Hey all, I've finally decided to address a pesky oil leak on my '72 U code Supreme. I think it's coming from the passenger side valve cover gasket so I have some questions.

First, it's an A/C car, so in order to get to the rear bottom bolt for the valve cover, I'm thinking I'll have to remove the A/C box, correct? (Unless someone knows of an easier way,) because I see no other way to get to that bolt. Not to mention the challenge of getting it back in with minimal clearance.

Second, there are two diagrams in the ASM, and I'm guessing the second one applies to my situation, correct? So, if I read it right, there are only two bolts holding the A/C box on, along with sealant. If I have to remove the box, how heavy is it, and what kind of sealant should I use upon installation?


Third, I have a set of cork gaskets that came with the car when I bought it. Should I use these with sealant, or just go with the metal inlaid rubber gaskets?

 

The valve cover will come out. It’s a tight fit but it can be done with the heater box in place.

I haven’t had any trouble with any reputable valve cover gasket manufacturer. Just make sure everything is clean, make sure the sealing surfaces are flat, and don’t over torque the bolts.

 

it's not the valve cover I'm worried about...it's the lower back bolt..minimal clearance between that and the A/C box. Very difficult to get a socket down there to loosen it up.

 

You won't be able to remove the box since you have an AC car. It contains the evaporator and disconnecting that will make you have to put a vacuum on the AC and recharge it. Use a 1/4 drive and wobble socket and you should be able to reach the back bolt.

 

Um...forgot to mention...A/C is inop and no compressor.

 

Dave - As Jesse suggested you don’t need to remove the evap box. You do need to upgrade your tool caddy with one or two swivel sockets to get access to that bolt and you’ll be fine. Lucky you the AC compressor is already a non-issue.

 

You could also try a flexible tool with a 1/4" drive socket if you have one.

 

I think I'll be able to figure something out. I see different thicknesses listed...3/32 and 11/64..does it matter? Also, to give more info on the leak, the oil is collecting on the oil filter and also onto the header. It's not that bad but when it collects on the header, it burns off and then I get a burnt oil smell in the passenger compartment. I've already changed the filter adapter gasket, so am on the right track with the valve cover gasket? I know the gaskets were replaced in 2017 at around 97,000 miles. I'm at 107,000 now, so could it be time for new gaskets?

 

I'd use the thicker gasket. For valve covers I've never had trouble with the cork or rubber gasket. I usually use RTV between the gasket and the valve cover.

Make sure it's not your oil filter housing gasket that's leaking. If it's the valve cover you should see oil on the head and the top of the headers. If it's the oil filter housing to block gasket you'll get oil on your oil filter and on the headers near the collectors.

 

See above ^^^ (my last post)

 

I’ve used cork with a very light RTV film on valve cover - never an issue - I like the cork gaskets. A oil filter bracket gasket should not need replacing at 10K miles if it was installed correctly. If you can’t find the leak drop in some UV dye, run the engine and visualize with black light.

 

Norm, what kind of sealant do you use, and is there a sequence for tightening the bolts? Also, it was the valve cover gaskets that were replaced 10,000 miles ago, not the adapter gasket. I did that about a year ago.

 

I had a tube of Permatex Black RTV laying about from my intake manifold gasket so I used some of that. Torque sequence I followed CSM recommendations. I’ll note that you should retorque after several cycles of driving and non-driving as bolts may loosen slightly from hot/cold swings in temp variations.

 

[QUOTE=Vintage

I’ll note that you should retorque after several cycles of driving and non-driving as bolts may loosen slightly from hot/cold swings in temp variations.[/QUOTE]

^^^^^^^^
You may want to try this before replacing the gaskets

 

As I was cleaning up from dinner tonight, that very thought crossed my mind, so that's what I'm gonna do, but will it throw off the "balance " of the sequencing, or do I need to check them all?

 

I just checked the CSM for torque specs, and noticed it didn't day anything about a specific "order" or tightening sequence. So based on that, your can start at one bolt and just go all the way around, is that right?

 

Dave - Follow a general/typical torque sequence much like you would wheel lug nuts - creating an “X” as you go around the wheel. You could go outside in or inside out then a final torque around the perimeter in either a CW or CCW direction. After several hot/cold (road speed/shutdown/rest) scenarios over several days, re-torque. You should be good-to-go.

EDIT: If you look in the CSM there is a diagram for torque sequence of the intake manifold. You can follow the same basic sequence pattern.

 

Sounds good Norm...thanks.

 

Norm, if I use any sort of attachment with a torque wrench, will that affect the amoumt of torque applied?

 

Well, yes to a slight degree as a torque wrench is designed to produce nominal torque values at 90 degree angles at a preselected distance (length). For the torque values you are applying to a ‘cover plate’, and non-integral non-critical non-moving component you’re fine remaining within select CSM torque values. Don’t over complicate this - it’s nothing more than a cover plate.

 

There is a formula or way to calculate the torque correction using an extension or swivel, but the torque spec on a small bolt like that is low enough a extension has a very slight effect.

 

Dave - You ask surprisingly good questions and I admire your ability to seek appropriate answers. Should you ever elect to evaluate torque values (in highly critical industries) you should examine some Coefficient Thermal Expansion values for select torque values - that’s when things become really ‘critical’.

 

I gotcha Norm...after all, it's not "Rocket" science, right? 🤣🤣🤣 Sorry...I couldn't help myself 🤣🤣🤣

 

I replaced a brand X engine's VC gaskets with cork and RTV on the cover side. Very carefully torqued down in steps. No leaks.

You may have to just use the box socket end of your combo wrench on that one bolt, but the idea behind the notched VC is to be able to service it with both the big block and the AC box and the booster there.

 

So what is the correct torque?...because I'm confused

 

I did some research and found out that its 7 ft lbs.
https://classicoldsmobile.com/forums...s-455-a-91482/

Why would the CSM show the other specs? Or am I missing something 🤔

 

I find a consistent, light though firm, even, final seating of the bolts while choked up on a 1/4 drive ratchet is just the right torque spec.

 

To remove the valve covers on some engines require removing A/C compressor brackets, alternator brackets, which use 5/16, 3/8 and 7/16 bolts. So instead of listing a torque spec for every single bolt, the manual just lists the torque for each bolt size.

Unless you have a inch pound torque wrench, the torque spec for the valve covers won’t mean much to you. Most torque wrenches will only go down to 20-25 lbs-ft, far above what valve covers need. 7lbs-ft is equal to 84 inch pounds, or about the same as “snug”.

 

I loosened all the bolts up today then re torqued them down. Followed a pattern of "middle to outside" and 'top to bottom " and it definitely helped. Took it out to run some errands and checked it when I got back. Still have some oil running down the filter, but not as bad as before, and the header was bone dry. I can live with that. Now, in regards to re torqing them again, does it depend on how often I drive it as to when I should check them, or is it just a set time frame?

 

Dave - It isn't a set time frame. Some of this depends on how hot the engine gets under what someone might consider normal driving conditions, which another person might not consider normal, type of driving, constant inner-city versus highway cruising, condition of 50 year old bolt threads (they do wear so you might consider new bolts if need be), etc. Re-torque them again in several days. I generally only re-torque them once/year - but, mine aren't leaking. Just keep an eye on them, retorque "at your leisure". Sounds like you're looking for something to do anyways.