Hello all, I just recently had my engine rebuilt: 454 bored .060 over mild cam and crank. Got it in car car today started, mech told me to run engine @ 2000rpm for 20min to break in. After about 10 min. temp was around 220 and climbing. I let it cool removed stat started back up and still 220 and higher. Definitely running hot, radiator started pukinghttps://www.corvetteforum.com/forums/images/smilies/frown5.gif


Cooling system: stock radiator, 2- perma cool 12" fans(pullers), at present time no stat. no shroud, no mechanical fan

 

Fixed it for you
Maybe get an infrared heat gun and see what your temp really is before tearing into it. Harbor Freight has 'em for about 30 bucks.

Pete

 

Thanks for the fix!

I installed an aftermarket gauge, do you think it is wrong?

Ill invest in the heat gun to make sure.

Thanks!

 

Couple of questions: did you connect the little hose above the water pump to the intake? It's a bypass hose and helps keep the water moving. I've tried capping my off and it only made the temps worse.
Second, did you burp the engine.........meaning, the engine is full of air after the rebuilt and you placed a thermostat in the intake. Upon firing up, the coolant is trying to push the air out yet the thermostat is keeping it in. I use a thermostat that has a little hole drilled in it from the factory.....it allows the air to escape. Option two, leave the radiator cap off while firing the engine up. It will let the extra air to escape and you can pour more radiator fluid in.

 

sounds like air in radiator and cooling system to me,
I had the same problem, it took 4-5 attempts to remove all Air,
then the system ran right at T-stat temp. with my 454.
C3's are difficult to fill, and remove all the air.

 

@snoopykissedlucy: I did remove the heater core and the small hose from pump to intake and plugged the holes. I left cap off radiator and drilled a small hole in stat.

Ill add the small hose and keep burping.

Thanks!

 

I can surmise what a mild cam profile is. But I'm puzzled what a mild crankshaft would be and how it might affect you cooling troubles?

 

Did you put a new temp sending probe in when you rebuild the motor? Make sure the probe and the gauge are compatible.

I just brought a 73 BB back to life after a 15 year rest. Got a new probe at XYZ Automotive and I got the same type readings your getting. I verified with a heat gun the gauge was reading incorrectly. After researching here on this forum I found out that the factory dash gauge has specific ohms reqrements for proper indication. Bought one from zip.com (27 bucks) now gauge reads correctly.

 

@Ibfurloughed

I had read the same forum about the temp probe. To verify I went to the nearest parts store and bought a cheap temp kit, came with probe, wire, and gauge. Still reading very high temps.

 

Where is your initial & total timing set; are you running a vacuum advance; and is the vacuum advance hooked up to manifold or ported vacuum?

Lars

 

When you're going to try to school someone instead of attempting to help, you might consider checking your shet first...

 

@ lars
To be honest, I have no idea on the timing. When I set it I was instructed to get #1 cylinder TDC and line distributor with #1 spark. Did that car sounds good, doesn't sound like ot is missing.

The vaccum advance is ported vaccum.

Thanks

 

Land Shark, you mention that the radiator was puking over so I would believe its hot.

Did you install a high flow water pump, don't see in your posts where you've mentioned anything about the pump.

I tried to remove the bypass hose from mine and it would do the same thing and worse. While driving the temps would jump high and than ease down and swing high again. When I added the bypass hose it stopped swinging, it still ran warmer than the T-stat but it stopped swinging high.

The only thing I could come up with is it was caused by cavitation.

Neal

 

I'm with Lars on this one, you cant get a good enough cooling system if the timing is retarded, especially on break in.

 

There's the source of your problem. Timing has a greater effect on engine run temp than just about any other issue. Get your total timing up around 36-38, make sure your initial is in the 16-18 degree range, and get your vacuum advance off ported vacuum and onto a manifold vacuum source. This will drop you engine temps by about 20 degrees. E-mail me for my timing papers if you need specific instructions. Timing will never cause an engine to "miss," so your timing can be off by 20 degrees with the only symptom being hot running and low power.

You can put a radiator from a diesel locomotive in your car, and it won't fix heat issues caused by bad timing.

Lars
V8FastCars@msn.com

 

Thanks lars for all the help!

Here is an article that backs up what you posted about ported Vs manifold:

Ported Vs. Manifold Source: Vacuum Advance

This was very helpful to me, so I thought I'd post it here:


This was written by a former GM engineer as a response to a similar question on a Camaro 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 again as you return to steady-state cruise, when the mixture again becomes lean.

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely.

 

Article written by John Hinckley

Here's one by Lars http://www.460ford.com/forum/showthread.php?t=117504

 

That article is posted without my permission, it has been altered, my Copywrite has been removed, and the article is grossly outdated and should not be used. I don't post any of my articles - obtain articles directly from me via e-mail request, and don't use the altered out-of-date garbage posted by Forums and individuals.

My article incorporates John Hinkley's and Duke Williams' articles and comments.

Lars
V8FastCars@msn.com

 

Wow, nice article by lars, '75

 

UPDATE: I set timing at 36 degrees, moved advance from port to manifold, added small hose from pump to intake.

at cruising speed 210 degrees
in traffic creeps past 230 degrees

I also noticed my oil pressure is very high, cold about 65-70psi
about the same when hot.