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914World.com _ 914World Garage _ 2.0 or not 2.0

Posted by: Teknon Mar 2 2005, 11:24 PM

Where do the holes go? Ok, there are two different types of 2.0 heads out there, that I know about.
The two hole type was made towards the end of the production years and did what?
Smog pump air pressure maybe, to where in the head and for what purpose?

And the one hole type head was to evacuate pressure under the valve cover to allow oil to easily lubricate the valvetrain by the air being vacuumed to the air intake. Right?

Has any one used either of these holes to superlube the valvetrain or other. Joe

Posted by: Rhodes71/914 Mar 2 2005, 11:44 PM

If I get your question, here is what I know...

The 75-76 heads have 2 holes on each head that go through to the exhaust valve and supposedly helped with emisions. I have these heads put they are now closed off.

I'm not sure what years actually came with the head breather already there but from what I understand all the 2.0 heads at least have the boss for the breather. They got through to the rocker area from the front of the cyl 1&2 head and the back of the cyl 3&4 head. They relieve excess pressure from the heads to keep the valve cover gaskets and Orings from leaking.

Posted by: Teknon Mar 3 2005, 12:02 AM

So basically the 75-76 heads are useless and should be plugged off, unless used in a running smog system.

But the 73-74 heads are helpful to the oiling system and should be used to relieve pressure in the head. Than this is the head when used with carbs is vented to a "puke box"

Thanks Sean

Posted by: ArtechnikA Mar 3 2005, 05:38 AM

QUOTE (Teknon @ Mar 3 2005, 12:24 AM)
...there are two different types of 2.0 heads out there, that I know about.

for completeness, we should mention that there are also 2,0 Bus heads that occasionally show up on "2,0" engines. those are 2-liter engines (and heads) but they are not 914 2,0 heads. it makes a big difference...

Posted by: Bleyseng Mar 3 2005, 08:34 AM

Super lube the valve train? Nah, tests show that the valve covers are half-filled with oil anyway! Roller rockers or needle bearinged rockers aren't needed unless you drysump maybe.

Posted by: brant Mar 3 2005, 09:18 AM

I'm just trying to learn and have no hands on experience with the 75-76 heads....

but....

about 3 weeks ago there was a thread that discussed the need to drill the pressure vent holes into the 75 style heads.

now I'm really confused.

I always heard that you block off the air ports on these heads, but then 3 weeks ago thought that you had to drill additional holes... Now I'm hearing that the late heads already have 2 holes in each head.

what gives?
is it that some do and some don't?

Posted by: ArtechnikA Mar 3 2005, 09:26 AM

QUOTE (brant @ Mar 3 2005, 10:18 AM)
about 3 weeks ago there was a thread that discussed the need to drill the pressure vent holes into the 75 style heads.

I always heard that you block off the air ports on these heads, but then 3 weeks ago thought that you had to drill additional holes... Now I'm hearing that the late heads already have 2 holes in each head.

what gives?

they're talking about two completely different things.

Thing One:
air pump cars pump air into the exhaust ports. it's an emissions thing.
if you don't have an air pump, you have to plug the holes into the exhaust ports that you aren't pumping air into.

Thing Two:
most cars work better if the rocker arm area of the head is vented.
i don't kow much about the specifics of what cars have vent ports in the heads and which don't, and why the ones that don't didn't. but it is these vent holes into the rocker arm ("valve cover") area of the head that people are talking about adding.

Zat help ?

Posted by: brant Mar 3 2005, 09:39 AM

Ok... maybe I got it. (1st to admit that I'm slow at times)

so on the late head that has 2 holes.. both of them are related to the air pump/emissions and no crank case venting exists?

thus you plug 2 holes (not 1 like I previously thought) and then drill yet a 3rd hole?

is that right?

thanks for helping my coffee-lacking self understand this!

TIA

Posted by: 914ghost Mar 3 2005, 09:46 AM

Yeah, the 76' style would have a hole for each cylinder and its piped directly into the exhaust port. Those are the hols you NEED to plug.
Then, (maybe) the 76' style has no hole to the actual valve cover area. This is the hole you would drill to "vent" to your breather box. One in each head or maybe better- just vent the valve cover.
clear as an unmuddied lake!
Do early and late 2.0 have all the same valve sizes? I assume so and the power difference comes from the smog system. (sorry to hijack the thread)
Bob O

Posted by: SLITS Mar 3 2005, 09:47 AM

Correct...the extra holes were to inject air into the exhaust stream to lower emissions. For normal use, you can have the heliarced up (from the inside of the port) or simply plugged with a pipe plug or bolt.

The "third" hole you are talking about is to do nothing but vent the rocker box. The internal pressure of an engine (due to blowby, etc) is vented to the atmosphere or plumbed to air cleaner. This saves seals and makes the engine run better. Even the smog heads have the "boss" for the venting of the rocker box. Merely drill a hole in it, tap it with the appropriate size pipe thread tap and screw in a 3/8" or so hose barb. Run the hoses to a "T" and then to the air cleaner or to a "catch tank".

Oh, and if you think spraying oil, downstream of the valve, is going to "superlube the valve stems and guides", all you will do is create a very noxious cloud of oil smoke behind you(more so than the normal 914).

Posted by: Headrage Mar 3 2005, 10:34 AM

I just did this. 1/4 NPT to 1/2 barbed fitting. Scary but fairly easy. I have a butt load of extra fittings if anybody needs them.

Posted by: newto914s Mar 3 2005, 08:33 PM

What if you have 76 2 liter heads with no smog equipment and you don't plug the emision holes in the head. Will the car A. not run, B. run worse, or C. run better?
Thanks
Samson

Posted by: nebreitling Mar 3 2005, 11:05 PM

QUOTE (newto914s @ Mar 3 2005, 06:33 PM)
What if you have 76 2 liter heads with no smog equipment and you don't plug the emision holes in the head. Will the car A. not run, B. run worse, or C. run better?

you need to plug those holes. otherwise, you have a combustion leak. the car may run (mine ran when one came out), but not well, and it'll sound like a racket.

ask me how i know...

Posted by: Teknon Mar 4 2005, 03:58 PM

QUOTE (SLITS @ Mar 3 2005, 09:47 AM)
Correct...the extra holes were to inject air into the exhaust stream to lower emissions. For normal use, you can have the heliarced up (from the inside of the port) or simply plugged with a pipe plug or bolt.

The "third" hole you are talking about is to do nothing but vent the rocker box. The internal pressure of an engine (due to blowby, etc) is vented to the atmosphere or plumbed to air cleaner. This saves seals and makes the engine run better. Even the smog heads have the "boss" for the venting of the rocker box. Merely drill a hole in it, tap it with the appropriate size pipe thread tap and screw in a 3/8" or so hose barb. Run the hoses to a "T" and then to the air cleaner or to a "catch tank".

Oh, and if you think spraying oil, downstream of the valve, is going to "superlube the valve stems and guides", all you will do is create a very noxious cloud of oil smoke behind you(more so than the normal 914).

I see the spot that has to be drilled like the older head. I’m gunna have that done. The non-drilled ones just got back from Rimco. $650, missing a stud and never mentioned to me it would be better to drill them out. They don't even have email or at least never answer it. No more business with them.

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Posted by: Teknon Mar 4 2005, 03:59 PM

And the one to be tapped

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