Road Draft Tube Conversion

[Figuarus]

ok guys, I hate to bug you, but I need confirmation about something.

I have the 283 SB with the hole for the road draft tube. I am getting oil filiming over and dripping from the block since that hole is just wide open.

I installed this type of "PCV" system a few weeks back.

It consists of two valve breathers with hoses coming off them that join to a "T" and up to the bottom of the air cleaner plate.

If I plug up the rear hold where the draft tube was, I will have to have ONE side of the valve cover have a full flow breather, while I run the suction line from the other side, right?

I just need to get confirmation.

thanks guys!

[61K10]

yes

[Figuarus]

Originally Posted by 61K10

yes

ok. with that being said, is this the BEST way of doing this?

[markeb01]

In my opinion, a better solution would be to utilize the road draft hole for a smog valve connection. The best/easiest way would be to obtain one of the vintage 1967(?) era smog adapters. I don’t know if these are being reproduced. It bolts into the hole with the original long road draft tube attaching bolt:


This connects to a PCV valve which in turn connects to the base of the carburetor or a full manifold vacuum port:


An alternate is to install a suitable grommet (I believe some valve cover grommets work fine) and simply plug the a suitable PCV valve into it, as shown on the six cylinder application:


In either situation this will evacuate the crankcase, keep the bottom end clean, and keep from building up pressure and causing the gaskets to leak. The valve covers then provide fresh air into the engine, whether from a direct/open breather or from the air filter.

[Figuarus]

so, then it's better to have the draft tube hole act as the suction port then?

does anyone know what size the hole actually is? I was thinking about using a freeze plug and making a hole in it to fit a pcv grommet and valve.

[bhc41051]

I wanted to use my original valve covers so I used this type system. The ventilator installs in the engine valley, I'm not positive but your draft tube system should have the ventilator. The PCV valve just screws into the rear of the carburetor.

[markeb01]

The engine should breathe front to back or side to side (or a combination). In these early engines with the road draft tube suction was created by vehicle movement causing negative pressure over the bottom of the road draft tube. Fresh air entered the crankcase through the oil fill tube breather on the intake manifold. The problem was if the vehicle never went over 25 mph (like a milk or local delivery truck) there never was sufficient suction to remove the crankcase fumes and tons of sludge built up.

With the advent of the smog valve regulated suction was provided by engine vacuum. In the transition period, connections were the same - rear of the engine and oil fill tube. As the system became more refined the OEM's put the PCV valve in one valve cover and the breather on the other. This arrangement still provided fresh air and suction to completely evacuate the crankcase fumes.

Here's a photo of the ventilator installed in the lifter valley:



Unless a previous owner removed it, your engine will have the ventilator if it has a hole for the road draft tube.

[Figuarus]

Originally Posted by markeb01

Unless a previous owner removed it, your engine will have the ventilator if it has a hole for the road draft tube.

I'm sure i have the baffle, but there's not enough suction. This is what I have now.

My makeshift "PCV" system

[jtrichard]

you need to get a soft plug/ core plug and plug that dirt intake hole

[Figuarus]

Originally Posted by jtrichard

you need to get a soft plug/ core plug and plug that dirt intake hole

It's more of an external engine lubricator hole.

Do you happen to know the size?

[Figuarus]

well looks like I'm going to have to try to plug that hole tomorrow. I went and picked up a bunch of plugs and a few PCV valves. I have a grommet to insert them into the plug as well. I'll report back with the results.

[Captainfab]

To plug the road draft tube hole, I believe you need a 1-1/4" freeze plug. Then you just need a breather in the valve cover on one side and a PCV valve in the cover on the other side. The PCV valve of course needs to be connected to manifold vacuum.

[Figuarus]

cap'n,

what's more advantageous? to have that suction flow from front to rear, or side to side?

[Captainfab]

I don't know if one is better than the other. The main objective is to ventilate the crankcase. To do that properly, air needs to enter (breather) and air with fumes and vapor needs to exit (PCV). If you can find the correct housing for the rear 'road draft' opening, that will accept a hose, then by all means use that with a vent at the front fill tube.

[Figuarus]

Well, i ended up going the PCV route.

I used a 1.25" steel freeze plug, and a small pcv grommet. Then i picked up a straight metal body pcv valve, and some 3/8ths fuel line.

I drilled a hole in the plug, and made the hole large enough to accommodate the grommet.

I have to remove the distributor in order to get a socket over the freeze plug and give it one good hard tap to get it to seat into the block

[PowerdbyChevy79]

Originally Posted by Figuarus

Well, i ended up going the PCV route.

I used a 1.25" steel freeze plug, and a small pcv grommet. Then i picked up a straight metal body pcv valve, and some 3/8ths fuel line.

I drilled a hole in the plug, and made the hole large enough to accommodate the grommet.

I have to remove the distributor in order to get a socket over the freeze plug and give it one good hard tap to get it to seat into the block

keep us posted on the outcome

[Figuarus]

I meant I had to remove it yesterday. Its all done.

[geezer#99]

Where did you plug the end of the 3/8" hose into?

[Figuarus]

Bottom of the air cleaner. It has a small fitting where you can attach a hose. Ill take a clearer picture and post the part numbers.

[geezer#99]

Then I see you still haven't got a working pcv. The pcv you installed in the draft tube needs to be hooked to the large vac port on your carb or a vac port on your intake.
You need manifold vacuum to make the pcv work.
Then a breather on the front of the motor on a valve cover that draws air from the air cleaner or just a breather on the valve cover works.

[chopper john]

intake or carb vacume only

[Figuarus]

Alright, I moved the intake line to the rear of the intake manifold. Looks like everything is good.

have the two breathers on the valve covers, and no problems have presented so far.

[geezer#99]

You gonna burn us off a pic or two??

[Figuarus]

Originally Posted by geezer#99

You gonna burn us off a pic or two??

yeah I am. I got home last night with a migraine, and ended up snoozing until midnight.

I'll get a picture posted here when i get to lunch.

[Figuarus]

FINALLY got a moment to post a picture.



I'll eventually end up moving this to the front vac port on the carb.