Mysterious SBC Oil leak

[Nabbott]

MarkWebb said:

hmm, as I said on 1st Jan

I know, I know - looks like you may have been 'on the money' - I just didn't want to believe it

Have decided that I may as well whip the box, clutch and flywheel off (he says casually like it's a trivial amount of spannering) at the same time. At least this way I can guarantee it gets sorted for the spring once and for all!!!!

[gt5594]

I have the same Rodeck alloy block - the torque settings, including the setting for your mystery fasteners are usually (lightly) stamped on the rear downward facing on the block, adjacent to the oil filter housing. Let me know if your fitting doesn't arrive, I have one.

Andrew

[Nabbott]

Steve_D said:

There are 2 types of Torx bits....Torx and Torx-Plus so that may be the difference.

It may also be a Tripple-Square which is more like a spline.

Steve

Congrats - it's a Torx Plus! You learn something new EVERY day playing with these cars ... torx plus - who knew?....

[Nabbott]

If Thor did metal work (beyond knocking out the occasional heavy hammer), I think this is the kind of big end engineering he'd be doing.

6 bolts - and look at the size of that thing!

[UltimaCH]

Nabbott said:

If Thor did metal work (beyond knocking out the occasional heavy hammer), I think this is the kind of big end engineering he'd be doing.

6 bolts - and look at the size of that thing!

Having removed that specific big end bearing support (massive indeed), do you need to torque up all the others too when reassembling?

[Nabbott]

Well I may as well (but hadn't given it much thought to be honest!)

[V8Dom]

DOESNT LOOK LIKE ANY EXCESS SILICON.... which means it hasnt excaped into the other areas to seal.

or have you wiped it clean

dom

[738 driver]

Try to get your hands on some quality thread lube so you get a correct torque setting and clamp force during rebuild. (Arp type)

Some builders offset the seal joint line by spinning it a few degrees in the bore to set the joint line away from the block/ cap joint line .... Others put a pinhead amount of quality build sealer on the seal joint faces ... Food for thought ..


Also on you rear main bearing check to see if one half of a shell has had a small chamfer filed from the centre toward to inner face on the joint line .... It provides better oil feed to lube the heavy "Pull " type clutch and reduces thrust face wear ... The chamfer should be 1-1.5 mm wide maximum and be sure it only extends from the centre of one shell half inward ..

Just a couple of old tips/tricks to consider ... Worth asking your builder for their view too ..

G luck

[Nabbott]

So bet you all thought I'd fixed this and forgotten to update you all??

NO - I've been buying a new house and spending WAY too much time on DIY since January to get the car back together. However tonight I finished whipping the gearbox, clutch, flywheel and adaptor plate assembly off to check the oil gallery and cam shaft plugs:




Now I don't know about anyone else but I have to conclude that there's no enough coming out of here to account for the vast leaks i was experiencing. The back of the adaptor plate was 'slightly oily' but nothing like what I was expecting had one of the plugs sprang a leak.

So unless anyone here has any better ideas I'm going to suggest that the rear crank oil seal was the culprit (and I could have been driving the car through this lovely weather over the last 2 weeks)

[Storer]

Looks dry to me.

More head scratching then...


Paul

[Nabbott]

Paul,

Logically I think it can only have been the rear rank oil seal. There aren't any places left for it to leak from (and its 100% engine oil not gearbox). The definitive test would have been to have driven the car having fitted the new crank seal but given it was December (and the only other place it could have been was these plugs) I decided to make 100% sure and tear it all to pieces.

If it leaks on the next drive I think I'll be making an insurance claim for total loss from a mysterious fire (e.g. Me setting light to the bloody thing 😄)

[Storer]

Nigel

If it is still leaking it may be worth checking all the engine breather pipes. Not sure about SBC but there are a few pipes on an LS.

Hope it is good to go when you get it back together.


Paul

[Nabbott]

Thanks Paul (so do I!). I checked the pipes pretty carefully there aren't that many even with the dry sump. Fingers crossed it's sorted this time around 😜

[Storer]

How do you vent the dry sump tank? Do you use a catch tank for the sump and engine breathers?

I get a tiny amount of oil from the catch tank breather as everything on my engine vents into it.


Paul

[Nabbott]

So the oil tank does have a breather but it's just vented to the open air (no catch tank). It could be loosing a bit from their but not anywhere as much as I was seeing

[V8Dom]

i had an oil leak recently and although i thought it was rear crank seal, the seal was fine... it ended up being the sump gasket... we replaced it with the latest rubber type instead of cork and its spotless.

also when the sump is off put it on a flat table and make sure its straight... amazing how many are bent as screw drivers etc are used to bend it off.

Dom

[gt5594]

Ok, if you are still struggling...take a really close look at the sealing on the rear horizontal valley plate under the Kinsler manifold. The Dragon Claw manifold can take a huge amount of fiddling about with seals and gaskets to get a good leak free seal. I look after an engine with exactly this set up and it took me several attempts to sort out a good seal here, with constant weeping at high revs. In the end I made up special alloy spacers, as there can be an unusually large (horizontal) gap to fill with this particular set up. Every small block you see appears slightly different...it's why we love them! Aluminium and magnesium have different expansion rates when heated and what looks ok on the bench cold can open up at high temps. Of course you would see this if your engine was dyno-ed but easy to miss if it was tuned on a hub dyno, which only runs for seconds.

Also, if you are running a 3 stage dry sump pump, i.e. 2 scavenge from the sump, with constant high revs you'll end up with (literally) a gallon of hot oil sitting in the valley plate, waiting to drain down into the crankcase. You can enlarge the drain holes next time you do a strip down, but the only way answer if you insist on revving the engine hard constantly (lovely noise by the way!) is to fit a 3rd scavenge stage and scavenge oil straight out of the front of the inlet manifold (magnesium, if Kinsler).

Absolutely not what you want to hear, but there's a fair chance that's your mysterious leak.

Hope this helps, you appear to have eliminated most other things.

Andrew

[Nabbott]

Right so I'm throwing in the towel on this oil leak - family, work and the fact that we're between 2 houses are conspiring against me.

Gentlemen - what I need now Is a trusted garage who know their way around a SBC that I can take the car to and they can fix the issue. Can anyone recommend anywhere in the south east? I'm in ascot for reference.

[Graham-P]

Down the road from you, Charles Dunn,
http://www.charlesdunn.uk.com/map.asp

4 SOHO MILL ESTATE
WOOBURN GREEN
NR. HIGH WYCOMBE
BUCKS. HP10 0PF
TEL: [phone]
FAX: [phone]

What he doesn't know about SBC isn't worth knowing. Sorted.

[Nabbott]

I seem to remember good things being said about Charles Dunn - great recommendation. Thanks.