Crankcase Breather Fix

oldskydog

Well Known Member
Supporting Member 10
Questions come up periodically concerning crankcase ventilation issues.
Here's how Chevy dealt with the problem on the 63 340hp engines and may have relevence to other years, as well.

Also, another mystery solved. I always wondered when and why the block castings were modified to change the oil filler area to the hole behind the timing cover. Note the last paragraph in the cover letter specifying the change over on engine number T 0316, or March 16, 1963.

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DonSSDD

Well Known Member
Supporting Member 2
Cecil, got any bulletins for carb "heat soak" issues?

Bob, maybe you should start a "Cecil's Bulletins" Sticky for all these posts.

Don
 

oldskydog

Well Known Member
Supporting Member 10
I don't think that was much of a problem before ethanol. I've read many posts on other forums about it and what they finally did to help the problem. I think the typcal solution was to use a phenolic spacer under the carb, block off the heat risers and make sure the fuel line from the pump doesn't make contact or come too close to the engine. Also upgrade to non ethanol fuel....avgas or whatever you can afford.
 

62impala409

 
Supporting Member 1
I have noticed that the guys running open element air cleaners and the 4" cowl induction fiberglass hoods have no hot start issues even when running with 10% ethanol fuel. My pal has a '66 Olds 442 with a 425 cube Mondello built motor, Holly Dominator carb, 4 " hood, pump gas. Fires after about one revolution even when hot. His other toy is a '74 Corvette that I installed a ZZ502 crate motor in. Same results. Big holly carb, 4" hood and 10% ethanol gas. I believe the cowl induction hood allows the engine heat to escape and/or the Holly carbs are less affected by volatile fuel. Leo
 

yellow wagon

Well Known Member
Supporting Member 2
The Holley carbs don't seem as affected by the garbage fuel Leo. The Holley on my old 327 would fire on the first crank also no matter the water temp on the hottest days. These Edelbrocks, crank crank crank crank then starts but needs a blip of the throttle every time
 

62impala409

 
Supporting Member 1
I have the 1/2" phenolic spacers and run pure gas as much as possible. I use the open air cleaner and should get rid of the hood pad. I do get quite a bit more crank time and the black smoke with the garbage gas.. Leo
 

oldskydog

Well Known Member
Supporting Member 10
One of the recurring themes is that after engine shutdown, the overheated cheap gas expands. overflows the bowl and drips into the intake causing the gas smell in your garage, washes the cylinder walls, mixes gas with your oil , empties the fuel bowl and makes for a vapor lock at worst or a hard start at best.
 

Randy

Well Known Member
Supporting Member 3
Questions come up periodically concerning crankcase ventilation issues.
Here's how Chevy dealt with the problem on the 63 340hp engines and may have relevence to other years, as well.

Cecil.......I love this info, but on mine it dosn't look like this picture at all. I have a 63 340 hp W, and the PCV valve sits in an opening on the intake, in the rear and to the right of the dist. I do not have the stock air filter. This is the way it's always been. I'll give you the intake # to see if this makes sence. The # is 3844465. currently it is hoked up to vacum port off of the carb. I have no info on any modifications to the W Thanks

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DonSSDD

Well Known Member
Supporting Member 2
One of the recurring themes is that after engine shutdown, the overheated cheap gas expands. overflows the bowl and drips into the intake causing the gas smell in your garage, washes the cylinder walls, mixes gas with your oil , empties the fuel bowl and makes for a vapor lock at worst or a hard start at best.

I did a google search, it came up with heat soak issues for all makes of carb and car, Chev, Ford, Dodge, Holley, Edelbrock, Carter, Rochester.

I had a 62 Chev car with 235 and a Rochester 2 barrel, it started hot or cold like it was fuel injected, 1/2 a turn on the starter.

On my 59 El Camino 283, I have a high torque starter, phenolic spacer, blocked the crossover, Pertronics, & use 91 octane (highest pump gas here) with no ethanol. Would changing the float level make any difference?

Don
 

DonSSDD

Well Known Member
Supporting Member 2
Randy, what you have is a 64/65 intake. The 63 340 HP has a hole on the back of the intake on the vertical surface on the driver side. It had a plug with a pipe coming out of it, then a rubber hose went to a PCV mounted with a right angle brass fitting on the base of the carb at the back.

Don
 

Randy

Well Known Member
Supporting Member 3
DSC01192 (Small).JPG Thanks for the info. I to checked it and came up with the same. But this is a little different, at the back of the intake there is some sort of plug but it's not on a pipe. (see drawing) The plug goes out verticle then turns horizontaly. As far ag I can tell, it is some sort of casting. On top of this is the PCV from there they use a rubber hose to the carb. I just need to know if this set up has been working or what should I do to make it work. Another thing, with all this vac. going to the PVC, is this starving the vac. for the power brakes?
 

Geary Trussell

Well Known Member
View attachment 20156 Thanks for the info. I to checked it and came up with the same. But this is a little different, at the back of the intake there is some sort of plug but it's not on a pipe. (see drawing) The plug goes out verticle then turns horizontaly. As far ag I can tell, it is some sort of casting. On top of this is the PCV from there they use a rubber hose to the carb. I just need to know if this set up has been working or what should I do to make it work. Another thing, with all this vac. going to the PVC, is this starving the vac. for the power brakes?

Am I missing something? Chevrolets service bulletin fix looks no different functionally than plumbing directly
from the intake opening to the air cleaner housing instead of splicing into the down draft tube. It would
seem to me it would be more effective not to splice into the draft tube.
 

scott hall

Well Known Member
Supporting Member 2
Don I have one of the early pertronics. Had in the 62 now in Dad's 60. It acts like it needs to charge up before you try to start. He turns the key on for like 20-30 seconds and then it seems to start with about 1 engine rotation. Yes it has 12 volts at all times. Just something we have found.
 

Randy

Well Known Member
Supporting Member 3
Am I missing something? Chevrolets service bulletin fix looks no different functionally than plumbing directly
from the intake opening to the air cleaner housing instead of splicing into the down draft tube. It would
seem to me it would be more effective not to splice into the draft tube.

On my set up, there is no down draft tube. It goes directly from the PVC to carb for vac. I'm just wondering if this set up is functional and am I not getting enough vac. for my power brakes. They seem to be working just fine, but could they even work better with more vac. I believe when I checked the vac. it was around 15-17lbs. or should I not worry about this?
 

Eric Kozmic

Well Known Member
Supporting Member 8
When I picked up my car 409/425, I was wondering why the vent hose coming off the oil filler tube had a screw blocking it off. It wasn't until I lifted up the air cleaner and noticed the "barb" on the bottom of the air cleaner was broken off. Thanks to Ralph from Ohio, he let me know there's supposed to be a hose going from the air cleaner to the oil filler tube.

I've subsequently also discovered a PCV valve on the back end of the rear carb (is this correct)? It appears as if I have 2 different ways of providing ventilation.

FYI - once I opened up the hose on the oil filler tube, I noticed I stopped having an oil leak on the timing cover.
 

DonSSDD

Well Known Member
Supporting Member 2
Don I have one of the early pertronics. Had in the 62 now in Dad's 60. It acts like it needs to charge up before you try to start. He turns the key on for like 20-30 seconds and then it seems to start with about 1 engine rotation. Yes it has 12 volts at all times. Just something we have found.

Thanks Scott, I'll check that out.

Don
 

DonSSDD

Well Known Member
Supporting Member 2
When I picked up my car 409/425, I was wondering why the vent hose coming off the oil filler tube had a screw blocking it off. It wasn't until I lifted up the air cleaner and noticed the "barb" on the bottom of the air cleaner was broken off. Thanks to Ralph from Ohio, he let me know there's supposed to be a hose going from the air cleaner to the oil filler tube.

I've subsequently also discovered a PCV valve on the back end of the rear carb (is this correct)? It appears as if I have 2 different ways of providing ventilation.

FYI - once I opened up the hose on the oil filler tube, I noticed I stopped having an oil leak on the timing cover.

Eric, the 63/64 vettes had a similar setup, the pcv on the back of the carb and tubes from the oil fill to the air cleaner, they are a bit different from each other (63-64), it seems GM was modifying this setup each year. Older GM's had the vented oil filler cap and no tube to the air cleaner, the cap gave the venting. In 63. they went to the sealed oil fill cap, so they needed the tubes for the venting.
 
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