Author Topic: Oil cap/breathers for vortec/centerbolt valve covers:  (Read 3793 times)

Offline Stewart G Griffin

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Oil cap/breathers for vortec/centerbolt valve covers:
« on: December 31, 2015, 10:19:21 PM »
What are some good sources of Oil caps and breathers for vortec/86' and up centerbolt valve covers?

Offline LTZ C20

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #1 on: December 31, 2015, 10:43:06 PM »
Factory or aftermarket?
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Offline Stewart G Griffin

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #2 on: January 01, 2016, 07:18:22 AM »
Doesn't matter--- whatever fits good.  Although i would prefer factory.

Offline enaberif

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #3 on: January 01, 2016, 10:48:19 AM »
I didn't think the centerbolt covers had provisions for a breather. They only had a spot for oil fill and for pcv valve?

Aftermarket may have a extra hole for a breather.

Offline blazer74

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #4 on: January 01, 2016, 11:07:22 AM »
These are centerbolt a I pulled off a 90's Chevy PU at a junk yard. One  side oil fill and breather hole.
Other side pvc hole.


Offline LTZ C20

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #5 on: January 01, 2016, 12:26:24 PM »
Blazer 74 got it. Those center bolt factory valve covers should fit any factory small block with provisions for center bolt covers. They have 3 holes. I had picked up a set also, was going to put them on my truck but I have aftermarket heads and they just wouldn't fit right so I ended getting something aftermarket. Those factory covers are really good and as long as you get good quality Felpro or GM gaskets and tighten them properly, they don't leak. You should be able to find multiple sets at any good sized junk yard with 1988+ trucks. Also, the factory black paint they come with is pretty industrial. It takes a lot to get them to really scratch or chip.

These are what I picked up from a local pick n pull.


These are what I ended up putting on instead.


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Offline enaberif

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #6 on: January 01, 2016, 12:27:13 PM »
Interesting. I've had a few centerbolt trucks and never noticed the breather.

Offline Stewart G Griffin

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #7 on: January 01, 2016, 08:00:17 PM »
i may try the salvage yard for an oil cap.   i am running the pcv filter from the air cleaner in the passenger side valve cover---this fits into the hole.   However, i discovered a little problem for the driver's side---i have nowhere to input to vapors from the engine.  Quadrajets of course, have an input on the front for this, but i'm running a 2G because both of my quadrajets are apparently fubar.  There's not really any place on the intake either.  i consider this a minor problem right now and will probably make a "draft tube" out of rubber hose for now.

2) At first i didn't want to use the centerbolt covers (the 4.3 came with centerbolts).  i wanted to run the conventional 55-85 4-bolt valve covers not to be traditional but to keep things simple and pure.

But i really like the centerbolts better and i think they seal better.   i also like ribbed belts and serpentine belts better over v-belts.  Again, before i didn't think i wanted to use them either.

It's still a small block, these are just improvements.

Offline LTZ C20

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #8 on: January 02, 2016, 01:37:13 PM »
Interesting. I've had a few centerbolt trucks and never noticed the breather.
The breather is just that little plastic tube with the rubber 90 elbow on the passenger side valve cover pic I posted. It normally plumbs into the air intake duct but on mine I shorted the tube up so it would align with breather on the stock air cleaner for my truck.
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Offline LTZ C20

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #9 on: January 02, 2016, 01:44:22 PM »
i may try the salvage yard for an oil cap.   i am running the pcv filter from the air cleaner in the passenger side valve cover---this fits into the hole.   However, i discovered a little problem for the driver's side---i have nowhere to input to vapors from the engine.  Quadrajets of course, have an input on the front for this, but i'm running a 2G because both of my quadrajets are apparently fubar.  There's not really any place on the intake either.  i consider this a minor problem right now and will probably make a "draft tube" out of rubber hose for now.

2) At first i didn't want to use the centerbolt covers (the 4.3 came with centerbolts).  i wanted to run the conventional 55-85 4-bolt valve covers not to be traditional but to keep things simple and pure.

But i really like the centerbolts better and i think they seal better.   i also like ribbed belts and serpentine belts better over v-belts.  Again, before i didn't think i wanted to use them either.

It's still a small block, these are just improvements.
Your right. Center bolts seal better because they spread the load and braces inside prevent over torqueing. Serpentine belts are better than 3 V-belts, that's why I put a factory serpentine on my truck. The improvements GM made to the small blocks from 88- late early 2000 when they stopped making them for production vehicles really did make them better. Like fuel injection, "vortec" heads and factory roller cams, which I also have in my truck. Waaaay better than flat tappet cams.
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Offline Stewart G Griffin

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #10 on: January 02, 2016, 09:48:58 PM »
i guess what i should have asked was, are the pcv valve, air cleaner breather to valve cover tube and oil cap the same size for the centerbolt covers as the original 55-86 valve covers?

The pcv valves, at least, appear to be the same size for both.

i have a little problem, which i'll describe in another post, but basically i can't easily run a pcv system---because i'm not using a quadrajet AND this 4.3 quadrajet manifold doesn't really have any other vacuum ports.  i DO want to eventually run a pcv, but for now since i need the truck running asap, i think i'm going to run two breathers.

Offline LTZ C20

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #11 on: January 02, 2016, 10:02:10 PM »
Pcv's them selves are the same size. The grommets are not. As for your issue of not being able to use a pcv, it only needs to be on manifold vacuum, so you can T it into anything else on manifold vacuum.
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Offline Stewart G Griffin

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #12 on: January 03, 2016, 08:04:47 AM »
Pcv's them selves are the same size. The grommets are not. As for your issue of not being able to use a pcv, it only needs to be on manifold vacuum, so you can T it into anything else on manifold vacuum.

There is a multi-port on this manifold that has the trans modulator connected to it.  i capped off the other openings. i don't remember what they are for, probably emissions stuff.  What i'm concerned about is if i put the pcv here and move the trans modulator to the carb, then cylinder #6 will be getting all the vapor?

If i move the vacuum for the power brake booster over to this multi-T and put pcv in on the back of the carb, in the large opening, then would this affect the trans-modulator?  In other words, if the trans modulator and power brake booster are sharing the same "T", would stepping on the brakes affect trans modulation?

Offline LTZ C20

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #13 on: January 03, 2016, 10:23:46 PM »
Trans modulator, brake booster, pcv valve and hvac vacuum supply are all on manifold vacuum. My brake booster and pcv are on a T to the same manifold vacuum port. My hvac supply is on a port on the back of the manifold, I don't have a trans modulator, I have a 4L60 trans.

I don't know if there is rule of thumb or guideline but I keep stuff that uses "alot" of vacuum together. For example, the size of the hose for booster and pcv are the same size on my truck so I put them on a T into a port that is the same size. The hvac supply doesn't use a lot of vacuum, so there is no need to be a large hose, so it on a smaller port. The distributor vacuum advance uses a small port also, so thus a small hose.

If I were in your situation, I would put the booster and pcv on 1 line and the trans and hvac supply on another. What ever cylinder a vacuum line is close to has no affect on its function.

Your truck may or may not have a hvac vacuum supply, I think the trucks that are heater only are cable driven systems, trucks with ac use engine vacuum.
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Offline LTZ C20

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Re: Oil cap/breathers for vortec/centerbolt valve covers:
« Reply #14 on: January 03, 2016, 10:24:05 PM »
Also, pictures would be a huge benefit here.
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