I am new to registry having bought my 1964C a couple of years back. I had pen in hand to sign purchase contract just prior to college graduation on a kelly green 1965SC with saddle interior. With the $4600 price being 65% of my gross pay and I knew nothing of tax and FICA deducts, I put the pen down. Regretted it ever since. Now I'm back in. My 64C had "top end" rebuild according to previous owner with larger displacement and Webers. Has leaked oil since. Leakdown test on #1 cyl read 80%. Later comp test was 60 #. The car runs fantastic.. It is strong and no unusual noises, etc. Is there a solution to this problem with the #1 cylinder other than a complete rebuild? Since it has been driven 25,000 miles like this, will there be damage if I continue to drive as is? Thanks for your input. I have been amazed at your collective knowledge of these special cars. I need to add that the oil leak is at the #1 cyl juncture to crankcase and its compression leak is between the head and the cylinder.

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Yes you could be lucky and find the problem on No 1 staightaway. Are the other compressions OK? The Manual does not give any real guidance on minimum values.
For a rebuilt unit all they state is a maximum variation between cylinders of 1.2Bar (17psi). If the compressions on the others are 110 to 125 psi that is good.
You can do nothing until the engine is out but make sure there is nothing silly like tight valve clearances on the one cylinder first.
Personally I would remove the head on one side, check the piston rings are not broken (common problem), remove both barrels and lap them on to the head seats. Check for full contact with "engineers blue". I suppose it would pay to take a quick look at the valves but then put it back together. You may find that that previous builder damaged a copper seal at the base of the cylinder which would explain the oil leak.
If you go for a a big rebuild then it could be several thousand dollars.
Go for it.
John

John

John may be onto something. If the cylinder base gasket is missing then the cylinder is effectively short and that will cause the compression leak. If the gasket is in place it is still possible that the cylinder itself could be short and that will cause poor sealing at both ends of the cylinder. You need to take that side apart and measure everything. Doing so is much cheaper than waiting for the BANG.

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Cliff Murray

 

'55 Cabriolet Racer

'57 Speedster

'59 Sunroof

'63 Coupe Pushrod GS 2133

'67 911 S

Jim, you didn't say and maybe don't know what "larger displacement" barrels and pistons are in the engine now. My first thought was that a Biral barrel has cracked, common on 912 'stock' displacement engines and possibly on a Chinese repro "big bore" set of similar manufacture (leaks, kills compression, etc) .... OR the set used wasn't measured for cylinder height matching, OR what them other boys said......
You may want to repost after a drive in a similar 356 with all the cylinders working in concert. You may find that the one 'along for the ride' doesn't make that ride quite so fantastic by comparison.
Welcome to the present 356 world and it's perpetual can o' worms as associated with any ~50 year old car.

Bruce Baker

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A leak down test should have pointed you in the direction you need to go. Not only does this test tell you the condition of the sealing properties of the rings, valves and head surfaces but will, to an informed mechanic, tell you where you are loosing the compression. Using a stethoscope you can probe the exhaust, intake at carb, around the head to barrel joint or oil filler to check for leaks at the valves, head sealing surface or rings. If you're loosing it from multiple areas a little oil thru the plug hole will seal the rings and give you a figure for the remainder of the leakage

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"Is there a solution to this problem with the #1 cylinder other than a complete rebuild?"
Dunno. You'll have to find what the problem is. But an 80% leak means you don't have a cylinder.

"Since it has been driven 25,000 miles like this, will there be damage if I continue to drive as is?"
Unless you have a real filter system, there's a good chance that the cause of the problem is spreading swarf through your engine.
As Cliff mentions, that can lead to a "BANG". If you have the original engine in the car, the "BANG" can mean you'll have to substitute a non-original engine.

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Oil leak at No. 1 cylinder and compression leak between No. 1 and the head is very suspicious. Locate a good shop that knows 356's. Have the engine pulled and at least remove the head on the right side. Pull the cylinder off the piston. That's the start. Driving with a known problem usually results in "subseqential damage" that's much worse and more expensive than the original problem.

Good luck and report on what the mechanic finds.

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Have you adjusted your valves since you bought it? Tight valves lead to burned valves.

Rainer is offering you some good advice. That will narrow your search for the problem.

Personally, I would pull the heads and P+C's. Have the valve job freshened up and check the condition of the guides. Maybe hone the cylinders and slip on some new rings. Lap the cylinders into the heads or maybe get a clean up fly cut on the heads if they don't seat properly. While your at it, pull the rods and put in some new bearings and rod nuts or at least check the condition of what you have. Since it's out, check the clutch condition, end play and put in a new main seal. It would be a good idea to weigh and balance the pistons and rods while they are out. All of this is pretty cheap parts-wise and you would have to do it within the next 10K miles anyway. Well worth the peace of mind and that engine that runs well now will run really well when your done!

Good luck!

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If the head job included flycutting the cylinder seats and NOT matching their depths w/in 0,013mm (.0005") in both planes and the cylinders aren't even in heights, you'll have a leak. Also, when heads are torqued, they should be done alternately @ 7ft.lb increments to final torque and checked twice more--this stresses the case evenly.
See the recent Registry magazine for a quick check of the cylinder heights (when on the case) w/a straight edge before the heads are installed.

Dick

Muddling through this first post, I have finally found all the responses. Wow! Thanks for such a comprehensive view. Going easiest to hardest, pulling #1 for cyling to block gasket check seems a good start. I will post what I find thought it may be a while until I do the work. Thanks

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In April 11, 2011 post I said I would report when problem found. Since previous owner said it had been that way since top end rebuild 20,000 miles previous, I decided to drive until winter. Teardown showed wavy washer missing from #1 cylinder headbolt. Who knows if left off in previous rebuild or broke and dislodged. Teardown found a broken piston land on #2. Rebuild complete with existing 1720cc Mahle cylinders. Used JE pstons 9.2:1 compression. Head machined due to damage from #1 cylinder "bouncing around" Another had a slight nick in top so all machined and then shimmed up. Front and read seals replaced and case leaks resealed. Whoever responded to my previous comment that the engine ran well with, "If it runs well now, just think how well it will run with all four cylinders." was surely right. Unbelievable how strong it runs! And with new rubber donuts in the rear torsion bars, it drives like porsche should. Thanks for all the input. Great Organization to which I am pleased to belong.

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Jim- Great news! Have fun with the new found power. Cliff

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Cliff Murray

 

'55 Cabriolet Racer

'57 Speedster

'59 Sunroof

'63 Coupe Pushrod GS 2133

'67 911 S