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TR4/4A TR4 - Sudden Oil Pressure Drop

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TRDejaVu

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When I got the barn-find last year it was in a non-running condition. As I had the sump off for a look-see I decided to change the con rod bearings on spec. The crank journals seemed reasonable and I put standard size bearing shells back in. I also dropped the center main bearing cap to look at that bearing; it all looked reasonable. I also changed the thrust washers. I used lots of assembly lube and babied the RPMs; I still haven't taken it above about 3500RPM and I don't gun it or labor it.

From the time I got it running last fall until yesterday afternoon it had 70PSI pressure at 2000 and about 40PSI at idle. Took it out tonight and I noticed that it only reached 30PSI at 2500RPM and about 15PSI at idle.

Symptoms:
- I have done 2 oil changes after about 250 miles each and it gets dirty quickly. I put that down to the block flushing through.

- A few days ago, I started to notice a bearing knock sound at startup, but it quickly went away.

I would appreciate any ideas as to the suddenness of this?
 
Ian, it could be a fluke, related to the pressure relief valve or the like. But considering you replaced the rod bearings, and that you're recently hearing a bit of a knock on start-up, I'd be wanting to pull that pan and recheck those bearings.

Were the replacement shells OEM Vandervell (very hard to find nowadays), or were they Glacier or other currently available replacement? Most of the currently available bearings simply aren't the quality of the originals. /bcforum/images/%%GRAEMLIN_URL%%/frown.gif
 
tdskip - original cannister type oil filter, not spin-on. Crossland brand from TRF. Castrol GTX 20-50. Engine temp always 185 to 195.

Andrew - the shells were from Moss, but I don't have the box anymore.

I was thinking that I would have to pull the pan, but I will look at the pressure relief valve first; maybe a bit of crud is trapped on the seat (doubtful but you never know).

It's just the suddenness that has surprised me.

First real issue that I have had with it, so I shouldn't complain too much - but I probably will.
 
That's funny I had the same issue with my '63 about two months ago. Came off the freeway after a long run ( with normal oil pressure @ 70 psi at speed ) and all the sudden the oil pressure dropped to 10 psi at idle at the stop light and would not go any higher that 50 after that. I found a small piece of carbonized oil on the relief valve seat. I guess the long run loosened it from somewhere in the oil circuit. /bcforum/images/%%GRAEMLIN_URL%%/crazy.gif
 
Hey Merlin,

Following your post, I brought forward my relief valve check by 1/2 day. Too dark to really tell if there was anything trapped, but I cleaned it through and that may just be it. I ran it in the garage at idle and I have strong pressure. Too late to take it out and really heat the oil up, so I will give it a run in the morning.

Touch wood.
 
Good luck tomorrow, I hope that was it ! /bcforum/images/%%GRAEMLIN_URL%%/driving.gif
 
Good Morn`n Ian; /bcforum/images/%%GRAEMLIN_URL%%/blush.gif

I was passing thru and saw your post:

Hope that Your Problem has been solved:

If Not; Give a Call to My Brit Mech. (Don Lawson, Northeastern Classics, Stbg - 570-424-6379): Ref my name; Russ Czura (Pronounced Chura):

I`m certain he would be happy to try and assist you over the phone:

Hey; There`s a Car Show this Sun (Mixed Bag of Cars - No Judging): There will be a few LBCs & My Friends Alfa-Romeo Duetto; Why not join us for the Fun and have a Brewski:

Its called the "West End Car Show" on Business RT.209 in Brodheadsville, PA; West End Fairgrounds:

There will be a Show @ "The Delaware Water Gap" on Sat. 30th. Similar to above/A few LBCs/Popular Voting/Beer etc:

See Ya All There;

Regards, Russ /bcforum/images/%%GRAEMLIN_URL%%/cheers.gif
 
UPDATE.
It appears that it was the relief valve. I took it for a good hard run this morning. Temp still steady at 185F and upon return the pressure was 30PSI at idle and 65PSI at 2000 RPM; rises to 70 at about 2200RPM.

I will monitor the cold start knock as well as the oil condition (it is not as bad as after the first oil change) and probably change it again soon. I had cleaned out the sump as well as anything else I could get to with the engine in-situ, so I'm hoping that it is just clearing through the oil ways.

I was hoping that I wouldn't have to touch anything as this engine doesn't leak; normally a sign of no oil. I have another engine and I will look at rebuilding that over the winter so that I have a "hot spare".

I can now get back to my original schedule where the next item on the list is to fit Miata seats. I love driving the car, but I am very aware that the original seats are whiplash waiting to happen. I also want to fit 3-point seat belts. Looks like I just hijacked my own thread.

Thanks to all who responded.

Russ, unfortunately I won't be able to make that show.
 
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