B heads rev limiter?
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the b-heads will make power all over the top end, its the cams and little things like that; that will decide what the motor will do.
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649 Posts
eh, maybe you should just get a set of c heads. they are torquier and u probably could shift lower
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ive seen some on ebay. brothers performance actually was selling a new intake manifold thats made for someone who swapped C-heads onto a teksid block that has an actuater that keeps things closed for torque then opens up at high rpm for more power. i think it was a ford racing piece.
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99 Posts
they stop around 6500-6800
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482 Posts
cam profile and runner length determine where peak power is. Don't worry if you want to spin to the moon to make power B's are where its at. Be prepared to pay $$$ for a solid 8,500+ rpm valvetrain.
-Mark
-Mark
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17,313 Posts
If it helps, the stock rev limiter in my Cobra is at 7k.
Just to inform you the B heads in the Cobra and Mark are slightly different actually.
Probably not enough for 90% to care but there is a slight raise in the middle of the two valves which shrouds them that is missing on the Cobra castings. I doubt its of much importance if you go FI but NA every little bit helps.
Are you aware of what else is different from Mark to Cobra? Intake, Cams, Ignition(Cops vs coilpacks), crank, and IMRC actuator.
right off the top of my head I'm going to say ditch the mark intake and cams. Get yourself a nice high rpm capable valvetrain like Mark mentioned. Get a well ported intake... very important as this and the cam are your two biggest sources of power NA. Convert to Coil on Plug ignition, ditch the IMRCs or figure out how to get them working with your computer. Ditch knock sensors since you arent boosting and your valvetrain will be too noisy above 7000 rpm for them to work well anyway... I dont think your computer can handle them anyway. Upgrade your fuel system and injectors. I personally would also go with very light weight rotating assembly and get it balanced well. You are going to be dealing with high rpm or you're wasting your time with these heads NA. They do however have 50cc+ larger ports than any other 4 valve head made and flow like gutter pipes once you get some RPM behind them. Especially with a .20 or more overbore. I've heard that really wakes up the B's.
I'm not an expert so dont rely 100% on what I've said but this should be a rough guide on what you need to do for a good NA B head build.
Probably not enough for 90% to care but there is a slight raise in the middle of the two valves which shrouds them that is missing on the Cobra castings. I doubt its of much importance if you go FI but NA every little bit helps.
Are you aware of what else is different from Mark to Cobra? Intake, Cams, Ignition(Cops vs coilpacks), crank, and IMRC actuator.
right off the top of my head I'm going to say ditch the mark intake and cams. Get yourself a nice high rpm capable valvetrain like Mark mentioned. Get a well ported intake... very important as this and the cam are your two biggest sources of power NA. Convert to Coil on Plug ignition, ditch the IMRCs or figure out how to get them working with your computer. Ditch knock sensors since you arent boosting and your valvetrain will be too noisy above 7000 rpm for them to work well anyway... I dont think your computer can handle them anyway. Upgrade your fuel system and injectors. I personally would also go with very light weight rotating assembly and get it balanced well. You are going to be dealing with high rpm or you're wasting your time with these heads NA. They do however have 50cc+ larger ports than any other 4 valve head made and flow like gutter pipes once you get some RPM behind them. Especially with a .20 or more overbore. I've heard that really wakes up the B's.
I'm not an expert so dont rely 100% on what I've said but this should be a rough guide on what you need to do for a good NA B head build.
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i have a light weight/balanced rotating assembly.. i am getting a 97 cobra intake. my motor is bored .020 over. do i just take the imrc plates off or do i replace them with something else?
what are knock sensors?
will 32 pound injectors and 255lph fuel pump be enough?
right when i looked at the mark intake i said and i quote "hell no!!!"
what are knock sensors?
will 32 pound injectors and 255lph fuel pump be enough?
right when i looked at the mark intake i said and i quote "hell no!!!"
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649 Posts
well the imrc's in the 98 cobra's were plastic. i deleted my imrc's by getting a set of 97 cobra imrc's which were aluminum, and i removed the rods and flaps, then had the holes that the rods went through welded shut. knock sensors retard timing (i think) when the motor detects knocking and pinging?? someone correct me if im wrong. 32lb injectors and a 255 would be enough for maybe 400hp ish, i believe
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17,313 Posts
No, he's saying he made IMRC-delete plates from a a set of the older aluminum units.
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649 Posts
well, you mite not have to. it depends on if your car has aluminum ones or plastic ones. im not sure on the mark8's. if you have aluminum ones, just do what i did. if you have the plastic ones, just do what i did lol! well, MMR makes delete kits, for like 250 bucks! so i did it for roughly 30 by selling my plastic ones, buyin aliminum ones, and then havin em welded up.
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