413 Motorhome

I found a 1972 motorhome with a 413 in it, Complete.

Are these still a good motor to build?

Or is it a high priced boat anchor?

Always wanted a 413, thinking about using it in a 2wd truck.

Thank you

Still a good motor to build?

I don't think they were ever a good motor to build for anything other than HD use, as designed.

The block, and maybe crank and rods are ok if you really want a small bore RB.

Other than the the rest is scrap. If someone gave it to you that would be a fair price, assuming they'd already pulled it too.

If memory serves, the heads are unique and have little to no value. The exhaust manifolds were prone to cracking, so good ones have some value if you can find the right buyer. See them on eBay.

Pistons were dished for low compression. Water pump setup is unique too, of no value. Oil pan of no value and limited applicability in my experience.

A good strong block with thick cylinder walls, typically can be bored out up to .120" for a 426 displacement bore. Good crankshaft and pretty standard connecting rods. I've seen 6 and 8 bolt crank flanges on them.

That said, I've one painted up on a stand in the pole barn. Put closed chamber heads on it and plan to use it for street use to move a station wagon around. Mine only had 45K miles on it. I paid $200 for mine several years back and was happy to pay that as good as it looked inside. I viewed it as a $200 short block in good condition.

Its a good starting point. However, as has been said the only thing from a performance standpoint on the "motorhome" version that's of any real use is the short block. Take that and add a good set of heads and better pistons and it can be a very respectable power maker.

Also, you only need to enlarge a 413s 4.18 bore +.70 to get to the 4.25 bore of the 426 wedge.

Pistons are low compression scrap and finding useful non-low compression off the shelf 413 pistons or 426 WEDGE pistons is tough. Sure you can pay to have custom pistons though $$$.

I sure wouldn't pay money for it.

Well the plain truth is that a 413 cubic inches it isn't large enough in cubic inches for its weight. A 4" stroke 340 with a decent set of heads will put it on the trailer.

As an industrial engine it was designed to make reliable horsepower for a long time. For car use it is really just a shortblock at best as everything above the shortblock is useless. But all the B/RB car stuff will bolt onto that shortblock.

YET,
It was, however, the original Max Wedge engine.
Hot Rod put a car type 413 in a Sweptline and ran 12s.
As 440 and 400 blocks become scarce, the 413 begins to look more attractive. If you're building an engine for a pickup truck the 413 is more attractive.

Chrysler engineers were really into fractions. The 413 bore was 4 3/16" which is 4.1875. Add 0.0625 and get 4.250.

As 413 blocks are next to worthless, I see no problem with boring them to 4.250. The 413 connecting rod is the same old LY 535 rod that was found in the bulk of 440s. A standard bore 383 piston plus a 413 rod plus a 4.15" crank will net around 472 cubic inches. Now we're talking enough cubic inches to matter.

There are some 413s that were built on 426 castings, no reason they couldn't go over 4.25. These are industrial engines. Check the casting number listings for examples.

My beef is that both 383s and 413s are usually listed for far more than they're worth because idiots think any Mopar bigblock is gold. I've seen motorhome 413s advertised for $800. Idiots!

It's ironic that the only person who'll sell you a 383 or 413 for what it is actually worth is a Mopar guy.

As the price of cast replacement pistons continues to rise, the custom forged piston becomes the better choice.

R.

I've used those blocks on several motors I've built to replace the 426 W blocks that where wore out. I have one in the shop now that I sonic tested last week, I will bore it from stock(4.170 or maybe there 4.180 stock ) to 4.250 and use a Mopar 4.150 stroke crank with stock Mopar rod journals and a set of Eagle 6.800 long Mopar H beam steel rods with a set of custom pistons to make a pump gas motor for my 1963 Plymouth Fury
It sonic tested okay, it won't go much above 4.25 safely though
I had the stock steel crankshaft offset ground down to 2.200 and increased the stroke to 3.910 for a 440 motorhome motor I have to make another 464 C.I. pump gas stroker with aluminum heads to sell

Are there any features of the industrial 413 that made it more efficient than consumer auto engines?

Was the factory camshaft very mild to give higher torque at lower rpm?

Was the carb set to a leaner than normal air to fuel ratio?

Efficient? No it was not designed to be efficient

Durability was it's major feature.

Thanks for clarifying my error on over bore. I was going on 45+ year old engine work I'd had done, plus tired brain cells.

As has been mentioned, they work good to replace 426W blocks, which were getting scarce even back then. My current 426W is a 413 block I'd bored to 426. It's certainly seen its' share of abuse over the years and hasn't failed me yet.

My 64 300 came with a 413. I rebuilt it, put on 906 heads, added the Street Hemi grind cam, a 750 and 4.10 gears out back. It scooted well enough.

But it didn't start as a MH 413.

The 361 and 413 industrial, H.D. truck, marine and other application blocks are a lot different looking than the same year and C.I. passenger block, to bad that they aren't much thicker on the cylinder walls

What kind of specs do factory industrial 413 camshafts have ?

From allpar

Quote
Just in 1969, the big block V8s had around sixty variations. There were 413s with two-barrel carburetors, for school buses and dump trucks. There were six blocks, five cylinder-head variations, four camshafts, three timing chains, four flywheels, four torque converters, five different oil pans, and many different linkage brackets
End quote

Many industrial 413s had gear driven cams .

I originally wanted to do that on my Polara but couldn't find a 413 block at the time. Wound up with a 440 instead.