283 block question

On the top of the engine twords the back behind the hole for the distributor is an extra hole.

Is that for a down draft tube?

If this is the case what is a down draft tube?

Thanks Gary

 

If it's a small threaded hole, That's where the oil pressure sending unit screws into.. Show us a picture of what your talking about..

 

Yes, commonly called a "road draft tube". It's function was to vent the block, before the days of PCV valves.

 

It's essentially a crankcase vent. The early 283s had a road draft tube that was bolted to that hole and extended down along the right sound of the block and exited near the bottom. It was supposed to suck out the vapors as you drove. The early engines would have also had a breather on the oil fill tube. This allowed the venting to flow by taking in air through the breather and out through the road draft tube.

Later blocks would have had a fitting in that hole with a hose connected to the air cleaner (I believe) with a PCV coming off of the oil fill tube to give ventilation flow. The has been a lot of discussion about crankcase venting here in the past. Do a search on "PCV." You should find a lot of info.

 

Road draft tube, curls down to vent crank case pressure down to the road.

 

Yeah, I had a PCV installed on mine so I was able to get a plug for the tube on my 283 if you cant find a Draft Tube..

 

Starting in 1963, the road draft tube was replaced by a right angle tin fitting that had a hose nipple on it for the PCV hose. The early PCV engines had a PCV valve that threaded into a brass fitting on the rear of the carb base.

 

ventilation,I had 63 model 283 that had a pcv valve in that orfice,but I have no idea where the adaptor came from.

 

Thanks Heathen. I guess what you're saying is that starting in '63 the PCV came off that hole and there was a vented cap on the oil fill tube? I've only had experience with the very early and the very late 283's. Now I know what happened in between. The '67 block (if I'm remembering right) had that hole vented to the aircleaner with a PCV coming off the oil fill tube (with no vented filler cap, of course).

 

There is a baffle that presses into the back of the block and has a small bolt or screw that holds it down. The baffle is under the intake. It sort of looks like a canister.

 

I always us one of these ... the factory PVC fitting for the later SBC ( until the end of 1967 )



The nipple connects a hose to the air cleaner base. Then I use a 66/67 V8 Nova oil fill tube with the fitting for a PVC ... shown here on my 40 Ford with the 283.



This set up really cleans up a engine ... no engine vapors, oily mess and drips under the road draft tupe.

 

There it is! That's the setup I was describing in my old '67.

 

My 67 283 Chevelle (an east coast car) had this PCV valve in the base of the 2bbl with a short hose to the fitting shown above. The fill tube used the standard push in breather for the air intake. Same idea as DRs above just a different routing. The Corvettes and other HP engines didn't have the carb base opening like the Rochester 2 bbl.

I do it this way on three deuces.

 

As roothawg stated, be sure and use the canister that mounts in the lifter valley and connects to the back of the block. You need it whether you use the pvc or down draft tube. It keeps the oil from blowing out the back and plugging the pvc or going out the tube.

 

what deuce roadster said--this is the way to do it--62 Corvettes had a similar piece for the rear hole but a PVC screwed right into it--make sure the canister is in the block under the intake or it will suck oil

 

This photo shows the cannister that olscrounger is talking about

 

I'm guessing these canisters are no longer available?

Gary

 

The canisters are available from Corvette resto suppliers. Check Paragon.

 

While searching for a way to get rid of, or at least replace, the vent tube connection on my 67 327 El Camino, I found this thread. This piece looks much cleaner than the factory setup on my car and less bulky. Do you know what year(s) this particular unit came on and/or where I might find one? It also looks like this takes a 3/8" or so I.D. hose which would be much easier to route. I'm running an aftermarket intake w/o oil fill tube and already have a PCV valve in one cover and a breather in the other for ventilation. Where did you run the hose from this particular connection? The bottom of the air cleaner?

Thanks for any help and direction you can provide.
DaleMc
ChevelleStuff.com

 

...or Corvette Central (part#301155). Draft tubes are also available.