Specific Bridgeport ?s
03-26-07, 08:39 PM
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Specific Bridgeport ?s
OK, so I'm looking to hopefully bridgeport my 12a in the very near future. Here are some specifics about it and I would like to know what I can expect performance/lifespan wise. I know this is a dead horse, but one more kick wouldn't hurt. 
The engine has ~160,000mi on it. It's currently torn down and getting all new seals/gaskets, hoses, etc... I'm not sure if I'll need new stationary gears, or if I should get carbon apex seals. Also, could it be possible the housings or plates are too worn to do this? I know I've not gotten everything so input would be great!
Use with a header and straight exhaust back to single muffler (not sure which kind), with possibly a 48 IDA.
Possible possibilties:
I would be doing to bridgeport myself, my first one. I want to be fairly reserved on this one and make triple sure I do NOT cut the water jacket. But not so much that there is no upgrade over a sp.
Or, do a half-bridge half-aggressive streetport. Same thing as above with the bridge side.
oh, and I don't really care TOO much out idle or noise, as this will be a weekend car.
Thanks guys!
The engine has ~160,000mi on it. It's currently torn down and getting all new seals/gaskets, hoses, etc... I'm not sure if I'll need new stationary gears, or if I should get carbon apex seals. Also, could it be possible the housings or plates are too worn to do this? I know I've not gotten everything so input would be great!
Use with a header and straight exhaust back to single muffler (not sure which kind), with possibly a 48 IDA.
Possible possibilties:
I would be doing to bridgeport myself, my first one. I want to be fairly reserved on this one and make triple sure I do NOT cut the water jacket. But not so much that there is no upgrade over a sp.
Or, do a half-bridge half-aggressive streetport. Same thing as above with the bridge side.
oh, and I don't really care TOO much out idle or noise, as this will be a weekend car.
Thanks guys!
03-27-07, 05:37 AM
#2
Lifespan depends on 2 things. 1. How much meat you leave for the bridge. 2. How much use you make of the powerband that has been moved way up and did you do the supporting mods to go with it?
If you want to learn more about bps, read the 'Engine Performance and Building sub-forum at nopistons.com. Pay particular attention to Judge Ito and BDC. There is also a line drawing on how to cut/taper a bridge for the best flow. If you can't fnd it. I have a copy somewhere.
Those supporting mods include hardened stationary gears, a must, 3-window bearings, definitly a good thing, and all of the oil/balancing mods you can afford. Clearnce, balancing and carbon apex seals are a big +. The needed high rpm mpds can easily add 700+ to the total engine build cost. The RB bp porting template is conservative and a good place to start.
Making an acrylic template to watch the seal travel and clearence is highly recomended. A 48 mm ida carb is the preferred carb, 51 mm for a full bp, along with a 2-1/2 to 3" exhaust system. A single muffler will not cut it for noise supression. I'm running 2 Magnaflows and it's still quite loud. A Borla pre-silencer would do better, (XR-1, race version, or the XS-1, Street version(quietest of the 2)).
How long the fresh rebuild lasts will depend on how you treat it and how worn the parts are to begin with. The RB template does not cut into the water jacket, it is close though and notching the rotor housing will give better flow. Housings will also need thier template to port the exhaust. What goes in, must come out, SDJ headers will give you the best flow, but they are no longer in production.
Now, the downsides of a bp. Low end torque, standing starts and steady state cruising below 3k rpm sucks, big time. With the 245/50/15" tires I have on mine with the stock 3.909 rear gears, I need to be in 2nd gear most of the time at 30 mph or below. Otherwise the engine chugs and bucks at anything below 3k. About 4k rpm, the engine begins to wake up, by 5k, hang on to your children or even the future ones, lol.
With the right carb, exhaust and high rpm internals, it will make power up to 9k rpm, even a little more. A bp is not the engine for the faint of heart and I cannot recommend a lightweight flywheel or a brass button clutch for stop and go city driving.
Any other questions, ask or search.
Now, just in case you have missed my now infamous sig lig line. included in it is a link to the online FSMs, carb manual and assorted rotatry reading material. Read, download and read again whatever you need. The last link is my project with a 12A 1/2-sp, 1/2 bp engine, and yes the 44 mm Mikuni PHH carb is too small for the porting but it limits the total cfm that flows in, the afrs are fine.
If you want to learn more about bps, read the 'Engine Performance and Building sub-forum at nopistons.com. Pay particular attention to Judge Ito and BDC. There is also a line drawing on how to cut/taper a bridge for the best flow. If you can't fnd it. I have a copy somewhere.
Those supporting mods include hardened stationary gears, a must, 3-window bearings, definitly a good thing, and all of the oil/balancing mods you can afford. Clearnce, balancing and carbon apex seals are a big +. The needed high rpm mpds can easily add 700+ to the total engine build cost. The RB bp porting template is conservative and a good place to start.
Making an acrylic template to watch the seal travel and clearence is highly recomended. A 48 mm ida carb is the preferred carb, 51 mm for a full bp, along with a 2-1/2 to 3" exhaust system. A single muffler will not cut it for noise supression. I'm running 2 Magnaflows and it's still quite loud. A Borla pre-silencer would do better, (XR-1, race version, or the XS-1, Street version(quietest of the 2)).
How long the fresh rebuild lasts will depend on how you treat it and how worn the parts are to begin with. The RB template does not cut into the water jacket, it is close though and notching the rotor housing will give better flow. Housings will also need thier template to port the exhaust. What goes in, must come out, SDJ headers will give you the best flow, but they are no longer in production.
Now, the downsides of a bp. Low end torque, standing starts and steady state cruising below 3k rpm sucks, big time. With the 245/50/15" tires I have on mine with the stock 3.909 rear gears, I need to be in 2nd gear most of the time at 30 mph or below. Otherwise the engine chugs and bucks at anything below 3k. About 4k rpm, the engine begins to wake up, by 5k, hang on to your children or even the future ones, lol.
With the right carb, exhaust and high rpm internals, it will make power up to 9k rpm, even a little more. A bp is not the engine for the faint of heart and I cannot recommend a lightweight flywheel or a brass button clutch for stop and go city driving.
Any other questions, ask or search.
Now, just in case you have missed my now infamous sig lig line. included in it is a link to the online FSMs, carb manual and assorted rotatry reading material. Read, download and read again whatever you need. The last link is my project with a 12A 1/2-sp, 1/2 bp engine, and yes the 44 mm Mikuni PHH carb is too small for the porting but it limits the total cfm that flows in, the afrs are fine.
03-27-07, 09:03 PM
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Wow, great stuff. I just want a good bit of opinions from people who actually have these mods. (like what Trochoid posted )
where can I get hardened stationary gears? Would it be possible to get the RB header DIY kit and make something that flows as well as the SDJ?
)where can I get hardened stationary gears? Would it be possible to get the RB header DIY kit and make something that flows as well as the SDJ?
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