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NickVyse

New Tii for my next M2 project. e12/e121 head question..

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It's complete, but for complete restoration. Question - is the early intake design (plastic intake runners) noticeably better than the late style? I've also read that the e12 head is little better in reality over the later e121 - but can someone enlighten me whether it's the pistons in this earlier engine that raise the compression ratio or whether it's the head?

Just running through options as the car comes with 2 early style Tii engines.

Best thing about the car - it's in Corsica, so I need a holiday to pick it up.

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Hey Nick,

A good friend of mine just returned from Corsica...you'll love it! ...and if this car was driven in Paris (noting the awesome decal!) then it has truly had the shit kicked out of it.....and that's glorious in "real sportscar" kinda way!

I have always....ALWAYS preferred the early tii runners, head, and compression ratio over the later cars. Early cars with plastic runners nearly ALL should have "121ti" heads...which are interchangeable with "121". the "ti" isn't anything special unique to the tii. Later tiis (mid 72 on) should all have "E12" casting heads. The pistons are not interchangeable, but builders can get equal power from either head/piston combo if tweaked / modified properly.

Why do I like the early cars?

less weight

higher compression (Euro spec were 10:1!!!)

awesome "prototype" look to the plastic runners - almost "experimental" in appearance. Sure you have to replace O rings every 5-10 years, and they CAN crack with age...but those are special cars to me. A 10:1 spec early tii is a completely different driving experience from even a later round light (let's say late 72 - 73) car. ....and the 74 US cars feel like luxury vehicles by comparison... far more refined, but heavier and FAR slower.

I'm all about the visceral with these cars. Noise/smells/aching limbs...all of it...maybe that's why I like inefficient, stinky, gulping, deafening, Webers.

Paul Wegweiser

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The intake and outtake valves of a e12 head are 2 mm in diameter larger. That's about the only difference I know of. Oh and the combustion chamber shape is a little different believe.

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Only the intake valves are larger on E12 heads (46mm vs 44mm) - the exhaust valve remains the same size (38mm)

E12 heads also have the "Dreikugelbrennraum".....tri-hemispherical cumbustion chambers!

Paul Wegweiser

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Hey Nick,

A good friend of mine just returned from Corsica...you'll love it! ...and if this car was driven in Paris (noting the awesome decal!) then it has truly had the shit kicked out of it.....and that's glorious in "real sportscar" kinda way!

My parts car from the South-West of France has the same Paris sticker - and good old Andreas at Mobile Tradition states that all 3 of my French 02's (I've mentally taken ownership of the Tii already) were delivered to Paris. I think that all French 02's probably arrived that way.

Corsica will have to wait until next month, but it's only a short hop across the water from here.

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those plastic runners are known to pop-out and/or melt when there is back fires.

the injection pump should have a different cone (v3? versus V4?)) to match the higher compression and different combustion chamber.

Different compression ratio and combustion chamber=different fueling needs.

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Most of the 121 heads I've come across or worked on had the larger valves-

and if it doesn't, it's not a big deal to open up the seat and runner that mm.

And it's worth it.

t

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Well I'll be a monkey's UNCLE! (avatar notwithstanding).

Indeed...my fiche jockey skills must be slipping. (it's only been a few years since I was doing this stuff daily - ugh). This sucks. How unbelieveably embarassing!

YES! BMW shows only ONE part number for the tii intake valves, regardless of VIN or cylinder head. I double checked on the valve seats, too....again - same as non tii E12 big valve heads.

So that means that 121"ti" heads all have big intakes while 121 (non "ti") heads got standard intake valves?

I guess I better shut up for a while and bathe in some humility. :-(

Paul Wegweiser

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Well I'll be a monkey's UNCLE! (avatar notwithstanding).

Indeed...my fiche jockey skills must be slipping. (it's only been a few years since I was doing this stuff daily - ugh). This sucks. How unbelieveably embarassing!

YES! BMW shows only ONE part number for the tii intake valves, regardless of VIN or cylinder head. I double checked on the valve seats, too....again - same as non tii E12 big valve heads.

So that means that 121"ti" heads all have big intakes while 121 (non "ti") heads got standard intake valves?

I guess I better shut up for a while and bathe in some humility. :-(

Paul Wegweiser

You were confusing the hell out of me there Paul - I'd read the Tii e121 heads had the same larger valves but I was putting it down to Internet 'fact' and bowing to your superior knowledge. I'm afraid all your credibility has now been blown and I shall never believe another word you say ;-)

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