed Eaton over those same roads- - - - -"slow" and "slower" was the order of the day. That drivetrain was a straight 5 speed transmission with a 3 speed rear axle setup. "Intermediate" axle ratio was one electric shift 2 speed in low, and the other in high, with the power divider taking up the difference.
Jerry

Jerry, I never had the misfortune to drive an 15 speed Eaton but we had one rig with a 16-speed Spicer and I had to read the instruction sheet every time I was assigned that truck. I remember reading that "the ratcheting sound will diminish as the driver gains skill." I was never able to make the ratcheting sound disappear. I hated it. Give me 2 sticks or a 10 speed and big power.

Ever drive a Maxi-Dyne straight 5 speed with the 1200-2100 RPM range? It was one of the first of the "fuel squeezer" engine designs that Cummins came out with a little later. An oldtimer I worked with for awhile compared it to "having a mule in the Kentucky derby!"

I drove a later KW with a "fuel squeezer" Cummins in it. Car drivers would give me the finger going up even the slight grade though downtown Seattle. I named that hill Hotel Hill. I could make 18 MPH pulling 80,000 lbs. of special Mt Rainier glacier water. Nordstrom's sold it for $4 per pint. Somebody made a lot of money on that haul and it wasn't me.

It was slower than the 170 Mack Thermodyne I once hauled hay with. I think it had an 8 speed. The company had two of them. Eventually the shop turned one of them up with bigger injectors and a higher wastegate pressure. One really had to watch the pyrometer after that. It didn't last long before somebody stuck a cylinder liner. Fortunately this was a an hourly trip not mileage. The only saving grace to that trip was that it was a trip to the woods by Mt Rainier and very pretty. I used a trash pump to load 6,000 gallons from the Carbon River. Just run the pump till water blew out the domes on top then shut it off.

Pretty interesting setup.

Another option to a T-5 if not needing an OD would be a NP-540 series, just like a 435 but with another gear. The closer ratios make hauling a load work well. They come with many bellhousing bolt patterns including GM, Ford, Dodge, etc. The 14” clutch models have a longer input shaft which is not very useful for our size trucks.

Ed

That's a very interesting option! I think the NP 540 had a OD variant as well.