Overheat after valve job

[yelcab1]

I need some help from the expertise of the board.

I helped my neighbor with his 2L engine on a 914-6, stock everything. To reseal the engine, we stripped his engine to the case, did not split the case, did not remove the pistons and cylinders, did a valve job, and reinstalled everything back in with fresh components in some places:

1. Valve job
2. New gasket set
3. Rebuilt the webers (changed the idle jets from 45 to 55)
4. Cleaned the oil cooler
5. Changed two oil lines
6. Had to change three rocker arms and shafts due to wear (I used rocker arms from a 3.2L engine, they seem to be identical in fit and size)
7. Had the alternator rebuilt. Painted the fan, fan housing, engine tins.
8. Changed the seals on the gearbox, and a synchro.

Did not change the internal thermostat.

Put everything back, timed the cams, tuned the carbs, new throttle and clutch cables, and ...

a) the car runs well enough at idle and 3000 RPM in the garage. There is a vacuum leak at the old butterfly shaft at the end of the carbs which we chose to leave alone.
b) at highway speed, after about 10 miles, the engine gets almost into the red zone for oil temp and he had to pull off to wait for it to cool down.

I am going to get the car back into my garage and check:

1. Oil pressure with a mech gauge
2. Fan belt tension
3. Spark plugs conditions
4. Whether the car runs leans or rich ...
5. Compression
6. Position of the drain plug sump plate (correct = bank 1-3 side of the engine)

Questions:
1. There is a Colortune device to check the lean/rich condition of the sparkplug hole. Where do I get them, and how do they work?
2. What else am I missing? What else should I check?

[KTL]

Can get the colortune on Amazon.

Amazon.com: Colortune Spark Plug to assist in the determining proper fuel mixture -14mm: Automotive

Paul Abbott endorses using this for tuning, so I tend to think it's a good tool. Paul really knows his stuff when it comes to Webers. Weber Carbs Technical

I got one in my toolbox from a Pelican as a thank you/payment for sharing some insight on carb setup and selling him some Weber parts. I have yet to use it though, so I can't share my direct experience yet. I do plan to use it eventually!

Those t-stat regulators can be buggers. Sometimes they just up and stop working. Since the 914-6 doesn't have a front cooler, it really needs that engine cooler to work. Especially considering that the engine cooler is very efficient- provides a lot of cooling despite its small size. It seems coolers in the pressure side of the oil system (as opposed to the scavenge side like the 911 front cooler) are really effective.

[yelcab1]

quick update and ...

car running OK but overheats on the freeway at 60 mph at 4000 rpm.

1. Engine oil sump plate was 90 degree out of position. Fixed and made no difference in overheating
2. Mechanical oil pressure gauge says engine develops 10 psi per 1K rpm until maxes out at 55-60 psi. Likely that is when the non-modified pressure protection circuit kicks in.
3. Colortune says half of the cylinders were running still lean, #1 cyl very lean due to a leaky butterfly shaft.

Questions:
60 psi seems a little low to me, or is that all I can expect from a non-modified oil galley engine case?

We are still getting popping due to lean condition at higher rpm.

Next, we will pull the distributor and clean that up.

[Steve@Rennsport]

Ignition timing????

[yelcab1]

Originally Posted by Steve@Rennsport

Ignition timing????

Checked that and adjusted to be right on at idle, using the mark on the flywheel which is visible on the 2L flywheel on the 914-6 engine.

Did not do that at high RPM yet, but will do so after the dizzy is cleaned up. I am hoping that the dizzy is a major source of the problem.

[Lapkritis]

Originally Posted by yelcab1

quick update and ...

Questions:
60 psi seems a little low to me, or is that all I can expect from a non-modified oil galley engine case?

That's about normal.

We are still getting popping due to lean condition at higher rpm.

Lean will get things white hot real fast. I would correct mixture before digging in further.

Next, we will pull the distributor and clean that up.

[yelcab1]

Originally Posted by Lapkritis

That's about normal.

Lean will get things white hot real fast. I would correct mixture before digging in further.

what causes lean running at higher RPM. The colortune shows blue flame during running, and then when the pop comes, it changes to white color inside the cylinder.

What causes lean running at higher RPM other than sticky dizzy?

[Lapkritis]

Jetting in the carb, fuel pump or pressure. Etc...

[Lapkritis]

If your cams are way over advanced then you can get nasty running too. Lean would have me check mixture first... but if the can timing is questionable then I'd confirm that as well.

[Steve@Rennsport]

Originally Posted by yelcab1

Checked that and adjusted to be right on at idle, using the mark on the flywheel which is visible on the 2L flywheel on the 914-6 engine.

Did not do that at high RPM yet, but will do so after the dizzy is cleaned up. I am hoping that the dizzy is a major source of the problem.

Idle timing doesn't matter; total timing at 6K is all that really counts. If that is too far advanced or retarded, the engine can run quite hot.

[yelcab1]

Additional clue:

3000 rpm all day, no issue
>4000 rpm, overheat.

I am pulling the thermostat to check its full operation, but ...

Does that sound like a funny distributor not keeping up with the advance issue?

[HawgRyder]

If in doubt about the distributer...pull it and clean everything...particularly the weights and assosiated hardware.
It is old...probably needs service anyway...and it doesn't take long.
A set of fly weights that does not swing all the way to the stop can give you retarded spark at higher RPM.
You can check it right in the engine very quickly...pull the cap...grab the rotor...give it a twist to see the movement...feel it carefully to see if there is any binding in the action.
Bob

[yelcab1]

More updates.

1. My neighbor told me that the overheating issue was there before the valve job too. So, that rules out the valve job as the cause.
2. The thermostat was removed, tested in a waterbath and the ports opened up fully as expected even before water boiled.
3. The distributor was able to advance timing to 30 degree BTDC at 6000 RPM, so that theory is out the window too.
4. Oil sump orientation is correct.

Oil pressure is 60 psi at full operating temp and 6,000 RPM. Roughly 10psi per 1000 rpm.

I am going to pull out the bypass valve and safety valve next.

More clues: During warming up, there is quite a bit of popping inside the muffler. After warming up, it all seems to run very well. No spitting at all from the carbs. The Colortune thing really helped with tuning the mixture.

When it runs hot, the temperature at the input line to the oil tank is 215F, oil filter is 160F, line at the output from the tank is 127F, the oil cooler external is 142F.

Next ideas other than above, anyone?

[HawgRyder]

Is it possible that mice or other critters got into the cooler area?
Sounds like when the thermostat opens...it's not getting the cooling from the on-engine cooler...or if you have a front cooler...perhaps the lines are either fouled or..(heaven forbid) someone crushed the lines.
Bob

[yelcab1]

There is only one oil cooler on the 914-6, on the engine. There is no mice nest on the top of the engine.

[thumbdoctor]

My guess would be throttle shaft seals admitting air at certain throttle openings and vacuum signal. Had it happen on a Ferrari 308 and the exhaust headers would glow orange.

[yelcab1]

You think so Doc? One of two carbs does leak at that spot although the lean condition affects only Cylinder 1 and we adjusted that out using the color tune.

My 308GT4 years ago had a glowing header but because of a bad float valve which dumped fuel into the one out of four carbs creating a rich condition with fuel burning in the header and not lean condition.

[Walt Fricke]

I think these readings indicate how difficult it is to check oil temps (other than grossly, as with failed thermostats or crushed front oil cooler lines) externally.

The oil leading to the tank should be the hottest. Since the first place that oil goes in the tank is through the filter, that should be next hottest. Assuming the oil cools some in the tank, the oil coming out of the tank to the engine should be cooler by a bit. And then, since the oil internally goes through the cooler (when the thermostat is open) before it gets to the working parts of the engine, and the temperature sensor, it should be somewhat cooler. Unless the engine case is so hot it reheats it. But I think comparing external cooler temperatures to temperature of the oil flowing through may be tricky. Is a cooler (or any oil tube) going to be in thermal equilibrium with the oil flowing through it? Boundary layer insulation?

In a race motor, oil temperatures of 215 F are not usually a cause for concern. Though the typical 911 AC highway temperatures cruising are in the 190 degree area, which is about where the thermostat opens/closes.

[yelcab1]

Walt, I agree that these temp readings cannot be 100% indicative. I used an Infrared hand held meter but I noticed that it had its limitations when the surround parts and air are so hot.

The reason that we need to fix this is the oil gauge was getting into just below the red zone, on a cool fall day, with the car cruising at 4000 RPM (not really working the engine that hard!). Once it gets that hot, even pulling over and idling, the car would take a long time to slowly come back down into mid-temp zone.

[HawgRyder]

If this were my engine...I think I would be taking the cover off to see down through the cylinders and oil cooler.
You say the temps go up during normal driving...and take a long time to come down.
The time element is what concerns me.
If there was enough air flow through the cooler (belt might be slipping..fins clogged...etc) then the temps would come down quickly when the engine was not being asked to make power.
Is it possible that the guide on the back of the alternator is wrong...missing...etc?
Is the fan turning at the correct speed (pulley size?).
Is this a 5 blade fan?
Air flow has to be the answer.
Bob