Subject: M90 engine is 1977-81 ( 93.5mm bore x 84mm stroke), it's the same bottom end in Author: bmw635 : 15700 posts Posted on: 2007-03-19 18:29:50

M1 except the twin cam M head. The M30 is 92mm bore x 86mm stroke. The best M30 engine is 1987-1989 635( perfect fit harness), 1989-1972 535/735 (shorter harness, may not fit in original location)- these are called M30B34. They're well tuned with lots of flexibility for chips/ modificiations. The 83-86 M30 in US has 186hp while the Euro M30 has higher compression with 216 hp. All of the M30/ M90 parts are interchangable depends on what you want.

$1500 for an M S38/ S88 is good price since they go for $4-7k in US.

As for S38 I think US get the 256hp M motor while S88 Euro M motor has 286 hp- totally different engine. A well tuned S88 motor with chip can produce over 300 hp.

Standard 5 spd with tall ratio is Getrag 265, the Getrag 280 (standard on M) is more heavy duty but rarer. LSD comes in 2.91 up to 3.91 but the lower ratio gives more fuel economy while losing low end acceleration.

Peter- OC, S.CA

3/98 AC Schnitzer 740IL, 88k mile, Dinans , clear lens, 100w Hella ,PowerFlex bushing, Alpine sub & amp. SC & NAV waiting for install!
5/86 Euro 635Csi, 230k mile, custom 3.7L engine , Bisltein Sport & Eibach, 3 pcs Epsilon superlite, SS MAF.

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