The Stovebolt Site Forums The Shop Area Engine Shop What's happening here?................

Started the 235 up after it's reconstruct a few days ago, I wasnt able to run it for long, as the electric fan wasnt beefy enuf to keep it cool for a good 20 minutes. But got about 5-8 minutes on it at 1500 rpm, and it felt and sounded good. Put a 19" flex fan on it today and went for broke, but developed some strange symptoms. Hopefully someone can tell me whats going on here.

The general specs.....'61 235cid. Pertronix installed, with their flame thrower coil. Holley/Weber 2bbl. with hot water choke. One wire alternator conversion. Road draft tube converted to pcv, vented to vac at intake. 180* thermostat, 19" flex fan. Everything is fresh, right down to the ignition switch and tumbler in the dash.

The symptoms....At start up until engine reaches 180* runs like a dream. Smooth, no noise or misfire. As the temp climbs just past 180* it develops a slight misfire, and starts to labor. Oil pressure at 37psi until then, it drops rapidly to 30, and then more slowly til it levels about 21psi. Meanwhile at the vac. gauge, at start up til 180* rapid bounce between 19" and 20". Havent dialed in the carb just yet. Again, at the magic number 180* Vac still bouncing rapid, but reading 21"-22". Voltage readings, Key on, not started, reading 6.7-6.9 at the coil, immediatly after starting, I'm getting 17.8 to 19.4!!!!!!at the coil. Once the operating temp is hit, I have 12.8-13.9 at the coil. I have repeated this scenario three times, so I dont believe that it is anything internal in the engine itself. Whats happening as it gets up to operating temp? Is this an ignition/electrical, or cooling problem? Thanks for any ideas.

I'll take a shot at this. I think you're describing unrelated problems, but lemme try:

1. "The symptoms....At start up until engine reaches 180* runs like a dream. Smooth, no noise or misfire. As the temp climbs just past 180* it develops a slight misfire, and starts to labor."

>>>This sounds to me like either your carb is too rich or the float level is set too high. When it's cold, having a rich mixture helps it, but when it heats up you seem to be getting too much gas into the engine and it's stumbling. When it does that, you might see a little black smoke from the tail pipe, and your spark plugs will be black and sooty, both of which would support this theory. Pull the screw out of the side of the float bowl and adjust the float until fuel is right at the threads. If that's not the problem, drop the jets down a step and see if it gets better.

2. "Oil pressure at 37psi until then, it drops rapidly to 30, and then more slowly til it levels about 21psi."

>>>This is nothing. When your oil is cold, pressure is higher. As it warms up, the oil thins out and pressure drops. It is a little low but not seriously so. Check your oil level and make sure it's not low. When engine bearings wear, the oil pressure drops. Nothing to worry about yet. I don't think this is your problem if you have a fresh rebuild, unless the clearances were a little on the loose side. Still, that's decent oil pressure. It climbs when you rev it...right?

3. "Meanwhile at the vac. gauge, at start up til 180* rapid bounce between 19" and 20". Havent dialed in the carb just yet. Again, at the magic number 180* Vac still bouncing rapid, but reading 21"-22"."

>>>This kind of sounds like leaking past the valves to me. How are your valve stem seals? Do you get a puff of oil on start up? If not, then you might have some leakage past the valve seats. A simple valve job is possible, but if your engine runs fine, I wouldn't worry too much about it.

4. "Voltage readings, Key on, not started, reading 6.7-6.9 at the coil, immediatly after starting, I'm getting 17.8 to 19.4!!!!!!at the coil. Once the operating temp is hit, I have 12.8-13.9 at the coil."

>>>That's a little strange. Okay, did you put a conventional 12 volt alternator on a 6 volt system? That's sort of what it sounds like. When it starts, the alternator senses a "low" voltage in your 6V battery and tries to charge it. If this is the case, then you're overcharging your battery which will kill it, frying components not designed for 12 volt operation, and overworking your alternator.
Definitely check this out and make sure to run a 6 volt generator or convert your system to 12 volts.

5. "I have repeated this scenario three times, so I dont believe that it is anything internal in the engine itself. Whats happening as it gets up to operating temp? Is this an ignition/electrical, or cooling problem?"

>>>I don't see how it could be a cooling problem. I also don't think there's really a problem with your engine. It may not be perfect, but seems to be happy until it starts getting fuel pouring into the engine. Get that fixed so you don't wash the cylinder walls and lose your ring seal. The electrical issue could be a huge problem if you're running a 12V alternator on a 6V system. Don't fire it back up until that's resolved.

I hope I'm on target with those symptoms. Write back if that raises any other questions.

Thanks HRDad, From your info, I'm thinking the main problem likely lies with the carburetor. Although the oil has remained at the same level, and very clean, I'm guessing a little too much fuel in the cylinder may cause some "washing" as you mention. May account for the drop in pressure? After engine has cooled a bit, I can re start, and have 37 psi, until the temp gets back to just over 180*
Leaking past the valve seals.....I hope not, the head was completly re built by a reputable local guy, new seals, all new valves, etc. With a total of maybe twenty five minutes of use, at idle, I dont think the head would be a problem, of course stranger things have happened.
The electrical system is 12 volt(1961 Apache 10). I removed the 12 volt generator, and ran the truck with a 12 volt alternator, before the tear down. But the voltage at 17+ volts bears more looking into along with the carb. Thanks for the places to start.

You said you have a Pertronix module.
That means you don't have 17-19 volts. Pertronix only guarantees them up to 16 volts and I suspect the reality is a little lower.
You could have a volt meter badly in need of calibration.
What you probably have, is a "floating ground". That means the battery neg post; the body ground; the frame ground; and/or the engine block may not all be sharing the same ground. Start engine, and while you're getting that 17 volts at the coil, put one volt meter lead on neg bat post(post, not cable clamp). With other lead, check voltage at engine block; frame; firewall; and radiator support. Also, read from post to the same bat clamp. Ideally you would read "0" volts at all these places. In reality, .2-.4 volts. Anything above .5 volts, FIX.
Do you really have a "one-wire" alternator? I suspect that you have a standard GM "three-wire", but that you have it wired incorrectly with only one wire. Above 1500 rpm when the alternator finally starts charging, the current flow in the charge wire, reverses and then you get the correct reading. Where do you have the ground lead for the volt meter connected?

These guys are very good at explaining why you should wire your alt with three wires.

http://www.madelectrical.com/electricaltech/onewire-threewire.shtml

They have several good pages of info, especially this next one that you should look at.
http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml

Richard, Thanks for the ideas. Yes I have Pertronix, but your statement, they only guarantee them to 16 volts confuses me. Should I take that to mean I should have more than 12-14.2 volts at the coil on startup?
I will perform the tests for floating ground you suggested. I did take my readings from the + side of coil direct to the - battery post and not the clamp, as you mentioned. My meter is a $4 Harbor Freight special, so you make a good point about "calibration".
Yes, I have a one wire alternator. A single 10 ga wire run to the top of the old regulator, with a new 10 ga run over to the battery side from there. Where there would normally be a two prong harness connector, there is a solid plastic plug on the rear edge of the alt.
I had read the madelectrical stuff when I was debating the one/three wire method. Obviously, I was sold on the one wire method anyway. I will review the info, especially the remote voltage sensing stuff again however. Thanks again.

No you should not have more than 12-14 volts at the coil (or at the battery) at startup. That's the maximum you should have.

A one-wire alternator requires "excitement" (no, don't show it Playboy centerfolds) to begin producing output current. 1500 rpm is usually the minimum speed to excite the alternator. This may be why you're seeing funny readings. If the motor hasn't been spun above 1500-2000 rpm, the alternator may not be charging.

On the other hand, as someone said, if you have a 6v battery, it may be sensing a low battery condition and trying to charge the hell out of it. I'd need to see the circuit to dig into that a little further.

As far as running poorly after it comes up to temp, that sounds like a choke (are you running an electric, heat stove or manual choke?) or vacuum leak peoblem. I'd hunt those areas down to make sure that they're not causing you grief.

Good luck.

Just a couple ideas:
The jumpy vacuum may be the result of a tight valve, that is, the lash is set too tight and the valve may not be closing all the way. I'd check and re-adjust them. A tight valve could also be causing your misfire. As far as the electrical goes, you don't need an external regulator anymore with a one-wire alt. You should just have that single wire go to the "Gen" or "Alt" post on the ammeter (NOT voltmeter!!!) if you have one or right to the + post on the battery if you don't have an ammeter. Good luck!

You should never get over 14-14.2 volts. Check
it at the battery. You could have abad regulator.
Make shure you have grounds from engine to frame
& to body. When that water heated choke goes off
the idle may be too lean. Try setting the idle
mixture alittle rich. That was aproblem with That
4 cyl. mustang carb. Try putting arag over the
carb at idle. If it smooths out it means too much
air in the idle system or a low float level. I
agree check the valve adjustments.

Temp creap given everything else is ok is too tight exhaust valves. Exhaust valves transfer heat to the water jacket. I found 180 too hot given similar circumstances, try a 165.

Ray
I'd agree that the screwy readings may be a result of not revving to excite the alt. the first time around. I got much more normal reads today after revving it today. 12.5-13.8 at coil, and 6.5-6.9 across coil. This is my first experience with a "one wire" set up. The '68 and the diesel both have standard three wire rigs.
The battery is 12 volt.

Southtowns
Thought about tight valves last night, they seemed fine but backed ALL of them off a half turn. (the intake as well as exhaust, if that makes a difference). It didnt change any of the symptoms.
I retained the old external regulator since it seems to feed power to the horn relay, and harness to the fuse block.

Wrenchbender
I will check the lean fuel condition tomorrow. I do have a ground wire from top of therm housing to the top bolt on old regulator. Hadnt thought of running one from engine to frame, as I assumed it was grounded thru motor mount points. I will run one as well, for peace of mind. I will check the exhaust valves again.

52pu
I cannot say how much creep there is, as it begins to go past 180, (182-185) that where the problems begin, and I shut it down. The concern I have, is 165* enuf to fully pull the choke off? Obviously, my first experience with water choke as well.

I should mention, that all of this is taking place in the garage. Not out on the road under an actual load. With a stiff 55 mph breeze blowing thru the radiator, the creep may not even be occuring.

Thanks all for your help, Tony

I believe your problem is retaining the external regulator with your new alternator. The 1 wire is supposed to go directly to the battery without any external regulator. Like the gentleman said above, run it through your amp guage if you have one then to the battery, or straight to the battery if you don't have an ammeter.

HOPE THIS HELPS,GO TO NAPA AND GET A 20.00 BLOCK TESTER AND CHECK IF IT PASSES,IF YOUR HEAD SURFACE WAS NOT MACHINED OR DONE CORECTLY YOU MAY DEVELOPE A HEAD GASKET LEAK FROM THE CYL TO COOLANT PORT ,THESE CAN BE SMALL AND CAUSE SLOW CREEP OF TEMP ,OIL PORT IS CLOSE BUY CAUSING FUEL CONTAMINATION OF OIL ,THINING IT DOWN AND TEMOP CAN THIN ALSO ,DEPENDING WHAT OIL YOU ARE RUNNING ,A GOOD 10-30 IS THE BEST FOR SBC'S THAT ARE HOPPED UP AND RUN WARMER THAN STOCK,ALSO IF YOU CANGED YOUR DIP STICK OR HAVE SLOW OIL RETURN YOU CAN CAUSE TEMP CREEP DUE TO LACK OF OIL IN PAN,AND A BLACKMAX ELEC FAN IS THE WAY TO GO THEY WILL OUTPERFORM ANY FLEX FAN ON THE ROAD AND BLOW THEM AWAY IN TRAFFIC ,HOPE THIS HELPS IF UI CAN HELP IN ANYWAY LET ME KNOW SHAYNE mpcr

Better advice is given above than I can give, but Tx Firefighter most likely solved your charging problem. Take out your old voltage regulator.

One-wire alternator "get exited" at different rpms. Mine starts charging between 900-100 rpm (it has ben working fine for over 8 years).

It sounds like you have hydraulic lifters ("..backed ALL of them off a half turn")? Are they hydraulic or mechanical? Who set them? Were they set hot (after 30 minutes of running, after reaching max temp)? If they were set cold, they will most likely be too tight and should be reset.

Keep trying and keep reporting back.