Cooling help

Ok. I have a 307 with new alum radiator. It has a 17 in steel fan. No fan couch. Just install a like new shroud from a member on the site. So. It cools great when under way but. When I idle for more then a couple of min it starts to climb. As soon as it starts moving weather it's 100 or 75 it always runs cool. Should I Chang fans?? Should I fun a couch. Thank you

If you aint movin, you aint coolin,,,,,,,we put a burger fan on all our vans,,,,,,pushes the air up into the radiator,,,,,,and a twist timer to set it and forget it,,,,,,,I use it to help cool when going up mountains or stopped in traffic,,,,,cools the doghouse, and me,,,,,,and blows away the gas smell when you shut down,,,,,,,,,,

make sure your timing is right and in my case the vacuum advance on my hei is hooked to the manifold, under the butterfly that is....this gives alot more advance at idle and highway low load cruise...this really helped my van run cooler at idle.

Timing is 2 degrees Before Top Dead Center,,,,,with the vacuum line disconnected and plugged,,,
Vacuum advance provides 15 degrees,,,,Centrifugal provides 28 degrees,,,,,,,, so by having the vacuum line going to manifold vacuum timing will retard as you take off.......so are you saying your van is idling at 17 degrees with full vacuum advance kicked in?

sounds like you might need a fan shroud, a fan couch (clutch)
will slow down the rotation of the fan at all speeds and might
make problem worse. how far from the radiator is your fan blade?
and do you have a fan shroud on it?

i cant remember my exact numbers right now, i think base timing was 4 to 8 btdc, im running hei, btw this is a 250/6, , then with vacuum advance hooked up it bumped up another 10 to 15...im pretty sure im idling around 20° btdc...

i have an aluminum 'mustang' radiator, 4 blade stock fan spaced out to within an inch of the radiator, and the van can idle all day like this. before, my vacuum advance was above the throttle plate and the van would get hot fairly quickly....i did this after reading an article written by a former gm engineer that explained it all..
maybe i can find the link..

,,,,,,, Jimmy,,,,,,what temp do you mean by HOT,,,,,,,what thermostat are you running,,,,,is that an accurate reading of your temp??

Great info I will respond after checking on the timing and thermostat. Thank You Jimmy

ok, i couldnt find the link but i copied a portion of the article, the end got chopped:
This was the post I found on a MOPAR forum during a google search.
This was written by a former GM engineer as a response to a similar question on a Corvette board:
As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative.



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

here is another one by someone else:
There are a number of stock GM HEI vacuum canisters available, over 15 or so. Selecting the RIGHT one is tough at best, and takes someone that KNOWS curves and settings to make it all work.



That said, you want the vacuum advance to work on FULL MANIFOLD VACUUM SOURCING, vacuum strong and present at IDLE, and NOT ported vacuum. This source should be at the BASE of the carb, NOT above the throttle plate.



It is also correct that all vacuum advances produce too much timing, IF the limiter bushing isn't installed on them. The limiter bushing is a rubber tube, mostly just rubber vacuum tubing, placed over the pull pin, to limit the pin travel, which reduces the over all degrees of vacuum advance crankshaft timing. This said, the "24" referred to on the canister IS the crankshaft amount of vacuum advance degrees that canister will produce, far too much for our needs.



A nice idle timing we would like to see os between 20 and 22 crankshaft degrees, but, if the initial is set there, the engine is usually too hard to start, and this is where CORRECT vacuum advance souring comes in. You state you now have 8 crankshaft degrees of initial timing, and the canister has 24 available, IF the stop busing is in place. IF the canister is on full manifold vacuum, as it should be, the vacuum advance will take the idle timing to 32 degrees, tar too many degrees. If the rubber limiter isn't there, as they degrade and fall off, never to be replaced when a new advance is mounted, then, the sky's the lkimit for idle timing.



Now, IF we set the initial to your 8 degrees, and make a simple sheet steel limiter and attach it to the vacuum advance mounting bar with two 6/32 machine screws, we can set the pin travel to .120 inch travel, for 12 crankshaft degrees, and make sure the canister is full manifold vacuum sourced, we now have an idle timing of 12 plus 8, 20 degrees, exactly what that engine wants.



We also have a situation where every stock canister has a different vacuum pull, along with different curve numbers, and this is why there are so many of them available, who knows what is what. The extremely simple solution to all this is the Crane 99600-1 adjustable vacuum advance kit, has 3 sets of mechanical advance springs, a pin limiter stop and a fully adjustable canister, giving EVERY stock GM setting, And everything in between them. The only modification is, the Crane stop plate needs to be mounted NOT where Crane says to put it, but on the OTHER side of the pin, towords the canister, NOT the end mounting screw. This is very easily done with one threaded hole and an 8/32 machine screw. The Crane method changed the vacuum pull spring strength with every degree adjustment, my modification separates the vacuum rate from the number of degrees selected, making vacuum advance tuning work, instead of compromising with every adjustment change.



If you are interested, I have a series of pictures and an outline on just how to correctly modify both the GM stock, and Crane advances to the correct way the stop plate should be, for both HEI and stock point distributors, along with the simple home made stops as well. There are even pictures on how to mount the Crane limiter plate to a stock GM vacuum advance, points or HEI.



If you want a picture set, there is no obligation, no ad, just simply e/mail me and ask for the one that fits your distributor, in this case an HEI, and I will send them to you.



Use this e/mail address, please.info@davessmallbodyheis.com and I will send same.



Also, I really don't advocate using ported vacuum, if there are those that still do use it, they have NO clue as to how a "load compensator" (vacuum advance) actually works in a non-EGR equipped internal combustion engine. The ONLY engines that require ported vacuum are those with a functioning EGR valve for EMISSIONS use, and there aren't many of them still running around these days.

Jimmy,,,,I stopped off at your Costco for a couple of Hot Dogs today,,,,,,tell me again how cool your van runs,,,,,,,,,,

Moving the vacuum advance to "ported" vacuum (from manifold vacuum) is something that started during the late sixties as a "smog" improvement.......
As originally designed, vacuum advance would draw from manifold vacuum and be "all in" with the throttle plates closed during low-load operations such as coasting or light throttle operation......When you stomp the throttle, the vacuum drops (as does the vacuum advance degrees) and the lost advance is replaced by the centrifugal advance..... (And by dropping the vac advance during acceleration, pinging is avoided) Total advance is only achieved during deceleration from a high RPM, though the centrifugal degrees diminish as the springs pull back on the weights......
Vacuum advance on manifold vacuum is an economy feature that rewards you with advance for using the throttle lightly.... Centrifugal advance is for acceleration......which, between the two cover the full range of load and rpm.......Think of the two advance schemes as a two-guitar jam!.... They replace and complement each other through the full ranges of accel/decal and load, as determined by vacuum and engine acceleration....The two advance schemes when at rest (engine shut off) allow for a lower "initial" timing number so that you don't have to crank the starter against too much initial timing!.... After firing up, you idle at degrees of vacuum advance....

This is probably too much info that nobody cares about anyway, but thought i'd share...

I think you may be better off trying to limit the vacuum advance using a set screw or different diaphragm, using ported vacuum from the carb and getting the timing as high as you can w/o detonation under load. I have my vacuum advance limited to 8 deg, I'm using ported vacuum and the initial is currently set at 12-14 btdc, but I think I can go up more just haven't messed with it lately. Definitely will run cooler with more initial advance, and you can turn the idle down further to that way, limiting any chance of run on.

I thought I posted that @ lunch, but I didn't.

i think this stuff is pretty interesting...anyway, moving to manifold vacuum advance helped my van run better so i thought id share. i guess Jimmy had a bad thermostat? or wasnt running hot at all?

I don't know about GM ignitions features, but the duraspark module will retard timing while cranking if the white wire is hooked up allowing more initial advance and still firing the engine no problem.

Thank you all great reading. I installed a 180 and was a 160 thermo I have a like new shroud I installed last night replacing the one that had some of the sides missing so I am hopping that this will move the air better. I also have the timing at 15% full advanced it runs great with no stall and smooth take off. Some here are wanting 1" from the radiator but with the stock shroud the fan is 3" and if I move it closer the fan will hit. Thank you jim.

Also the thermo was opening at 160% on my stove as well as the new 180% I installed. I also installed a gauge last year and its right on Temp.

Ok. With the new shroud, 180 thermostat and timing set it runs at 197 at idle and running down the road at 182. Thanks for all the help guys.