200 Block Question

I have just removed my gearbox, clutch and flywheel to see where and oil leak s coming from. We had 3 sets of eyes on it on the hoist prior to removal and seeing i have already done a main seal, i fixed it last year, it hasn’t been a problem since, we had nothing on the flywheel face, clutch side but one run on the inspection cover side indicating a plug on back of block, i thought all welsh plugs were there for water, the one behind the camshaft i take it can leak oil? This is the only obvious place. To be sure is it recommended to pressure test the motor? I wiped down the rear main and back of block and will look tomorrow as i have no light now.

yes the plug behind the cam can and does leak oil. remember it plugs up the rear cam bearing. there might also be a smaller plug, probably 1/4" or so, on the oil galley side of the cam than can also leak. it was put in for two reasons, one it made it easy to run the oil galley in the block, and that hole needed to be sealed off, and two it makes it easier to clean out the oil galley when rebuilding the engine.

the cam plug is usually fairly easy to seal because of its size, but the smaller galley plug is harder. what the V8 guys do is tap the opening for a pipe plug. just be sure you dont set it too deep and block oil to the rear cam bearing.

xrwagon":c6ohwbqx said:

I have just removed my gearbox, clutch and flywheel to see where and oil leak s coming from. We had 3 sets of eyes on it on the hoist prior to removal and seeing i have already done a main seal, i fixed it last year, it hasn’t been a problem since, we had nothing on the flywheel face, clutch side but one run on the inspection cover side indicating a plug on back of block, i thought all welsh plugs were there for water, the one behind the camshaft i take it can leak oil? This is the only obvious place. To be sure is it recommended to pressure test the motor? I wiped down the rear main and back of block and will look tomorrow as i have no light now.

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X2 Yes! Did you also remove the tin spacer "Block Plate" too? Behind it and on the camshaft side of the engine are the small soft plugs or they may be a pipe threaded plug these are for the oil galleys, and then the cam soft plug (Welsh plug). Those would be the only areas that can leak engine oil on the back of the block inside the bell housing. Other potenel leak areas besides the rear main seal that you have already fixed, you should also look at the rear head gasket area (there is an oil passage for rocker arm oiling at rear corner of block) and the pan gasket sometimes they can leak and run down into the bell housing area. The other side of the engine has a soft plug / welsh plug this is for the blocks water cooling passages if it looks like its an old rusty steel type soft plug I would consider replacing it while you have it apart, but if its a brass type plug no worries your good to go. Check your transmission input shaft seal they too can leak oil though you would find the leak to be on the flywheel face and clutch side or thrown around to the inside of the bell housing. Yes if the engine is still together pressurize the oil system to better see where your oil leak is coming from. Good luck.

yes spacer is off, i was thinking pressure testing will see where the leak is, understandably i am a bit over fixing leaks, so far i have done the rear main seal, gearbox twice its been out now.

I hear you it's not fun to have pull it apart more then once!

Silly me cleaned all the back of the block, and any trace evidence of the leak, lucky i haven’t touched the spacer, it has the leak as being the welsch plug behind the cam, when i do this, does anyone recommend painting the rear of the block, i was thinking of doing that, may help with sealing a small amount.

yes you can paint the rear of the block. i suggest using a little permatex #2 on the edges of the plug though to seal the oil passage there.

I would Clean it with Brake Parts Cleaner , blow dry then run " The Right Stuff " around the Plug , using your finger to push it in the small crevices , That is the only product that I swear by to seal even in an oil environment , RTV will Skin over oil , The Right Stuff will stick through , although getting it as clean as possible first is very important

cant find the leak yet, going to put flywheel back on and starter, get her going and see whats happening. I’ll run it without the box, maybe 5 mins or so ager cleaning everything,