 backdate 76 GC heads to 73-74 GA or GB heads |
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| SuperDave |
 Mar 3 2009, 12:09 PM
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#1
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Newbie  Group: Members Posts: 5 Joined: 6-January 09 From: Oklahoma City area Member No.: 9,907 Region Association: Southwest Region  |
I'm a newbie here. I've tried searching pelican and here to no avail. My apologies if this has been covered before...
I am very close to buying a 76 2.0 to replace the 1.7 in my 72. The 2.0 still has the original heads and emissions equipment. I've read enough to know the emissions equipment made the car run hotter and less efficiently and my state (Oklahoma) doesn't require it so I'm planning on removing the air injection. Three questions: Are 73-74 heads a bolt-on for the GC engine? If so, would I gain anything by replacing my 76 heads with GA/GB heads or should I just fill in the holes like was discussed in a recent thread? I've heard the valve sizes are different between 73-74 and 75-76 heads, but haven't been able to verify this. True or false? Thanks! David |
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| SLITS |
Mar 3 2009, 12:36 PM
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#2
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None  |
Nothing I have seen or read indicates any valve size difference on the 2.0 heads.
Only difference I know of is the lack of breather ports and the addition of air injection holes in the exhaust ports. Air injection holes can be plugged or welded up. Breather ports can be added as the boss is still cast into the heads. I've swapped them back an forth. In other words , save your money and work with the late heads. Now, there is a big difference between 2.0L BUS heads and 2.0L 914 heads. |
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| SirAndy |
Mar 3 2009, 12:40 PM
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#3
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Resident German Group: Admin Posts: 41,675 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(SLITS @ Mar 3 2009, 10:36 AM)  Nothing I have seen or read indicates any valve size difference on the 2.0 heads. Only difference I know of is the lack of breather ports and the addition of air injection holes in the exhaust ports. Air injection holes can be plugged or welded up. Breather ports can be added as the boss is still cast into the heads. I've swapped them back an forth. In other words , save your money and work with the late heads. Now, there is a big difference between 2.0L BUS heads and 2.0L 914 heads. (IMG:style_emoticons/default/agree.gif) with Schlitz ... PS: (IMG:style_emoticons/default/welcome.png) |
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| SuperDave |
Mar 3 2009, 01:10 PM
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#4
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Newbie Group: Members Posts: 5 Joined: 6-January 09 From: Oklahoma City area Member No.: 9,907 Region Association: Southwest Region |
Dang, that was fast! Thanks....
I knew about the air injection holes, but what is this about adding breather ports? Assume I know nothing (IMG:style_emoticons/default/confused24.gif) |
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| type47 |
Mar 3 2009, 02:18 PM
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#5
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Viermeister Group: Members Posts: 4,254 Joined: 7-August 03 From: Vienna, VA Member No.: 994 Region Association: MidAtlantic Region |
Breather ports are little pipes that allow relief of air pressure formed in the crankcase to escape and be put into the intake system. On the upper side of the head, but off to the side will be a "boss" which is a little raised area through which a hole can be drilled and a pipe located. Hoses are then attached to the pipes and routed to a collection junction (anti-flashback valve, a little 3-way connector) then to the air cleaner assembly to be burned with combustion gases. Actually, I didn't know that GC heads did not have the pipes (among the many things I don't know). If your heads do not have the pipes, I suppose you'd have to remove the heads to install them (would require dropping the engine). To replace the emissions injectors with plugs should not require engine removal. Awkward, but it should be able to be done with engine in.
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| SirAndy |
Mar 3 2009, 02:23 PM
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#6
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Resident German Group: Admin Posts: 41,675 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
Btw. some people have had success by adding a port to the valve covers. Which obviously can be done with the engine in the car.
That should work just fine, if you can get it to not leak ... (IMG:style_emoticons/default/biggrin.gif) Andy |
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| r_towle |
Mar 3 2009, 02:58 PM
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#7
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Custom Member Group: Members Posts: 24,588 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States 
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No one has explained why some have the head breather ports and some do not...
Any ideas? Rich |
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| SirAndy |
Mar 3 2009, 03:07 PM
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#8
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Resident German Group: Admin Posts: 41,675 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(r_towle @ Mar 3 2009, 12:58 PM) No one has explained why some have the head breather ports and some do not... Any ideas? Well, early cars didn't have them, they were added later in the production. My guess would be either they are beneficial to the life cycle of the engine or they are emission related. (IMG:style_emoticons/default/idea.gif) Andy |
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| SuperDave |
Mar 3 2009, 04:23 PM
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#9
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Newbie Group: Members Posts: 5 Joined: 6-January 09 From: Oklahoma City area Member No.: 9,907 Region Association: Southwest Region |
QUOTE(SirAndy @ Mar 3 2009, 03:07 PM) QUOTE(r_towle @ Mar 3 2009, 12:58 PM) No one has explained why some have the head breather ports and some do not... Any ideas? Well, early cars didn't have them, they were added later in the production. My guess would be either they are beneficial to the life cycle of the engine or they are emission related. (IMG:style_emoticons/default/idea.gif) Andy Sounds like venting the crankcase and reburning the gases is both helpful on emissions and helps increase longevity: http://en.wikipedia.org/wiki/Positive_Crankcase_Ventilation Seems to me that early cars wouldn't have breather tubes, and later cars would. Am I missing something? I don't have the motor or I'd go look! |
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| hcdmueller |
Mar 3 2009, 04:23 PM
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#10
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????????????? Group: Members Posts: 542 Joined: 4-February 06 From: UK Member No.: 5,527 Region Association: England
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L-Jet cars don't have them. The breather system on the 75/76 2.0L is different from the early D-Jet cars. There is no PCV valve at the oil filler. It is just a 3/4" dia port that goes straight into the airbox. I guess Porsche figured that head ports weren't necessary since the crankcase breather had a steady vacuum on it.
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| Bleyseng |
Mar 3 2009, 07:27 PM
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#11
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
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| wertygrog |
Mar 3 2009, 08:09 PM
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#12
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wertygrog Group: Members Posts: 428 Joined: 12-November 05 From: Long Beach, CA Member No.: 5,114 Region Association: Southern California |
how can one tell the difference between 2.0L bus and 914 heads?
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| bobhasissues |
Mar 3 2009, 08:49 PM
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#13
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seemingly endless issues with my 914 Group: Members Posts: 218 Joined: 13-February 07 From: Chicagoland Member No.: 7,532 Region Association: None |
QUOTE(wertygrog @ Mar 3 2009, 06:09 PM) how can one tell the difference between 2.0L bus and 914 heads? The foremost telltale sign is 2.0 Bus heads have four intake bolts. 2.0 914 heads have three intake bolts. |
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| type47 |
Mar 4 2009, 09:07 AM
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#14
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Viermeister Group: Members Posts: 4,254 Joined: 7-August 03 From: Vienna, VA Member No.: 994 Region Association: MidAtlantic Region |
QUOTE(hcdmueller @ Mar 3 2009, 03:23 PM) L-Jet cars don't have them. hmmm, my '74 has 'em..... (IMG:style_emoticons/default/idea.gif) |
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| hcdmueller |
Mar 4 2009, 03:23 PM
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#15
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????????????? Group: Members Posts: 542 Joined: 4-February 06 From: UK Member No.: 5,527 Region Association: England
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QUOTE(type47 @ Mar 4 2009, 04:07 PM) QUOTE(hcdmueller @ Mar 3 2009, 03:23 PM) L-Jet cars don't have them. hmmm, my '74 has 'em..... (IMG:style_emoticons/default/idea.gif) Does it still have the L Jet? My understanding is that the L Jet system doesn't like unmeasured air sources past the air flow meter. Where do your ports connect to in the FI system? |
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| SuperDave |
Mar 4 2009, 10:12 PM
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#16
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Newbie Group: Members Posts: 5 Joined: 6-January 09 From: Oklahoma City area Member No.: 9,907 Region Association: Southwest Region |
QUOTE(hcdmueller @ Mar 4 2009, 03:23 PM) QUOTE(type47 @ Mar 4 2009, 04:07 PM) QUOTE(hcdmueller @ Mar 3 2009, 03:23 PM) L-Jet cars don't have them. hmmm, my '74 has 'em..... (IMG:style_emoticons/default/idea.gif) Does it still have the L Jet? My understanding is that the L Jet system doesn't like unmeasured air sources past the air flow meter. Where do your ports connect to in the FI system? This article http://www.pelicanparts.com/914/How_to_buy_a_914.htm has a lot of good info and says of the '75 L-jet cars "Some cars get EGR tubes..." This discussion of 914 engine differences was also helpful to me: http://forums.pelicanparts.com/showthread....;threadid=54211 Thanks for all the help! |
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