Since my engine build-up I still have some heat problems with hot weather and long idling or in traffic jam/slow moving traffic.

Engine is a 408 with 10.5:1 CR flat top pistons, 2V open chamber heads, headers, electric fan, recurved duraspark dizzy with 10 deg. ignition advance and a 180° F thermostat.

I´ve removed all the EGR stuff. Now my question is : can a ported vacuum switch (to be mounted near the water pump) help me cool down the temp by regulating the ignition advance with manifold vacuum during idling.

From what I know this ported vacuum switch belongs to the EGR stuff but can this switch work without EGR ? The only vacuum hoses I´m running is ported vacuum from carburator to distributor and one from manifold to the C6.

So when I put a ported vacuum switch in how do I have to route the vacuum hoses ? 1. from manifold to switch, 2. from carb to switch and 3. from switch to dizzy ?


Any input is appreciated, thank you Tom

 

In theory yes, reality- there are a few supporting variables such as A/F mix, etc. IMHO, if you are getting hot at low speed that is typically 1) not enough air flowing, 2) inadequate heat exchange (ie radiator with not enough fins &/or tubes) or the coolant is passing too quickly or too slowly to allow for heat absorbsion & dispersion.

....some of IMHO's...............

E-Fans: Supposedly the curve blades are quieter but, in the aftermarket world 99% of the e-fans are junk in terms of design & quality IMHO. The OEM units flow anywhere from 50% to 200% more CFM than the "Hi Perf" aftermarket units, last for years in real world daily, all weather use and are quiet- and are less expensive in most cases!

I bought (last summer) a replacement assembly for my wife's 1997 Cougar Sport (V8) (the bearings in the e-motor were starting to whine).....the entire assembly including the shroud was $120 with tax (I bought the entire assembly because the motor itself was $80).

You will also hear/read about people having issues/concerns with their engines running warm/hot, once it is really verified and there are no mechanical issues, 99% it can be traced right to these HP Aftermarket fans.....those using oem units- I have never in 20 years heard of an issue related to them in any way in regards to cooling.

There are many on the market to choose from…..you can check out this thread which has a great listing of all sorts of great alternatives…..
Custom Electric Fan install - Taurus + Aluminum Shroud - Vintage Mustang Forums

Radiators: I know many seem to be under the impression (marketing) that aluminum construction by itself will enhance cooling, there is a little more to it than that...and in many instances buyers are actually comparing apples to oranges when comparing a copper core spec to an aluminum spec radiator. US Radiator has a nice vid on their site that yeah, it does talk about the company a bit, but also talks about Copper vs aluminum & gives a good presentation of design limitations.

Link: U.S. Radiator | The Difference Is In The Tooling

Hope this helps!

 

.. X 2... problem is prolly fan related... fan blowing wrong direction, not close enough to the radiator, needs a shroud to ensure air is pulled or pushed through radiator, fan blades not angled enough/not moving enough air/fan motor too weak...

.. My first guess is usually no spring in lower radiator hose and/or no pressurization of cooling system, but that usually only causes overheating above 50 MPH...

.. Other possibility is bad heat sender/gauge... are you diagnosing overheating only by gauge or is it actually boiling over with 50/50 water/antifreeexe mix?

.. If flat top pistons and stock 2bbl. 76-79cc chamber heads, your actual compression ratio prolly about 9.5:1...

http://www.summitracing.com/popup/ca...ion-calculator

 

Hey this is a lot of input, thanks for your IMHO´s and the links !

Guess I should give some additional info on the engine.
The engine just as the whole truck had a complete restauration and got hot tanked to clean all the cooling and oiling passages.
The radiator has been overhauled and the radiator block is new. Upper and lower radiator hoses are new. Water pump is new.

Well, there are a trans oil cooler and a engine oil cooler in front of the radiator, this may complicate the air flow.

The E-fan is a Flex-a-lite Black Magic Xtreme, thought it was the best choice in power and fit for my size of radiator. It has a big shroud that covers nearly the whole rad block, the blades rotate about half an inch from the fins. It blows in the right direction and - from my view - pulls a lot of air.

Gauges and senders are new stuff from VDO.

To list all these goodies does not ban them from misfunction ... but hey, it´s all new stuff. When there is something to supect for me it might be not enough air flow in spite of the new E-fan. I can go back to the belt-driven fan but I would like to keep my idea of this E-fan ....

But the basic question was the ported vacuum switch and it´s supposed help in reducing temperature by vary the timing advance - just for the technical solution.

And - the compression IS that high .... I bought this set of KB pistons from TMI and the advertised CR of 10.5 turned to be 10.66 in fact with 76cc heads and some milling on heads and block. Once fitted the pistons popped some thousandth over the deck, destroyed my calculation of a matching CR and gave me some serious problems with detonations.

Well anyway, thanks for your input and hoping for some more.

 

The factory setup - at least in the early 80s - did just that.

I forget the specifics of exactly how it's done, but it used at least two such temperature-actuated switches to feed manifold vacuum to the advance when the engine was getting too warm at idle.

 

What temp does your fan kick in/out? How much fan is sticking out from the shroud? Sucker fan should have 2/3 toward rad and 1/3 toward engine.
Do you have an auxiliary header tank for the radiator?

 

That´s right Chris, but will the switch do the intended work without the EGR stuff ?

 

.. The only ported vacuum I've ever heard of is a ported vacuum outlet on the carb. to block vacuum to the distributor vacuum advance when idling and allow that vacuum at part throttle cruising for better MPG...

.. Some vehicles also have a vacuum valve on the engine water outlet that in extreme cold winter weather/cold engine supplies vacuum to an air door vacuum motor in the inlet of the air cleaner to pull warm air off the exhaust manifold stove to prevent freezing up the condensation in the carburetor/freezing the carburetor(which is no fun)... you don't want that hot air going into the carb. most of the time...

.. There is also the EGR (ExhaustGasRecirculation) system anti-pollution control system that opens a valve that is usually in the intake manifold to allow hot exhaust air in the intake manifold to enter the engine at times...

.. Having positive deck pistons shouldn't be causing you detonation, should actually be lessening it... assuming you have head gasket that provides .030" - .040" quench distance, max ignition advance of 34-38 degrees, and gas of sufficient octane... like 91-94 octane pump gas plus an ounce or two of kerosene per tankful...

 

@ BuzzLOL : I´m thinking of this : Standard Motor Ported Vacuum Switches PVS14 - SummitRacing.com

 

@ crsmiffy : fan kicks in at 88° C ( 190° F ) and there is no auxiliary radiator tank. The fan is sticking out approx. 1/2 inch and the proportions are around 2/3 to rad and 1/3 to engine. The pic below may help.

 

what are the CFM's of the fans output. 3000cfm or 5000cfm or 1000cfm? got me thinking! On your distributor have you checked for rotor to distrib cap contact alignment. If not close to proper alignment this could promote a cross fire within cap. is the distributor cap vented? needs to be if not. I run a MSD with phaseable rotor and check these things and correct if off a little. have to adjust every time you adjust your timing for optimum results.

 

What the factory configuration did was apply manifold vacuum to the distributor advance during overly-hot idle, this raises the idle speed and thereby increases the fan speed and coolant throughput.

This won't help you with an electric fan although I guess you could try it... get a 3-port vacuum switch that opens at a high temperature... this type switch would have connections for two vacuum sources and one connection for the device receiving the flip-flopped vacuum supply. It'd raise your idle speed and coolant flow but I think you'd be applying a Band-Aid® on a symptom instead of treating the cause of the problem which is most likely someplace else.

What I see people do with the Windsor engines sometimes is use the wrong water pump - one intended for a serpentine belt setup, it spins the other direction and the impeller inside is changed to accommodate that. If that impeller is spinning backwards, coolant flow isn't so good. But I doubt that's your problem on an M-block, I don't think they ever came with serp-belt setups.

I agree with checking the basics... remove the cap, start the engine and let it warm up 'til the thermostat opens. Look inside the radiator and you should see a healthy flow of coolant.

Also, the cap might not be holding pressure.

That radiator looks smaller than I'd expect to see but I doubt it's the cause of your problem. I'm assuming you verified the existence of a problem and aren't relying on factory gauges....

 

something i see is a small cap distrib and have to be a little more careful on cross fire within cap. make sure your cap is vented to releas gases within distrib while running. If cross fire present within cap and no vent causes to fire cylinder before or after actual cyl firing. I now have a spare cap with hole next to contact and see actual firing position with a timing light. Any questions drop a message.

 

@ Wyoming :

fan has 3300 CFM output. Interesting info on the vented dizzy cap .... never heard of this. What are the benefits of one or two extra holes in the cap ?
Prevent from gases or moisture ? Guess the cap does not seal to the dizzy base that much and should allow some air to flow.

But what is the relationship to higher engine temps at idle, please ?

 

Well you´re right a E-fan won´t help me when I use a vacuum switch, I did not know it works by raising the idle speed. The more I think about it I feel it´s the wrong way.

Guess the E-fan doesn´t pull enough air. On a really hot day in a traffic jam the temp slowly raises from 82° C up, at 88° C the fan kicks in but it fails to reduce the temp, just holds around 90° C and raises more and more under some conditions.

The cooling system is OK, as I said before hot tanked block, new radiator block, new water pump, a correct 180° F robertshaw thermostat, new VDO gauges ..... opening the rad cap shows a good flow of fluid.

I suspect the engine build-up with a big improvement of power from 150 to 360 HP has changed the whole arrangement. Maybe I´m going back to the old belted-driven fan and wait for hot weather.

Thanks a lot for this input !