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Discussion Starter #1
where do the B heads stop making power if anyone knows.. thanks
 

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mm's nitrous mod
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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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Discussion Starter #3
ok.. im doing the 4v swap for the more flow/more rev.. i just dont wanna still be shifting at 6k!:(
 

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eh, maybe you should just get a set of c heads. they are torquier and u probably could shift lower
 

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Discussion Starter #5
well the thing is i found a mark vii motor for 350... for everything.. i just cant pass it up.. im looking for some c heads... anyone know somebody?
 

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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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N/A 4v Guru
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Are you asking if you can rev past 6k? or do you wanna know if they make power under 6?
 

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Discussion Starter #9
i was asking where they stop making power??
i just know with these 2v's they cant make power above 6k without the proper head work/cam/intake combo
 

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They will make power to the upper 6k range. The heads aren't the issue at that rpm it starts to be the cams and intake.
 

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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
 

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Discussion Starter #12
its just a basic 2v to 4v swap.. just trying too see where i need to set my rev limiter for and where these heads will make power.. until i get out of college then these heads will see the 8500 range
 

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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.
 
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Discussion Starter #15
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!!!"
 

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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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Discussion Starter #17
so i have to have the imrc plates but i should go to aluminum ones?
 

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Discussion Starter #19
oooh i see.. how much will the imrc delete kit run me roughly
 

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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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