Tii plastic vs metal intake runners

[gwb72tii]

Anyone know what VIN or production date BMW switched from plastic to metal intake runners?

TIA

[Conserv]

VIN 2761944 was the first U.S.-spec tii with aluminum intake runners and an E12 head. I believe VIN 2761944 was manufactured in early June 1972. But this first changeover was only temporary. Something must have interrupted parts, or assembly, or operation. So, at VIN 2762015, U.S.-spec tii’s reverted to plastic runners and 121 heads. This was probably on June 21, 1972 or thereabouts. Finally, with VIN 2762373, U.S.-spec tii’s switched again to aluminum intake runners and E12 heads. This was in very late July or early August 1972. There may have been some exceptions to this general chronology. We don’t, however, know more background about the changeover, or why the changeover of Euro-spec tii’s may have differed somewhat from the changeover of U.S.-spec tii’s.

 

Regards,

 

Steve

 

Edited February 25, 2020 by Conserv

[Einspritz]

Please don't replace the plastic runners with the aftermarket metal substitutes as it will change the volume and path messing up the helmholtz effect of the intake, thereby making LESS power.

 

Installed correctly, even though the replacement plastic tubes are stiffer, will last a good long time if you don't overtighten the clamps. The seal is due to the O Ring and not the clamps.....

 

the O rings are of a specific size and flexibility (so don't get them at your local ACE) and you need to heat the tubes with a heat gun, or boil them in water to get them to pop on "easily".

 

Snug the clamps just enough to keep the tube from backing off.....

[Mike Self]

12 hours ago, Conserv said:

We don’t, however, know more background about the changeover, or why the changeover of Euro-spec tii’s may have differed somewhat from the changeover of U.S.-spec tii’s.

Based on what we know about BMW factory operations of the time--especially WRT US spec cars--I'd wager that Hans or Fritz discovered a pile of 121 tii-specific cylinder heads (not drilled for mechanical fuel pumps etc) in a dark corner somewhere in the factory, and those thrifty Germans "used up stock" so as not to waste 'em. 

 

Just a guess, but based on other similar "use up stock" situations we've encountered ('72 Nevada cars, '74 Turkis cars, blue vs black interiors on 68 and 69 cars etc)

 

mike

[Gordon]

I have 2762096 and it came with plastic intake runners.  I bought the motor from Jeff Ireland years ago who parted out a 72 tii that made its way to So Cal with way too much midwest rust.  The motor didn't look right in my 74 tii so the plastic intake runners were sold and aluminum intake runners were installed. 

[AceAndrew]

23 hours ago, Conserv said:

VIN 2761944 was the first U.S.-spec tii with aluminum intake runners and an E12 head. I believe VIN 2761944 was manufactured in early June 1972. But this first changeover was only temporary. Something must have interrupted parts, or assembly, or operation. So, at VIN 2762015, U.S.-spec tii’s reverted to plastic runners and 121 heads. This was probably on June 21, 1972 or thereabouts. Finally, with VIN 2762373, U.S.-spec tii’s switched again to aluminum intake runners and E12 heads. This was probably in very late July or early August 1972. There may have been some exceptions to this general chronology. We don’t, however, know more background about the changeover, or why the changeover of Euro-spec tii’s may have differed somewhat from the changeover of U.S.-spec tii’s.

 

Regards,

 

Steve

 

 

Just Steve... droppin some knowledge on us plebeians. 

 

 

[Conserv]

28 minutes ago, AceAndrew said:

 

Just Steve... droppin some knowledge on us plebeians. 

 

 

Well... I got the VIN numbers from Paul Wegweiser and Rob Torres... so I didn’t have to do much work! 
 

Best regards,

 

Steve