running hot
 

my project truck is finally able to start. I remember when I bought it, it got hot in traffic and at stop lights, but did not over heat on the freeway home. So now I'm working on the engine in the driveway at idle and it gets hot pretty quick, almost to the red in less than 10 minutes. (does anyone know the numbers on the stock gauge, how hot is it when it first hits red, and where should it stay, around the middle?)

It seems like it takes a long time for the thermostat to open, but it does open. I remember changing it (185), and thinking back, I forgot to check for the arrow pointing to front, is that a big deal? And it is doing pretty much what it was when I got it, should I take that apart?

Other info: a/c was added to the vehicle, don't have that belt on now, but there is a condenser in front of the main for the a/c. Maybe that's blocking the air? That a/c fan is not coming on (vehicle has a regular mechanical fan,though), but then again, the a/c is off. Also, when the engine is idling, I hear a noise, much like a power steering pump low on fluid. Not real loud, but it is definitely there and coming from the engine, probably the front of the engine. If my water pump would going, I'm thinking gm water pumps have a seep hole, and I'm not losing fluid, so thinking the water pump is ok? Timing is at 0 at idle.

Re: running hot
 

How old is the radiator?

If it's the original 40 year old radiator... it probably needs to either be rodded out, core replaced, or the whole thing replaced.

Gary

Re: running hot
 

Unless that A/C condenser is badly plugged, it won't block airflow significantly. Is it actually overheating, or is it possibly a bad reading on the gauge? Could be a bad gauge / bad sending unit.

Re: running hot
 

thanx replies. I have no idea age of radiator, i see it has been welded around the neck, probably pretty old. I drained it, does not look toooo coroaded from what I can see, fluid is new. I does not leak. Condenser does not look too plugged.

It hasn't blown over, but sure seems really hot. gauge moves to just below red, and back down as it cools. not sure how I can test that.

Re: running hot
 

Does it have a shroud and where's the fan in the shroud?
Original fan?

Re: running hot
 

if it heats up fast, the thermostat should open up fast once it gets to 185. get a cheap mechanical temp gauge at your local auto parts store and see what it reads. you don't have to put on dash, just let it lay by the engine . if it reads normal temps, either mount it at the dash or remove it and hook the other one back up..

Re: running hot
 

Four things I would do in that situation:

1] Check coolant viscousity with a squeeze-bulb gauge. Prestone makes one that's about $5 in all auto parts stores. Hygrometer, I think? In Miami, you won't need as much polypropylene-glycol as someone in Minnesota. You could maybe go 55% water--45% antifreeze, or 60/40. You don't need to worry about the block freezing.

2] Radiator caps go bad over time. Buy a good new one. You want a 16 PSI cap, since you have an A/C system. Even if it's inactive.

3] I ran an AutoMeter mechanical water temperture gauge because I had problems with the OEM electric temp gauge. Much better temp indication, and not dependant on voltage.

4] Try a 160* thermostat.

Re: running hot
 

me i'd go to the super market and buy a cheap thermometer and take the temp of the coolant and find out exactly what hot is hot and a `160thermo wont make it run any cooler so save yerself that moneyr

Re: running hot
 

Timing is Zero at idle? That could be a factor in overheating... I think since yours is pre emissions you may want to try looking into whether you need all of your vacuum advance (BTDC) to be in at idle provided:

1.) you are using full manifold vacuum at your vacuum advance unit - and
2.) you are using a Vacuum Advance unit that maxes out at 2Mg below the vacuum produced by your engine at idle.

If you are using a vacuum advance unit that is stiffer than that produced by your engine at idle (or say 50 RPM above) and does not max out at 2" Mg below what your engine produces at idle then things will be different

Also If you are using ported vacuum then things are different

Be advised I am not familiar with your particular engine but I use this is a general starting point and if you get pinging then removing that takes precedence because things tend to wear out and the tolerances stack up..

This is just how I think about this and not what I am advising anyone to do - also since I don't know your set up there are hundreds of reasons my suggestions could be completely wrong..

Try a search on Google or on this site for "Idle Cooling" and maybe the term "Timing"..

Re: running hot
 

Yeah, I agree, 160* t-stat won't help.

As asked above, is there a fan shroud? And what type fan does it have?

Re: running hot
 

Crazy things happen but it sounds like your thermo is in upside down. 😁
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Re: running hot
 

Pull the stat and make sure its installed correctly, re time to 12 degrees before top dead center with the vacuum line unhooked from the distributor and plugged it so no vacuum leak to the carb.

There is a weep hole on the water pump but a noise could be a bad bearing. or bearing on the alt?

Per CDowns suggestion, don't pop the rad cap to check the temp unless you want to take a scalding hot shower in coolant, an option would be to open the radiator petcock and drain some into a container.

Re: running hot
 

old guys xare smart enough to remove a radiator cap without getting burnt young guys oh well gotta learn sometrime

Re: running hot
 

Don't remove the radiator cap when hot, there's no "safe" way to do it no matter how old you are. Let those that claim otherwise keep at it, but don't imitate. I know someone who tried and failed, and fortunately only has minimal facial scarring.

- Make sure timing is set correctly, at least 6-8 BTDC, ideally a little more these days
- Make sure your fan clutch is working correctly, dragging when hot
- Make sure your fan shroud is in place and sealed up

If you don't have a shroud or you have some bogus flex fan in there, all bets are off. You need at LEAST the factory parts in place for the engine to cool properly.

Re: running hot
 

Yep, it can be done -- that's just one of the things I learned in my part-time service station job before I was old enough to drive. :lol:

Re: running hot
 

Come on you clowns, you're going to get someone scalded like there's a secret to safely taking a rad cap off.

If you're talking about draining fluid from the petcock until there's no pressure left whatsoever, say so.

Just making it sound like if you're manly enough and old and wise enough you can just take the rad cap off a hot engine isn't fair to someone who might not understand you.

Re: running hot
 

Clowns?? That's a bit harsh and judgemental, don'tcha think? I could call you names too but that seems a bit childish.

It has nothing to do with being manly or old. It's just common sense. I have done it safely many times and can explain how I was taught. If someone tries it and fails, that's entirely on them.

You need to cool the radiator. With the engine idling, run cool water over the top of the radiator and spray the cooling fins. It takes a few minutes. When you think it's cool enough, slowly gradually carefully crack the radiator cap open. There will still be pressure and you can still get scalded. Protect your hand with a glove, shop rag, anything -- the more the better -- between you and the cap. At this point you are not removing the cap, just cracking it open to gradually release pressure. You may need to run more cool water over the radiator. Once you can loosen the cap without hot water or steam escaping, it's safe to remove the cap.

Hope that wasn't too much for you to deal with....

Re: running hot
 

Nope. My mom was a burn ward nurse. You see things and hear things and meet patients and you'll take them seriously too.

EVERY single severe burn patient eventually comes to the admission of "The mistake I made was", and I don't want someone on here to be scalded because people with bravado wrote about doing dangerous things with impunity.

If I save one person from a burn while annoying 50 others, I'll take it.

No, you typed real slow so that I could read it. I'm not endorsing it but since you included an explanation of HOW you do it, I think that's far better than leaving people to guess and fail, right? Sort of all I asked, so thanks.

Re: running hot
 

:lol:

Gary

Re: running hot
 

First, I have taken radiator caps off of hot engines, and can do it safely. I hate to see an argument about this, but I do know that you have to be careful with advice. A shop teacher once told me a story about when he told someone that if you could turn the pulley on an alternator, the belt was too loose. Some fool tried it with the engine running and ended up with a mangled hand - so you have to be careful.

Anyway,


Thanx for all the replies. To address some of the points:

1. the radiator cap is new 16psi.
2. the coolant is new, 50-50 with distilled water
3. I guess a cheap mechanical temp gauge is not a bad idea, not sure how or where to hook it up? I really do think the engine is getting too hot, after years of tinkering on cars, I just think it is.
4. suprized on the timing advice. I looked it up, and I'm pretty sure it said 0 is the required timing. I did the timing with the vacuum to the distributer plugged. The vacuum is the only vacuum port on the engine, and it comes from the base of the carb. I will retime it.
5. @ swamp rat: I'm gonna reinstall the thermostat. I tend to agree that the alternator is most likely the sound I'm hearing. Bummer, one more thing to replace.

6. as far as the shroud, I have none, just a little thing on the very top to keep you from touching the fan. The fan appears stock (I have no idea) non-clutch, non-flex. It has a spacer and is about 4 inches from the radiator. I have what appears to be a 2 core radiator.

Should I get a shroud? Do you gentlemen think my fan is sufficient?

thanks again.

dave

Re: running hot
 

From your first post:
Given its history of getting hot, I would definitely recommend a shroud and a thermal clutch fan.

Re: running hot
 

You have a 6 cyl, those never came with a fan shroud, only what you mentioned. There are lots of guys running that dinky little finger saver and their inlines don't overheat. While there's nothing wrong with a shroud and clutch fan and in fact, it's a great addition, it seems as though there's still something wrong. I'd hate to see you invest money in a band-aid first, rather than a solution. A shroud and clutch fan could possibly keep the engine cool enough to operate, but aren't necessarily the cause of the overheating issue, IF in fact, it's a mechanical fault and not a faulty old gauge.

Re: running hot
 

On the V8's you can just pull the upper radiator hose and look down the neck of the thermostat housing to verify that the thermostat is installed correctly... to me that would be easier than pulling the housing itself.

Especially if use Gascacinch or other sealer on those thermostat cover gaskets..

Another possibility is an air bubble in your cooling system - on the small blocks some advise drilling a 1/8" hole through the thermostat to help bleed the air out when filling the system; but it is not necessary.

I'll try to attach a PDF below to help with more details on setting the ignition timing.

If you are using the original timing advance spec from the late 1960's that was for leaded gas.

The best advice in my opinion came from Bruce's write-up about timing from his "Its Just a Pickup" build page (around page 27 of that? somewhere around there).

Its for a 72 SBC but his process for setting ignition timing is super logical and excellently written.

Re: running hot
 

Here's the links to Bruce's write-up on ignition timing.. the first one was post #712 of his build page and you'd also want to read his follow-up which was shortly thereafter..

Many thanks to Bruce for all he has helped with his efforts!


http://67-72chevytrucks.com/vboard/s...&postcount=712


http://67-72chevytrucks.com/vboard/s...318544&page=29

Re: running hot
 

L6s don't come with a fanshroud. If it's not OEM you don't need it. They may be critical for V8s but a six doesn't need one. There's a big black fingerguard over the fan but that's all.
A bigger radiator would help. Operating in southern Florida, you may want to think "tropical". I live in Tucson -- I have 4 tier cores on my trucks with V8s and a 3 tier on my 292 L6. The OEM L6 radiator was also about 3 inches shorter [narrower] than the V8 radiators. It's very hard to get an L6-specific radiator anymore. For about the same money, the V8 radiator fits and works great, once you move the brackets on top and bottom out to their new marks. Longer hoses may also be necessary, IDK.
I like the Stant "safety cap" it has a red lever so you can pull up the lever to release pressure, then twist open after the steam has blown off.

Re: running hot
 

Agreed on all points. I completely missed that it is a 6-cylinder. Guess I'm guilty of assuming SBC until someone yells at me to get my attention.

Re: running hot
 

You should also "BURP" the system. Jack up the right front of the truck so the radiator cap is at a high point. You can squeeze the bottom radiator hose to induce the bubbles to rise. Air will make its way up and out.
Sounds simple but it works.

Re: running hot
 

I agree with making sure the thermostat isn't reversed; I have done it.
I also have had an engine overheat because the timing was too retarded. I run my 307 at 12 degrees and it runs a lot cooler than the 2 degrees the manual says.

Re: running hot
 

Sorry to keep harping on ignition timing as your potential likely solution for running hot - but it is just a gut feeling.

You took the trouble to use distilled water - that says a lot in my book - and is a good sign among other things of what I observe as your sound instincts.

I found another good free source to help eliminate ignition timing as the source of your running hot issue - I still like our board member Bruce's thinking - but this is kind of a third opinion since you after all are kind of betting your motor on the decisions you end up making here and whose advice you listen to in attempting to correct the situation..

Here is a link to a Google scanned book: (at least previews are scanned; not the whole book)

https://books.google.com/books/about...d=8fsgc6GWR2wC

That link should take you to Google's preview of the 2004 3rd edition of the following book:

How to Build & Power Tune Distributor-Type Ignition Systems By Des Hammill

Google has extensive previews of that book so if you start reading on page 19 Google should let you look through the each consecutive page and it looks to me as if it will be helpful for your issue. So I'd suggest starting at page 19 and reading through at least about page 31..

One observation - there is no way around the fact that one way or another you do need to know exactly how many degrees of mechanical advance are built in to your exact distributor before you can set your initial timing accurately. For example if you just blindly set it at 11, 12, 13 BTDC and then spin your motor up to 3000 RPM; you are taking a big bet..

Sorry to keep talking about small blocks when you have a straight six - but after all there is a lot more info about ignition timing written out there about SBC 350's so I think it is still helpful to take the SBC 350 V8 ignition information into account and do your best to translate the theory or the principles into your inline six situation.. - but anyway just as an example; small block chevy distributors from the 60's and 70's eras have designed in mechanical advance ranging from 18 to 34 degrees (of crankshaft advance mechanical timing) built in; and so in my opinion I believe that you have to know what you have before you can set the initial timing on a points distributor..

One little tip I just learned is that many cam plates on the Delco-Remy Distributors had the number of designed-in mechanical degrees stamped into the Cam Plate... so that might be a good thing to check for starters..

Best of luck

Re: running hot
 

Dave , what is your ignition set up? Points, Pertronix, or HEI? Timing is easy to set up on the Chevy L6. Stock one barrel carb?
Also if you get a mechanical water temp gauge, the sensor input threads into the drivers side of the head, replacing the electrical water temp sensor. A pipe of 1/8'' diamenter feeds thru the firewall to the gauge under the dash. You may need a gauge holder, but many temp gauges come with one.

Re: running hot
 

I don't think anyone has suggested it yet. But it could be as simple as a bad thermostat. In the past I've had two bad ones from brand new. Which caused the temp to rise very quickly.

Now I test thermostats in a pot of water on the stove. place the thermostat in a pot of water. heat the water and note when and if it opens with a temp gauge. A standard kitchen one should do.
Good luck

Re: running hot
 

Thanx Grommit. That stuff brings me back to my days in college, lots of reading and learning.

Just trying to get it to start easily and run fair and cool at the moment. Once I can get there, I will dig into that with a vengeance.

Re: running hot
 

@68 orange. As far as I can tell, everything is stock. It's a points distributer, 1 barrel Rochester (just purchased).

Anyone know how to set the dwell? I have no meter, and the cap has no window. I just want to get it close, does not have to be perfect at this point, that can come later with the excellent reading provided by grommit.:)

I would think the accelerator pump would be preset correct as I just bought the carb from summit. Anyone know how to adjust it to make sure?

thanx all

Re: running hot
 

played with the timing. seems to run a little cooler. Gauge gets 1/2 inch or so from the red and didn't go up for about 10 minutes. Anyone know the numbers? Where does yours sit? engine did seem a little cooler, I think the gauge works, but not at all sure it is completly accurate. Trying to avoid spending money on the mechanical for the moment.

Re: running hot
 

The vacuum line going to the distributor should have no vacuum at idle; it's called "ported" vacuum and is a signal that represents part throttle load, which is where the vacuum advance can adds more advance.

At WOT, there's no vacuum. At idle, no vacuum. In between, ported vacuum.

Generally if it's below the level of the throttle blades, it's manifold vacuum. Above is usually ported, but that's not always the case.

Re: running hot
 

Thanx. So how can I use vacuum to help tune?

Re: running hot
 

Using vacuum, such as a vacuum gauge to tune, is done by connecting it to a full vacuum source. Then the carburetor is adjusted at idle, to produce maximum vacuum read on the gauge. This does work particularly well, but can only be done AFTER all other issues are sorted out, or it will just throw things off and you'll chase your tail.

Vacuum as in vacuum advance of a distributor, shouldn't NEED to be adjusted on a stock engine, as long as the components are in good condition. Custom applications and adding performance parts usually requires a vac advance to be tuned.

Sounds like timing was a factor in your engine running hot. You really should take it out and do some real-world driving and simulate some conditions to be sure it's running cooler.

Re: running hot
 

Yep, like lefty says, no adjustment related to vacuum advance. You can get adjustable cans and lock out stock ones but generally only needed with significant engine modifications.

Get yourself a good initial advance (10 or 12 or whatever was decided) and see if its solved. If you go much more than that you'll likely need to lock out some vacuum advance, but that'd be indicative of the wrong solution, probably.

Re: running hot
 

L6 POINT-TRIGGER TIMING:
Get fresh set of Points and Condenser; remove old parts and replace. Bump rotor to point at #1 Cylinder, Timing Mark should be near timing tab off harmonic balancer and point to 0. Bump so points arm is on 6-sided cam and open most. Adjust gap with 2 screwdrivers** to .019 for new [.016 for used]. Plug Vac Advance temporarly.
Inspect cap and rotor. Reassemble if good. Start engine and after loosening distributor hold down bolt [9/16"] rotate distributor until groove in HB flashes at Zero mark on timing tab. You can advance from there if necessary.
To set Dwell you need a Dwell Meter*. Hook meter leads to Coil (+) and Ground, as specified in Meter instructions. Read on Six Cylinder scale. To make adjustments, shut off the engine, remove Dist. cap and rotor and use 2 screwdrivers to close or open the points gap, Closer gap = more degrees of dwell. [The option to adjust while running, with an allen key thru a 'window' is a V8-only thing.] Reset dwell gap and replace rotor and cap, start up and note readings again. It's still a trial and error process.
* With the popularity of HEI ignitions it's harder to find dwell meters. Check yard sales, swap meets, and used tool shops. I'll look up the p/n on my Sears Dwell/Tach/Voltmeter later. They may still have then in stock.
** The 2 Screwdrivers technique: One large flat blade on big screw in middle of pointset, one smaller flatblade in Gap hole to tweek points gap open or closed. When desired gap is RIGHT ON, lock down with big screwdriver.
OBTW Spark Plugs should be gapped to .035 for points.
Sorry I'm no help with the Monojet. I ditched mine in 1978 for a 4 Bbl Holley on an Offy intake.
Hope this helps.