" If you want a quick recognition of the engine" look at the exhaust manifold(s): Small blocks are a wye, exiting straight down between cylinders 3 & 5 and 4 & 6, as shown in your pictures; Big Blocks are straight (angling downward at the rear) exiting just past cylinders 7 and 8. Also, big block valve covers are wider than they are tall, while 350/400s are almost the same height as width.

quote:

while 350/400s are almost the same height as width.

I hope it's not a 400, in Chevys this is a Siamese cylinder block and compounds the already inherent heat issue in an RV application. Pontiac 400s are a big block and have the water jacket between the cylinders, but Chevy wanted the weight advantage I guess.

quote:

Originally posted by Moonbeam-Express:
I hope it's not a 400...

Unless the engine has been changed, there's no chance of that... The Chevy 400 was mfg between 1970–1981.

Edited to add: 1970-1975 2-barrel <> 1974-1981 4-barrel

I'm sticking with my earlier guess. More so, now that I've seen a picture.

quote:

Originally posted by Bill N.Y.:
21 footer from 1971 should be a 350.

Edit to better reflect what I meant:
1970-1975 2-barrel
1974-1980 4-barrel

quote:

Unless the engine has been changed, there's no chance of that... The Chevy 400 was mfg between 1970–1981.

Is that because you know they never used it (which is a good thing)? The RV is a 1971 which falls between the build years of the 400 from what you stated. Just curious.

wikipedia.org/wiki/Chevrolet_small-block_engine#400

Sorry about that... I saw the 4bbl intake manifold and read that they only came factory with a 2bbl back in 1970-1975. The first year with a 4bbl was 1974.

I don't know why I copied that instead?

quote:

The only block of this family, 400 cu in (6.6 L) small-block, was introduced in 1970 and produced for 10 years. It was loosely based on the medium journal 350 and had a 4.125-inch (104.8 mm) bore and a 3.75-inch (95.3 mm) stroke. The 400 differed from other small blocks in that the cylinders were siamesed, used a 2.65” large journal, and oftentimes had one more freeze plug on both the left and right sides of the block. Initial output was 265 hp (198 kW) and was only available equipped with a 2-barrel carburetor. In 1974 a 4-barrel version of the 400 was introduced, while the 2-barrel version stopped production in 1975.

The Chevy 400 was mfg between 1970–1981
1970-1975 2-barrel <> 1974-1981 4-barrel

Its a small block. It has the center dump exhaust manifolds (ram's horn). They are the good ones. Small blocks also had a lot of rear dump manifolds, which were much less desirable.

Another vote for an Edelbrock Performer manifold.

I use Holleys for hot rods and boats. For an RV, the doghouse heat is unkind go the narrow little float bowl gaskets. Long periods of sitting also take their toll on those same gaskets. Shrink. Leak. There is a plug underneath the Q jet that can leak. Most good carb men can handle that.

The Q jet gives better light throttle mileage.

What do you plan on doing to the engine?

Thank you for all the input and support. Our initial plan is to just get the engine running (which we finally achomplished yesterday). We had some wiring issues, the previous owner had a bypass ignition switch wired that was not allowing the starter to disengage the fly-wheel, which we finally figured out!

The plan now is to re-wire the original ignition, clean out the fuel tank/lines, inspect the brakes and lines, and hopefully get the generator running.

Once we have that all completed a complete restoration of the interior will be in order...

I have read quite a bit about using an acid/water mixture to clean out the fuel tank and then a re-sealer to ensure no rusting, anyone have any advice on the best way to clean out a fuel tank that has been sitting for 4 years?

It's a 350 V-8 engine with a 4BBL carb. If my
memory is still good, we (Chev) only offered the
350 V-8 on the 125 and 137 wheelbase chassis. A
2BBL carb engine was never used on the motorhome chassis.
Jake Jacobson