Re: 71 350 running hot coolant backup up problem
 

According to auto zone both of them are OE recommended. 180-195.

I would think it depends on if you have the 307 are the 350 just guessing here. Either one should work just fine though.
I have to agree with the other's. I would be taking the radiator out and have it rodded out are buy a new one.:chevy:

Re: 71 350 running hot coolant backup up problem
 

If it's in my shop I drain the system and run a scope down the radiator filler cap and look at the cores for blockage, it there is replace or recore the radiator. It needs a fan shroud with a good clutch, 195 degree tstat that is new, fill with proper mix coolant, run till its flowing and install the cap to pressurize. Using the digital thermometer you can scan the tstat housing for temp and it should run around 200. You can scan areas on the radiator for heat, it should be even, if it has cold spots then its plugged. That should get you fixed. If that's not it then it is not good, pulling water pump and looking for blockage in the block or heads assuming your thermometer is accurate. It is normal to have some coolant loss from the overflow hose due to fluid expansion by the way. If it gets hot and is not boiling over and just running in the 200 range its ok.

Re: 71 350 running hot coolant backup up problem
 

ok just to level set here is an update, I realize the first gen small blocks have a coolant bypass in the block and the water pump on the passenger side, but just in case that was clogged I added a bypass hose from the intake manifold to the water pump, very common thing especially if you have vortec heads, lets call it insurance

this may have dropped the operating temps 5 degrees or so, not 100% sure because the ambient temperatures have dropped from the first test by like 10 degrees by the time I tested this fix, so who knows

we'll leave it on for now

pic of red engine is not my engine just some pic I stole off the interwebs, just thought this pic would be helpful for those of you following along at home, LOL (don't mind that "this needs to be drilled" comment)

Re: 71 350 running hot coolant backup up problem
 

OK, so back to the Timing thing, I did some more testing and I found that the vacuum can on the distributor was kaput, did not respond to my vacuum pump at all, so I decided to replace it with a Crane Cams adjustable one just because that's what I had in my pesky inventory of junk

It appears that the new can is good for an additional 14 degrees of timing so 12 degrees initial plus 14 vacuum advance (since I am hooked up to manifold vacuum) gives us 26 degrees, so where is the other 10 coming from? (edited 2/9/2017)

whoa additional 14 degrees for a total of 36* at idle that's allot! or that's too much? remember this can is adjustable so we can adjust it, and we need to start somewhere, so this is a start

now before we start WWW III arguing over weather to use Ported Vacuum or Manifold Vacuum or Vacuum at all, LOL I will take the truck for a test spin

Re: 71 350 running hot coolant backup up problem
 

Gary, how’s those scars doing ?

Re: 71 350 running hot coolant backup up problem
 

Looks like the Crane vacuum can is missing it's rubber sleeve bushing that goes over the tip of the actuator rod where it contacts the advance plate... that will take the 24 degrees that you mention down some - say .086 for example would be 8 crankshaft degrees advance - So in other words you end up with way too much without the bushing cushioning the stop.

You can use vacuum hose but it breaks down so you have to keep an eye on it.

Also that guy who used to be on this forum a lot who worked for Delco Remy in the 1960's on distributor design has a DIY with photos on how to fab a positive stop for the vacuum can pull rod so that you can run manifold vacuum without risk of too much advance... or alternatively Crane makes an adjustable plate too as you know.

Edit:

I just remembered the guy I mentioned his name is Dave Ray - I have some of his how-to photos but since I don't have rights to publish them I'd refer you to Mr. Ray if you want his input- he is very well known and should be easy to find.

Re: 71 350 running hot coolant backup up problem
 

Well, I stand corrected! Thank you!

Re: 71 350 running hot coolant backup up problem
 

This is what JEGS shows comes in the kit, I don't see the bushing, do you? Am I missing something?

Re: 71 350 running hot coolant backup up problem - Test #1
 

ok, guys here are the results of the first test drive

195 Thermostat, running water only, 12 degrees initial timing

as you can see we were averaging over 200 still, here I caught it at 201* F degrees close but a bit hot for my taste

Re: 71 350 running hot coolant backup up problem - Test #2
 

ok, guys here are the results of the second test drive, this is for everyone insisting I run Coolant

195 Thermostat, running 50/50 water coolant mix, still 12 degrees initial timing

as you can see we were averaging over 200 still, here I caught it at 206* F degrees so technically it was running even hotter with the 50/50 mix, but I did not expect any improvement with coolant since it does nothing for the operating temperature it just shifts the freezing/boiling points, but that's a common misconception

Re: 71 350 running hot coolant backup up problem - Test #2
 

Scarred for life! :lol:

Try a different gauge.

Try a different radiator.

Gary

Re: 71 350 running hot coolant backup up problem
 

Have you checked the cap?:chevy:

Re: 71 350 running hot coolant backup up problem
 

Not sure how much I can quote Mr. Ray and stay within fair use but here are a few of his good thoughts on this topic and hopefully this is enough to help:

"Notice that the OEM GM advance has an addition to the pull pin that passes through the advance mounting bracket, a section of rubber hose is covering the pin, through the mounting plate. This rubber tube (stop bushing) is there to both cushion the advance at full degrees stop, and LIMITS STOP degrees down to the correct specification for that advance/engine application.
These rubber stops usually degrade over the years an engine goes through running the bushing against the stop slot, and engine heat cycles, chemicals that get under the distributor cap, and can disintegrate, and/or fall off the pull pin, eliminating correct degree stop.
The after-market advance shown does not have any stop on the pin, as they are NOT supplied with the advance, and, when used thus, gives far, far too many degrees of vacuum advance for the application."


All I can say is I've researched this enough to satisfy myself anyway - not trying to convince anyone here. I agree with you about starting world war three on manifold verses ported.. LOL I just liked the way Dave Ray thinks on this topic and his advice has worked for me.

Re: 71 350 running hot coolant backup up problem
 

There are a myriad of advance chambers, with different strokes and vacuum actuation requirements. I disagree with Mr Ray.

Re: 71 350 running hot coolant backup up problem
 

yes and it is a brand new cap

Re: 71 350 running hot coolant backup up problem
 

I was looking through the thread and don't see where you got an IR temp gun and confirmed that the engine is actually this hot?

Re: 71 350 running hot coolant backup up problem
 

the fun continues, whilst pickup up a 180* thermostat I procured a brand new filler neck jobbie since my old one was pitted, the new one not only is it chrome (joke) comes with a reusable rubber O-ring, so lets see if this one seals more better

baby steps people, baby steps

Re: 71 350 running hot coolant backup up problem
 

Do not care about the t stat temp, its going to run at 195 ish or 180 ish, it won't make it run hotter.

What matters if the t stat works. Looks like it does. Confirm the actual temp with a temp gun or mechanical gauge.

Re: 71 350 running hot coolant backup up problem
 

Confirm the actual temp with a temp gun or mechanical gauge instead of spending all of this money on guesses.

Re: 71 350 running hot coolant backup up problem
 

Re: 71 350 running hot coolant backup up problem
 

Confirm the actual temp with a temp gun or mechanical gauge instead of spending all of this money on guesses.

Re: 71 350 running hot coolant backup up problem
 

Check my thread on Oxalic Acid then flush with Washing Soda.

Re: 71 350 running hot coolant backup up problem - Test #3
 

so here are the results of the third test drive, this one is for all of you who suggested swapping to a 180* thermostat

180 Thermostat, running 50/50 water coolant mix, still 12 degrees initial timing

as you can see we were averaging in the high 190s, here I caught it at 199* F degrees this only proves now we are masking the problem instead of fixing it, how do I know that?, well my '74 truck is running a 180* thermostat and it operates at you guessed it 180* degrees year round

Re: 71 350 running hot coolant backup up problem
 

I hear you, thanks for sharing but aint that what the tiny alan wrench is for to twist and turn the adjustable vacuum pod to adjust the vacuum to your liking, as opposed to the non adjustable OEM can which lacked that feature?

Re: 71 350 running hot coolant backup up problem
 

So what's next? Well I don't like how deep my flex fan sits in the fan shroud, so I picked up a 1/2 inch spacer to replace the stock spacer and move it back some.

I recon the proper fan/shroud position is 50% of the blades in the shroud the other 50% sticking out.

Here are the pics of what it looks like now, the photos themselves may be old but the fan position hasn't changed since they were taken.