Ive heard that some guys are burying there tach after they go to a direct fire setup. Is this safe on a stockport 12A? For instance is running my stockport 12A up to 8000rpm okay? As long as its within temp range (not even close to overheating)?

 

Not really. With stock internals the rotors start to chatter a bit at around 6500 RPMs. At 8K, they are chattering quite a bit more. It has something to do with the apex seals not being able to stay in contact with the housings. Simialar to high revving a piston engine and valves floating. Also since the housings are bolted together they have a slight flex between them, and this causes a vibration which adds to the chattering. I am sure someone else will jump in. Also the chattering of the rotors (high rpms) will reduce apex seal life which could cause in premature seal failure.

With the direct fire - It does help and the only reason I switched back to stock was for simplicity and my quest for a "clean" looking engine bay. On a side note, I have ran my engine up to 8K on multiple occasions, and so has a friend of mine who has a stockport. Neither of us have owned our cars that long though. If you are going to do it (rev high), I say only do it in 1st and 2nd gear.

 

Chattering sucks. The more you get on the housings, the more they are prone to flaking too. Its a result of over-reving too much with steel apex seals. There is no reason to exceed 7500rpm on a completely unmodified 12a. When you add in headers, light flywheel, intake upgrades, it pushes the powerband higher and more aging will occur when the engine is rev'd above roughly 6500rpm. There is not a lot you can do. I am convinced that using pre-mix keeps the apex seals and rotors cleaner and better lub'd though. That doesn't fix the chattering though. You could use carbon apex seals which don't hurt anything, even when they break typically, but they fail more easily and don't seal well at low rpm.

Anyone, What company re-surfaces the rotor housings? Wonder if any of their coatings handle the high rpm and bouncing of the apex seals any better.

Think the bottom line is to keep the engine below 7000rpm most of the time, and if you have bridgeporting, then get carbon seals, otherwise you should be fine for the most part.

 

hmmm, well that sounds about right with my open exhaust and intake, the car seems to make the best power around 6000rpm to 7000rpm, and i usually catch it and shift as soon as it gets close which is never over 7500rpm. But this chattering you guys speak of? I guess i havent expierenced it, cuz i have no clue what you are talking about.

 

www.jhbperformance.com resurfaces rotor housings and also provides lots of info about their work

 

Mike, it's when the apex seal jumps off the housing. It then slams back into housing possibly causing flakes. if you look at the housing, it occurs at the "bump" i.e. right by plugs and right after exhaust. BTW mike what was that place with the 3L220. All the places in BC don't have it or were closed. Also how much did you pay for it. /Hijack

 

mine revs smoothly to 8k. 30k on professionaly rebuilt stockport. been doing it for almost 4 years with no ill effects.

 

ron i sent you a pm, and my new R&P will be here tuesday!