66 SBC 327 Road draft breathing system - Impala Tech
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post #1 of 9 (permalink) Old 09-07-2020, 01:30 PM Thread Starter
 
 
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66 SBC 327 Road draft breathing system

Hello everyone, I recently acquired a 66 sbc 327 block from a friend I noticed it has the PCV/road draft breathing system at the back of the block. I am using a good Edelbrock 600 cfm that I've had and I'm wondering how does this all work where does it connect to? also should I should use an aftermarket intake also valve covers? sorry this is my first 327 I am using 😁 I've always had SBC 350's and would like to try the 327 for a change any help would be much appreciated Thank You!
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post #2 of 9 (permalink) Old 09-07-2020, 02:30 PM
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If you buy an aftermarket intake it will have to have either a hole already drilled for your oil fill tube or a boss cast in the front that can be drilled to accept an oil fill tube. hat oil fill tube is the air inlet for your PCV that is drawing vacuum from the back of the carb's base plate or an elbow in the intake manifold. This half inch vacuum line also feeds your power brake booster if you have such as an option on your car.

Compare this Edelbrock manifold for your year car:

https://www.lmperformance.com/113143...iABEgJBy_D_BwE

With the same manifold for a newer car that has valve covers with the oil fill and PCV gromet in the valve cover:

https://www.edelbrock.com/performer-...fold-2701.html

Valve covers need to be old school (no breathers in the valve cover) either sheet metal or cast aluminum to retain the Positive Crankcase Ventilation system. Here is a castr aluminum version of what you have now:

https://yourcovers.com/valve_cover_i...06_cast_lg.jpg

They are also available with a script saying Corvette in cast aluminum.

Big Dave
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post #3 of 9 (permalink) Old 09-07-2020, 11:12 PM
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I am no expert on 66, but Big Dave's description might vary.
I do know in 64 they had two systems, the earlier one that Big Dave described "standard". In California, an early effort at emissions control law resulted in the "closed positive ventilation" type.



Googling some 66 327 pictures, I see a both the closed type with a cap and the breather on the fill tube. I would suggest referring to the shop manual.

1964 Impala 4 door sedan

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post #4 of 9 (permalink) Old 09-07-2020, 11:22 PM
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my '67 283 came with a vented filler cap. I was going to install an aluminum Edelbrock Performer and drill out the blank for filler tube but local machine shop refused because (as they pointed out) the steel filler tube would get loose in the aluminum hole and probably rattle loose. Instead, I went to the jyard and found an old steel valve cover stamped with "Chevrolet' script, precisely measured a hole for the PCV breather valve between the rocker arms, cut and bent back the resulting tabs, then installed the breather valve. Perfect fit.
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post #5 of 9 (permalink) Old 09-08-2020, 09:35 AM
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Quote:
Originally Posted by 65_&_67_Impala View Post
my '67 283 came with a vented filler cap. I was going to install an aluminum Edelbrock Performer and drill out the blank for filler tube but local machine shop refused because (as they pointed out) the steel filler tube would get loose in the aluminum hole and probably rattle loose. Instead, I went to the jyard and found an old steel valve cover stamped with "Chevrolet' script, precisely measured a hole for the PCV breather valve between the rocker arms, cut and bent back the resulting tabs, then installed the breather valve. Perfect fit.

There's no reason the tube would 'get loose in the aluminum hole and probably rattle loose' BECAUSE the manifold is aluminum.

It may if installed wrong, or the original tube was damaged.

Edelbrock sells a 4803 tube. Attached are the install instructions. For OEM 'black' tube:

https://show-cars.com/product/2050

GM used the aluminum intakes on the small block in the Z28 (a 302), and some C2 327 Corvettes.

You did what you did, but you did not have to. There is NO inherent incompatibility.

NOT being critical. Just informative.

Pete
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post #6 of 9 (permalink) Old 09-08-2020, 10:29 AM
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The tube is a press fit (interference as the tube is bigger than the hole). If the tube doesn't fit then the tube has shrunk from being hammered in at an angle once too often or the manifold has become enlarged by the tube forcing the hole bigger (highly unlikely. Every loose fitting oil fill tube I have ever seen had a taper at the bottom where the ends were bent in by installing it off plumb. You could go to a muffler shop and have them enlarge the tube on a pipe expander but getting the size right would be difficult at best. Tubes are cheap and that is the way I would fix the situation.

The vented versus non vented caps was a California thing as that reflected early smog rules instituted by California that consumed about twelve percent of all car sales back in the sixties. GM couldn't afford to loose the California market so they, and the rest of the country knuckled under to the power industry of California that didn't want to pay to clear up the real cause of pollution in the valley, by installing smog devices on cars.

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post #7 of 9 (permalink) Old 09-08-2020, 11:30 AM
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japete, this was back in 1994. the reason it would rattle around in the hole (as explained to me) because as the metal warmed up and cooled down, different rates of expansion for steel tube vs aluminum intake would cause a potential looseness issue (their words not mine).
possibly this would never have been an issue, but WTH did I know back then? the only thing I did recognize was that if they were correct, there's no going back from drilling a hole.

and after much reflection, my solution may not have been the best idea either because with hot oil splashing around and nothing to protect it from being splashed directly on the installed rubber ring holding the breather on.....
we'll never know because of a series of life's circumstances, that engine block is still sitting in my garage 25 years later. with only 30 minutes hour of run time.

as for being critical, it takes a hll of a lot more than that to offend me. you're gonna have to work a lot harder to offend me if you were trying!

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post #8 of 9 (permalink) Old 09-08-2020, 02:33 PM
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Quote:
Originally Posted by 65_&_67_Impala View Post
japete, this was back in 1994. the reason it would rattle around in the hole (as explained to me) because as the metal warmed up and cooled down, different rates of expansion for steel tube vs aluminum intake would cause a potential looseness issue (their words not mine).
possibly this would never have been an issue, but WTH did I know back then? the only thing I did recognize was that if they were correct, there's no going back from drilling a hole.

and after much reflection, my solution may not have been the best idea either because with hot oil splashing around and nothing to protect it from being splashed directly on the installed rubber ring holding the breather on.....
we'll never know because of a series of life's circumstances, that engine block is still sitting in my garage 25 years later. with only 30 minutes hour of run time.

as for being critical, it takes a hll of a lot more than that to offend me. you're gonna have to work a lot harder to offend me if you were trying!



To steal a line from one of my favorite Lyle Lovett songs:

"...penguins are so sensitive..."

I did NOT mistake you for a penguin

BUT, you were fed a bunch of donkey doo back in '94. I say that to inform other readers who may not know the reality.

To steal another line, this time from Jerry Jeff Walker:

"...the man in the big hat is buying..."

I'd wear the 'big hat' and salute you if given the opportunity.

Pete

Last edited by japete92; 09-09-2020 at 08:57 AM.
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post #9 of 9 (permalink) Old 09-08-2020, 11:44 PM
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Perfect example would be the L79's that GM made with aluminum intakes and steel oil filler tubes installed from the factory. Just try getting one of those suckers out, it's sometimes not a fun job!
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