Oil Cooler air flow

[Mark Roth]

We finally discovered the cause of my oil leaks which I will post later in that thread. The mounting studs for the oil cooler had snapped off as seen in one of the photos. Long story. A new issue has arisen during repair. The engine has about 12,000 miles since a complete rebuild by a reputable shop in Southern California. New quality pistons and cylinders were installed at that time. Upon disassembly it was discovered that the number three P&C had unusual wear although all P&Cs were somewhat prematurely worn. My mechanic noticed that the top of the cylinder is blue, indicating overheating. Photos of the number three P&C are attached. I had installed a new NLA aluminum cooler in 2000, when they first came out. Notice the eight vertical fins, same as the original steel cooler. Photos attac problems reported. I believe him. hed. The aluminum fins are thicker. The new Stoddard cooler has five vertical fins. The cooler was redesigned somewhere along the way. A 20% increase in cooling capacity and air flow is claimed. Photo attached. 23,000 miles from cooler installation to the rebuild in CA and then 12,000 since the rebuild.

The engine oil temperature gauge has rarely if ever gone over vertical and, if so, less than 5/8. My mechanic and the builder in CA are wondering if the old style aluminum cooler was restricting just enough air to cause the number three cylinder to run hot.

I asked Brad Ripley at NLA if he heard any reports about this and he said that he hadn't. Said that they had sold over 500 coolers with no problems reported. I believe him.

My mechanic doesn't want me to have the same P&C problems and doesn't like not knowing the cause of overheating.

All opinions regarding the cause of the overheating would be appreciated.

[Martin Benade]

I wonder if that ring groove wear is from detonation more than heat. Hopefully one of the real experts will identify this.

[C J Murray]

Is that is a JE forged piston?

I would not blame the oil cooler. It looks more like detonation to me.

What was the accurately measured CR?

What cam was used and was the cam advanced at all!

How did the last P&Cs look?

[C J Murray]

Is that erosion at the very top of the cylinder? Looks like detonation.

[Ron LaDow]

Unless that piston has a hell of a dome, or it's a 30* piston in a 22* head, or the chamber is 55ccs I don't think the cause is detonation from C/R

file.jpg (135.36 KiB) Viewed 2143 times

That carbon oil deposit is nearly the width of the top ring land; say .20"? No way you're going to get 9:1CR with that deck height.
Cliff, look at that area in the red circle; looks like carbon falling off a pretty smooth bore. Not seeing any clear detonation damage.

[Dick Weiss]

Mark,

The early original steel cooler for the early 'A's had a double row of 8-tubes; Later, they had full depth of 6-rows.
The early aluminum cooler (from Stoddard) had 5-rows of full depth, but a California vender has a new 4-row aluminum cooler available.
The steel coolers may be slightly better in splitting the air better than the "blunt edges" of the aluminum cooler even tho the mesh/grills
have similar gaps between them--held up to a light for a visual look. IMHO is the air flow gets "stumbled" entering the tubes and you definitely
need the 28 blade fan. The 16-blade fan works OK w/the un-meshed cooler--unless the engine has many modifications giving a lotta heat.
Years ago, I asked Stoddard which tubes feed the outlet hole back to the case; 3-rows or 2-rows? Didn't receive an answer and I didn't cut one open.

Years ago, I mounted an aluminum cooler on 1-engine--the owner wanted it installed; It didn't change the gauge reading very much. Dunno where it's located today, but I don't have any problems even w/the originals during 95+ degree days. If the cooler pad eventually leaks from a crack or even broken (had 2- of them--1-was mine), I just bonded and reinforced them. No teardowns for machining! Cracked hole(s) get thin diameter & headed sleeves.
My 'C' coupe was sold to a member in KY for a 'resto' after 2004--haven't heard anything if it did or not yet. I still have the other case in my archives.

Your cylinder photo still shows the honing-crosshatch surface and the top/reversal of the compression ring; Is there a measured ring-land there?
I can't imagine the worn ring land being caused by pre-detonation; Usually piston erosion happens, but there's always a 1st!

Dick

[Dick Weiss]

Mark,

I forgot to mention that your case has the "weld job" on the cooler's pad; Hope the case interdrillings didn't get somewhat restricted!!!!!!!

Dick

[Mark Roth]

I was going to mention in the other thread that Dick was very kind to furnish expert advice to Hans about the technical aspects of the oil cooler mounting problem and the correct specifications for the P&Cs. Thank you again Dick. This is a C car so the fan is the later version. As I said, the temp gauge never got above 5/8. Straight up was tested at about 212 degrees. I was running Redline 10-40 after the CA break in. Don’t know what the prior to rebuild P&Cs looked like. Here’s what was used for the rebuild and now. Hans measured every part and they were spot on out of the box.

NLA-103-901-88 Big Bore 1720cc 86mm Piston / Cylinder Set of Four, for 356C 356SC and 912. Balanced JE Forged Pistons with Biral Cylinders. Replaces 61610390188

$1,237.47
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NLA-103-901-88
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Big Bore 86mm piston/cylinder set. Forged pistons with Biral (iron with aluminum fins) cylinders. Fits all 356C 356SC and 912
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Big Bore 1720cc 86mm Piston / Cylinder Set of Four, for 356C 356SC and 912. Balanced JE Forged Pistons with Biral Cylinders. Replaces 61610390188

[Ron LaDow]

Image 071 and 069: The ring groove is damaged at ~04* (on a 360* clocking), obviously from ring movement at that end alone with no other similar damage in the images posted. WIH would cause one end of one ring to 'flutter' such as to cause that damage? I've never seen a ring-gap location stay in place during dyno-pulls; the gaps are never where you so carefully aligned them after the pulls.
Like Cliff, I tend to see detonation as a pretty common cause of 'stuff'', but I don't see it here. Beats my pair of jacks for now.
Added by edit, and I make no accusation, but if the ring lands were damaged somehow, the rings would not be free to rotate (which they all do; see above), and that one end would be captured to flutter right there.
If you have not yet removed the rings, here's a chance to find out if the top ring is prevented from rotating. Please let us know.

[C J Murray]

At the very tippy top of the cylinder it has the appearance of a cratered surface, erosion, as can be caused by detonation. I can't be certain by looking at a picture but if the surface has craters then something powerful did the damage, detonation. I could just be seeing the light reflection of the carbon surface.

The ring groove is interesting, never seen that before. I am certain that it is not a JE failure, they are indestructible. However there are companies selling kits with JE pistons and Chinese cylinders and who knows brand rings. There is a reason that some parts are more expensive than others. When I use JE pistons I use their rings also. The same is true of the wrist pin cir-clip type. JE specifies a round section groove and clip and a tapered end on the wrist pin. Some suppliers of kits with JE pistons supply them with square grooves, flat clips, and no taper on the wrist pin. This is not nearly as bullet proof.

What came first, the oil or the destruction of the rings? Oil causes detonation and detonation causes oil. I don't know but there is a lot of carbon on the piston.

Were the rings gapped correctly?

Were the rings a correct fit in the groove?

[Vic Skirmants]

Is that top ring still in one piece, or is it broken?

[Neil Bardsley]

Very naively put lots of engines, mine included have Alu coolers without having the problems you are experiencing. I would look elsewhere.

[Mark Roth]

I’m going to let Hans answer the technical questions if he wants to join in. I know that the ring is still intact. Hans' concern was that the top of the cylinder was blue which indicated to him that the cylinder was too hot.

I hate to add this but here goes-I started hearing a whooping sound AFTER the oil leaks started which was right before I shut the engine down. The sound was so loud that I would have noticed it before as I am tuned into the sounds of the car. Hans found a paper towel in the fan. I have no idea how it got there as I didn’t use paper towels. He thinks that that might have caused overheating but as I said I hadn’t heard the sound before. See photos. Not really relevant going forward.

Back to the original question- has anyone heard of the early oil cooler restricting airflow enough to cause the cylinders to overheat? We are considering pulling the engine and changing the cooler but it’s not cheap.

[Wes Bender]

Long distance troubleshooting is difficult at best. The event with the towel is IMPORTANT information and it would help to know that up front. Did anything else untoward occur?

[Mark Roth]

No. As I mentioned, I heard the whoosh sound right before I brought the car into the shop. Never heard it before. I didn't put it out there at first as I didn't want to detour the topic into the P&C but that's where the discussion went. I added the paper towel information for those who are into that detour. Hans was concerned about the blue color of the cylinder top.

Our concern is whether the first generation aluminum oil cooler would cause the number three cylinder to overheat. We talked to the CA builder last week about the oil leak as discussed in this topic:viewtopic.php?f=1&t=47205

The CA builder is the one who brought the first generation oil cooler question up as he said that he had recently heard that the cooler was causing problems. I hadn't seen that in the 20+ years on the talk list and forum.