By Corky Guenther
When I was in the Navy, there was a popular question and answer: What is the difference between a “Fairy Tale” and a “Sea Story”? A Fairy Tale starts: “Once upon a time”, A “Sea Story” starts: “This ain’t no s—t!”.
I am not sure which this is, probably somewhere in between. A little history. It all started - as they say- with a tired TC both body and soul if you will pardon the pun, at somewhere around 90-95k miles on the original restoration with around 70k (following a broken crankshaft) of trouble-free motoring. Never giving a thought to getting in the car, turning the key, pulling the starter, and heading off. From Massachusetts to Gatlinburg, TN; from North Carolina to Reno, a couple of GOFs in NH, to name a few. No matter, anywhere we wanted to go. So, after committing stupid and creasing a fender, a major refresh was undertaken. The body part started at one body shop in Hickory and though there was progress, it was slow, and we found another shop in Lenoir which was much closer and faster, working full time rather than “in between”. After the body was complete, we started on the soul (OK – Heart) i.e., a complete rebuild of the engine. Don’t ask me why I delayed the engine until after the body. The reason is lost to history. Dave Ahrendt and Dean Sprague, long suffering both, as will be seen, helped pull (and reinstall) the engine. We discovered that what I thought was a .080 overbore was .100 so we went to .120. This was a complete rebuild, main bearing saddles align honed, block skimmed to assure the deck was flat, head ditto, valves, guides and seals replaced, new cam (roller with corresponding tappets and pushrods) etc., the works. We assembled and reinstalled the engine and started the 500-mile break in. After about two hundred miles, the valve train became very noisy. Turns out that you can install the XPAG rocker shaft backwards which results in no oil being supplied to the rocker assembly. Rocker bushings do not function well without oil, at least not for long. So, off with its head! And back to the machine shop with it. New rocker bushings, a couple of new valves, all lapped, reassembled, and re-installed. The remainder of the break-in was uneventful.
We drove the car to MG2016 in Louisville and back, but the engine was consuming oil at an unacceptable rate and fouling plugs. One evening, while out for a local drive, it started missing and I thought it had fouled the plugs again, but it was a blown head gasket 3-4. With Dave and Dean’s assistance the engine was pulled again: #2. Tear down revealed detonation damage to ring lands and piston pin bearings (stiff rotation) across the board. Though .140 pistons were (maybe are) available, we decided to sleeve the block back to standard. The crankshaft (Moss replacement) remained and is still at standard, both main and rod journals. Coincidentally we discovered that the camshaft had lobe damage and it was replaced. We (Dave, Dean and I), reassembled and reinstalled the engine again. We drove it for a while and encountered a distributor problem. I do not remember the exact symptoms but with an already arranged trip to Chattanooga in the offing, traded distributors with Dave. We drove to Chattanooga for a show (about three hundred miles one way) and still had oil consumption and plug fouling problems. On the way home, that distributor seized. Made a nice knot of the plug wires. This resulted in the cam gear being chipped and so another pulling of the engine: #3 (Dave and Dean assisting again) and tear down. We found that the rings were detonation damaged. After this failure, we decided that we could re-ring the pistons as there was no significant land damage. We did ceramic coat the pistons, reassembled and reinstalled. After Dave's distributor seized, I had mine rebuilt by Jeff Schlemmer at Advanced Distributors who said it was the worst he had seen. Because of this, I had ascribed the first rebuild failure (at .120 over) to this distributor which had been "rebuilt", perhaps this was erroneous given subsequent history. At any rate, oil consumption after break-in did not diminish.
This brings us to the Summer of 2020. While Covid reduced TC activities, I noticed that it was increasingly difficult to start requiring full choke and multiple attempts before one cylinder would catch and eventually it would run. This was most apparent during the North Carolina MG Car Club Fall Mountain Tour when each morning, it took about 15 minutes of “hit and miss” to get to a running engine. I did not devote a lot of thought to this problem during the 2020-2021 winter as I am rebuilding the "B". Around the 1st of April, I decided to devote some time to what I thought would be a tune up. That's when I discovered how rich the carbs were set. Turned out that pulling the choke did not provide much enrichment because the jets were so low to start with. A serious investigation started. First, I borrowed a valve and hose assembly for a small propane tank from Jim Conley and used that to check for vacuum leaks. I found that there was some leakage at one of the carburetor flanges. I had had Joe Curto re-bush and replace the spindles a couple of years previously so no problems there. I had a set of TD carb bodies configured for the TC, so I swapped them without making any difference.
As a result of seal (rear main Moss) leakage I have installed a PCV valve. For reference, Dave Ahrendt has the exact same installation on his TC. The next obvious place to look was the PCV setup. I removed the PCV setup and blocked the intake manifold connection, no change in behavior. Just to be sure, I reinstalled the original intake manifold (no vacuum tap). No change in behavior. Dave re-tuned his TC paying particular attention to the jet setting from the recommended initial settings (he had to lean his slightly). Then he came over and we started again on my TC and found (as expected by me at least) that the carbs had to be enriched significantly to get it to run and were still indicating lean. Testing with the propane probe revealed no air leaks at the carb shafts, flanges or anywhere around the manifold. While swapping the intake manifolds, I noticed what I thought was oil in the intakes. I pulled the intake manifold and confirmed oil in the intake tracts. The usual suspects would be intake valve seals/guides. That did not make any sense given the mileage since the head was redone. Speculation ran rampant and settled on “maybe the head is cracked”. Since we (Dave, Dean, me and our machinist) could not think of anything else to do, I pulled the head and took it for analysis. To further address that speculation, a two-fold approach. Jim Conley had the XPAG engine from his TD completely apart and returned from the machine shop and he volunteered his head to use as an experiment while I took my head back to the machine shop to be crack checked and have the valve seals/guides evaluated. As we all suspected and I at least hoped, Jim’s head made no difference. So, after our success, I removed Jim’s and reinstalled mine, crack tested. Our machinist did find small cracks in 4 (I think) valve guide bosses in the ports, but they do not go through to the top of the head. We put everything back together.
Here we were. Dave, I think – I know it was not me, suggested swapping intake systems between Dave’s car and mine. We installed Dave's complete intake setup on my car. It started and ran acceptably right off. It would have needed a little fine tuning, but it proved the point. To confirm, we took my complete intake setup and installed it on Dave's car. It would neither start nor run without massive amounts of choke. Suspicions confirmed, twice! Now what to do next? Dave suggested swapping suction chambers, his for mine. We put his on my car and voila! Ran acceptably. Just by chance, Dave held one of my pistons up to one of his and noticed that my needle was significantly (about .150 after measuring) longer than his. OK then. We looked at my needles, they are marked ES, the standard XPAG needle. His too. Swapped his needles into my pistons /carbs and all was well. Ordered new needles from Joe Curto.
The Problem: Mis labeled carburetor needles. They were labeled ES but in retrospect, obviously are not. We spent weeks looking for excess air flow as the cause of the presumed lean condition. Turned out that the air flow was OK, the fuel flow was apparently inadequate.
All the above leads me to the conclusion that running lean has been the circumstance all along, since the initial rebuild when the then new needles were installed. Perhaps growing with time. Three rebuilds later with new needles, the car runs well but produces a fair amount of smoke after idling and is still consuming a considerable amount of oil and fouling the plugs. We’re going to continue to run it to see if it improves.
The pessimist in me thinks that the rings have been compromised once more. Time will tell.
