Overheating and heater valve

[montreal]

I've been getting stuck into the 310 for the last few days.
It's the 1st time I've lloked over it in detail. It's not really too bad but I do have a different outlook than most!
Anyway, I spent a while working out the Rochester carb. It now opens all 4 barrels nicely and has had a good clean but not disassembly. We had an overheating problem the other day when I was flooring it on a long straight. It only managed 68 mph so its missing some power. On inspection I think the distributor timing is out.
What should it be for 95 RON fuel?
It was also virtually empty of coolant. I am hoping that its not a head gasket problem as the radiator cap was stuck on. I have managed to free it and used about 6 litres to fill it.
When I ran it at a standstill I noticed steam/water on the floor of the passenger footwell. The heater matrix is here and a stream of water was jetting throught the vent!!
I would like to pull the heater out and get a replacement matrix made ideally. Maybe some Radweld but I dont like to use that stuff too much. As I have a small trup planned next week.....My question is does the heater valve in the side of the box completely shut off the water flow into the heater if closed manually? The heater has one hose in and one hose out coming from the enging back through a firewall. If I leave it closed I can come back to it and just leave the heating off.

D

[idroba]

The Heater valve in the P30 chasis GM motorhomes does not shut the water off completely, and even if it did, since there is a supply and return from the block, and if you have a core leak, which I think I understand you do, it would not stop the leak as there would be pressure on both the supply and return sides.

For temporary use, to bypass the heater core, just make a U out of a piece of heater hose and run it from the engine supply to the engine return, eliminating the heater core loop completely.

(former 310 owner)

[92landyacht]

Agreed... bypassing the heater core is your only option until you can replace the damage core. Radiator sealant will most likely cause more issues and probably not fix the problem for any duration. You can either run the inlet to the outlet with a single hose or plug both ends of the lines going to the heater core. In a pinch I've disconnected the hoses from the heater core and simply folded the hose ends over and clamped them in place. You have a leak in the coolant system. Until you seal that leak you will always over heat.

Your lack of power is most likely not related to the over heating but is of some concern. Check your compression on all cylinders. That will give you an idea of the health of your engine. If compression figures look good then it could be fuel, timing or even a brake issue. That fact that you've been messing with the carb could be of some concern as well.

[montreal]

Back to it today....
You were correct in saying that the valve does not close off the flow to the heater completely. Manually moving the valve did not work. Yes I will have to block the ends of the flow and returns from the heads or make a loop.
Long term I'll be fixing the heater matrix. Is there a Chevy item or do I need to get one made locally to size? In the P30 manual it recommends an upgrade of the heater valve to include a bypass as part of the valve to help regulate the heat. Has ayone done this?
I think the overheating is fixed but I cant be sure until the leak is sealed. All the barrels open when I stamp on the throttle at idle. Removed a bit of carpet under the pedal and also reset the kickdown switch....time will tell if it worked.
What are the timeing specs anyone...?
Oh yes. The PO fitted an overflow bottle but it's cracked. Can I just get a Chevy p30 bottle and bracket?

[Bfrank]

Try Mill Supply they have lots of GM P-30 Parts and heater parts
http://www.Millsupply.com

[Keyair]

Overflow tank from the radiator is easy... well here it was...
This generic one worked and perfectly and cost $8..



I just noticed I have coolant dripping on the passenger side, so I will be getting into the bypass hose soon and maybe pulling the heater matrix/core out too!

[Gypsy Jo]

Heater core
I took mine to the radiator shop he ordered a new core and put my tanks ,sides , back on . Cost around $110.
Jo

[PeterH-350LE]

Originally Posted by montreal

Back to it today....
...Long term I'll be fixing the heater matrix. Is there a Chevy item or do I need to get one made locally to size? In the P30 manual it recommends an upgrade of the heater valve to include a bypass as part of the valve to help regulate the heat. Has ayone done this?
...

Lucky you have the heater core that can be recored by any good radiator shop. When I restored my old 79, I found the heater core was missing, surprise.. I ended up making a drawing of size and mounting brackets and had a local radiator build me one from scratch.
If you want to regulate the heat, keep the heater core in the coolant loop and turn the heater on when it runs too hot. But I would first dig a little deeper and find the real cause of the overheating problem.