Head vent ports, needed? Options

[yarin]

While pulling my carbs off I noticed that each head has an air vent. One was capped off, the other was open.

Where should these go and why are they needed? Will capping these contribute to oil leaks?

Here is a pic I found: http://www.914world.com/bbs2/uploads/blog-1...-1131214564.jpg

Thanks

[dmenche914]

Basically the crank case vent vents the case, and head vents the heads. The heads and case do have a pathway between them, via the push rod tubes, but they evidently did not flow enough to vent the heads via the case per the factory. The pushrod tubes are used for oil flow back to case.

You will improve ventalation with head venting. The head is an area of potential oil leak (big leak prone gasket) so extra venting of it may help leaks specifically from that area more so than from say the case halves.

If it is easy to ad at this point it might be worth doing. I have run 1.7l stock motors without them (early cars lacked them) I have had them not leak much at all, so you not adding them will not for sure cause a leak. But it can help prevent them.

Big faster turning motors require more venting, as they kick up more air/oil, and may have more blow by.

in Summary:

If you are running a stock small motor and don't want to ad them, then don't worry about it too much. early cars lacked them, and they did not have huge leak problems, however it can't hurt to ad them if you want. The amount of power gain with a smaller stock motor is likely minimal cause the pressures are not that high anyway. (a hopped up motor would see more power increase, as pressures can build up much higher unless extra venting is added.)

I would definatly re-attach them if the car was factory equiped with head venting. (just cause the factory had added them for some good reason) and diffenatly ad it to any big high rev hopped up motor for sure.

hope that answers your main question.

As far as where it goes, with carbs you need to vent them into the air cleaner or a breather box. Either method works. If you have a hopped up motor you will have more oil spray, and you either collect it in the breather box, and periodically clean it, or burn it thru the carbs. The factory way with injection was to burn it. The hoses hooked up to the air cleaner. On your carbs you will need to have three fittings, one each for the heads, and one for the case vent lines. they could all go to one carb or spread out on both carbs.

you may need to do some fabrication. If you vent to the air cleaner, and you have lots of blow by and such, you may end up with an oily carb.

good luck! (Nice engine bay, super clean, new hoses! Nice)

PS I wonder if smog laws had the biggest impact on the factories call to ad head vents later in the model years? In which case you would be running cleaner if you ad them??? maybe??? anyone know effect on emissions?