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#101 |
laying low
![]() Join Date: Mar 2001
Location: Searcy, Ark. USA
Posts: 13,240
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Re: 71 350 running hot coolant backup up problem
Without reading through this whole thread I will ask this.
Was there mention of bubbles in the radiator? Test for exhaust gas contamination in the coolant? Stock exhaust manifolds? Stuck heat riser? One thing is for sure. If the stock cooling system worked when new it can still work efficiently today.
__________________
Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross |
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#102 |
Registered User
![]() Join Date: Jul 2015
Location: 2nd left past the stump on a dirt road.
Posts: 2,629
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Re: 71 350 running hot coolant backup up problem
That cheap Spectorico heat radio is not what you think it is.
Hmm, lets water pass, I get bowl of rice. yea dinner tonight! I think I will go back to the factory tomorrow there fore I shall not starve. |
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#103 |
Registered User
Join Date: Apr 2017
Location: Colorado Springs
Posts: 129
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Re: 71 350 running hot coolant backup up problem
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#104 |
Registered User
Join Date: Nov 2014
Location: Lincoln City DE
Posts: 1,292
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Re: 71 350 running hot coolant backup up problem
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__________________
Stan 67 swb BLU MULE posted via flip-fone |
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#105 | |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
Quote:
So the car idles at 800 RPM in Park and Neutral and drops to 600 RPM in gear ie Drive or Reverse. |
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#106 |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
I do not, but the opposite is happening when I drive the temperature drops, I believe it is due to the air rushing against the front of the truck ie the grille and being forced through the radiator.
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#107 | |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
Quote:
Took it to a couple radiator shops in town they said they get lots of cracked aluminum radiators all the time, and they don't weld aluminum, said take it to a welder, I called a welding shop and they said they won't weld it cause they can't see the crack unless they remove the tanks, which they don't do cause they are not a radiator shop. |
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#108 |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
Here is a rather interesting RPM Test:
I went for a cruise then I pulled into a parking lot and I simulated a traffic stop say at a stop sign or a red light, cause that's when the temp climbs. So I left the truck in Drive and just stood on the brake. After 2 minutes it went from 175ish to 190* and kept climbing for 5 minutes. This was at 600 RPM. Disclaimer I know 190* is not hot, I get it, but in the past it would shoot over 200*, so tonight may have been colder out etc... I doubt simply hooking up a Tach fixed my overheating problem, LOL. Then I decided to just put the truck in Park and see what happens. The temp immediately started to drop, in two minutes it was down to 180* then after five minutes dropped to 175*. This was at 800 RPM So I thought to myself... self: what if I increase my idle speed therefor increasing the in gear RPMs. Well I had to creep up the idle RPMs to 1000 in order to get the in Drive or Reverse RPMs to 700 and at those settings the truck ran hot just like it did at 600 RPM. Just sharing that tid bit. Last edited by Gregski; 02-08-2018 at 02:07 AM. |
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#109 |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
The one thing I have not changed yet is the flex fan, so I am scratching my head on that. You would think that if it cools at 800 RPM it should cool at 600 RPM, from what I gather, a flex fan flattens out at higher RPMs when it is no longer needed (assuming the vehicle is moving at speed) not at lower RPMs, am I missing something?
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#110 | ||
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,638
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Re: 71 350 running hot coolant backup up problem
Quote:
I posted the following back on page 3 of this thread and I stand by it. Flex fans are junk in my opinion. A proper clutch fan will pull more air when needed at idle than a flex fan is able to. Quote:
__________________
- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#111 |
Scrapper 1
Join Date: Jan 2007
Location: Riverside Calif
Posts: 1,649
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Re: 71 350 running hot coolant backup up problem
I'm not one for flex fans.Give me a 7 blade ford dodge or GM fan any day.Thats only when i running a fan clutch.If i'm not.Give me that old 4 blade fan.
The GM extreme Heavy duty for the 1975-77 454 engine.I had to put one on my 3/4 ton It use to get hot sitting in a drive thru.It still gets hot. My good friend I went to see him pulled up in his drive way smelled something burning.So i pup the hood.We looked to see if something was wrong He grabbed the top radiator hose it was Rock Hard. I have one of there pressure re leaver caps on the radiator It was blowing air in to my catch can.The hose got lose. He had me fire up the engine again with in 30 sec my top hose was Rock hard. Means i have a cracked block cracked head or i have a crack in my head gasket.So i would check to see if you have a cracked anything cus your engine in pushing compression into your Motor.That will keep your water pump from wanting to turn or let your thirmistate from opening at all This in the Number one reason whay you always run a heater core in your trucks Always. If your truck ever starts heating up turn on the heater don't care if its 120 out side you fry or the truck fry's.Then you still FRY. A working heater makes your truck work so much better.If you ever want to put in a manual chock and its 30 degrees out side and you want to let your truck warm up turn on the heater You will love your truck more.Do it right and it will give you lasting service. |
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#112 |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
I hear you, not sure if I posted this already, but a clutch fan was my Plan A, but the seven blade one I pulled off of a square body at the local Pick 'N' Pull did not fit inside my shroud, see pic below.
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#113 | |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
Quote:
I appreciate the feedback non the less, I am also learning a ton myself at this point and I am glad I have another vehicle to drive while I [ahem] WE figure it out, LOL |
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#114 |
Registered User
Join Date: Apr 2017
Location: Colorado Springs
Posts: 129
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Re: 71 350 running hot coolant backup up problem
Man it sounds like you've got it pretty narrowed down. Airflow!
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#115 | |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,638
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Re: 71 350 running hot coolant backup up problem
Quote:
Good info here: http://www.haydenauto.com/featured%2...s/content.aspx
__________________
- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#116 |
laying low
![]() Join Date: Mar 2001
Location: Searcy, Ark. USA
Posts: 13,240
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Re: 71 350 running hot coolant backup up problem
Doesn't the big block engines use larger diameter blades? That looks like one.
__________________
Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross |
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#117 | |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
Quote:
the clutch fan measures 19 inches and my flex fan, which fits the radiator shroud appears to be 18 inches |
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#118 | |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
Quote:
Not going against your advice it's just what I had laying around the workshop, and my '74 runs peachy with one. |
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#119 |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
and a little stare and compare of the two 18" fans, the mechanical? and the flex fan
full frontal and backside |
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#120 |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
so Test Results with the conventional four blade fan.
In a nutshell, no change, no difference than with the flex fan. Cruising around the wind blows at the front of the truck so with either fan the temp gauge reads in the mid 175*s, but that's to be expected as the air overcomes the fans ability, I just wanted to level set Now, in Park or in Neutral the truck is fine it will idle at 800 RPM in the low 180*s F, same with both type of fans And in Drive or in Reverse with my foot on the brake (the RPMs drop to 600) the temp starts climbing, it will reach mid 195*s in five minutes and slowly keep creeping up above 200* eventually (about ten minutes later) again same with both fans So I shift back to Park and watch the temps immediately start to drop, the gauge will return back down to the mid 185* or so, again same with both types of fans just wanted to report that |
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#121 | ||
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
Quote:
Quote:
Here is a brilliant article by Jeff Smith: Understanding Vacuum Advance and Why You Need It Hey, don't count yourself out just yet brother, I know for a fact timing was the initial culprit. Remember when I discovered I had a bad vacuum advance canister, well, replacing that can fixed my overheating problem at idle, ie in Park/Neutral, since the truck likes Manifold Vacuum, ie lots of advance at idle Last edited by Gregski; 02-09-2018 at 07:45 AM. |
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#122 |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,832
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Re: 71 350 running hot coolant backup up problem
this is by far the best ignition timing and vacuum advance write up out here on the Internets so I am cut and pasting it into this thread, of course giving credit and a ton of thanks to the brilliant and gracious author Vacuum Advance- how is it supposed to work? complements of ChevyTalk.org
TIMING AND VACUUM ADVANCE 101 The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency. The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation. At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph). When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean. The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic. Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it. If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more. What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone. Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam. For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts. Bill - 55 Chevy 210 2 Door Sedan Hot Rod http://imgur.com/a/CfOc6 68 Caddy Coupe DeVille Kustom http://imgur.com/a/m7gdR |
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#123 |
Registered User
![]() Join Date: Jul 2015
Location: 2nd left past the stump on a dirt road.
Posts: 2,629
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Re: 71 350 running hot coolant backup up problem
I went through my distributor after reading this one:
http://www.crankshaftcoalition.com/w...EI_distributor Its all about controlling the burn! ![]() Your carb may also have something to do with it. Systems all need to work together to achieve maximum efficiency. |
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