This hole is present on my L33 BLOCK and is NOT present on my original LS1 or LQ4 blocks.

First, what is this hole, and second, does this hole go deep enough into the block to be the source of my large oil leak, meaning it needs plugged?

Quick answer appreciated, I have my DD taken apart. I did search and didn't see anyone else asking this.

 

Has this been cleaned up? If it wasn't too oily or at all, I doubt it is leaking.
Is it tapped? It might just be a blind hole.

 

Yes it was cleaned up. I didn't see the hole until I cleaned things up and yanked the cam sensor, am swapping valley pan gasket because I've been chasing an oil leak for months. It is threaded, doesn't seem closed when I put slight air to it but hard to tell. It was all grimy back there so I suspect it's possible it could have been leaking.

If nobody knows the answer I'll just try to plug it with a bolt since it appears to be threaded. Boy I hope this was the source of my oil leak.

If anyone knows please let me know!!!

 

That hole doesn’t go anywhere. I looked at my dead L33 block

 

I'm trying to remember for sure but on my LQ4 core ,,,, i think that hole was one of the bolts that holds the gizmo that protects the fuel rail from hitting the firewall in a wreck..

 

Thanks guys, appreciate you helping me. That cowl really makes it tough to get in there to see.

The hunt for the leak continues, if reseating the Cam Sensor and reseating my OPS relo line and redoing the valleypan gasket doesn't solve the leak then I guess it must be rear main, I've already changed crank sensor and also valve cover gaskets twice. Couldn't see anything on flexplate but that's gotta be it otherwise.

This is one of those times where a clean showroom engine would really pay off, with a grimy DD it's nearly impossible to trace an oil leak backwards up the bellhousing even with dye and a lift and hours of trying.

 

I have used the UB die in the oil , you have to have the car in the air, put the die in start it and have a UV flashlight, the glow shows up very quickly on most leaks...
Once it leaks for a while the whole engine will glow so its only good for a right now location test..

 

Chasing oil leaks can be fun. I found one priming an engine without the accessories on it. I have seen several engines with holes that were designed to be blind that were either drilled too deep from the factory or the casting cracked when thing like accessories or manifolds were bolted on. This L31 head was factory drilled into the oil drain back area and I shoved a bolt into it so I could continue priming. I cleaned the oil out of it and put the alternator bracket stud there with some PTFE sealer. I had a 4.7L in my Dakota that leaked oil through an exhaust bolt only discovered it putting headers on it. I have also seen a SBC and LS head with exhaust manifold bolt holes drilled straight into coolant. So basically check everything. If it is leaking through a bolt hole make sure it has a PTFE sealed bolt or stud in it.



Also on the cam and crank sensors, always use a new o'ring anytime you remove it and lubricate it with some oil or ATF prior to install. Anything less usually results in pinching the o'ring or shoving it out of its groove and an oil leak.

 

I'd love to get new Orings but I guess their size is somewhat unknown, most people apparently just buy a new cam sensor rather than deal with that. This cam sensor isn't that old, was new when I put then engine together, so hoping it'll not leak. I'll have everything clean and lube the heck out of it LOL

I know this is a bit hacky, but while this is all opened up I am going to try to build a little "dam" with a long bead of red RTV at the top rear edge of the block behind the OPS and Cam Sensor so if anything up there leaks it'll hopefully pool up and become VERY obvious for the short duration of my leak pursuit. The block has a natural pool area minus a back wall, I'm going to create that back wall temporarily, just a few millimeters high. It only needs to last while I chase this oil leak around the bellhousing. If that cam sensor or OPS or valley cover leak back there after I reassemble that should make it VERY apparent even with a flashlight and a mirror. Leak's pretty bad, I'll know 10 minutes after starting it.

Yea I know this sort of hacky stuff drives some of you purists nuts LOL but this is a very dirty beat up $4500 DD trans am not a show car.

 

In late. O'ring info...
O-Ring Size Chart | USA AS568 Standard O-Ring Sizes (marcorubber.com)

 

Good site for orings, thanks for sharing. Just did a quickie check.. according to this thread:

https://ls1tech.com/forums/generatio...l#post20380800

the correct size should be 14mm ID X 19.5mm OD. That combination wasn't listed on the marcorubber site that I could find as a standard size.

The closest that site shows is 13.94ID 19.18OD which ends up being the 113 which was already shot down.

Also that thread listed theoringstore.com as a possible source. Maybe if I get time I'll research better and find out what material and see if there's a source out there for these. I'd LOVE to have a few on hand.

 

There is a guy on ebay that claims to be selling the proper size, do a search for LS1 cam sensor oring.

 

I just looked on the bag... It appears he's selling just 1 ring and showing it as a box of 8.
At the bargain price of only $23+.

 

Sounds like it'd be cheaper just to buy a new sensor, lol.

 

That might work if it's an OP sensor leak, but if it's the cam sensor o-ring, the leak will go down inside the back cover, externally you won't even see it. There's a post on here somewhere that shows the path it will take. Also, the crank sensor uses the same size o-ring, which can also leak, in that case should be easier to see where it's coming from there will be oil dripping from the starter bolts. Getting to the crank sensor is a lot more of a PITA in my opinion, since you have to remove the starter from below.
Also, there's an old GM part # for o-rings, 1989866, that might be the right size. It's definitely not a standard size that you can easily find.

 

Thanks, was not aware that the cam sensor leak could be down low in the rear, very helpful!!!

The leak remains and the pool is empty/dry LOL. I think there's literally nothing else that can leak back there other than rear main (or forementioned cam sensor). Rehash: valve covers replaced twice, crank sensor replaced, valley cover replaced, OPS resealed and showing clean, cam sensor reseated and looks clean from the top, PCV and other hoses seem dry.

Trans coming out now to look at rear main and that cam sensor possibility. Gotta be one of the two. It's a bad leak or I'd wait till spring, it drips at that low point where trans and oil pan meet up but is wet on sides too including drips on starter bolt and wet around driver flex inspection hole. It really didn't seem to be flinging off of the flexplate though. There's a thousand threads already posted on leaks like this so I already know there's no real easy way to find a leak like this on a dirty grimy engine... Oh well. I'll find it eventually. When I put the L33 in, the rear main was perfect. And although I've been boosting it like 12psi max I don't think I have "too much" crankcase pressure since my valvecovers and pcv hoses vent to atmosphere and I've never seen anything like dipstick blowing out or anything.

While it's apart I'll check the back of the oil pan although I wouldn't expect that to have a constant leak while idling in a driveway. Can't think of anything else that can leak that bad while just sitting in a driveway idling.

EDIT: Once trans is out I'm gonna put the flexplate/starter back on it and probably start it and look for the leak. if anyone has any reason why I shouldn't do that please let me know.. I don't imagine it's any different than an engine run stand, right? lol I'll eyeball it before I do in case I'm missing something.

EDIT 2: lots of threads of people doing this, need to make sure it's in N or P (may need to trick the trans harness) but it won't harm the engine or anything apparently. I'm going for it LOL