Tryed the search now trying here on general questions.

[Alshere59]

First car 1950 Plymouth Special deluxe 218 three in the tree.

First I'm buying a rebuilt R7 overdrive. What is the biggest difference between that and an R10. Both seem to do the same function. Reliability/flexability/combination??

Second is engine related.

My 218 has about 45-50 psi on the oil pressure guage for the first few minutes. Then drops to 20 psi it will build back up on long slow runs. This is a recent change it used to stay at 45-50 psi. Oil pump? Engine rebuild?

Symptoms: I have noticed blue smoke when useing the engine braking. The compression test shows fine with 98 +- 2 psi on all but one cylinder 5 shows a drop of 15 psi. Also has an very occasional backfire through carb during warm up. So burnt exhaust valve?

Anyway If anyone can shed any light please let me know. I am looking for a 230 to rebuild but was hoping my current engine would last. Not rich by any means.

May do a valve job on existing and look for the 230. Im in Ohio if any one knows of one available.

Thanks in advance for any advice or opinions.

Al

[greg g]

For your oil pressure, it is not unusual for the pressure to drop at idle, even the owners manual says not to worry about low reading at idle as long as it comes back up with revs and porvides 30 or more psi at driving speed. You might have a sticky plunger in the pressure relief assembly. ( take a look during the past couple of weeks there were two or three threads with pretty comprehensive coverage of relief plungers and springs etc.)

Smoking o deceleration usually indicates worn valve guide/seals. As high manifold vacuum pulls oil through the guides into the combustion chamber. It might also idicate a sticky or burned valve or worn rings.

Two things to do is to pull the spark plug on the low cylinder and add a couple squirts of oil and repeat the compression test. An increased reading will indicate worn rings. Also a vacuum gauge reading at idle will tell you a great deal about the engines internal condition. One of the things that shows up regularly with these engines is broken upper rings, and and erosion of the top ring groove of the piston. Several folks who have pulled down engines have found this condition. Not sure if this is a symptom of pre ignition spark knock or just a metallurgey problem.

You can make your 218 a 230 by swapping the rotating parts, as teh stroke deminsion is the difference in cubic inches 4 3/8 vs 4 5/8.

As for the OD, I believe the difference is that the r 10 is electrically controlled upshif and kickdown where the older r7 is manually controlled. The r10 can also provide OD to 2nd gear effectivley giving a 5 speed transmission. I do not have an OD so there are folks here who are sarter than me regarding the setup particulars. Eithe will give you a more relaxed cruising rpm at highway speed.

Go to www.secondchancegarage.com and check out their section on readig and interpreting vacuum gauge readings.

[Alshere59]

Thanks Greg g

The vaccum gauge sounds like the way to go. Haven't used one in years as most of my recent cars are newesh. Either way your time is apreciated. I will revisit the compression tester also but that sounds like a burned exhaust. Not a total nube but not the sharpest crayon either.

The OD still has me puzzled a bit. From reading it looks like the R7 kicks in at 25 miles an hour. Is that only in third? I guess that question will be answered fairly soon. Waiting on clutch pressure plate etc as I only want to do it once.

The 230 was so I could keep driving the original engine while rebuilding the other. So I will keep looking.

Thanks again.

Al

[daddyo23]

Your oil pressure will also drop like that if you're low on oil.

[Alshere59]

Thanks Daddyo. I looked at that as well. I was hoping it was low.