Bridgeport 12A in an MG Midget
10-07-2002, 01:06 PM
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I couldn't really add to the bridgeport 12A thread in the 'other forum' other than to say that the bridgeport is calling to me. I've already got a 17mm oil pump and a modded oil pressure regulator. The engine is a '73 12A and is apart and clean. I just need another rear 'side plate' and they would all need to be ported.
A couple weirdnesses about the '71-'73 engines other than the twin dizzies is they also had a top mounted starter. The car originally had one of these 12As in it when I got it. I have since fitted a 13B with a bottom mounted starter. I'm finishing up the 13B install this week and I'm going to drive it around after a brake job and other misc roadworthy issues are solved. After those problems are sorted out, I'll be preparing the 12A. It failed due to a rotor imbalance and a badly scored and worn 12mm oil pump (previous owner's fault, and/or maybe the oil overheated?) That's why I've got a known decent running 13B in it right now.
I have a matched set of FB rotors (most likely '85 since the front cover from this engine has a 12A turbo oil return line casting under the OMP). I'd like to use them in my '73 rotor housings and I hope the chrome will be strong enough to handle the iron seals. I'd also like to use a '74-'78 rear end housing (side plate) so I can retain the bottom mounted starter (in case I get a Weber). All I'd need to do is delete two tensions bolts. Mind you the old engines have two more tensions bolts than RX-7 engines, so it'll break even (hmm, bad pun). I just don't want to run the risk of deleting four bolts by using an RX-7 end housing. Thus I'm forced to use a '74-'78 'plate. I've got a known good one in my four port 13B which needs to be rebuilt thanks to an EGR intermediate housing with its tiny ports. Very Dumb since it cannot be ported very much. I think I could get away with tearing this engine down while building the 12A at the same time. At least the 13B could get away with an RX-7 end plate if need be.
Should I get a Mazdatrix bridgeport template? Should I just bridge the secondaries? I still want low RPM drivability and could block the channels that run between primaries and secondaries on a stock intake manifold. It's going into my MG Midget project so I can't fit a Racing Beat intake manifold, but I do have a Holley to Nikki bolt pattern adaptor. I know the flow won't be as high with a stock manifold, but it's a compromise in such a small car. I also have access to an RB modded Holley carb (550CFM for a 13B should work on a half bridged 12A with fully seperate runners).
Thoughts?
A couple weirdnesses about the '71-'73 engines other than the twin dizzies is they also had a top mounted starter. The car originally had one of these 12As in it when I got it. I have since fitted a 13B with a bottom mounted starter. I'm finishing up the 13B install this week and I'm going to drive it around after a brake job and other misc roadworthy issues are solved. After those problems are sorted out, I'll be preparing the 12A. It failed due to a rotor imbalance and a badly scored and worn 12mm oil pump (previous owner's fault, and/or maybe the oil overheated?) That's why I've got a known decent running 13B in it right now.
I have a matched set of FB rotors (most likely '85 since the front cover from this engine has a 12A turbo oil return line casting under the OMP). I'd like to use them in my '73 rotor housings and I hope the chrome will be strong enough to handle the iron seals. I'd also like to use a '74-'78 rear end housing (side plate) so I can retain the bottom mounted starter (in case I get a Weber). All I'd need to do is delete two tensions bolts. Mind you the old engines have two more tensions bolts than RX-7 engines, so it'll break even (hmm, bad pun). I just don't want to run the risk of deleting four bolts by using an RX-7 end housing. Thus I'm forced to use a '74-'78 'plate. I've got a known good one in my four port 13B which needs to be rebuilt thanks to an EGR intermediate housing with its tiny ports. Very Dumb since it cannot be ported very much. I think I could get away with tearing this engine down while building the 12A at the same time. At least the 13B could get away with an RX-7 end plate if need be.
Should I get a Mazdatrix bridgeport template? Should I just bridge the secondaries? I still want low RPM drivability and could block the channels that run between primaries and secondaries on a stock intake manifold. It's going into my MG Midget project so I can't fit a Racing Beat intake manifold, but I do have a Holley to Nikki bolt pattern adaptor. I know the flow won't be as high with a stock manifold, but it's a compromise in such a small car. I also have access to an RB modded Holley carb (550CFM for a 13B should work on a half bridged 12A with fully seperate runners).
Thoughts?
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