'Big Time Dilemma' '69 911T

Jip · 10:33 AM

'Gents. Roadslayer here. Semi-Newbee.

After a 14 year resto-modification of my '69 911T, I finally got'er on the road last spring. The good running engine was stowed since '92. With engine reinstalled and overhauled Webers it took me two days to get it fired up. Couple more days of fine tuning the carburetors and she runs like a top. Well,,,almost. With 3 valve adjustments just to make sure, a compression test reveals about 170 psi in all cylinders except #6 which is 25 to 45psi. Depending on what it feels like doing.

I drove the car all last summer for about 700 miles. It runs like a top except for the occasional pop at idle from #6. Doesn't use oil, smoke or make noise and has plenty of getup and go.
I bought the car in '89. The paperwork from '82 indicates the engine was overhauled at 46,000 miles. It read 72,000 miles in '89 and now read 102,000 miles. My initial suspicion was a stuck ring and it would free itself up if I drove it. Yesterday I cobbled together an airline to charge the cylinder. There doesn't appear to be air seeping past the valves. However I do hear air flowing threw the oil cooler in front of #6. Plus I can hear it in the oil tank.
OK. So here's my dilemma. I spoke to my sharp ass mechanic and he said there's nothing wrong with fixing one cylinder if the rest of the engine is OK. In a perfect world I'd like to someday build a mildly hot rod motor from my T. Or buy an 'OK' 3.0 and maybe put my Webers on top. At any rate, what should I do? If I start to repair one cylinder($) and wind up breaking half the 40 year old studs($$$$$) am I likely to end up with a completely disassembled engine needing a $10,000 rebuild with money I don't have. Or should I continue to drive my T motor and save up for, at a much later date a 3.0? I'm no stranger to mechanics. Have a rather nice shop full of the appropriate toys and have made my living around engines both quite large and small. Any advice at all would be 'boocoo' appreciated.

'Cheers' Roadslayer

304065 · 04-22-2008, 10:39 AM

The critical fact in all of that is "air flowing through the oil cooler." This doesn't make sense- are you getting air out of the crankcase breather? The oil system has a pickup line at the bottom of the cooler which flows to the pressure pump which sends oil through the cooler and then to the bearings and cam spraybars. There's really no way to get air into the oil cooler by pressurizing the cylinder.

Search here for "leakdown test" for instructions on the equipment and procedures to follow to determine the source of your compression loss. I suppose the other thing could be a severely broken cylinder head on #6 which is allowing air to flow out the side next to the cooler.

911T engines don't make good hotrod cores because you have to change EVERYTHING. That said, as long as you don't split the case there is nothing wrong with pulling the engine and tearing down the starboard bank of cylinders to repair one cylinder. It's just very hard to resist the temptation to fix everything given the labor involved and the likelihood that you will be back inside in the near future anyway. But no reason to break studs IF IF IF the correct procedures are adhered to.

Jip · 04-22-2008, 11:08 AM

Thanks very much, John. After yesterdays diagnosis I called it quits while I stewed on it for a while. I did think of a blown head gasket by the cooler but I can hear air when I stick my ear in the oil tank. I plan to get under it as we speak to make further determinations and maybe move on to 'Plan B.5.'

'Cheers' Roadslayer

Flieger · Flieger's Garage

FWIW, I would drive it as long as it runs well without bugging you too much. Save up for the motor you dream of and when this motor finally gets too bad, swap them and let the T motor be a core for someone else's project.

My $.02

Jip · 04-22-2008, 05:34 PM

Well,,,I might just do that. Today I removed the lower valve cover to check,again, the valve lash. A OK. With air piped into the cylinder I hear air rushing by. I thought it may be the exhaust valve. Still might be. However I still hear air in the oil tank and when I disconnected the crankcase vent line I hear air there too. Seeing how the car runs fine on 5 3/8th cylinders maybe I'll just drive for a few years and find an OK 3.0 or something. I'd kinda' like to take a learner course on this engine but I'm afraid if I open it up it'll explode in my face and cost a bunch of money I'm not prepared to spend.

Oh. And just one more small detail. Last fall when I put it back up on stands I checked the oil. There wasn't any. OK, so I used 9 quarts of oil in 700 miles. No big deal. Right? So the other day when I fired it up for the first time since October I added four quarts of oil before I started it. Then when I started it and checked the oil,,,surprise.

Now there's 'WAY' too much. So I siphoned out about 4 quarts and everthing's hunky dory. This morning there's no oil on the dipstick. So what's it doing? I know. Bet it's leaking past the check valve in the oil pump and filling the crankcase like my Harley did for twenty years. Until I fixed it last November. And,and,and,,,when I removed the lower rocker cover 3+ quarts of oil collected in the nice clean tray I'd put under the starboard cylinder bank. Just like I knew that was going to happen.
Yep! Maybe I'll just drive the little guy and save up for that 1200hp twin turbo fuel dragster motor I'm going to build someday.

'Cheers' Roadslayer

Flieger · Flieger's Garage

You are checking the oil with the engine running at operating temperature on a level surface, right?

Forgive this if it is an obvious question.

The oil will drain back into the sump as it sits. This is normal.

Jip · 04-22-2008, 06:50 PM

Well, now that you mention it, last fall I did some more rerouting of the oil lines for the cooler I added during it's 'resto-mod.' Before I disconnected the lines from the oil tank I drained only about a quart of oil from the tank. Now to my knowlege, the thermostat on the oil lines, that is, the thermostat forward of the right rear tire has never opened since I put the car on the road. The engine never gets over 180 degrees and as I understand the thermostat opens at something like 190 or so. BUT, I thought maybe just a little bit of seepage was going past the thermostat as it was perhaps ever so slightly opening. With all of the coolers lines and the cooler itself empty of oil I hoped or at least thought for a moment maybe eight quarts of high priced oil was going there. Guess not as the lines have always been cold to the touch. Even on hot days.

To make along story short,yes, last fall I knew to check the oil when it's running. Yesterday I sure as hell forgot. And thankfully, no harm done. I really appreciate your patience. Maybe I'll try out the cigarette lighter. I can't possibly break that. Could I?

'Cheers' Roadslayer

'Cheers'

304065 · 04-23-2008, 05:48 AM

OK, air in the oil tank is different than air in the oil cooler.

Air rushing into the oil tank means blowby, a broken ring or two on that cylinder.

I never touch my cigarette lighter, those things can kill you.

911pcars · 04-23-2008, 09:53 AM

Slim chance breaking a stud in a 911T, they're regular steel, nothing fancy.

Since you've isolated #6 as the leaking cylinder, I'd disassemble the right bank and repair the piston and/or cylinder. I wouldn't continue with a right bank valve job unless it's done on both sides.

There's a temptation to go further than necessary on repairs to the long block. You'll have to take into consideration the overall condition of the engine and whether it's worth it for your long term needs. A minimal fix might be a good idea while you work on an improved engine on the side.

Your tech sounds like a wise person.

Sherwood

Jip · 08:23 PM

The engine is in very good shape. Or appears to be. When it was out and on the floor I removed the rocker covers to adjust the valves and overhauled the Webers. They were in good condition too. As is the distributor. If I flog this engine it's worth '0'. If I fix it it's worth more than '0'. But not much. If I save up for an 'OK' engine, what's that. $5,000? $8,000? Maybe I'll get out my pocket calculator and do a little arithmatic. Also, if I fix this engine it might last many more years and I could 'outgrow' this desire to build a fuel dragster motor and buy something sensible,,,like a 40' boat.

'Cheers' Roadslayer

911pcars · 04-23-2008, 10:13 PM

If you wander over to the for sale area, there's a rebuilt 2.7 long block that sounds good.

Sherwood

deathpunk dan · 04-25-2008, 10:01 AM

People sell very nice 2.0 - 2.4 T engines on here quite often, and usually for pretty short money, ie a couple of grand.

If my car's engine developed a terminal illness, there's no way I'd spend $10k rebuilding the 2.2T. I'd buy something like that fully rebuilt 2.7 posted above for $4k and run my webers with it (likely gaining what, 50+ hp over a tired 2.2T), and save the # matching engine for theoretical future resto.

just a thought.

kenikh · 04-25-2008, 03:01 PM

Yep, buy someone else's project on the cheap.

Jip · 04-26-2008, 07:56 PM

Yep! Sounds like a plan. I cruised the 'for sale' column and found lots of possibilities. I might go exporing in my T motor for educational purposes while I plot and scheme for a project motor. My T motor just needs a ring/piston/cylinder job on #6 and should be fine after that. I think. I've been studying my books to build up the nerve and with a little patience and time may be able to pull it off. Might be a winter project. The rest of the car is pretty much like new and I might need a reason to take it all apart again. Plus I can start by selling my very nice 7X16 Fuchs on the for sale column.

'Cheers' Roadslayer