Head bolt re-torque, yes or no?

[CookeD]

Allright, here is a good question, and one for the "If it isn't broken, don't fix it" camp...

I worked on the CS over the weekend, and have had an oil leak at the back of the head since I got it running a couple of years back. Last year I replaced the gasket on the rear cam plate, as initially I thought the leak was coming from there. That job was a PITA, and I'm not certain that I actually got the plate on without ruining the gasket during install... The leak didn't go away, but also hasn't gotten any worse, so I'm thinking that the rear cam plate wasn't the source of the leak, and that the fix is sound.

So this weekend I replaced the oil pressure sending unit, as the one that was on there was very dirty/oily, and I read in a previous post that the sending unit can also be a source of leaks. So, this is a wait and see thing-- If the leak goes away, that was my problem.

In the meantime, I'm wondering if a head gasket issue could also be a source of oil leaks. If what I've seen by mechanic-ing on my car is accurate, I'm thinking that my head has never been off and/or messed with, as I still have the '73 casting stamp, low miles, and can pretty much tell that things are undisturbed under the hood, as everything is about the same level of dirty. I know that just because the head hasn't been replaced does not guarantee that it hasn't been off, but I'm thinking if it had been off, someone probably would have chucked it for a new one.

So the main reason for this post-- On a head that has been on for eons, has unknown history, but doesn't have water issues, should I re-torque the head bolts? Further, should a re-torque be done anyway as part of normal maintenance, and/or if the motor still runs and only leaks a bit of oil, should I just check and fill the oil and not worry about it? The motor runs great, so I don't want to do something uber-stupid either way.

TIA,

John

 

[x_atlas0]

The head studs, based on what others have told me about other M30s, are designed to yeild on install, so you get the strain-hardening effect. As a result, re-using old head studs is a very bad idea.

If you want a reuseable set, ARP makes a M30 head stud set.

 

[AndyM]

The head studs, based on what others have told me about other M30s, are designed to yeild on install, so you get the strain-hardening effect. As a result, re-using old head studs is a very bad idea.

If you want a reuseable set, ARP makes a M30 head stud set.

I don't believe this is correct. They can be reused and should be retorqued once after initial install using a torque angle gauge. At least that was the proper procedure for my 3.5.

As far as the leak goes, did you use the proper fiber washer under the right bolt on the cam plate? If not, it'll still leak just the same. If you still can't find it, try using flourescent dye and a blacklight. You'll pinpoint the leak in no time.

 

[CookeD]

Hey guys,

Yes, I used the correct gasket on the cam plate, and I'm fairly certain that I did the repair correctly. With the engine in the car, you just can't see anything back there to make sure that it's all going together fine, and I still have that crazy foam firewall insulation, making it even more difficult to know that all is well.

No, the head is not coming off. But, as you said Andy, I've read that you do a re-torque once (I think it's even in the owner's manual regarding service), and then leave the bolts and the head alone. That's really my question, as I'm just wondering if this should be done, and if this could also cause an oil leak.

 

[chicane]

The head studs, based on what others have told me about other M30s, are designed to yeild on install, so you get the strain-hardening effect. As a result, re-using old head studs is a very bad idea.

If you want a reuseable set, ARP makes a M30 head stud set.

I don't believe this is correct. They can be reused and should be retorqued once after initial install using a torque angle gauge.

I would definitely replace the head studs. The M20 on the E30 was notorious for head stud failures especially those who chose to reuse the studs. It seems to me that what is most valuable here is your time and labor and that is is cheap insurance to install new studs and have the piece of mind versus the alternative.

 

[AndyM]

To answer the original question, you really shouldn't need to touch the head bolts again. But if the oil really is seeping from the head gasket, it may be time to replace it. If it were mine, I may try to retorque it to spec (can't make it any worse), but I'd also order a new head gasket. Also, on the cam plate, just to be clear, I'm actually talking about the small washer that seals one of the bolts from the outside -- if you neglect to install it or its on the wrong bolt, you end up with a leak. I'm not sure that came across the first time and I'm always a big fan of fixing only what's broken. Did you use teflon tape or some pipe sealer on the sending unit? It'll probably leak if you didn't.

By the way, the M20 is a whole different animal and the head bolt failures are unique to that motor. I routinely reuse M10 and M30 head bolts without issue. The only reason I would replace the head bolts on a stock motor is if there's reason to believe they've been stretched or the strength compromised, which is highly unlikely.

 

[CookeD]

Andy,

Thanks, you've answered my question regarding the head bolts.

Regarding the cam plate-- I re-assembled it exactly as it came off, except that I replaced the gasket that goes between the plate and the head. I can't remember installing a gasket on any of the bolts when re-attaching (last year), though I re-assembed the same way it came apart, being careful to keep the bolts in the same locations.

Based on what you posted, I just opened up the Blue Book, and I see exactly what you mean (self-sealing disc). Luckily, it looks like it's the easiest bolt to get to, and it's either going to be there or it isn't, so I'll also try this.

Thanks again...