Sideplate differences?
02-14-10, 03:31 PM
#1
Sideplate differences?
I have noticed that even on same type motors, there can be a difference on ports and other things. There are apparently different end and center plates too. I believe it was an N.O.? plate for a 12a I saw that had small ports and odd intake size. I know there are others as well. Is there a place to see all the different types and the differences? It would sure be helpful to have when shopping for engines, plates and doing porting, as well as planning builds. Thanks,
Ray
Ray
02-14-10, 04:06 PM
#2
There is no single website as far as I know. Of course I've memorized it all so I never found the need. 
'74-'75 3B (have the nice '74 ports)
'76-'78 non nitrided R5
'79-'80 nitrided R5
'81-'85 nitrided Y, some with threaded heater core fittings, some with pressed in and all '83-'85 had a pressed in T fitting for the beehive.
As you've seen, some J-spec engines had NO intermediate plates with runners and ports the same size as GSL-SE, but without fuel injector bungs. Some nitrided R5 rear plates had 17 or 18 tension bolts (depends on year from early '80s up to probably '83) and usually lacked an oil pressure hole. All early non nitrided R5 and 3B plates had 19 tension bolts and an oil pressure hole.
'74-'75 3B (have the nice '74 ports)
'76-'78 non nitrided R5
'79-'80 nitrided R5
'81-'85 nitrided Y, some with threaded heater core fittings, some with pressed in and all '83-'85 had a pressed in T fitting for the beehive.
As you've seen, some J-spec engines had NO intermediate plates with runners and ports the same size as GSL-SE, but without fuel injector bungs. Some nitrided R5 rear plates had 17 or 18 tension bolts (depends on year from early '80s up to probably '83) and usually lacked an oil pressure hole. All early non nitrided R5 and 3B plates had 19 tension bolts and an oil pressure hole.
02-14-10, 04:35 PM
#3
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hmm, i know we've talked about it before, might wanna search this section under the name 'jeff20b'
basically for a 12A in the US there is the following, i'll refer to these in sets of 3 irons, just for simplicity. with the mazda part number
"2090" set, 68?-73. old old old 12A, rx2/3. small ports and runners, these are HEAVY
"1881" set, 74-75. rx2/3 in 74 mazda revised the engines, they got 3mm iron seals, single side seals from dual. a single dual point distributor replaced the dual distributor setup. runner size is similar to the earlier motors, but the intake ports add 10 degrees of duration. basically a street port.
"8871" 76-80. rx3/7 in 76 the ports got smaller. center iron gets a taller runner. for the rx7 the irons get a nitride coating, which is grey vs the early irons black paint.
"N201" in 81-82 these irons are refined a little (less weight). the heater hose connection is pressed in, vs threaded, they add the oil pressure sending unit hole. air injection passages change for the catalytic converter.
N231/N249 83-85 basically the same as the N201, except the heater hose is a T for the beehive oil cooler.
there are some NON US variations
"4352" 70's.. factory filled ports, for P port engines. X casting....
"N225" 82-85 6 port engine. center is normal, but the outer ports are different, like an 84-92 non turbo engine.
"N236" 83-85 12A turbo engine. these must be a lot like the n201's but smaller ports and runners.
basically for a 12A in the US there is the following, i'll refer to these in sets of 3 irons, just for simplicity. with the mazda part number
"2090" set, 68?-73. old old old 12A, rx2/3. small ports and runners, these are HEAVY
"1881" set, 74-75. rx2/3 in 74 mazda revised the engines, they got 3mm iron seals, single side seals from dual. a single dual point distributor replaced the dual distributor setup. runner size is similar to the earlier motors, but the intake ports add 10 degrees of duration. basically a street port.
"8871" 76-80. rx3/7 in 76 the ports got smaller. center iron gets a taller runner. for the rx7 the irons get a nitride coating, which is grey vs the early irons black paint.
"N201" in 81-82 these irons are refined a little (less weight). the heater hose connection is pressed in, vs threaded, they add the oil pressure sending unit hole. air injection passages change for the catalytic converter.
N231/N249 83-85 basically the same as the N201, except the heater hose is a T for the beehive oil cooler.
there are some NON US variations
"4352" 70's.. factory filled ports, for P port engines. X casting....
"N225" 82-85 6 port engine. center is normal, but the outer ports are different, like an 84-92 non turbo engine.
"N236" 83-85 12A turbo engine. these must be a lot like the n201's but smaller ports and runners.
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