View original topic: Oil pressure, temperature and how it relates to cooling
Chupa7hingy Sat Oct 17, 2020 6:22 pm

I just installed some new oil pressure and temperature gauges in my 2074 dual relief motor. As soon as I fired it up, I thought I had a problem, as the pressure was over 70psi cold (I had straight 40 VR1 for break in). When I put in the temp sensor in the relief, I noticed it had a grooved plunger and chrome spring. Recognized it as the Empi booster setup, so I pulled those and installed a stock style CB performance set and changed the oil at the same time to VR1 10-30, 40-45 cold, but down to 15-20 hot, much better, right?

Well, I'm wondering if I have a cooling problem because as I got hot, it just kept getting hotter, at least according to the temp gauge (which I'm still trying to diagnose if it's accurate or off). On the highway, I kept climbing past 220 to 240, topping out on the gauge at 260 before I chickened out and turned it off. Smelled hot (burning oil), but that was possibly because my breather hose came loose and got some oil on my heater box. Pressure was never below 15 at idle.

Questions as I try and work through this: Am I understanding that a closed relief piston pushes oil through the cooler? Then cold high pressures bypass and hot low pressures flow through? If this is the case, would putting the heavier spring in the relief put more oil through the cooler? What about using the grooved plunger with the stock spring (its taller and would have more pressure on it). Does the grooved piston do anything on a dual relief (I seem to have read it doesn't).

I know there are other things to do, like verify my temp gauge is accurate (it very well might not be), but I have to get my temp gun out of the attic to test this, just tryign to get some of the intel out of the way. Thank you all!

One thing I know will be asked, but I forgot to add earlier. It is not a full flow case. I'm also using the pressure sensor with the ISP West manifold that goes in place of the idiot light sensor and tapping into that with the idiot light.although the engine was built for me by my father-in-law, I wasn't 100% sure of all of the internal parts. I believe I have a 26 mm oil pump, but labeled as " heavy duty ".

Chupa7hingy Sat Oct 17, 2020 9:30 pm

Follow-upon my troubleshooting. I took it for another drive, capping off the heater tubes, just in case there was a leak I was unaware of that might be robbing my oil cooler of airflow. While I was initially happy, because it appeared I was hovering at 220-230 this time, I was starting to smoke from the heater insulation because they were so hot :shock:

Took my temp gun, hit the case by the sensor, and was happy to see it was pretty close to the gauge reading (it showed 210 on the outside of the case, so I an guessing the actual sensor is probably no more than 10 off, if that).

I'm thinking I'm running lean... That would explain the heat issues as well, right?

I was previously having hesitation/stumbling issues prior, and increasing the idle and mains solved that problem. Maybe I didn't go far enough? HPMX duals, 55 idle and 135 mains. I think I will try and pull a plug tomorrow. They are a PITA to get to though...

andybla Sun Oct 18, 2020 11:23 am

if i recall correctly, when cold, the oil goes directly to the engine, when getting at operating temperature, the plunger opens and the oil begins to flow through the oil cooler.

i was always learned not to mess with the plunger system, that best was stock. Unless there is a high flow oil pump installed..

also, see this thread

W1K1 Mon Oct 19, 2020 8:15 am

I tried for a while to change jetting, timing, etc to get my 1904cc to run cooler on the highway. Driving in town even in 30c + days it never got over 210F, highway on the other hand was 1/2 hour of driving would get to 220-230F and climbing. I added the sandwich plate under the filter and added the sertrab cooler and fan switch. It doesn't go above 200f now. I am using my modified heat exchangers and tubes, which don't show in the pictures.

Chupa7hingy Mon Oct 19, 2020 8:24 pm

W1K1, your pics have inspired me twice now! I don't think I have a cooling problem so much as a heating one. AF gauge came today, variety of jets inbound, and I'll test the timing again before I start this weekend. Motor melted rings once already, but we discovered the mechanical advance distributor was allowing nearly double the advance it should have. Funny, it never knocked and ran great...right until it didn't, that is. :x

Discovering this, we were sure we found the culprit and rebuilt without much more thought about it. FF to this past week and I was sure there were no problems...until I installed gauges and saw what was actually going on inside. NOw I suspect the prior issue was a combo of too much advance AND too lean. Hope I didn't start to melt any rings this time.

Anyway, if the internals are fine, I'm sure I'll get her under control with the right fuel mix (presuming the timing is OK). If/when the time comes to redo the pistons/cylinders, I may downsize a bit to 90.5s and a smaller crank for better cooling. The 2074 is more than enough as is for this car. In the mean time, is there any way to add a cooler like W1K1's without being full flowed? Is ther any adapter that taps into the stock ports on top?

W1K1 Tue Oct 20, 2020 7:35 am

so you have a 2074cc that has a case hasn't been tapped and plugged?
that's unusual for a performance build to not be, the case oil galleys need a good cleaning after machining for bigger stroke and cylinders. has this adapter to go with a pump cover with the outlet, not ideal, but it works

I had Brothers Machine weld in the full flow ports when I had mine machined and plugged.

Chupa7hingy Tue Oct 20, 2020 8:45 pm

The original plan wasn't for a "performance build". In fact, my original idea was for a 1776, then I was talked into an 1835, then when cutting for an arm came into the picture, settled on the 2074 as recommended by a local VW shop. Not to hot-rod, but to have easy torque on demand for a heavier car. May have overshot for my planned driving. The recommendation was to NOT full flow as it was mostly a cruiser (although as can be read from a prior post of mine, I was sold a pressure booster relief instead of a stock setup, so I dunno...)

Original plans were to stay under 2000, and I should have stuck with my gut. Anyway, if the motor bellies up again, I'll revisit doing it different, including shrinking and making provisions for remote cooling/filtering. Parts came in today (yay!) and I'll be trying my hand at tuning the carbs this weekend. Thank you all.

BTW, here is a photo. She really deserves a solid motor.

W1K1 Wed Oct 21, 2020 7:53 am


if I were to do it over.... always bigger.
Although the 1904cc was a nice bump in HP from the stock 1600 and it worked around town quite well for keeping up with modern traffic.

Chupa7hingy Sat Oct 24, 2020 10:07 pm

14.8 at idle, 14.7 WOT, and 15.1 at freeway cruising speed. Made up a little stand alone setup with a small toolbox and a small AGM battery. Plugged into one of the bungs on the Vintage Speed muffler, ran through the pop-out, and had my daughter read me numbers as we drove.

I currently have 55 idles, 135 mains, and 170 airs. I have a few sets of jets, so based on my readings, should I go up one or two idle sizes and one or two mains? Thinking of leaving the airs, but I have 185s sitting around too.

Bobnotch Sun Oct 25, 2020 10:56 am

If you're doing the jet changes to a set of Solex carbs, I'd probably bump up to a set 28 mm venturi's, then adjust my jetting. If you're running something else, then you'll have to work around them.

Chupa7hingy Sun Oct 25, 2020 11:29 am

Bobnotch wrote: If you're doing the jet changes to a set of Solex carbs, I'd probably bump up to a set 28 mm venturi's, then adjust my jetting. If you're running something else, then you'll have to work around them.

Sorry, thought I mentioned it earlier. HPMX 40s. It does have the 28 venturis.

74 Thing Sun Oct 25, 2020 8:58 pm

You are running lean at 14.7:1 at WOT

W1K1 Mon Oct 26, 2020 12:05 pm

Quote: 14.8 at idle, 14.7 WOT, and 15.1 at freeway cruising speed.

12.5-13.2 at WOT is what you're shooting for, the idle and freeway cruise at light throttle would be okay

rosevillain Mon Oct 26, 2020 2:45 pm

Pop over to the Performance/ Engines forum and check out the tuning with a wideband thread.

Not that these guys can't get you there. Beautiful car!

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