Mazda BP8 Engine Short Block Interchange

Mazda BP8 Engine Short Block Interchange

By Randy Stocker

Many people have used the less expensive FWD based BP8 motors when doing a performance engine build-up or when they are looking for a replacement engine from junkyards vs a genuine Miata engine. The same basic 1.8L DOHC BP8 motor was used in the 90-98 Protege, 91-96 Ford Escort GT, 94+ Miata, 91-96 Mercury Tracer LTS, 94-97 Kia Sephia GS but there are some subtile differences.

The block from 90-98 uses a oil filter mount that is recessed into the block slightly and the 99+ blocks use a mount that is more flush. This means you may have to buy the proper length oil filter extension pipe

BP8oilfilterpad.jpg  (19 KB) BPescortfiltermount.jpg (15 KB) 90-98 mount.

BP8oilfilterpad99.jpg  (19 KB) liftercomptop.jpg (23 KB) 99+ mount

MazdaBoilfilterpipeextension.jpg (14 KB)

The 1.6 pipe is the shortest. The 1.8 pipes are longer since they have to account for the additional length of the oil cooler. The 99 pipe is in the middle and the 90-98 pipe is the longest. The 99+ pipe part number is BP4W-10-319

Japanese spec cam. BPescortvs99Miataoilpassagefittings.jpg (13KB) Threaded Oil Passages. Mazda18blockdifferences.jpg (13KB)

The 90-95 blocks have a threaded plug access to the oil gallary for use in turbo engines. This feature is very handy for aftermarket turbo installations which use an oil feed since you just install your oil line in the threaded hole. The 96+ block eliminates the machining for the threaded hole.

BPescortvs99Miatawaterpump.jpg (19 KB)

The 90-93 block uses a water pump with a threaded boss for the timing belt adjuster pulley while the 94+ block has the threaded hole cast into the block and the water pump just has an open passage for the bolt to pass through and then thread into the block. If you are going to use a later water puump on an ealier block then some people have found using a large washer as a backing plate with a lock nut worked for them.

Special Thanks to Mike Pitts for some of the pics!

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