Guys Looking for some guidance here building a french block Flathead for a 34 ford Hot rod Read a lot of stuff on blocking off the Draft tube area of the Pan and not using the draft tube at all. There is one vent in the rear of Manifold for putting oil in engine and it has a breather style cap. Some say you can just block off the vent of the oil pan and do nothing else . Some say if you do that you need to put a Offy style Breather on the left forward side of pan . Some say you need a elaborate PVC system . and another talks about a channel you need to make in the oil pan and Block pan surface so oil that gets up there can drain back . So Can any one shed some light on this for me PLEASE. I sure would appreciate it . Oh by the way there is no draft tube in the Block Just the round hole is there to put the tube in THANK YOU Clyde 28075
The crankcase needs to BREATH or you end up with oil leaks from the built up pressure pushing oil out where you don't want it to go out. Either a road draft tube or positive crankcase ventilation system aka PCV valve. Breather for the air to flow in, road draft or PCV for the air to be drawn out.
Road draft tubes were designed to draw engine vapors out of the engine while the car was moving. The upper capped vent actually drawing in air. Yes as engines wore out and that was usually in 40-50,000 miles the under side of the car got covered in oil and at idle the upper vent gave off a burnt oil smell. Let’s say you close off the road draft tube... all the oil vapors are coming to the top to get out of the engine as they have no where else to go. I wouldn’t want that. An engine in good condition with a PCV system will work fine but if it’s worn the blowby vapors can be too much for the tune up to over come. I’ve kept the road draft tube on my engine and bought a top Stant breather cap with a 1/2” hose fitting and ran it to the air cleaner housing. Seem to not only keep the smell away but there is little to no oil film on the bottom of the car.
Engines are an air pump. Think about it. If the rings are bad, it pushes oil out the top. Oil gets past the rings if crankcase pressure overcomes ring sealing. Witch happens as quick as the rings start to lose they're seal. Hence road draft tube. When you see oil fumes puffing out the road draft tube just sitting and running, the rings have lost a lot of their seal. Back in the day it was normal for these old engines to push pressure AND smoke at temperature out the road draft tube. If you want to put a PCV valve on your engine that didn't have one originally don't expect to get rid of smoke, only redirect everything back into the engine and hope you can re-burn some of it. JMO Lippy
You have to be careful with draft (air circulation) on a flathead. I put a Mercury in my '51 Ford. with finned heads etc. I thought the engine looked good, except for the oil fill tube that stuck up about a foot, and looked like an ostrich wearing a German army helmet. I decided to fix it, and got a chrome fill tube about 6" long with a chrome cap and installed it in the engine. I thought it looked a whole lot better. The first time I checked the oil. the entire right side of the engine was covered with oil; the head, engine pan and even the battery. I cleaned everything off and went ahead with my business. The next oil check, and the same thing; the right side of the engine was again covered in oil. This time, I got smart and re-installed the stock height oil fill tube and cap after I cleaned the engine up again. Problem solved, the engine has stayed clean as a whistle since. It is my belief that shortening the fill tube brought the filler car area down to the level where it was affected by the air flow from the fan. This caused a low pressure area around the top of the filler tube that actually caused the air flow through the engine to go in the opposite way (up the road draft tube and out the filler cap). Bottom line? These things have to breath, and breath properly.
THANK YOU Everybody Your Expertise and experience are very valuable Resource . Sounds like to Me Eliminating The Road draft tube is not a good Idea
My input is a tad off topic but I just finished a thread regarding something similar, only my flathead has a 471 blower which made the issues worse. I built the engine with a breather in the rear (fuel pump stand) and another in the pan. The motor leaked oil out the front seal, the rear seal and the pan breather. The result was oil sprayed all over the under side and several drips on the floor every night after a drive. Say nothing about the smell of hot oil being blown in through the cowl vent. I added a vacuum source and installed a PCV valve in the road draft hole which I had previously blocked. I also blocked the pan breather as an after thought the other night. I drove the car to work yesterday and I wasn't easy on it. This morning reveals no leaks, no drips at all on the floor, pan is dry and the odor was eliminated (though I kinda miss it). A totally different animal. Don't block that tube, you may regret it.
Gentleman, My engine builder for my '53 Mercury engine, also blocked off the opening for the draft tube, and incorporated a PCV valve, into the oil fill breather cap... That wasn't working.. I installed a Road Draft Tube, which reduced the amount oil leaking somewhat, but not enough for me... At one of my club meetings, a member who had oil leaks, on his overhead valve engine, brought up a problem solving PCV valve, that he installed and has eliminated the leaks... It is an adjustable PCV valve, made by M/E Wagner, (www.mewagner.com).... I have just purchased one, along with a inline adapter... I will install it as soon I receive a needed vacuum gauge, and let you all know of my progress... The cost of the valve might seem a little high, but it's how you value the outcome.... "you only get what you pay for"
Your engine builder doesn't understand the 8BA ventilation design. The pcv should be installed in place of the road draft tube, NOT into the oil fill cap, which renders the pcv useless. Air enters the oil fill cap, circulates through the valve chest and crankcase then exits up through the front stand pipe (under the intake) and into the road draft, or pcv if installed. A 3/8" hose should run between the pcv and intake vacuum. A pcv can only work if installed correctly.
I did the whole pcv under the intake deal....took it all out and put the road draft tube back on. It just plain works.
The main purpose of crankcase ventilation is to remove water condensation in the block and secondarily to remove blowby. Air flow through either PCV or draft is needed to remove the condensate, otherwise your oil gets ruined and sludgy. If you want to remove the draft tube, PCV systems aren't "elaborate", they are simple.
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