Hey All

just wanted to get an experienced view of if there are any issues with placing an oil temp sensor into the 1/4 npt port by the distributor. The sensor protrudes into the block by about 1.5 inches so really just wanted a sense of it would obstruct oil flow. From googling it looks like that port serves no engine lubrication purpose (i.e. designed for sensors)

Getting my car ready for some track time in the next few months and so looking to install a oil temp gauge to keep an eye on things. The port above the oil filter is stock used for the oil pressure sensor

 

It'll measure block temp, not oil temp, if installed there.

Much better to measure the oil temp in the pan.

That port is the end of one of the critical oil passages inside the engine; the one that runs from the bottom of the block beside the rear main journal, up to the cam where 3 front-to-rear passages meet it to carry the oil further toward its destinations.

A quick note on your profile: you don't have 3.43 gears. There's no such thing. Gear numbers are always the ratio of 2 integers, those being the count of the teeth on the ring and the pinion. As such, only certain numbers are possible. You might have for example, 3.42, which is 12 teeth on the pinion and 41 on the ring. A few other common ratios include 3.73 (41 & 11), 3.08 (12 & 37 or 13 & 40), and 2.73 (15 & 41). One is usually a prime number, and both prime is preferred; 11, 13, 37, 41, and 43 are very common for this application.

 

thanks Sofa - ref it not being in the ideal location - is that because oil is unlikely to shot up to the probe regularly? Through googling I read about leaks from that port so presumably some oil is making its way there.

Car is a MM5 R6P 91 Trans Am with the factory rear axle. Will have a gander at the build sheet when I get 5 mins

 

Oil is ALWAYS there when the engine is running. As described, it's the end of one of the critical feed passages that feeds oil to the entire engine.





The problem will be, the amount of oil that a sensor can contact there, compared to the amount of cast iron it MUST contact just to install it, will cause its reading to be DOMINATED by the casting it's screwed into. I'd suspect that the result would be about 90% or more skewed toward the casting. I.e. if there was a difference of, say, 10° between the temp of the oil and the temp of the casting, the sensor output would be somewhere between the 2 temps; only about 1° different from the casting temp butt 9° different from the oil temp. In a word, useless for measuring oil temp.

An oil temp sensor belongs in the pan or an external line such as to a cooler, where it's immersed in oil and contacting nothing else.

 

Your car has a 3:42 gear ratio (RPO GU6). I mentioned it in your thread about VATS. Reply #12. I figured you just fat fingered the number when typing it in.

RPO MM5 just means installation provisions for a 5 speed manual transmission. It does denote which 5 speed manual transmission was installed in the car. In your case it is a Borg Warner World Class T5 (RPO MK6) close ratio 5 speed manual transmission instead of the Borg Warner World Class T5 (RPO M39) wide ratio 5 speed manual transmission. Close ratio vs wide ratio in this case only applies to the 5th gear overdrive ratio. First through fourth gear in the M39 and MK6 are the same. Fifth gear overdrive had a gear ratio that was numerically higher and closer to the fourth gear ratio of 1 to 1 thus having a smaller gap in the gear ratio between 4th and 5th allowing for the car to pull harder down long high speed straightaways on a race track. Fifth gear overdrive in a M39 5 speed is a fuel economy/highway cruising gear ratio.

 

Insightful both- ty

I think a sump probe installation may be beyond my capabilities (though will research a bit more) and so am thinking of copying the c4 corvette setup for now of the temp probe above the oil filter port and oil pressure from the discussed port by the distributor

 

I think you might have missed the point of Sofas reply.

If you install the oil temp sensor anywhere directly into cast iron block or heads the heat will radiate through that cast iron and corrupt the oil temp reading you are trying to measure. To be reliably accurate the oil temp sensor should be in the oil pan submersed in oil, or in an external oil line (which you probably don't have) submersed in oil. This way it is measuring the general temperature of the oil and not a localized hot or cold spot.

 

I have a sensor for oil temp in the port above the oil filter and the pressure sensor next to the distributor and they both work fine; and by fine I mean i'm not looking at the indicated temp as scientific truth, it could be a ford gauge with reading of (meh - ok -- bad) and it would work. I am not tracking the vehicle so an approximated understanding of the oil temp is totally fine in my situation. Now transmission fluid is another story... That I have the sensor tee'd into the cooler feed line so I know what the working temperature of the trans is rather than a pan mounted sensor which would tell you the average temperature of the fluid.

Honestly if it's that important that you know exactly what your temps are, you should be using k type thermocouple probes in both a pressurized oil passage and the sump with a logger, not a gauge.

 

i'm intrigued about the heat soak piece- I mean it makes sense (much like the MAT vs IAT), but surely the coolant sensor screwed into the block would suffer the same fate - and yet it seems to respond quite quickly once the fans come on (i.e. cooling the coolant)

would an oil filter sandwich plate with 1/8npt fittings be suitably divorced from the block to at least be meaningfully accurate enough to indicate to me when I should be moving to a cool down lap - or would there be no real delta with a fitting there and the port about the oil filter in the block (given the metal to metal contact of the sandwich plate to the block)

I still suffer from PTSD from changing the sump in situ so looking to avoid but appreciate that may be the better location for an accurate reading (notwithstanding exiled350s point also taking a reading from a pressurised source which was also my understanding)

 

The coolant sensor does suffer the same fate. However, all that coolant running through the block (with corresponding controls like the thermostat and fans) is what regulates the block temperature. The block tends to be around the same temperature as the coolant, with exception for localized hot spots like the immediate area around the cylinders.

I doubt a metal sandwich plate and fittings would be enough isolation from the heat soak, but you could try it and find out.

 

I agree with others that the sensor should be in the pan, but I'd think that it could also go here, and have enough oil turbulence/oil hitting the face of the sensor to get you a pretty good reading. It's sort of far from a water jacket too, and the cast iron in that area would me more influenced by oil temp than water, IMO.