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Jul 21st, 2025 | | | | Joined: Sep 2009 Posts: 433 'Bolter | | 'Bolter Joined: Sep 2009 Posts: 433 | What is the purposes of this this hole ? It is to the left of the fuel pump and is about 3/16 in. in diameter. After I got the engine running oil leaked out of it. The hole has no visible threads. 1960 235 truck engine.
1954 Chevy 3104 3 Window Hydra-Matic in my family for over 60 Years
Once in a while you get shown the light in the strangest of places if you look at it right... "Scarlet Begonias" Grateful Dead 1974
| | | | | Joined: Aug 2012 Posts: 1,214 Shop Shark | | Shop Shark Joined: Aug 2012 Posts: 1,214 | It looks like one of the two screw holes that secures the road tubes oil deflector plate. If so that means the plate wasn't installed by whomever worked or rebuilt the bottom end.
The purpose of the plate is to deflect the oil being splashed around via the rotating mass in the engine from directly entering and then exiting out the road draft tube.
It's an easy to overlook minor part on a rebuild, unfortunately I know.... | | | | | Joined: Sep 2009 Posts: 433 'Bolter | | 'Bolter Joined: Sep 2009 Posts: 433 | It looks like one of the two screw holes that secures the road tubes oil deflector plate. If so that means the plate wasn't installed by whomever worked or rebuilt the bottom end.
The purpose of the plate is to deflect the oil being splashed around via the rotating mass in the engine from directly entering and then exiting out the road draft tube.
It's an easy to overlook minor part on a rebuild, unfortunately I know.... The down draft tube secures at a different place, lower and towards the distributor see pic. It is plugged with the brass colored bolt in the pic. Michael...
1954 Chevy 3104 3 Window Hydra-Matic in my family for over 60 Years
Once in a while you get shown the light in the strangest of places if you look at it right... "Scarlet Begonias" Grateful Dead 1974
| | | | | Joined: Sep 2009 Posts: 123 'Bolter | | 'Bolter Joined: Sep 2009 Posts: 123 | | | | | | Joined: Apr 2007 Posts: 1,002 'Bolter | | 'Bolter Joined: Apr 2007 Posts: 1,002 | Volfandt is correct, although his terminology may be a bit confusing. That hole is for a screw that attaches a baffle that deflects oil as he mentioned so that oil does not travel up the draft tube. It has nothing to do with attaching the draft tube itself. The hole is not threaded because the screw threads into the baffle itself. You need that baffle and I believe it can be attached after you drop the oil pan. | | | | | Joined: Aug 2012 Posts: 1,214 Shop Shark | | Shop Shark Joined: Aug 2012 Posts: 1,214 | Yes, it can be installed by dropping the pan. BTDT... Don't forget to apply some locktite to the screws and the copper washers on the screws outside the block.
| | | | | Joined: Sep 2009 Posts: 433 'Bolter | | 'Bolter Joined: Sep 2009 Posts: 433 | My engine did not have a baffle when I sent it of to get it rebuilt. It might had one from the factory but that was long ago...
1954 Chevy 3104 3 Window Hydra-Matic in my family for over 60 Years
Once in a while you get shown the light in the strangest of places if you look at it right... "Scarlet Begonias" Grateful Dead 1974
| | | | | Joined: Sep 2013 Posts: 1,288 'Bolter | | 'Bolter Joined: Sep 2013 Posts: 1,288 | I should really offer many of my suggestions with this disclaimer: "proceed at your own risk". That said if I had the problem discussed above I'd consider using this approach. Good Luck RonR
1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1964 CJ5
| | | | | Joined: Aug 2012 Posts: 1,214 Shop Shark | | Shop Shark Joined: Aug 2012 Posts: 1,214 | Tain't no "might" to it LOL.....
The road vent tube has baffles and mesh to help keep the oil in and evacuate gases out. Sometimes it gets so clogged the by products of ignition and blowby find alternative methods of exiting the engine. Those sources include seals and slightly ill fitting gaskets. If you see excessive oil leaks out of those places it might be a good indicator to remove and clean out the draft tube. It'll probably be accumilating alot of oil by products sans that deflector plate.
Dave | | | | | Joined: Mar 2010 Posts: 10,059 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,059 | Since this engine has lived many miles without a baffle, it is very likely that the road draft tube is so full of baked on oil, that it no longer functions as designed. And since it is full of this baked on oil, it is longer able to suck any more oil out of the crankcase through the road draft tube even though there is no baffle in place.
So now what to do?
You need a way to evacuate harmful fumes from the crankcase to prevent destroying your engine way before its time.
I will bet you do not have a functional road draft tube. It can be fixed.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Sep 2009 Posts: 433 'Bolter | | 'Bolter Joined: Sep 2009 Posts: 433 | I checked the road draft tube while the engine was idling and felt warm air inside the bottom of the tube. This engine is a fresh rebuilt engine. I cleaned the road draft tube a few years ago. It was very dirty then. It looked pretty good before I put it on. Will check it again.
1954 Chevy 3104 3 Window Hydra-Matic in my family for over 60 Years
Once in a while you get shown the light in the strangest of places if you look at it right... "Scarlet Begonias" Grateful Dead 1974
| | | | | Joined: Jun 2009 Posts: 231 'Bolter | | 'Bolter Joined: Jun 2009 Posts: 231 | I'm the guy that asked this question earlier (someone posted the link). This is another long thread so I'm sorry if you already figured it out, but yes, It was indeed for the screw that held the deflector plate inside the block. I dropped the pan and installed it.
'53 Chevy 3604 Five Window Cab ('56 235)
| | | | | Joined: Sep 2009 Posts: 433 'Bolter | | 'Bolter Joined: Sep 2009 Posts: 433 | I'm the guy that asked this question earlier (someone posted the link). This is another long thread so I'm sorry if you already figured it out, but yes, It was indeed for the screw that held the deflector plate inside the block. I dropped the pan and installed it. Thanks Paul, I did several combinations of searches to find an answer to this question but came up with no results. This engine ran for many years with out a baffle probably will be ok for now.
1954 Chevy 3104 3 Window Hydra-Matic in my family for over 60 Years
Once in a while you get shown the light in the strangest of places if you look at it right... "Scarlet Begonias" Grateful Dead 1974
| | | | | Joined: Jun 2009 Posts: 231 'Bolter | | 'Bolter Joined: Jun 2009 Posts: 231 | If you need any photos of what it looks like, I'm sure I've got one somewhere. I only put mine in because i found it after putting it back together and figured I'd better do it because i didn't know what would happen if i didn't. I will tell you dropping that pan and getting it back together with that 4 piece gasket was a huge pain in my a**. I wont do that again unless absolutely necessary.
'53 Chevy 3604 Five Window Cab ('56 235)
| | | | | Joined: Sep 2009 Posts: 433 'Bolter | | 'Bolter Joined: Sep 2009 Posts: 433 | If you need any photos of what it looks like, I'm sure I've got one somewhere. I only put mine in because i found it after putting it back together and figured I'd better do it because i didn't know what would happen if i didn't. I will tell you dropping that pan and getting it back together with that 4 piece gasket was a huge pain in my a**. I wont do that again unless absolutely necessary. That is why I not jumping right on fixing it and more importantly I do not want to void any warranty the shop has from rebuilding the engine. I will let them know there should have been a baffle there but not their fault because there was not one in the engine when they got it.
1954 Chevy 3104 3 Window Hydra-Matic in my family for over 60 Years
Once in a while you get shown the light in the strangest of places if you look at it right... "Scarlet Begonias" Grateful Dead 1974
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