[buwalda]

PopsGTO [ July 1 post ],
I also have a 66 GTO & it ALSO overheated on the highway. I'll bet you are using a clutch fan, because that is what made my GTO run hot on the highway. I tried a few different fan/clutch combinations & they ALL ran hot. I switched to the Pontiac Ram Air 7 blade flex fan & that reduced the highway temps. Also tried a Flex a lite flex fan & it too reduced the temp. I believe the clutch fan free wheels at highway speeds & acts like a baffle, causing temp to rise. Also, clutch=slippage=less rpm turned by fan.


To George K's question about stamped v cast impeller results,

There seem to be many variables that can affect results [ better or worse ]: T'stat rating, T'stat design [ standard, high flow, opening area ], ignition timing, jetting, scale in coolant jackets, under or overdriven water pump pulley, fan-to-radiator distance, shroud/no shroud, radiator condition, small coolant passages blocked in head gaskets?, matching hole in water xover opened to same size as head core hole [ E'brock manifolds have terrible mismatch here ], etc

[pops66gto]

Geoff,
We are using a single electric fac/shroud combo from a 1990 Ford Escort and a Griffin 26x19" rad. I don't know what step we are going to try next but I want to rule out the lean condition on the highway and then we might switch to a shroud and flex fan. thanks for the help. I listed my entire combo pn page 24 I think. thanks
-karl

[68lemans462]

Just wanted to add that this trick worked like a charm for me. I had about .125" of clearance between the impeller/divider plate. I knocked it down to .060. I run a 160 tstat with a griffin aluminum radiator. When it would get HOT outside, it would creep up to about 190 and would stay there. now the needle is permanently stuck on 160. GREAT TIP!!!

[Gordy Doyle]

George thanks for the advice. I did find the full cast unit after searching many different auto parts stores.
Unfortuneately it didn't solve my problem. Here's my setup sure hope somebody can help on this.
I just installed the rebuilt 455 bored .040 over. #96 heads, a mild hyd. perf. cam (recomended for this combo) new 4 core factory style rad, the cast impeller wp, new divider plate (massaged for better flow), new thermostat (twice), new temp sending unit (twice), new fan clutch, 7 blade fan, new hoses (yes, spring in lower hose)

AND it STILL RUNS HOT!
It'll start right up, run good, but within a few minutes that temp is just climbing and climbing. I shut it off as soon as it pegs the guage.

I have noticed that the heater hoses seem to get a lot hotter than the upper hose. Also I'm concerned about oiling because when i first started it up it took forever to get oil coming out of the pushrods. It eventually did come out and make a mess but it seemed like it took a long time. Now when i look into the oil cap hole in valve cover it doesn't seem like i can see oil sloshing around. Is this normal? How long should it take to get oil on initial startup>
Thanks for the help
Gordy

Also before the initial startup I primed the egine by running the drill to pump oil to rockers. I never could get oil through pushrods this way. And it seemed like it took alot of force to turn the oil pump.

[soupman]

I had a Buick 455 that always overheated. No matter what I tried didn't help. Root cause of the problem was the rotating assembly was tight, like it wasn't as loose as it should be. It created alot of internal friction = heat. Thats when I learned that the internal engine assembly is important for running cooler. This 455 in my 72 T/A, with cam, etc. will run cool allday. I can let it idle for a 1/2 hour still runs around 180. This motor was built by Nunzi about 5 years ago, 25K miles on it.

[faintember]

Ok...after 26 pages of reading and no beer, i am a bit confused. lol i have a '66 lemans with a 400 out of a '72 trans-am. i know i need the 11-bolt design pump, but where where the best places/best pumps for these 11-bolt pumps. Did any of the 11-bolt guys further modify the plate that is near the impeller with an new water pump? Thanks.

[george kujanski]

Gordy, it will take a fair amount of force to turn the pump.

if you are above thermostat temp, the upper hose better get as hot as the heater hoses or you are not getting coolant from the engine to the radiator, i.e. a flow problem of some kind. If both heater hose are hot, the pump must at least be moving coolant thru that loop.

I haven't primed my engine for awhile so I don't remember the specifics of oil flow thru the pushrods. As soupman says, high friction will cause excessive heating.

Cameron, as you may have read, getting a proper 11 bolt pump is a crapshoot. You just have to go and check them. Clearance between the plate and impeller vane should be minimum. One member put them together without a gasket, did the adjustment with a BFH, and then checked the clearance with the gasket to make sure there was no interference. That should be optimum.

George

[Junkyard Dog]

One more thing to complete the description of my cooling system on the previous page. I forgot to add that the spring in the lower radiator hose was completely corroded and only existed in a few small, one-inch chunks that were stuck in the hose.

I have no plausible explanation for why my car did not overheat.

Maybe it is the weather down here in Atlanta.

[aerosmyth]

TO: Poncho Cast Impeller Forum, aerosmyth back online.

Been a busy few weeks. Took a side trip from overheating and changed out a 'grabby' Zoom kevlar clutch for a high-marcel Centerforce. This effort was its own study in clutches and resonant chassis nodes (chatter). Ask offline if interested. Then there is the valve stem seal study now at completion. Had Teflon Conteco positive seals that created a perfect pickup sump/funnel to draw copious oil volume from the puddle at the base of the valve spring and shim. Replaced with garter spring vitons from Manley. All valves guides were SOAKing in oil when the old teflons were removed. Now to see if this WS-motor has broken its quart per 200 mile habit.

Now on to the heat heat generation side of the cooling equation. All compression calculations said I built a 9.5 to 9.8 to 1 engine, but doing my compression check to see if I fried anything, I get 190/195 on all 8 after the final 4th or 5th compression. Some websites and my engine guy say this is closer to 10.5:1 which for FAST burn pump gas is a HEAT generator and possible 'silent detonator'. BTW cam is a Comp XE262 timed at 0. My thought is that
if cylinder pressure is indeed this high, I still need real 1966
Enco 100 gasoline (put a Tiger in the tank).

Now the story on the radiator baffling. The three pass baffle scheme in my ORIGINAL 4 row (180 tube) Harrison didnt help or hurt cooling. Remained at 7-9 delta T on hiway runs (see earlier mini report) Only problem was that now I detect a 'howl' right at 2800-3200 RPM (righto, hiway speed). My thought is that due to the closed volute pump effectiveness (Watercooler-see earlier image), that coolant is now 'wooshing' up and down into the tanks, entraining air and possibly cavitating the pump. The 'radiators-r-us' guy will take it apart and return it back to the way the nicely paid thermal engineers at GM designed it.

SO, finally a question. Through all this pump tweaking on this forum has any one measured the change in DELTA-Temp before and after a good pump exchange? Did anyone note any radiators plugged then liberated by a good RODDING out?

Me thinks I might be visiting airports for 100LL untill I get the time to solve the heat generation equation (retard my current grind?).

whew...this is a long story....sorry. aero

[aerosmyth]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by GR8ONE68:
Here is my combination:

455+.060" = 469CI, 6X-8 Heads milled to 100cc's, 1.77" Exhaust valves, ported, push rod holes elongated. Block "0" Decked = 9.3:1 static CR. RAIV Cam w/1.65:1 roller rockers, RPM Manifold, Hedman Hedders, 2.5" flowmaster exhaust system with "H" pipe, dynomax super turbo mufflers, Edelbrock 750 Carb. <HR></BLOCKQUOTE>

GR8ONE68, aerosmyth here. What static cranking PRESSURE do you see (fully pumped-up, strokes as required). Im seeing 190+ on a calculated 9.8:1 rebuild. Im trying to solve the heat generation side of the equation. Thanks, aero

[Malky]

aerosmyth,
I like your style - assume the harder the sell,the bigger the bull****. Good luck with the Viton seals. The Teflon seals are crap, IMHO. Viton is the way to go.
Cavitation of the water pump is an interesting possibility. Few people in the industrial pump business design a pump to behave predictably at variable RPM, especially such a huge range as 600 RPM to 6000 RPM. I would love to see some papers from the big 3 since they must have analyzed the hell out of this, but I am out of my depth dealing with this RPM range. George, most industrial pumps run at a fixed speed. A pump that runs happily at 600 RPM will tend to cavitate at 6000 RPM. I suppose you could deliberately use the performance drop associated with cavitation to reduce the HP demand at high RPM. Anyone know of any papers by OEM's on water pump design?

[george kujanski]

Malky, interesting thought. Any members here belong to the SAE? They have papers on darn near everything automotive. Members can get copies of the papers.

On the heating subject, I've forgotten to mention anything about the possibility of auto trans cars contributing to the heat generation problem as the trans lines go to a heat exchanger in the radiator tank. this jog anyone's memory as a possibility?

George

[convbird]

George, I put in a trany cooler thinking it would help. I didn't see any difference in my temperature. That's not to say it won't help someone else. I'm running a 3000 rpm stall.

[matrix]

I have a 70 GTO with a slightly warmed over 400. Runs at 190 - 195 constantly with a 180 thermostat, clutch fan, new copper 4 core radiator, stamped impeller pump. I have also been reading the "Vacuum advance" post where it is suggested that hooking to manifold vacuum gives you more advance at idle and will help the engine run cooler at idle. This is how i had my car set up and it was running well. But since i always think it can be better i switched to ported vacuum and also made the necessary adjustments to the idle speed and mixture. Well the temp gauge promptly went to 210 at idle. Before it would sit at 195 forever. So i switchd back and forth from manifold to ported vacuum and made many slight adjustments to the idle mixture. always the same result: ported=210 manifold =195. I switched back and forth at least 5 times with a 5 minute cool down cruise between each. I have managed to find a cast impeller pump and will install it and clearance the backing plate this weekend. I will let you know how it goes.

[Junkyard Dog]

But Matrix, did you tune the engine at all after switching to ported vacuum? What I mean is, what was the base timing and did you change the idle mixture to add more fuel?

[matrix]

Timing is 10 degrees initial and 32 total. Never changed the timing as I have found that 32 total works best for my car considering the 10.25-1 comp. But yes I did reset the idle mixture by ear and by vacuum gauge. I also tried varying it a little in each direction thinking that a little richer may make it run cooler. oh, and my stock vacuum advance ads 20 degrees when fully engaged. so there is no question that on my particular car the extra 20 degrees advance at idle makes it run cooler. I do have to say that I think it ran a little better on the ported vacuum but that may just be mental. I have no numbers to support this. I think next I may try bumping my initial timing to 14 degrees without the vac advance and see if it will idle at 195 with this setting . If it does i will then try to limit the mechanical advance for the desired 32 total.

[george kujanski]

Good data, matrix.

George

[buwalda]

I have made a few comments on the benefits of manifold connected vacuum advance under other headings, so I will not repeat them here. Matrix's experience, ONCE AGAIN, shows that vac adv connected to manifold vacuum improves engine eficiency by providing more initial timing at idle, & this is proved by the 15 degree temperature drop when compared to ported vacuum use.

[Rugratman]

As opposed to the vacuum hooked off the carb stud ?
My car has a splitter off the back of the manifold = One to the Brakes, One to the trans.

The distributer is hooked up to the carb stud.
Should I switch them around?

[george kujanski]

rugratman: I believe the carb stud has full mainfold vac and is correct. Put your finger over the tube at idle. If you feel suction, that's it.

George