realistic approach to 400RWHP N/A

[xblitzkriegx]

id like this thread to be a realistic approach to attaining 400rwhp in a cobra thats still streetable [ie, it can idle for 10 minutes in 100 degree heat and not explode] and doesnt require 8000rpm to make power AND use b heads. think of this as an acedemic exercise and possibly a repository for other people. ive not heard anyone [im sure there are people who have...] whove made 400rwhp n/a on a streetable 4v. 380ish seems to be most common.

i consider myself a car guy and fairly knowledgeable about engines but i admittedly have little experience with a 4v mod motor. my current Cobra is 100% stock down to the oem 1997 plug wires. runs fine.

heres what i think ill need: headwork, no porting, just bowl work, clean up and a really good vavle job. a SRI, 90mm maf, 42lb injectors, cam somewhere in the 230ish range @ 0.050-degreed accordingly, related hardware for cams, 11.5:1 pistons, good forged rod, underdrive pullies [not piggyback], electric water pump, long tubes 1 3/4 to 3"collector, non catted x-pipe. forgot to add, i have easy access to E85 so CR isnt an issue. i wouldnt be afraid to go 12 or even 12.5:1. e85 is 1.5 miles from my house.

for funsies, please dont mention c heads. i know theyd prolly make more but thats not the point. im interested in doing this with b heads...and still be streetable. also, im not 100% against a stroker but id like to avoid it if possible.

thoughts?

 

[ZAPPY]

The only problem is that with the b heads u will need to spin the motor higher to make that type of hp. I also think u will need a little more cam like 240 duration or more.. A stroker would be in ur best interest to make that type of power and be streetable. If ur not against usin e 85 the more the compression the better.

 

[svtcobralover]

A stroker is the only way you'll come even close to 400rwhp. And for the money, you're better off just putting a Coyote engine in the car with a FRPP controls pack and call it a day. A stroker motor alone is going to cost $5-6k. The reliability of a Coyote sounds just so much easier and you're already close to 400rwhp right out of the box.

Just my .02c

 

[98BABCobra]

And for the money, you're better off just putting a Coyote engine in the car with a FRPP controls pack and call it a day. A stroker motor alone is going to cost $5-6k.

^^^This. The money you will spend to make that amount of power N/A will highly outweigh the return in my opinion. For the money you will spend you could put together a really nice supercharged setup and see a lot more power.

 

[ZAPPY]

^^^This. The money you will spend to make that amount of power N/A will highly outweigh the return in my opinion. For the money you will spend you could put together a really nice supercharged setup and see a lot more power.

I agree with your statement but not everyone wants to go the easy route and just put some forced induction on. Imho it take a lot more know how to make a fast na combo. :rockon:

 

[encasedmetal]

I agree with your statement but not everyone wants to go the easy route and just put some forced induction on. Imho it take a lot more know how to make a fast na combo. :rockon:

the OP is already taking the easy route by not researching a topic that is covered monthly in this section of the svtp site alone.

 

[ZAPPY]

I think it is just a tad different in this case as the op wants to use the b heads as we all know r not the greatest for na combos. But I dont think his goals r very realistic as to be streetable and not rev it high and not use a stroker setup. :shrug:

 

[na svt]

A 281ci, B headed engine will require very long duration cams and a good amount of compression and this leads to terrible driveability and reliability. The only way to make a decent powercurve with B heads is to add cubic inches and a BB/Stroker is the most "streetable" way to get there. Its compression can be kept moderate and the cams would not require the engine to be spun to 8000rpm.

Why bottleneck the engine with B heads?

this will get you to your hp goal but tq will suffer greatly:

stock stroke/bore
12.5:1
e85
Comp 106500s
short runner intake
ported heads

 

[ZAPPY]

Hey Zach I know this is off topic, but I love ur avatar. What gives? Lol!:thumbsup:

 

[ZAPPY]

A 281ci, B headed engine will require very long duration cams and a good amount of compression and this leads to terrible driveability and reliability. The only way to make a decent powercurve with B heads is to add cubic inches and a BB/Stroker is the most "streetable" way to get there. Its compression can be kept moderate and the cams would not require the engine to be spun to 8000rpm.

Why bottleneck the engine with B heads?

Guess who just joined the party!!!! I have to ask as well why the b heads?????

 

[encasedmetal]

Hey Zach I know this is off topic, but I love ur avatar. What gives? Lol!:thumbsup:

taste the rainbow

 

[crazycarlo]

Honestly there is a reason you don't see a lot of 96-01 cobras running around making big NA power. It takes a lot of $$$ and most ppl would rather spend less money and get more power with forced induction. I've been on this forum since 05 and I don't think I've seen 3 cars that are true street friendly NA 400 HP cars.

 

[xblitzkriegx]

A 281ci, B headed engine will require very long duration cams and a good amount of compression and this leads to terrible driveability and reliability. The only way to make a decent powercurve with B heads is to add cubic inches and a BB/Stroker is the most "streetable" way to get there. Its compression can be kept moderate and the cams would not require the engine to be spun to 8000rpm.

Why bottleneck the engine with B heads?

this will get you to your hp goal but tq will suffer greatly:

stock stroke/bore
12.5:1
e85
Comp 106500s
short runner intake
ported heads

*sigh* i know the b head ports are huge. i underestimated just how big they are. i imagine thats why torque will be terrible. just not enough potential flow from a 4.6l engine under 8000rpm bleh. im going to also guess that they probably wouldnt be much better on a 5.4 either. i mean, better than a 4.6 but still giant.

i was really hoping to use stock parts that the cobra came with just because i thought it might be a fun challenge. ive seen various b headed cars with cams and other mods hitting between 350-380hp but none had high compression AND port work AND SRI all at once.

well, i like to think that it could be done but it doesnt appear so, not with b heads, and especially without a stroker. bleh.

so in keeping with a realistic approach and to retain a someone stealthy solution would be: 03/04 c heads/marauder heads...Mach1 intake lower and an adapter to keep the b head upper intake.

also, i should offer my version of what i think streetable is? a streetable engine to me is one thatll make vacuum for brakes and idle in hot weather without overheating. everything else is fair game. 1000rpm idle is ok with me. having the engine run rough under 2000rpm is ok too. ive owned/built engines that didnt clean up till 2000rpm and it was great fun. they werent mod motors though.

i still think itd be kinda fun to try to get a b headed motor to 400rwhp on stock stroke. sucks that itd take 8000rpm to do it.

 

[na svt]

also, i should offer my version of what i think streetable is? a streetable engine to me is one thatll make vacuum for brakes and idle in hot weather without overheating. everything else is fair game. 1000rpm idle is ok with me. having the engine run rough under 2000rpm is ok too. ive owned/built engines that didnt clean up till 2000rpm and it was great fun. they werent mod motors though.

i still think itd be kinda fun to try to get a b headed motor to 400rwhp on stock stroke. sucks that itd take 8000rpm to do it.

E85 and 12.5:1 compression will run cool, even in hot temps. These cars do not use vacuum to operate the powerbrakes.

A C head combo will require high RPMs or high compression to make the power. the reason for that is the intake manifold options. The Sullivan will get you to 400rw with moderate compression but require high RPMs to do so. The stock intake will maek great midrange power but at 6300rpm it's done. So, a stock intake'd combo with 12.5:1 on e85 and moderate cams will get you there with a shitload of midrange power.

If only I had the time to adapt a B intake onto C heads...that would be the best of both worlds.:rockon:

 

[CJK440]

I set off on the same quest about a while ago to replace the B head 4.6 / D1SC combo I had in the car before. I wanted more low end and midrange than the centri combo, get 400 peak flywheel HP and wanted to do it on a budget. A tall order.

I started with the same ideas as you, retaining the B heads etc. but after discussions on here, plans changed.

I built an 11.5:1 5.0L shortblock and instead of my original plan of keeping B heads I went to C's. Since I was on a budget, instead of paying a premium for 03/04 heads, I bought a complete 99 Continental motor and stole the 99/01 C heads off of it. I performed a very restrained bowl blend job at hole just to improve the poor transition from port casting and bowl machining. Since I was interested in low and mid, I used a Mach lower with Cobra lid. I just cleaned up the casting in the windows where the air passes from upper to the runners below. Since I was on a budget, I couldn't swing cams and from everybody told me this is what will keep me from reaching the 400 flywheel number I was looking for. I ended up using my stock 97 cobra cams. Maybe I'll put in cams later.

I beleive the consensus was the motor should make 365/370 flywheel IIRC. Didn't make it to a dyno yet. It feels good but definatley runs out of steam at 6500 ish.

The combo I have running now.

Saleen 3.8 crank, manley rods and Manley pistons in an NVH Mach block.
11.5:1 CR
99 C heads bowl blended
97 Cobra cams degreed as per na svt suggestion
Mach stock length Lower, cobra upper stock TB
Mac Long tubes
Self tuned

I toyed with a B head upper but ended up keeping the C upper. Wiring changes were minimal, fuel rail adapting was easy, and it all fits under my STB after a minor tweak to it.

For what I use the car for I am happy with it.

 

[xblitzkriegx]

E85 and 12.5:1 compression will run cool, even in hot temps. These cars do not use vacuum to operate the powerbrakes.

A C head combo will require high RPMs or high compression to make the power. the reason for that is the intake manifold options. The Sullivan will get you to 400rw with moderate compression but require high RPMs to do so. The stock intake will maek great midrange power but at 6300rpm it's done. So, a stock intake'd combo with 12.5:1 on e85 and moderate cams will get you there with a shitload of midrange power.

If only I had the time to adapt a B intake onto C heads...that would be the best of both worlds.:rockon:

i have no experience with e85. i would highly enjoy a ton of CR and i have steady and close supply of e85 here.

i cant find much info on a b head sully intake, only a stillborn dual tb version that never panned out? i see a c head sully intake but it seems its for carb/tbi? the mmr unit is pointless below 7000rpm from what i see and have read. the runners are open and it just looks like someone copied a generic sheet metal intake and welded it to imrc deletes. i feel its pretty lazy not to extend the runners to go inside the plenum and have them radiused. they could have the square port taper to round for better flow. just....a lot of what seems to me common sense things to make that intake so much better. then again, maybe they tried it and saw no gains. i feel theres much to be had there.

 

[na svt]

i cant find much info on a b head sully intake, only a stillborn dual tb version that never panned out? i see a c head sully intake but it seems its for carb/tbi? the mmr unit is pointless below 7000rpm from what i see and have read. the runners are open and it just looks like someone copied a generic sheet metal intake and welded it to imrc deletes. i feel its pretty lazy not to extend the runners to go inside the plenum and have them radiused. they could have the square port taper to round for better flow. just....a lot of what seems to me common sense things to make that intake so much better. then again, maybe they tried it and saw no gains. i feel theres much to be had there.

There is no Sullivan intake for B heads and the MMR intake is no good. Your options are B heads with a short runner or C heads with a stock intake or 10" short runner. The Sullivan for C heads is a good piece but requires a minumum shift point of 8000 to work well on a small cube motor.