[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