[Firebob]

I hear you jones. I read your post about your dads car. That was what kind of got me started on this one. Sounds like you have found the right solution for it. I'm hoping I can get there as well. But then you're talking about a much different size and configuration of engine compartment. It may be as simple as the underhood heat is just evacuated better from your Abody better than my Fbody and it doesn't trap as much heat in there. Actually the Firebird, with the flex fan on it would idle all day long in the garage and stop heating at slightly above the Thermo opening and generally speaking I can go anywhere anytime I want to and not have an issue but it's the particular situation of high outside temps and stop and go, or very slow moving, condition that is when my operation shows its issue. I'm attempting to remedy THAT problem for good so I won't ever have to worry about being in that situation again. The current radiator, stock shroud and flex fan didn't do it. I have no reason to think that a clutch fan, with basically the same operation under that circumstance, would be any better hence the elect fan experiment. I think if I find the right elect combo it will work. Possibly a great radiator and a clutch or flex fan and shroud would work as well. If none of the elects get the job done I will start all over with a great radiator and see where that goes.

I appreciate all the input and ideas being presented. It's much easier to work through when you have real world experiences to work from. Sure saves a lot of time and money too I'm sure.

Does anybody sell a blank shroud that you can cut you own holes in or will I have to make my own?

[Steve C.]

A fwiw, Ron Davis 1969 Camaro radiator/shroud unit utilizes dual 13" Spal fans

http://rondavisradiators.com/Top%20v...1-16CA6769.jpg

If you search universal fan shrouds you can get many sources. But as already brought forward in theses discussions the design is very important. Larry found out that !

https://www.northernfactory.com/knowledge/shrouds

https://pitstopusa.com/c-134583-cool...-shrouds.html#


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[Formulajones]

I feel the biggest improvement you can make Bob would be the radiator at this point and then go from there.

I've run 4 core coppers in everything here. Out of all of them, I switched 2 of them over to aluminum radiators and they both showed a substantial cooling improvement with no other changes. I'm talking about a "good" aluminum radiator that comes with 2 rows of very wide 1 1/4" tubes.
Dad's car was no different. Switched that one from his 4 core copper to the aluminum and it's a good 20 degrees better than the best temps we got with the 4 core copper.

[Scott65]

Robert, does the sniper control your timing? Have you experimented with the timing curve? It will seem counterintuitive, but my car cools MUCH cooler at idle and cruise speeds with more timing. Not saying this is your problem, but if you have easy control of the timing, some experimentation might be worthwhile.

[Formulajones]

Agree with Scott. I've found a substantial improvement with every car here buy adding some idle timing. Even on the cars that have very efficient engines and plenty of compression. The added benefit is also more engine vacuum and a smoother idle if you run a rambunctious camshaft.

Gets back to what I mentioned before in another thread. There are many contributors to engine temps and tune is a big one.

[steve25]

More timing at idle and at just off idle makes for more running cylinder pressure and it gets more or all of the burn done when it should , like in 72 to 74 degrees of Crank rotation, and this pumps out the Exh gasses better.
It's really just that simple!

The longer it takes for a given amount of fuel & air to burn the hotter the motor will run

[Firebob]

Yes, the sniper controls my timing. I have it set at 14@idle, 38@2k and 34 @ WOT.
Do you think it would be better if I added 10 more degrees to the idle timing(24 degrees total)? Issues with detonation coming off a stop?

[Scott65]

You know your combination better than I do, so I'm hesitant to make a specific recommendation. I will tell you that mine is set from idle to 1400 at 35 degrees. 36 at 2000, 38 at 2500, and 40 at 3000. All this at low map values, below 50.(except specifically at 900-1100, as my rowdy cam idles at around 75 kpa). In other words, at low load, it will handle a lot of advance, and it runs 15-20 degrees cooler than it did years ago with a curve closer to yours. Above 70kpa and 3500, I drop it back to 36, just because I haven't had a chance to dial in the fuel curve at those values yet. I think you would be safe to try 10 degrees at a time(at least in the idle to 2000 rpm range to start). A caveat, I'm not familiar with how much timing control you have, if its linear, try 5 degrees at atime instead. Try to keep it a controlled experiment. Maybe a warm up cruise like it is currently, return to home base, then add the 10 degrees, sit and idle and watch. I'll bet you'll see the temps come down before your eyes at idle, but if not it will be in a safe spot where you can simply shut it off and cool down. If however, you see it idling cooler, take off on another similar drive, and watch the temps at cruise. If you see improvement, then add some more, and repeat the analysis. Listen carefully for any signs of detonation, especially at moderate throttle increase, especially leaning into it in high gear with no kickdown/downshift, that will be the spot for trouble if there is to be any. Acceleration enrichment should help the faster tip in be less sensitive. For a point of reference, mine is 10.4:1 aluminum heads, 248/252 @ .050 cam, and 3.31 gears, switch pitch stall, which is about 1400 on the low side, 3650 lb. I dont have detonation issues. If you have higher compression, a smaller cam, less overlap etc yours could be more sensitive to detonation. FWIW

[Scott65]

After re-reading both our posts, dont add any at 2000, but below that experiment with more. 5-10 degrees at a time, according to your comfort level.

[Firebob]

Easy enough to give it a try. I do have slightly moe comp(10.7) and a little smaller cam (232/241). I'll be playing close attention to everything though. Once I get this timing set where I want it I'll be able to go in and smooth the curve so it's not so twitchy. It's supposed to be warm here tomorrow so I should be able to get some testing done. I'm curious to see what kind of difference it makes.

[Formulabruce]

Having worked on many Pontiac engines at the dealership under warranty and otherwise, I can say much has changed.
1. All 60's to mid 70's engines ran on LEADED fuel when new. That fuel was much more dense.
2. Due to lead, they could cool valves and run much higher compression, and much higher octane fuel
3, Thermostats and plug temps got bumped up at first to help with burning off Co, but later they figured out a EGR would cool the intake gases.
4. Gas today is way less dense, and has more octane due to Alcohol. Therefore it naturally wants to run hotter, with less power. ( look at a miles per tank on a new car sticker vs the fuel you put in it)
5. GM engineers tested Shroud technology at great lengths. They had drilled holes all over them and inserted vacuum gauges to test the pull at each point.
6. Weather it works or not, you cant ignore common sense and run a Flat piece of meta on the back of a radiator and a fan with less than 1 inch and expect it to have efficient cooling.
When that does work, the fan does double time to cool the area where it can work, some folks add more fans, then add "pushers" too.
Bottom line, you can run the engine at 185-190 with 44 plugs and a 160 or 170 T stat, and still "boil off" all the moisture you think is in the oil with a stock cooling system and a slightly over stock engine.
Millions of dollars get wasted each year because someone says to someone else, "Hey, I run this" and it works for me. While each build is different, a person should be able to keep a 9:1 Pontiac engine cool enough to run the ac, and not cook the transmission.
If you want to run at or over 200, put in a trans cooler.
There is a reason why Pontiacs have fan shrouds and clutch fans, etc for Millions of cars, for many years, Because it works, and they did NOT want service recalls.
Just my 2 cents.... but I like reliability and efficient cooling..

[Scott65]

I did find a YouTube video of the sniper timing control. You should have good adjustability. I did not see it working "live". Does it have a marker the follows the cells that are in use in the timing table? If so, you should be able to know where to safely add timing in the idle and high vacuum cruise areas. These areas should not be imminently dangerous as far as detonation. Leave a buffer between the high vacuum cruise areas and where you start to transition to higher load. If you see gains in cooling, you can go back and find the sweet spot for the transition areas separately. Good luck, and hopefully you'll see some improvements in cooling. Let us know how it turns out.

[Formulajones]

Like Scott mentioned, there is no reason for concern to have anywhere from 43-48 degrees of timing at light cruise in the high vacuum light throttle areas, when mechanical is all in and some added vacuum advance on top. That's what a vacuum advance does for you on a conventional setup. Same deal on the computer that Scott mentions with the biggest difference being it's much more precise and small changes can be made in small areas.

Most cases here, I'll run as much as 14-16 initial and then add another 10 degrees or so of idle timing with vacuum advance on top of that and see if the engine likes it. On tip in vacuum drops so the added vacuum timing drops at the same time rpm rises and mechanical adds a little. You can accomplish the same on a lap top too and do it more precisely. It's a game of cat and mouse and will take some experimenting as every engine is different but it's well worth the time and effort.

[Cliff R]

The key to success with this cooling stuff is to build an engine that doesn't dump tons of heat into the coolant in the first place.

WAY before we knew much about combustion efficiency we just bought cams because it may have worked well for someone else based mostly if not completely on "seat of the pants" assessments and telling a few tall tales about how the car would run 10's, walk on water and leap tall buildings in a single bound, etc.

As much good information as is out there today it just absolutely kills me that a week doesn't go by that someone calls up here and kills a half hour or so of my time telling me how their new engine build idles like chit, runs hot, overheats, pings on pump gas, has to be "two footed" at stoplights to keep from stalling, and it stinks out the exhaust so bad the wife woln't ride in it! When I ask why they put in a Thump-Ya-Mutha cam on a 107LSA and unhooked the vacuum advance they very quickly tell me that their engine builder said that cam worked great in billy-bobs engine and that they NEVER use vacuum advance on any of their engine builds.....LOL.

So I get to be the bearer of bad news and tell them that no amount of money spent on the carb is going to correct the fundamental issues at hand....the lowering of the compression ratio to use pump gas then throwing in some cam that ought to be used in a circle track engine that spends most of it's time at 5000-7000rpms!

I know I'm being a little sarcastic here but believe it or not I go this sort of thing ALL THE TIME with potential customers.

As far as engine running temps, thermal efficiency, etc, theory is trumped by practical application. IF we followed the rules and theory we'd all be running thermostats with 195-210 degree open points like most modern engines do, then tuning to the brink of extinction to make sure timing/fuel curves are spot on across the entire load/speed range.

In the real World you'll find yourself hard pressed to successfully use a thermostat much past 180 degrees for most of these engines. They are half a century old and have seen a zillion heating/cooling cycles, and for the most part just HUGE chunks of iron and giant heat sink. Modern engines are not only much thinner, lighter and almost always topped with aluminum heads, they have superior designs and greatly improved combustion efficiency plus enough cooling system to always keep them in check no matter what conditions they are operated in. That's just the way it is.

There are also a good many opinions on how hot these engines should run, and to this day I know a LOT of folks who run 160 degree thermostats or none at all and say they just do it because that's worked for them dating clear back 30-50 years when they first got into the hobby. A good percentage also block off the heat crossover in the intake manifold which IMHO isn't a good idea for a lot of these applications, but that's another topic and full of varying opinions on the subject.

What I do here is to take steps during the engine building process to make the engine as efficient as possible on this new fuel while still making optimum power for the octane available. We also insure that the cooling system is more than adequate for the task at hand. I've found that quench is a pretty big player with heat production that dumps into the coolant rather than pushes the pistons down then quietly exits thru the exhaust. Without exception ALL the troubled engines we've taken on to help out had a lot of quench in them. Another common denominator is camshaft selection. I am NOT going to start an LSA debate here, but for the most part relatively small cams on tight LSA's just add to the heat production problem, plus they don't make chit for power in the these engines from what I've seen.

Perfect example came rolling in here last weekend. I LOVE real stories. About a year ago I restored a carb for a 454 LS5 in a 1970 Chevelle SS. It's a near perfect high end restoration. The engine was supposed to be built to "stock" specs with the only real deviation was a "custom ground" flat hydraulic cam very close to stock specs.

So I build the carb and from day one the customer isn't overly happy with the way it runs. He complains enough that I ended up having him trailer the car here. A spent a few minutes with it, checking everything and it just isn't a happy engine. Idles a little "quirky", poor response with the mixture screws, slow throttle response and just doesn't make much power. So I ask the owner to provide the cam specs and he digs thru his cell phone and comes up with 260 something advertised duration and 220 @ .050" on a 112 LSA. (Better suited to a mild 350 build IMHO)

Cripe, not nearly enough cam for the big 454 and it's acting like it. It won't take any timing at all without "bucking" the started heat soaked and actually detonates when you fire it up when it's hot. I retard the timing to 8 initial and it's still idling dead smooth and sound more like a 350 in a station wagon than the big LS5 in a Super Sport.

I end up taking all the bypass air out of the carb (big block Chevy Q-jets use and require a butt-ton of it) and leaning up the idle system a bunch to make this engine happy at idle. It still doesn't make much power or run well but now it will idle down with the speed screw against the stop. It also heats up FAST, and you can't get within 10 feet of it after it runs a couple of minutes!

I tell the owner to yank the cam and put something quite a bit bigger in it to cure the issues. He's not happy with my suggestions, so I fire up the 455 in the Ventura and it idles ten times better and sounds better with a WAY bigger camshaft in it. I didn't dare take him for a ride because he would have amputated that cam out of his engine as soon as we got back to the shop when he realized what he was missing!

So I basically "crutch" fixed the big LS5 until he can get the cam swapped out. He texted me the next day and said that even after pulling all the timing out and re-tuning the carb it's still pinging everyplace and lackluster performance. I hope he swaps out the cam before the pistons end up in the oil pan!

Anyhow, as it relates to this topic it's just difficult to get past the laws of physics with these things. A 454 or 455 Pontiac is NOT going to be happy when the compression ratio is 10.5 to 1 and you put a tiny little cam in it. It's going to makes tons of cylinder pressure and ping, run hot, probably overheat and not make optimum power. So it's better, in all cases to get the fundamental stuff right during the engine building process rather than getting the engine in place then find out you can't get it to work well, or control the engine running temps, etc.

So to top this story I get a call late yesterday from a Pontiac owner who had a "guru" do all the machine work for his 1970 455, #64 heads and supply him with a Comp Cam (pretty sure he said High Energy) with 212/212/110 specs. He's having all sorts of running issues with it and it doesn't make crap for power....imagine that?........Cliff