Chevy C30

[WeedDog]

Hello Small-Block enthusiasts:

I'm a shade tree mechanic who enjoys a challenge, and here's one: A friend dropped off a 1977 Chevy C30 Motor Home for me to look over. He's leaving Wisconsin for Arizona soon, and wanted to know if the beast was roadworthy. She's powered by a 400cu inch Chevy V-8, drives dual rear wheels through a propeller shaft attached to a TH400 transmission, and has 109,000 original miles on the odometer. Her curb weight is a hefty 10,500lbs.

He paid $1500 for it, and the sale included a very complete (and very LONG) maintenance history.

The engine has burned valves in two of the rear cylinders. (Is anyone surprised?) I read that one solution to this is to, during a rebuild, install heads that have added steam holes. Have any of you done this?

And although it is a 1977 model year vehicle, the engine block may have been in storage after it was manufactured. I mention this because it may have been made in 1975 or 1976 when leaded fuel was intended to power the engine, and hardened valve seats may not have been installed. Now the 1977 Owner's manual clearly states that unleaded fuel be used. But leaded fuel would have allowed the valve seats to operate at cooler temps than unleaded fuel. This suggests a snafu that doomed the engine to burned valves.

Any tips on how to prevent a recurrence of burned valves is very welcome.

But I also suggested to him that swapping in a Chevy 350 might be a better fix. It appears I could bolt it right on to the TH400, and the 350 does not appear to have the cooling problems that can damage the 400cu inch engine. But does the 350 have other quirks or limitations that prevent a swap in this instance?

It seems, too, that he would end up with a power plant of very comparable horsepower and torque. But what else do I need to know?

 

[ChevyHiPro]

The Small Block 400 was notorious for the coolant holes at the rear cylinders being smaller, for clearance between the cylinder bore and the edge of the head/block.
So, they clogged with mineral/rust/crud build up quicker, causing higher operating temps in the head and oil leaks around the valve guides and burnt valves.

If a guy had the stripped block and heads boiled out in a chemical tank, so all the water passages are fully open, then rebuilt the engine, filled the cooling system with either 100% antifreeze, or a 50 - 50 mix of antifreeze and distilled water (steam distilled) and changed the coolant every two years, on schedule, it would probably not have a blockage problem for a long time.

On the other hand, pulling the 400 (it would have to be done to rebuild) and stuffing a healthy 350 in there would be a piece of cake, bolt right up.
Due to the weight of the beast, I think I'd add a couple of cheap tricks to the 350, to boost the HP and Torque.
Chevy has an RV cam for the small block that has a somewhat higher lift and longer duration for more torque, but it's not radical.
That coupled with a set of stamped, roller tip rocker arms with a 1.6 ratio would add considerable HP and torque, but a minimal effect to gas mileage.
Couple that with an Edelbrock Airgap intake manifold, stick the carb on it that came off the 400 and a set of Flowtech Afterburner headers and that setup would cost about $625 complete (see below) and would add a lot of torque and HP to the 350 for pulling the lumbering beast about, with reasonable gas mileage.

Cost;
GM RV Cam = $75
Stamped roller tip rocker arms, 1.6 ratio = $100
EdelBrock Airgap intake = $250
Flowtech Afterburner Headers, painted = $150

To get some of that stuff cheaper, shop around on Craigslist for used stuff, or the internet for discounted new stuff, save some more.
For another $50, throw on a K&N 14" diameter, 3" high air filter in a $25 Edelbrock air filter holder and add some more torque.

All of the accessories from the 400 will bolt right up to the 350, brackets and all.

If it's decided to rebuild the 400, I would add the same tricks to it that are listed above!
Again, more torque, HP, without damaging the fuel mileage.

Ps. I forgot to add some exhaust pipe to fit to the mufflers form the headers on the motor home.
I'd cut and weld''em up myself, with Turbo mufflers towards the rear end.
Done it a bunch of times, no problem.

Good luck with your project!

Ps. If a 350 is put in the motor hiome, let me know, I'll take the burnt up, worn out 400 off their hands for cheap.

 

[hurst01]

There would be better intakes for the engine than the AirGap. You are talking an engine that would be mostly for under 4000 RPM, and the AirGap is not the most desirable.
Were it me and I wanted to use a 350, I would look around for a good later model engine from the very late 80s to the late 90s with a factory roller cam and let it go. High performance parts on an RV engine is very inefficient. I have tried several of the RV cams and the only thing I got out of it was a gas hog and no performance.

 

[ChevyHiPro]

Hello Ed!
Thanks for the insightful comments!


IMHO your absolutely right, in an RV, especially a motor home type, the normal operating range will be up to 4K rpm, and more torque is always a good idea getting the lumbering beasts (10,500 #'s!) up to highway speed.


Granted, there are better torque producing intakes than the Airgap.
I was commenting with a concern primarily towards the budget!
Ain't that normally the case!!

Around where I live (south central Texas) a guy can usually find a used Edelbrock intake for cheap.
Of course, he'll have to check it out close for broken studs, bent and cracked mounting flanges and such.
:roll:

A late model ('87 and up) roller cam/lifter engine would be the best way to go, but most of the wrecking yards know what they got and generally the roller cam/lifter engines will cost more (probably a fair amount) than a non-roller.
Also, most of the truck engines, pretty much to today, have hydraulic roller cams, but straight hydraulic lifters, not the hydraulic roller lifters.
So, the torque output is about that of the regular hydraulic cam setups.
:shock:
Of course, the wrecking yard guy probably won't go to the trouble to add that tidbit of info!


Anyway, welcome to the forum and we appreciate your your learned comments!
Don't be a stranger here abouts!