No thermostat and oil pressure variation

[EPChester]

My atomic 4 was rebuilt a couple of years ago and I installed a fresh
water cooling system, but I have just finished a two week cruise and
had some issues:

1. Just before I left, the engine was overheating and I discovered
two problems - my temp sending unit was bad so I replaced that and
bought a laser heat sensing gun so I could always check it. I also
found that the thermostat was locking up. I didn't have time to get a
new one, so I just took it out.
a. The engine hums along at about 130 degrees- is it a problem to
have it run that cool?

b. Now that I have this fancy heat gun I get all kinds of info I
never had before and I find that even when the gauge says 130, the
head on the manifold side is at 210 to 260 degrees. Is that okay?

2. Because there has been a shortage of wind, I have been using the
engine a lot and the oil pressure has been variable. I have both an
electric and mechanical gauge so I know the numbers are real. It is a
late model engine but I switched the oil pressure adjustment device to
the early model screw with a pointed end.

a. When it starts cold, the pressure is about 50. After an hour or
so of running it the pressure has dropped to 40 and after 90 minutes,
it drops to 30, and at idle it drops to 20. I tried at that point to
adjust the pressure, but even turning the screw two full turns had no
effect on the oil pressure. I had to back it off because it then hit
80 when cold. So, is it a problem to cruise at 30, and then try to
anchor or pick up a mooring at 20?

Is it possible that these problems are related?

[sastanley]

I am guessing the oil pressure drops a little as it thins out. I have been using multi-viscosity oil to try and combat this problem. My oil pressure usually comes up a little bit as the oil gets hot, but I am sometimes under 10 psi at idle. If I rev it up pretty high in neutral I can get 35-40, but never under load and at cruise RPM...it is usually right around 15-20 PSI.

Don Moyer has reported that Universal says that 1 PSI per 100 RPM is adequate and safe for the motor (i.e. 10 PSI @ 1,000 rpm - 20 @ 2,000, etc.) - I am just barely at this threshold, but would like to improve...it doesn't sound like you are anywhere near this.

To take a stab at your other question, I don't think they are related...your fancy laser gauge could be useful in fine tuning the ability to more evenly cool the engine though.

What is the condition of the diverter in the water jacket side plate? The Moyer modification to this (since the OEM ones tend to disintegrate over time, is supposed to help shoot some water between cyls #2 & #3 to help cool the manifold side of the block.

P.S. > Welcome to the forum.

[Dave Neptune]

Temps

EP, I have been running without a thermostat at around 130 degrees for 26 years now. I have had absolutely no problems with anything related. Maybe I have incured some extra wear. However the motor runs strong and has never been out, it is going on it's 40th year of running.
RE the oil. My engine starts quickly and will idle below 1000 RPM's within 1 minute of starting. I only use the choke to get her started then open within less than 30 seconds at aroung 1200RPM. When checking the oil-preassure after start it runs around 40~45 PSI. After running for about 20~30 minutes at cruise the O/P is at 35~40 PSI and stays there that's around 1800/2100 RPM's which is where I cruise at. When I have motored across the chanel 5 1/2 hours and return to idle (600 RPM) to pick up my mooring the O/P is around 15~20 PSI. I only use a straight 30wt. oil and a half pint of STP oil treatment. I change oil every 100 hours or so as the "Bypass type oil filter" I use keeps the oil clear no matter how old I have let it get.

Dave Neptune
1970 E-35 MkII original A-4 still ticking!

[Dave Neptune]

Temps pt II

EP, using your "heat sensor" will give you different temps all over the head especially since the A-4 is an "L-head or flathead" type engine. There are cool spots where the water is and hot spots where the exhaust is carried through the head to the exhaust manifold. Just make sure that your water temp gage is functioning properly.
Also if you are running without a thermostat YOU MUST RUN A RESTRICTION IN THE BYPASS LINE or not enough water circulates through the block. That can generate a false reading as a lot of COLD water will be mixed into the thermostat housing and can give an inaccurate reading of the temp of the water coming to the housing through the block. This is very important if you run without the thermostat.

Dave Neptune

[sastanley]

Good point Dave. I am basically running with my restriction adjustment about 95% closed, and it drops the operating temp about 10 degs (RWC) and stabilizes the fluctuations by forcing most of the cooling water thru the block & up thru thermostat...Without the restriction or t-stat, the majority of the water goes right over the top of the housing and to the manifold, I assume mostly missing the block.

[smosher]

I also do not have a thermostat and its runs between 120 - 130. I do not have a restrictor. What is that ?

As far as oil goes I use straight 30 weight and my pressures echo what Dave seens on his. I do not add anything to the oil and change it at the end of the year @ 40 hours and I burn maybe 30 - 35 gallons of gas a year.

Steve

[Mark S]

I do not have a restrictor. What is that ?

Some of us have replaced the hose that runs from the T fitting on the side of the water jacket to the thermostat housing with a pipe and a ball valve. You can see it in the panoramic view of the engine on the home page of the website. Without a thermostat to close off that water line when the engine gets warm, some substantial portion of the water flow from the pump is diverted away from the water jacket directly to the thermostat housing and thence to the exhaust manifold, never reaching the interior of the block. If you are reading 130 degrees without restricting that water line, I'll bet restricting it will lower your temperature down to 100+ degrees. Don recommends having that water line shut when running without a thermostat.

Mark

[Dave Neptune]

Restriction

smosher, I use a ball valve in the bypass line and it is about (just guessing) 2/3~~3/4 closed.

I have run with the valve open and the temp shows lower which is I think because there is so much cold water intering the thermostst housing from the bypass line. As I slowly close off the valve the temp starts to rise a little as the water from the warm block is flowing more warmed water through the housing and past the sensor. At around 3/4 closed things seem to stabalize and there is very little variation in temp regardless of load after about 20 minutes. When I drop back to idle the temp still seems to hold steady (it does drop a little) between 130~~140 degrees.

Dave Neptune

[smosher]

Some of us have replaced the hose that runs from the T fitting on the side of the water jacket to the thermostat housing with a pipe and a ball valve. You can see it in the panoramic view of the engine on the home page of the website. Without a thermostat to close off that water line when the engine gets warm, some substantial portion of the water flow from the pump is diverted away from the water jacket directly to the thermostat housing and thence to the exhaust manifold, never reaching the interior of the block. If you are reading 130 degrees without restricting that water line, I'll bet restricting it will lower your temperature down to 100+ degrees. Don recommends having that water line shut when running without a thermostat.

Mark

I don't have a bypass and with no thermostat it runs 120 - 130. I can't see why I would want to run the A4 cooler, If anything I thought warmer is better. BUt I'm raw water cooled so the magic temp is 140.

Looks like it a ball valve with a couple of hose barbs. I can do that. There's not much left for me to upgrade and hey I was headed to the boat this we anyway.

So after I install this I gather by closing the valve will force more water through the block will will cause the engine to run hotter. Since I'm raw water cooled I adjust the bypass valve for engine temp to @ 140.

Is that the goal ?

[Mark S]

Smosher,

I think you'd only want the bypass if you had a thermostat. If you don't plan on having a thermostat, why install the bypass? Somewhere on the forum you'll see a thread of mine from June or July about 100+ degree temperatures on my RWC late model A4 and Don's input. I figured out at some point that my thermostat was stuck open or otherwise not functioning as it should and the unregulated raw water was keeping temperatures down. I guess some people use the ball valve to regulate temperature but I don't because Don advised me to keep the ball valve shut so that temperatures through the water jacket would be more uniform. One time I had the valve somewhat open and that was enough to raise the temperature at the sending unit to 130 or so degrees. One engine project I have for the winter is to get a new thermostat and housing so that temperatures will be properly regulated.

Mark

[Marian Claire]

Smosher. A ball valve in the line out of the manifold will give you total control of the temp. My RWC early model has one line in, one line out with ball valve and no by pass or T-stat. Works great if you have access to adjust the valve. Dan S/V Marian Claire

[Dave Neptune]

Exit restriction??

Dan, the restriction on the exit sounds very workable, however I wonder if this effects the life of the impeller? AND/OR is there enough water flowing to really cool the exhaust?

Dave Neptune

[Mark S]

I guess the issue is where you put the restriction in water flow that regulates temperature -- on the top of the block where the thermostat is, or at the exhaust where Dan's ball valve is. Is one location better than the other, and, if so, why? (Sounds like an examination question!)

Mark

[Don Moyer]

I think we need to remember that Dan's engine is an early model. To get the same "one line and one line out" configuration on a late model engine you would have to totally close off the bypass loop before trying to regulate the total flow through the engine.

[Marian Claire]

When I first set this up I had the ball valve before the water pump. I ran that way for about 250 to 300 hrs. In talking to Don he recommended I move it. The pump can handle head pressure better than low water flow. I now have run for about 400 hrs. I have not noticed any extra heat down stream from the manifold but will keep an eye on it now that you mention it. Dan S/V Marian Claire