The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1947 - 1959 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 07-14-2021, 06:37 PM   #1
daveshilling
Senior Member
 
daveshilling's Avatar
 
Join Date: Jan 2013
Location: roseville
Posts: 822
Need Ideas for a Chevy 235 PCV and brake booster to coexist

Truck Geniuses, I have a challenge I'm trying to resolve without making it look like crap or buy too many expensive brass fittings.

I have a 3/8" steel line headed to the intake manifold to tap into the vacuum port that is commonly plugged.

I also have a vacuum hose coming from the brake booster that needs vacuum from that same location.

I have the ability to add an inverted flare fitting to the steel line. I'd really prefer not to drill another hole in the manifold....what approach would yall take to cleanly integrate both of these hoses into this one port?

The intake manifold vacuum port is 3/8" NPT. Any ideas?

So far I thought of an 3/8 NPT male to 3/8 npt female tee, then add a 3/8 NPT to 3/8 hose barb on one side, and a 3/8 NPT to 3/8 OD inverted flare adapter to the other... and thats a whole lotta fittings and crap.
daveshilling is offline   Reply With Quote
Old 07-14-2021, 09:17 PM   #2
1project2many
Registered User
 
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,149
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Could you use a fitting with multiple ports? GM often resolved these issues with specially made fittings. There are many versions.

https://www.google.com/search?q=gm+v...w=1024&bih=622


1project2many is offline   Reply With Quote
Old 07-14-2021, 10:43 PM   #3
Wrenchbender Ret
Registered User
 
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,190
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

you can't run the PCV hose off the vacuum outlet in the Intake manifold behind the carb. It feeds off the back cyls. & will cause a bad miss at idle & low speeds & cause a rough idle. The power brake unit only draws vacuum on desceleration so it won't cause this unless the booster dia. is leaking. There usually is an outlet at the bbase of the carb for the PCV system.
George
Wrenchbender Ret is offline   Reply With Quote
Old 07-14-2021, 11:20 PM   #4
Zenwren
Registered User
 
Join Date: Feb 2017
Location: S.E. Arizona
Posts: 52
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

I can't comment on what Wrenchbender says, but I have mine set up exactly how you are describing, I used this fitting... https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
with 3/8" line threaded into each side, then ran the hard lines to the PVC and booster. So far I've only yard driven the truck but it seems to work fine. You will need a 1/4" to 3/8" reducer/adapter bushing to fit into your manifold.
Zenwren is offline   Reply With Quote
Old 07-15-2021, 03:28 AM   #5
mr48chev
Registered User
 
mr48chev's Avatar
 
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,245
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

What Zenwren suggested should work.

I'd suggest putting a check valve in the line to the booster and you may end up needing a vacuum booster tank for the brakes
They are sold by Summit, Jegs and other speed outfits for cammed up cars with vacuum boosters on the brakes to store up vacuum. That would let you have reserve vacuum for the brakes.
Example https://www.summitracing.com/parts/s...+5ba29eacb7da9

I think some of the big luxury sedans in the 70s and maybe 80's with all the miles of vacuum hose and vacuum controlled stuff had reserve tanks but have no idea and those barges are few and far between in wrecking yards now.
__________________
Founding member of the too many projects, too little time and money club.

My ongoing truck projects:
48 Chev 3100 that will run a 292 Six.
71 GMC 2500 that is getting a Cad 500 transplant.
77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.
mr48chev is offline   Reply With Quote
Old 07-15-2021, 11:54 AM   #6
_Ogre
Registered User
 
_Ogre's Avatar
 
Join Date: Jan 2012
Location: Motown
Posts: 7,660
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by Wrenchbender Ret View Post
you can't run the PCV hose off the vacuum outlet in the Intake manifold behind the carb. It feeds off the back cyls. & will cause a bad miss at idle & low speeds & cause a rough idle. The power brake unit only draws vacuum on desceleration so it won't cause this unless the booster dia. is leaking. There usually is an outlet at the bbase of the carb for the PCV system.
George
this ogre agrees with wrenchbender. every pcv i've retrofitted went into the bottom of the air cleaner. the pcv valve is an engineered vacuum leak, it might be possible to adjust for it with a carb
__________________
cool, an ogre smiley Ogre's 58 Truk build

how to put your truck year and build thread into your signature
shop air compressor timer
_Ogre is offline   Reply With Quote
Old 07-15-2021, 12:58 PM   #7
Zenwren
Registered User
 
Join Date: Feb 2017
Location: S.E. Arizona
Posts: 52
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by _Ogre View Post
this ogre agrees with wrenchbender. every pcv i've retrofitted went into the bottom of the air cleaner. the pcv valve is an engineered vacuum leak, it might be possible to adjust for it with a carb
Are we both talking about a 235 and not an SBC? I know V8's draw vacuum off the rear cylinders but the vacuum port on a 235 is directly below the carb and an open log manifold? A PVC system will draw fresh air into the crankcase from the air cleaner housing but still needs a feed from the crankcase gasses into the intake (vacuum) stream going into the combustion chambers.

Zenwren is offline   Reply With Quote
Old 07-15-2021, 04:42 PM   #8
Wrenchbender Ret
Registered User
 
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,190
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by Zenwren View Post
Are we both talking about a 235 and not an SBC? I know V8's draw vacuum off the rear cylinders but the vacuum port on a 235 is directly below the carb and an open log manifold? A PVC system will draw fresh air into the crankcase from the air cleaner housing but still needs a feed from the crankcase gasses into the intake (vacuum) stream going into the combustion chambers.

Yes, I had v-8 on my mind. Sorry.
George
Wrenchbender Ret is offline   Reply With Quote
Old 07-16-2021, 12:04 AM   #9
mr48chev
Registered User
 
mr48chev's Avatar
 
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,245
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

This is my crusty 292. 500 bucks worth of polished aluminum in boxes and it is still grimy.



PVC line runs from back of valve cover to the intake. Red arrow.

The plug on the outside of the intake would be for the brake booster. I see no reason to not run them of one Tee though .

A breather with an actual filter in it will work fine at the filler hole of the cover. The line to the air cleaner on top of the carb just insures clean air going into the engine from the factory stand point.
__________________
Founding member of the too many projects, too little time and money club.

My ongoing truck projects:
48 Chev 3100 that will run a 292 Six.
71 GMC 2500 that is getting a Cad 500 transplant.
77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

Last edited by mr48chev; 07-16-2021 at 12:10 AM.
mr48chev is offline   Reply With Quote
Old 07-16-2021, 12:26 AM   #10
G&R's57GMC
Senior Member
 
G&R's57GMC's Avatar
 
Join Date: Aug 2010
Location: Shasta Lake, CA.
Posts: 1,619
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Dave don’t forget to install a vapor separator in the booster line high on the firewall.

If you don’t in time the oil/fuel vapors we do a number on the p/b booster diaphragm and you’ll have to replace it .
__________________
Glen & Jane's Rides
‘57 GMC NAPCO Long Bed V8 4 speed Bought 2008
7 other cars & trucks , 5 trailers
'56 Chevy Long Bed I6, 4 speed Bought 1990 Sold 8.22.2020
’56 GMC Suburban Pickup V8, 4 speed Hydramatic Bought 1996 Sold 10.11.2020
My Other Tinkerings http://67-72chevytrucks.com/vboard/s...75#post8967275
G&R's57GMC is offline   Reply With Quote
Old 07-16-2021, 08:10 AM   #11
1project2many
Registered User
 
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,149
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
The line to the air cleaner on top of the carb just insures clean air going into the engine from the factory stand point.
It also helps ensure the crankcase air is warm which reduces tendency for heavy hydrocarbons to settle and build deposits in the crankcase.

Another option might be to use a spacer under the carburetor and add as many fittings as necessary. A phenolic spacer would insulate the carb slightly and could help prevent or reduce unwanted fuel vaporization. Today's fuel definitely does not perform like gasoline in the '40s and '50s.
1project2many is offline   Reply With Quote
Old 07-16-2021, 11:08 AM   #12
mr48chev
Registered User
 
mr48chev's Avatar
 
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,245
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by 1project2many View Post
It also helps ensure the crankcase air is warm which reduces tendency for heavy hydrocarbons to settle and build deposits in the crankcase.


Another option might be to use a spacer under the carburetor and add as many fittings as necessary. A phenolic spacer would insulate the carb slightly and could help prevent or reduce unwanted fuel vaporization. Today's fuel definitely does not perform like gasoline in the '40s and '50s.
I never heard that one in all the time I have worked on cars including all the years I did it for a living. The only time there is warm air at the air cleaner is when the heat tube valve is letting heat in thought the tube that goes to the exhaust manifold but as soon as the temp is up to normal that closes so only cool air goes though the air cleaner.

Ford did that for years on their V8 engines using an aluminum plate with passages for what ever setup they were needing vacuum for.
__________________
Founding member of the too many projects, too little time and money club.

My ongoing truck projects:
48 Chev 3100 that will run a 292 Six.
71 GMC 2500 that is getting a Cad 500 transplant.
77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.
mr48chev is offline   Reply With Quote
Old 07-16-2021, 02:06 PM   #13
1project2many
Registered User
 
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,149
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
I never heard that one in all the time I have worked on cars including all the years I did it for a living.
I know. We never used to think about stuff like that. Hell, in the '70s if the engine made 200k miles we figured it was a miracle. These days 200k miles is about the time a vehicle goes to the third owner.

Most of the thermac systems try to maintain a minimum of 90 degrees for emissions. But getting warm air into the crankcase sooner helps get the engine to temp quicker and helps keep water and blowby from condensing on the engine walls. And most folks are installing the PCV to "clean up" the inside of the engine, so why not go the extra step? It isn't going to make an engine run a million miles. IMO it's more like taking time to make sure the electrical connections are all clean if you're already replacing wires.
1project2many is offline   Reply With Quote
Old 07-16-2021, 03:01 PM   #14
geezer#99
Registered User
 
geezer#99's Avatar
 
Join Date: Aug 2009
Location: Bowser
Posts: 13,494
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

I’m a bunch confused here.
Thermac controls inlet air temperature into the intake and cylinders.
Not into the crankcase.
geezer#99 is offline   Reply With Quote
Old 07-16-2021, 06:50 PM   #15
1project2many
Registered User
 
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,149
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
I’m a bunch confused here.
Thermac controls inlet air temperature into the intake and cylinders.
Not into the crankcase.
Well, it does both on systems from maybe '79 and up. Closed PCV system connects to the manifold or carb base at one end and the air cleaner at the other. Under most conditions the carb end makes vacuum and draws air from the air cleaner into the valve cover, through the engine, then into the carb base. In this system air temp in the air cleaner is warmed through thermac so air going into the PCV is thermac air.

It's up to the builder of course and ultimately it likely makes only a small difference. My '36 Plymouth hasn't gotten a PCV even though Mopar offered a "Vacuumatic Crankcase Ventilator" modification for those engines. I keep thinking about it and it's likely I'm going to do it eventually. The garbage the builds up in that block is incredible, even running detergent oils.


For closed type PCV look at the bottom half of this drawing...


Last edited by 1project2many; 07-16-2021 at 06:58 PM.
1project2many is offline   Reply With Quote
Old 07-16-2021, 07:35 PM   #16
geezer#99
Registered User
 
geezer#99's Avatar
 
Join Date: Aug 2009
Location: Bowser
Posts: 13,494
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

I see what you’re getting at but likely that warm air won’t make any difference in the crankcase temperature. Minuscule amount of warmish air mixing with a huge volume of air in the crankcase likely doesn’t amount to much.
Likely better heating for the crankcase could be had from an oil pan heater or water jacket block heater which helps on initial start up and run.
geezer#99 is offline   Reply With Quote
Old 07-16-2021, 08:28 PM   #17
1project2many
Registered User
 
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,149
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by geezer#99 View Post
I see what you’re getting at but likely that warm air won’t make any difference in the crankcase temperature. Minuscule amount of warmish air mixing with a huge volume of air in the crankcase likely doesn’t amount to much.
Likely better heating for the crankcase could be had from an oil pan heater or water jacket block heater which helps on initial start up and run.
Agreed it's not much. But if you're going through the effort to install one, why not set it up for max benefit. The flip side is that if you happen to go on the highway with oem gears any blowby will go into the air cleaner instead of out the valve cover breather.

I just wanted point out something that most folks don't think about...
1project2many is offline   Reply With Quote
Old 07-20-2021, 12:29 AM   #18
daveshilling
Senior Member
 
daveshilling's Avatar
 
Join Date: Jan 2013
Location: roseville
Posts: 822
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by 1project2many View Post
Could you use a fitting with multiple ports? GM often resolved these issues with specially made fittings. There are many versions.
I could potentially use something like that if I were doing hose on both sides. Currently I have a hard line for the PCV, although I could switch to all rubber hose if I had to.
daveshilling is offline   Reply With Quote
Old 07-20-2021, 12:31 AM   #19
daveshilling
Senior Member
 
daveshilling's Avatar
 
Join Date: Jan 2013
Location: roseville
Posts: 822
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by Zenwren View Post
I can't comment on what Wrenchbender says, but I have mine set up exactly how you are describing, I used this fitting... https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
with 3/8" line threaded into each side, then ran the hard lines to the PVC and booster. So far I've only yard driven the truck but it seems to work fine. You will need a 1/4" to 3/8" reducer/adapter bushing to fit into your manifold.
Oh, I didn't think about running a hard line to the booster.. that would be pretty cool. I assume you were able to flare the line somehow and add rubber hose to meet up with the booster end of things. Good to know you have the configuration I'm thinking about and its working!
daveshilling is offline   Reply With Quote
Old 07-20-2021, 12:37 AM   #20
daveshilling
Senior Member
 
daveshilling's Avatar
 
Join Date: Jan 2013
Location: roseville
Posts: 822
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by G&R's57GMC View Post
Dave don’t forget to install a vapor separator in the booster line high on the firewall.

If you don’t in time the oil/fuel vapors we do a number on the p/b booster diaphragm and you’ll have to replace it .
Yep, I'll be doing that one again for sure.
daveshilling is offline   Reply With Quote
Old 07-20-2021, 12:53 AM   #21
daveshilling
Senior Member
 
daveshilling's Avatar
 
Join Date: Jan 2013
Location: roseville
Posts: 822
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by _Ogre View Post
this ogre agrees with wrenchbender. every pcv i've retrofitted went into the bottom of the air cleaner. the pcv valve is an engineered vacuum leak, it might be possible to adjust for it with a carb
This is replacing the road draft tube in the 235, so by nature its not a valve cover=> air cleaner type. That being said, feeding it into the air cleaner could reduce the need to lean out the fuel potentially.



Quote:
Another option might be to use a spacer under the carburetor and add as many fittings as necessary.
A spacer is actually GM standard on the 235's. I couldn't find one that had a vacuum port in it. That's a smart idea but a custom item that may be out of my budget for this particular truck.



Here is a link to the PCV conversion I'm doing that replaces the road draft tube.
daveshilling is offline   Reply With Quote
Old 07-20-2021, 03:38 PM   #22
daveshilling
Senior Member
 
daveshilling's Avatar
 
Join Date: Jan 2013
Location: roseville
Posts: 822
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Well I had the bright idea of contacting the guy who created this how-to and he affirmed what ZenWren said, that compiling together the brass fittings is the most straightforward option, so I'll likely take that approach and I'll post photos on this thread when I'm done for search purposes.
daveshilling is offline   Reply With Quote
Old 07-22-2021, 10:03 PM   #23
Divine 59
Registered User
 
Join Date: Sep 2011
Location: Austin, TX
Posts: 306
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

This is a good way to eliminate the road draft tube.

http://devestechnet.com/Home/PCVInstall

Many good tech articles and options for the Chevy and GMC sixes.
__________________
My Build Thread http://s95.photobucket.com/user/drop...?sort=3&page=1
Divine 59 is offline   Reply With Quote
Old 07-22-2021, 11:06 PM   #24
mr48chev
Registered User
 
mr48chev's Avatar
 
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,245
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Now that my brain kicked into gear, I have changed a couple of stock valve cover 235's to PCV by cutting off the road draft tube an inch or so from the tube it runs off and putting a rubber plug for a PCV valve in the cut off end and sticking the PCV valve in it.

I think that we did it on one we built in the school shop that one of my students who did a lot of work on it now owns.
__________________
Founding member of the too many projects, too little time and money club.

My ongoing truck projects:
48 Chev 3100 that will run a 292 Six.
71 GMC 2500 that is getting a Cad 500 transplant.
77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.
mr48chev is offline   Reply With Quote
Old 07-23-2021, 12:41 AM   #25
daveshilling
Senior Member
 
daveshilling's Avatar
 
Join Date: Jan 2013
Location: roseville
Posts: 822
Re: Need Ideas for a Chevy 235 PCV and brake booster to coexist

Quote:
Originally Posted by mr48chev View Post
Now that my brain kicked into gear, I have changed a couple of stock valve cover 235's to PCV by cutting off the road draft tube an inch or so from the tube it runs off and putting a rubber plug for a PCV valve in the cut off end and sticking the PCV valve in it.

I think that we did it on one we built in the school shop that one of my students who did a lot of work on it now owns.
I went all the way and put the PCV directly in its place
Attached Images
 
daveshilling is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 05:34 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com