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Old 01-12-2018, 01:48 AM   #51
Gregski
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Re: 71 350 running hot coolant backup up problem

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Originally Posted by Gromit View Post
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.
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?
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Old 01-12-2018, 01:55 AM   #52
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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.
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Old 01-12-2018, 02:20 AM   #53
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Re: 71 350 running hot coolant backup up problem

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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 would throw the flex fan as far as possible and get a proper heavy duty fan clutch with a good OEM-type 7-blade fan bolted to it. That's what came on my K20 with a 350 and factory A/C. In 41 years, the only time it ran hot was when a clutch unit failed and I tried a flex fan. Didn't take me long to get rid of it and put the right one back on.

Just my 2 cents...
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Old 01-12-2018, 07:59 AM   #54
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Wink Re: 71 350 running hot coolant backup up problem

The fan shroud should be blocked off so that all the air pulled with the fan comes through it and not around it. The blades should be about right 50/50 but as stated a good stock fan blade will help you. Those flex fans are not for street driven vehicles and if you have AC your never going to keep it cool.
Again 180* thermastat is reading high 190's is pretty normal. It's not going to run 180* unless you do some work are buy a good aluminium radaitor.It doesn't matter what your other truck is running it has nothing to do with it.
It's a completely different vehicle.

Now if you want to swap the radiator out in both to see then yea go for it.

It wouldn't surprise me if it's the sendor for that gauge.
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It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
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Old 01-12-2018, 06:01 PM   #55
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Re: 71 350 running hot coolant backup up problem

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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?

Yes but remember you are only affecting the rate of the vacuum advance portion of your total advance with that Allen trim screw. So let's say your vacuum advance will deliver up to 20 crankshaft degrees of ignition advance. You have set 12 crankshaft degrees of initial advance; so now you're POTENTIALLY up to 32 crankshaft degrees; and then your centrifugal or mechanical gives you another 24 crankshaft degrees beyond that, if you don't limit the vacuum actuator that would potentially be a total of 56 crankshaft degrees ignition advance.. way too much.

(note I have zero experience with the HEI)

I know what you are thinking and it does make sense that if you turn the Allen screw of the vacuum pot so that at your max idle 21 Hg it is only giving you a known amount of advance - but I think it is not recommended to depend on that - and I think that is why Crane also makes the adjustable stop plate and the stop plate and adjustable pot are meant to work together.

I feel bad bringing up timing if it hijacks your original overheating problem and there are such good posts already on this forum from people far more qualified than me. For example Bruce88 did a whole series on timing in his build post - starting with post #712 and it is just a masterpiece of logic.

I think if you have your initial at 12 BTDC and you are sure of your TDC and balancer mark and you set it with the vacuum advance disconnected and you know there was no centrifugal advance coming in at your 850 RPM idle that should be enough to eliminate insufficiently advanced timing as the cause of your overheating.

I guess if that is all the case and it were me I might then check to see if the heat is coming from your automatic transmission rather than the motor... assuming of course you are running the trans fluid through the factory heat exchanger in the radiator
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Old 01-12-2018, 08:07 PM   #56
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Re: 71 350 running hot coolant backup up problem - Test #3

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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
Confirm the actual temp with a temp gun or mechanical gauge instead of spending all of this money on guesses. Your new fangle gauge and sender may be off.
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Old 01-12-2018, 08:08 PM   #57
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Re: 71 350 running hot coolant backup up problem

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So what's next?
Confirm the actual temp with a temp gun or mechanical gauge instead of spending all of this money on guesses.
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Old 01-12-2018, 08:09 PM   #58
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Re: 71 350 running hot coolant backup up problem

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Originally Posted by Andy4639 View Post
It wouldn't surprise me if it's the sendor for that gauge.
See above.
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Old 01-13-2018, 12:54 PM   #59
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Re: 71 350 running hot coolant backup up problem

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Confirm the actual temp with a temp gun or mechanical gauge instead of spending all of this money on guesses.
These are not guesses, I am proving hypothesis, some people said its because I am running water, well I already had coolant so I tried it with 50/50, others said try a different thermostat, ok, a thermostat was only $7 bucks and a gasket was only $2 bucks, hardly any money. The $15 I spent on a new water neck was because the old one had a leak because it was pitted.

And not trying to argue with you but what exactly is a temp gun going to tell me, it will not match the temp on the gauge anyway. If I point it at the upper radiator hose it will read different, if I point at the driver metal cylinder head it will read different, if I pointed at the lower radiator hose it will read different, and different again for the intake manifold by the thermostat. So honestly and not facetiously what am I going to do with all those numbers when non of them will match my gauge.

And I know something aint right because of the lack of flow in the radiator, that's the first thing I said, it backs up.
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Old 01-13-2018, 01:15 PM   #60
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Re: 71 350 running hot coolant backup up problem

I use those temp guns as a second opinion type of confirmation. It can just confirm that the gauge isn’t way out of whack. It should read reasonably close to the gauge when you shoot it at the metal surface by the sender.
It also can be handy to see just how well your radiator is cooling. Check the temp difference between inlet and outlet hoses and compare that to a known good vehicle. You can also find cold spots by scanning the radiator surface.
If you think the radiator has blockage, get it rodded/cored or replace it. You should be running cooler than you are.
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Old 01-13-2018, 02:16 PM   #61
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Re: 71 350 running hot coolant backup up problem

Can't see clearly but as another mentioned check the gaps between the radiator and shroud (only effective at lower speeds and idle) so that the air drawn is through the core. I remember someone telling me that those carbs are notorious for being jetted rich out of the box and that many people change the jets before even installing - maybe someone went too lean? (I run Q-jets so don't have much experience with those) Have you read the spark plugs after a run? BTW you should connect the PCV valve if you're already driving it around. Using an IR gun on the location of the temp probe would be another piece of useful information.
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Old 01-13-2018, 03:26 PM   #62
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Re: 71 350 running hot coolant backup up problem

got an update for you all that could explain why my fan is shoved so deep inside that radiator shroud, I am running a long water pump PN: 31228 so time to replace it, I belive a short snout water pump is the proper pump for these trucks, even with my short 1/2 spacer the fan still rubs against the alternator so best way to move it back is to use a short water pump and not keep piling on bandates on top of bandates
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Old 01-13-2018, 04:01 PM   #63
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Thumbs up Re: 71 350 running hot coolant backup up problem

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And I know something aint right because of the lack of flow in the radiator, that's the first thing I said, it backs up.
What do you mean backs up? Is the lower hose collapsing when it's running?

The temp gun will tell you if the gauge is in the ball park are not. If the gauge reads 206 and the temp gun pointed at the senor reads 190 then you know it's in the gauge.
As stated it will give you some good info on the temps at different points of motor.
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Seeing the USA in a 71


Upstate SC GM Truck Club
2013,14 and 2016 Hot Rod Pour Tour


http://upstategmtrucks.com/



Get out and drive the truck this summer and have some fun!
It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
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Old 01-13-2018, 06:24 PM   #64
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Re: 71 350 running hot coolant backup up problem

Temp guns are cheap enough..... can't think of a good reason not to have one.
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Old 01-13-2018, 06:43 PM   #65
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Re: 71 350 running hot coolant backup up problem

If you switch to the correct short pump, you will need to use all the correct brackety that goes with running a short pump or your belts won't line up. You have a later model setup with the alternator on the passenger side. The short pump setup has the alternator on the drivers side.

Gary
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Old 01-13-2018, 08:53 PM   #66
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Re: 71 350 running hot coolant backup up problem

have the radiator checked for blockage or get a new one...and I don't understand why you wont check your engine with a heat gun...
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Old 01-13-2018, 10:25 PM   #67
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Re: 71 350 running hot coolant backup up problem

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Originally Posted by GASoline71 View Post
If you switch to the correct short pump, you will need to use all the correct brackety that goes with running a short pump or your belts won't line up. You have a later model setup with the alternator on the passenger side. The short pump setup has the alternator on the drivers side.

Gary
Thanks Gary, yes I just found this out when I went to buy the right brackets from my Parts Pimp, lol. I enjoy learning things like this, its fun. Time to relocate accessories and make this thing right, tired of going to the Parts House and saying its a '71 but try this year for this part and that year for that part.
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Old 01-13-2018, 10:27 PM   #68
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Re: 71 350 running hot coolant backup up problem

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have the radiator checked for blockage or get a new one...and I don't understand why you wont check your engine with a heat gun...
I hear you, and I will I just don't have one so I need to buy one that's all. I never said I won't do it, I was just trying to catch up to everyones advice, one step at a time.
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