Technical Timing, backfiring and overheating

What diameter is the fan? How much of the radiator does it cover? What does the manufacturer claim the CFM is?

 

Most of the time a car runs hot at idle or in stop & go traffic people point to a lack of air flow as the cause. I think just as important as air flow is coolant flow. One reason the engine cools down when speed picks up is due to an increase in coolant flow rate as the engine rpms increase, as well as an increase in air flow. Guys have solved this issue with a smaller diameter water pump pulley, and/or a high flow water pump. Ignore the guys that post about the urban myth of the coolant flowing too fast, and the need to slow it down, they don't understand basic heat transfer science.

Re the timing, there is a thread here on the HAMB somewhere (unfortunately I can't find it, not coming up with the right sequence of search words) where the poster explains a somewhat common situation with certain SBC's with real low compression rates, where the typical ignition time rules don't work correctly for these engines; and what they need is greatly advanced timing vs what we typically see. From everything you've posted above, I'm thinking that may be the case with your engine. I'm with the poster above that recommended setting the timing by ear and going with it. I've done the same with the 283 in my A pickup. I installed a vacuum gauge and a tuning tach and I watched the gauge/tach and listened to the engine as I slowly advanced the timing at low idle, and I played around with going too far and bringing it back down several times until I finally advanced it to the point of maximum rpms and vacuum then backed it off just a little and tightened it down there, and it's been running like that for a few years. If you get it too far advanced you will have starting problems, the starter will have a hard time turning the engine over. If that's the case, back it off a little more until it starts without dragging the starter motor down. And call it good. But it's not advanced timing that will cause the engine to run hot, it's slow timing that will do that. So as long as your timing isn't retarded that's not causing the heating condition.

Good luck, hope that helps

 

The radiator core is 20x20x2.5 and it's a 16in fan. I don't know the claimed cfm as it was already installed on the radiator when I got it.

 

I had engine over heating problems at idle with a 283 SBC in my Model A Roadster with an Eldebrock carb and a Delco HEI distributor. The vacuum line to the distributor was on a ported outlet. I changed the line to the full manifold vacuum outlet. This solved the problem and the engine was smoother running. I set the timing by first disconnecting and plugging the vacuum line from the distributor, set the idle speed and mixture, and then the adjusted the timing. Next I reconnected the vacuum line to the full vacuum port on the carb. This raised the engine speed. I readjusted the idle speed and idle mixture. This gave me full vacuum advance at the distributor at idle. The full advance keeps engine temp down as a more retarded setting will make the engine run hotter. Just a suggestion.

 

Is there a way you can determine which crate engine you have? I have no experience with GM crate engines but is it possible the crate engine came with a reverse rotation water pump? I have never run a reverse rotation pump on an engine designed for a standard rotation pump so I don't know what the exact symptoms would be but it might be worth checking. I would ***ume the wrong rotation would cause issues at any rpm but .... Even if the person bought the water pump as a standard rotation unit, it could have been boxed incorrectly. I am aware that the serpentine belt SBC engines used a reverse rotation water pump so if this particular crate engine was marketed as a replacement for a serpentine belt vehicle, it could have the wrong pump on it. Long shot but worth checking off your list maybe.

As for the HEI, I only run factory GM HEI's and have never had an issue. Doesn't mean you aren't having an issue with your HEI but I have found them to be unbelievably reliable. My point being, I'd be inclined to fix a faulty HEI before I replaced it with anything other than another GM HEI.

Also, make sure both advance mechanisms are working in the dist. Turning the rotor and having it spring back verifies centrifugal advance is working but you also need to test the vacuum advance too. Stick a hose on it and ****, and watch the plate move, then put your tongue on the end of the hose and make sure it holds vacuum.

 

I don't know what motor it is. I know the pistons are bored .030 over and it's got a 350 crank. That's the extent of what I know

 

My understanding is a genuine 'crate engine' is a completely new engine. If yours is .030 over then it is most likely a used engine that has been rebuilt. It could be a legit 'crate engine' that has been rebuilt but I'd bet it's just a rebuilt so it's doubtful it has the wrong water pump.

Might be worth checking the casting/stamped numbers to get an better idea of what engine it is you have. I haven't heard an engine diesel in many years ... it would be nice to determine what your compression ratio is or did the dieseling stop when you sorted out the plug wires?

 

So I just drove to get my daughter from school which is half day and half city driving. Freeway it was fine and sitting at stoplights it got warm but not quite as warm as it did before. Whatever I'm doing, I'm heading in the right direction

 

In cases where the cooling system is weak for whatever reason.....auto parts stores sell stuff called Water Wetter..dont know what it does, but it does lower temperatures and it might lower the spike you're seeing at idle. It is kind of a band aid in your situation, but it might keep you from overheating your motor or blowing a headgasket.

 

I had an electric fan reverse polarity on me one time. Went from a puller to a pusher without notice. I doubt that's your problem, but check air-flow. I am the king of getting spark plug wires crossed, so I know how that goes. No one has mentioned a vacuum gauge yet, so I will. great diagnostic tool, and good for setting the timing. Good luck.

 

Not sure if I should start a new thread or continue this one.

So I've changed the plugs, wires, cap and rotor. I pulled the carb and rebuilt it. I actually found some nastiness in the carb so that was a good thing. While I had the carb off I had the idea to pull the holly off of my plymouth and try that one since both are 600cfm's. The car ran a little better but not much. I finished rebuilding the edelbrock and installed it. The engine ran the best it's run since I've owned it. That was the point I realized I didn't hook up the break booster vacuum hose and had a m***ive vacuum leak. As soon as I hooked the hose up it went right back to running like ****. This whole time I was convinced a vacuum leak was one of my main issues....

 

Some of the loveliness I found in the carb

 

I get it about hot summer days. Lots of good pointers here, but you mentioned the eng runs rough. Might be a long shot but I would take another look at the carb admixture and fuel idle setting. Too lean can create heat.