1978 Chevy 30 motorhome

SoCalDesertRider wrote:

tatest wrote:
Chevrolet's first "big block," the W-series truck engine, was originally as small as 348 (grew to 409 and the Z-11 427) but that won't be in a 1978, GM stopped using it when Chevrolet introduced the Mark IV (366, 396, 402, 427, 454, 502, 572) in 1966.

So the 350 is a version of the original small-block V8 (262, 265, 267, 283, 302, 305, 307, 327, 350, 400 working with combinations of six different cylinder bores and five stroke lengths). Most likely it is an LT-9 "heavy emissions" build, available only in 3/4 or larger chassis. Rated 160 HP at 3800 RPM, 250 lb-ft at 2800. Not a screamer, but design to run at full load all day. Engine code will be "M" on the VIN.

I would say you can tow with this engine, and the TurboHydramatic 400 it is most likely paired with. It is just not going to accelerate quickly, nor go up hills very fast, but should be able to handle any Interstate grades in second gear, and any grade on which you can get enough traction in first. One of the guys in our RV club pulls his 30 foot trailer behind an old G20 van with the LT-9 and TH-400, but he doesn't go very fast, usually limiting his speed to 55-60. Only problem he ever had was losing power when the rear fuel pump started failing.

Most likely limitation will be the hitch, which can be changed out, if the OEM frame rails extend to the rear of the vehicle. This is not always the case with RVs, some manufacturers extended frames, I've seen others hang the house over the back of the chassis to make some nice big storage space. But probably not in 1978.

In that vintage of motorhome, I would be looking for P30 chassis with the 454, or the Dodge chassis with the 440. While not rated for much more than 30-40% more HP than the Chevy 350 or Chrysler 360 small blocks, these big block engines were rated with at least 100 lb-ft more torque, and they got that at engine speeds about 1000 RPM lower. Won't be climbing hills faster, but engine doesn't have to scream to do it.

I see someone far more knowledgeable has already responded! :b

I don't remember the 366 and 572 big blocks. I'm guessing they were used in the big trucks, like the C50, C60?

The 366 (and tall-deck 427) were used in medium-duty (C50 and C5500 and up) trucks and school buses (thousands of Blue Birds were built on GMC C5500 chassis with propane-burning 366s)...I think the 427s also went into boats. The 572 is only sold as a crate engine.