Hello all,
im sure this has been covered in the past but i wanted to make sure I have the latest/best info.
I am blessed to have just brought home a one owner 1983 Z28 with 6800 miles. Basically like new in every way.
Only issue is it has weeping valve covers at the rear and although it burns off and doesn’t drip, the smell consumes the cabin. I want to keep the car fully stock. I know this seems to be a routine problem. What gives me the best chances to resolve the leaks? Is there an aftermarket cover that would retain all the mounting properties/connections as stock but would seal better? If not, should I ensure the stock covers are not warped and go with the best gasket available? What is the best current gasket?
Are there any specific install tips/steps that would help ensure a seal?
I am competent to do the repair but am hoping to only do it once.

 

Use your stock covers. Look at them closely: you'll notice (I can see these things through your fenders) that the bolts have been overtightened, and the flanges where they seal to the head are now punched in around the bolt holes and the reverse (upwards) in the middle, such that they stand NO CHANCE WHATSOEVER of ever sealing. Take them off, clean them up especially where the gasket goes, and turn them upside down. With your BFH, gently and lovingly massage the flange into the correct shape (flat), plus a little bit more, such that when you turn them over right side up, the bolt holes are about 1/8" to ¼" above the rest of the flange. You may need to massage the center of them between the bolt holes downwards, towards the head, as well, depending on how enthusiastically they were overtightened (sorry, I can't see them THAT well ). The goal is, to get them to where the entire flange will be pressed HARD against the head before the bolt holes even begin to touch the gasket.

Get some load spreaders https://www.summitracing.com/parts/fel-es72676 and longer screws than the factory ones. ¾" long is about right to take up the extra thickness of the load spreaders. I usually use stainless Phillips head ones from the hardware store: with the Phillips head, it's all butt IMPOSSIBLE to EVER overtighten them unless you use a drill or something. Use these gaskets https://www.summitracing.com/parts/fel-1628. DO NOT use ANY gaskets from ANY mfr that have cork in them: it's 2025, we have better materials to use to seal up hot engines with nowadays, than efffffing TREE BARK (which is what cork is). Note carefully that the gaskets are NOT symmetrical; that is, they have a definite intake side and exhaust side, just as the VCs do (the VCs are NOT symmetrical either); the exh side is the one with the extra reinforcing flange all the way down, butt the intake side is almost flat in the middle, to avoid interference with the manifold. Also, if you happen to get ones that have 2 sets of holes on one side, the extra pair of holes are for 55 - 59 heads whose VC screw holes aren't directly across from each other, and the extra holes go on the intake side. Schmeeeeer abuncha gorilla snot on the VC and one side of the gasket; wait about a half hour for it to set up; install the gaskets to the VCs, paying careful attention to put the wide flat side of the gasket on the exh side of the VC. Schmeeeer grease on the surface of the gasket that will mate to the head, and install. The PCV valve belongs in the driver's side VC toward the front, and the PCV makeup air fitting belongs in the pass side VC toward the rear. RESIST the temptation to put the oil fill cap where you "like" or "want" it: put it together RIGHT, like I just described. Tighten the screws ONLY until the load spreader pushes the VC down at the screw to where the VC flange is flat and parallel to the head surface: DO NOT continue to tighten until the screws punch out the hole areas again like they are now.

 

I use Fel-Pro rubber gaskets. No leaks...

 

Thanks very much for sharing all the info!
just so I am clear:
-gorilla snot-is that the 3M weatherstrip adhesive? Thats all I’ve heard called that.
-GS between valve cover and gasket and then only grease between gasket and head?

 

Yes. Either the traditional yellow or the black variety works the same.

Yes. That way you can get the VC back off without destroying anything.

 

thank you for clarifying.
last question. Have you ever replaced the bolts with studs? Was thinking this might simplify things for me but wanted to see if there are any downsides to using them.
thanks!

 

No. Never tried that. Never seemed to be necessary. Some engines in other kinds of cars are made that way though, and it always made taking glued-down VCs off a PITA.

I should also have mentioned, it helps to bend the load spreaders up in the center a little bit, such that the screw holes are above the VC before tightening; that way when you tighten the screws, the spreaders put pressure on their ends long before the center reaches the VC. Makes the pressure that much more even all the way across. Can't go too far with that though; the screws can only be just so long before they bottom out, so the total "travel" in all the parts - spreaders, VCs, and gaskets - can't be more than that.

And I would also note that the standard Phillips bit size for ¼" screws is #3, NOT #2 like drywall screws and such. Gotta use the right bit or you'll strip em.

 

I use 1/4"-20 flange bolts, but instead of a 7/16" head, they are a 3/8" head...

 

Thanks all. I am considering the studs. If I do that I guess I don’t really need to glue the gaskets to the VC’s before installing or do you still recommend that for sealing purposes?

 

A typical early 80s small block came with the factory Corvair style load spreaders and many had OE studs in place of the normal bolts. Then again most of the SBC engines I have been into from that time period were truck, marine and industrial engines that were configured to run under heavy load for long periods of time. This GM parts diagram is for an ~82-86 305 or 350 G-van application, my 10/82 van had corvair spreaders and studs. Our 1980 C10 350 2bbl built in 79 had the same corvair load spreaders and wire loom brackets but used bolts, real PITA to get everything lined back up when re-installing the valve covers. My 1985 Monte Carlo SS 305 HO had flat not Corvair style factory spreaders and valve cover studs. I prefer studs to bolts. Makes installing the valve covers much easier. You can still buy the thick, flat OE spreaders vs the cheesy thin aftermarket ones or Corvair style that has stepped ends. 14082321 is the GM part number for the flat load spreaders which were a better design than the Corvair spreaders as they seem to distribute the clamping force more evenly and they are about $5-6 ea.

 

Yes you definitely need to glue the gaskets to the VCs. They won't necessarily hold their shape otherwise.

Factory load spreaders are CRAP. They are little thin things, flat, only about 1" long, and narrow at the ends.

The FelPro ones are AT LEAST twice as thick and are around 4" long, have the ends bent into a "foot" shape, and are the full width of the flange all the way out.

Compare the garbage in van man's GM diagram (callout #12) with the ones I linked you to.



If you go with studs, use nuts with a flange.

 

Those are the Corvair spreaders that were factory on my 1980 C10 and 1983 G20 van. Search the part number I gave. The factory spreaders in that diagram are nearly twice as thick as those Corvair style. They have a long flat contact patch not the 2 little humps on the ends.

 

This is the factory spreader number I gave. It was the last and best factory style spreader. GM replaced the earlier 80s Corvair style spreaders with these. These are like a 1/4" thick and 4" wide. GM 14082321. These are beveled along the length, when you install them, they flatten out along the whole length. My 1985 Monte Carlo SS L69 had these on it.

 

The ones I posted are FelPro ES-72676.

The archaic part you are posting lacks the "foot" at the ends of the bars. The FelPro piece is about 40 - 50% wider and around ½" longer at each end. Thickness is about the same. The FP is also wider around the bolt hole, where it's weeeeeeeekest to begin with. Just, ALTOGETHER SUPERIOR to the GM piece in every way.

Once again: https://www.summitracing.com/parts/fel-es72676

Or perhaps one might prefer: https://www.autozone.com/external-en...676/580534_0_0

 

Those are the same Corvair spreader GM put on the earlier engines. They are thinner than the part number I gave and the number I gave has a much longer and wider contact pattern with the valve cover. The little necked up feet at the end are worthless compared to the whole bar being beveled as the GM number I gave. The GM number I gave is the newest GM design and best working spreader ever built for a perimeter bolt SBC. The number I gave is practically as wide as the flange.

 

The GM number I gave is actually thicker overall and thicker around the mounting bolt holes than the Corvair style Felpros you posted. They actually call them out in some applications as a spring bar. The center sits higher than the ends when they are oriented correctly and they flatten out when you put pressure on them. GM used these on engines that had factory studs only. GM stamped both sides as well with the orientation. I have probably used these on 20 small blocks now and they work better than any others I have used. I have used them on a couple of Pontiac V8s as well.

 

The Fel-Pro load spreaders may be an improvement, but my factory spreaders work great. 'Just need a good gasket, and don't over-tighten the bolts.
As Sofa said; glue the gasket to the valve cover. You can use weathersteip adhesive ("gorilla snot"), or RTV...

 

I personally do not glue valve cover gaskets in place. Studs allow them to slide on followed by the covers.

 

Thank you all for all the replies and info!