I wouldn't freak out about it just yet. Yes, you certainly should have run the RPM's up right away. The point of running it at high RPM during cam break-in is to keep the cam lobes flooded with oil as they wear in. The lobes are only splash lubed by oil slung off the crank and you get a lot more oil slung up there at higher RPM's. BUT! the valve spring pressures in these old engines were relatively low. It's a lot more critical in a high performance engine running higher valve spring pressures. You might not have hurt it at all. The easiest way to check is to dig up the lobe lift specs for the cam, pull off the valve cover, and install a dial indicator on each rocker directly above the pushrod and check to see if the actual lift matches the specs. The peace of mind would be worth the hassle of finding a dial indicator to borrow. Irregardless, make sure you run it at break-in speed the next time you have it fired up. It's still important to get it done so that the lobes and tappets wear in properly.

 

It might also be a good idea to change the oil and filter before your next start up, too, just in case.

 

The next time the truck runs should be within the next few days......school is keeping me really busy, and I haven't had a chance to get to it.

Either way, thanks all for the input. Hopefully, I should be able to get it started soon.

 

Started it again today.

It idled at at an unknown rpm for the first 10-15 seconds until I verified it had good oil pressure and it started to run ok.

Then it was off to 1000 rpm, wouldn't go up for a couple seconds.....then it got to 13-1400 rpm. It wouldn't go farther for about 15 seconds.

Then it was off to 17-1800. It sat there for maybe a minute or two.

Then it sat at 2000 for about 7-8 minutes. A total of about 10 minutes of break in time.


It for some reason ran for a few hard minutes without budging the temp gauge whatsoever. Then in a miraculous moment(of me not watching it) is just went up to 140 and kept going from there. It got up to about 190 and then I started spraying with a little spray bottle of water. It seemed to stay at or around 210 for probably 3-5 minutes, then I ran out of water......It got up to about 215 and I told my dad to kill it. The gauge eventually read about 220 and didn't go any further.

It's unfortunate that I'm gonna have to go back and do another 5-8 minutes of break in....but the temp was rising, and I was running out of gas...so I stopped. Leave it for maybe Sunday.

Upon shutting it off, steam was shooting out of the radiator over flow.............again. Even with the cooling system full of 50/50(not too full). ......I wonder if it's getting hotter than the gauge reads, I can't believe 50/50 should be boiling or spewing out like that at only 220º.....Whatever, what do I know.

I know this is a pointless update, but some of you know how to read between lines a little better and may be able to give me some feedback.

Thank you.

 

Actually not pointless, it sounds very familiar! It sounds like everything is going the way it should. Put plenty of gas in it, and use the highest octain gas you can get - it will help with cooler running and preignition (pinging) if the engine gets hot.

Don't fill up the radiator. Leave about 3 inches of space on the coolant. Basically, it is vomiting up all the air trapped in your engine, and that air gets REAL hot. Remember it doesn't have coolant mixed in it. Air also compresses as the engine heats so when trapped behind a closed thermostat, it's going to push hard when it gets free. Also, the coolant will expand and if you start cold and full, it should overflow about 2 quarts when it gets hot. 215 to 220 is not unrerasonable - it's gonna get that hot especially stationary.

If you are worried about gauge accuracy run up and buy a laser temp gun and check out the coolant temps at different places during your run up process.

Keep charging - you are doing fine!

 

Hi!
First go to Walmart and buy one of their 10.00 pump up garden sprayers, The kind with a plastic tank, a hose and a spray wand with a pump handle on top. They hold about a gallon or two. The tip of the wand is adjustable and can be set for a wide fine spray like a spraygun. When spraying the radiator to cool it concentrate on the lower 1/2 that's the hottest area. A large box fan (also available at Wally world and your local big box DIY stores for less than 20.00) set to blow thru the radiator will also help with the cooling, just be careful not to mix electricity with water!
Your temp gauge probably doesn't register <140*.
Boil over after shutoff is common, the engine has hot spots in it, especially around the top of the cylinders where the metal temp is quite a bit hotter than the coolant, that's the purpose of the coolant to come in contact with those areas, quench and move that heat to the radiator and the radiator removes it to the air (remember: you remove heat, not "add" cool, spraying or blowing air thru the radiator doesn't cool it, it helps it remove more heat.) When you shut off the engine the coolant suddenly stops moving, the engine hot spots locally heat it up past it's boiling point. The steam that forms expands much more than the space the liquid previously took up. The only place that pressure and steam can vent is out the radiator overflow and you get boilover. Drag racers have this problem all the time. What they do is put an electric pump in the coolant line (usually utilizing the heater hose connections) and an electric fan on the radiator. By turning on the fan and pump after shutting off the engine they keep the coolant circulating and cooling the engine until the temp at those hot spots drops well below the boiling point.
Your only option, short of installing an electric pump is to keep the engine as cool as possible, especially immediately before shutting it off.

 

That's a much better and more specific explanation AX!

 

Julie--Thanks a lot. I left about 2" of room as you said in a previous post. About higher octane fuel....this trucks comp ratio can't be above 8:1.......I though high octane fuel can actually be bad if the comp ration in an engine is too low? So I've been using Chevron regular 87 octane so-far.

AX--We have a little pressure sprayer that seemed to work fine...but I will go take a look at what you suggested, anything that helps. I'm afraid of putting too much water and fatiguing the rad. We also had a quite powerful box-type fan blowing on the rad...but it wasn't direct.....I felt I could have put it in a better spot.

Thats funny you should say that.

After letting it run for that time, my Dad questioned that maybe we should let it idle and cool for a minute. I told him NO and that it needed to idle as little as possible, so we shut it down.

Was he right? Even before the cam is broken in(idle is BAD)?

Thank you again.

 

I really don't believe a couple minute idling before shutting it down will hurt your cam any. Put the box fan up on a chair or something that brings it into better alignment no more than about 18" in front of the radiator blowing full speed. You aren't going to hurt the radiator by water spraying it as long as the coolant is moving thru it. We fill our spray bottle with ice water to cool our radiator and tires on a hot day.

 

If you are doing all this and the temp is still climbing like that,'d be checking the timing to make sure you don't have it too far advanced. The timing should be set with the vacuum hose to the distributor disconnected and plugged at the carb at idle.

 

I've never heard the compression ratio VS high octain fuel being a problem in an older design engine - perhaps the modern EFI things that are computer monitored for mixture and have 2000 pound of pollution control stuff that's true, but higher octain gas would be better for your older design engine while you are doing this.

Also, your discussion with AX brings me to ask a question: Will idling the engine help cool it down, or actually make it run warmer due to less air being pulled by the fan. But on the other hand, the coolant will be in the radiator longer. But on the other hand it will also be in the engine longer - absorbing more heat.

Watch it, and let us know.

PS and when AX says "at idle" he means (I think) the correct idle rpm for the engine. If you adjust the timing it will increase or decrease the idle rpm - which should then be reset to the correct rpm.

 

I guess I didn't make it clear I meant allow it to cool down by idling for a couple minutes while continuing to heavily spray the radiator and blowng air thru it with the fan.
I think what MB was refering to is that high octane gas in a low compression engine will not improve the performance and can actually cause it to make LESS power than on a lower octane. This is true. The best performance will come from the lowest octane fuel the engine will run on without preignition pinging under a heavy load.
Correct me if I'm wrong Julie, but I think you suggested high octane fuel because you were concerned that the engine's abnormally high temp might cause preignition with the lower octane fuel. Fact is I ran my lawn mower on 106 octane racing gas yesterday because it was all I had on hand and the lawn needed mowing. I also doubted that the gas was 106 O any more since it had been sitting in the plastic can since Sept.

 

Bet the valves are clean!

 

AX--I have a confession to make. I have statically times the motor, but I have not used a timing light on it yet. And to add insult to injury, I have completely forgotten about the vacuum advance tube. It has been completely unhooked, and the inlet for the tube on the carb left open(uncapped).

......What does this mean for an engine running at 2000rpm? I thought the vacuum advance was only for very high rpm?

Julie--OK, I am going to use 89 octane next time. Is that enough? Or should I use 91? You should know that's as good as it gets here in CA.

The idle is usually at around 450-500, which is exactly what the shop manual says. However, sometimes it'll be at around 7-800 for some reason......I'll sort that out.

Next time I run it, I'll make sure to let it idle for a minute or so and keep helping it out.

But here's my scenario: OK, we've been running it for 7 minutes of break-in. It has been at 210 for a few minutes, just like last time. But now, it's starting to just peak over the 210 mark on the gauge--so I know it is slowly getting hotter. So I say it's time to call it quits.

Now we proceed to do the whole "idle-to-cool" thing. We let it go back down to idle, and continue to have a fan blowing and water spraying........but the temp keeps slowly climbing. Not it's at about 215 on the gauge, and slowly getting close to 220.....

What is the best decision at this point? Shut it down, or continue to let it run for another 30 seconds?



Oh, and one more thing......The engine diesels TERRIBLY every time we've ran the motor and let it warm up. Could this be a gas-octane issue, or is this most likely a timing problem? We have to shut it off by choking the carb with our hands.

 

Oye Vey! Those are really important points. N0 wonder you are having problems

Your timing and idle mixture have got to be WAY off. First, the vacuum advance is a gradual advance and works increasingly as you increase rpm. so you can't set the timing with it hooked up.

Next, with that vacuum line left open, you have a substantial vacuum leak - bad news. That will also change all your idle, mixture and timing settings.

You need to take a step back and take care of this stuff before you run the motor again - these things will have a SIGNIFICANT impact on how the engine runs, the timing, and the operating temperature.

And if it diesels on shut off, that is preignition. That will break your engine - not good. That's the heat and your vacuum leak- 91 octain will help some, but you have to put the motor in proper running order before you run it again.

Forget about any of the other insignificant rumors you have heard about gas, etc, and do this to the letter:

First, put the 91 octain gas in the truck - just do it.

Second, place a vacuum hose on the carb/manufold vacuum inlet for your distributor vacuum advance, leave it disconnected from the vacuum advance AND PLUG IT.

Third, hook up the timing light, vacuum gauge, and tachometer, and start the truck. Chances are the idle rpm will shoot up high with the vacuum leak plugged.

Fourth, reset the idle rpm to the proper setting, then set the timing to the proper setting, then set the idle mixture to the highest vacuum reading you can get.

Fifth, reset the idle rpm if necessary to 500 rpm. Check the timing again for the proper setting and adjust it as necessary. Continue to check and reset timing and idle rpm until both are correct at the same time. Then, shut the engine off.

Let it sit for about 5 minutes to distribute heat and start it up again and recheck the idle rpm, timing and idle mixture. Reconnect the vacuum advance hose to the distributor. Run it for 20 minutes at 2000 rpm spraying the radiator as necessary with water and using the box fans. Allow it to go up to 230 degrees before you feel the need to shut it off.

I'll bet it shuts off with no problem now, and will run cooler.

DO NOTrun it at idle after the 20 minute break-in. There's insufficient air flow through the radiator and insufficient coolant circulation that will cause it to overheat at this point - shut it off.

Then, it should be fine and cam broken in. Don't run it again until you are ready to drive it except for a possible battery charge once a week for 2-3 minutes.

One last thing, if it still diesels on shut down (and it shouldn't now) DO NOT use unprotected hands to choke it off. If it backfires you could loose fingers or significantly burn you hands. Use a folded up wet towel and hold it on with the hand. It shouldn't, and if it does there's another problem

AX? Any corrections or additions?