As im starting my turbo 4v build, im looking into parts. I keep seeing a lot of b head this, c head that. I thought I was sold on the c head combo. But just recently, I got 2 separate dyno's from 2 people here where I live with very similar results and wonder, whats really going on.

On the first dyno, '03 factory cobra short block (crank,rods,pistons 8.5:1 compression motor), '93 b heads freshened up with valve job and factory valves and springs, '93 mark viii cams, imrc deleted, 98 cobra intake, t04b 60-1 rear mount turbo, e85, t45, 3.27 gears (also thinks stock springs, even though new, are causing his low power curve)

Second dyno, mark viii teksid block, forged internals, 10:1 compression, 03 cobra heads, i think 03' cobra cams, mach 1 intake, 67 mm turbo, e85, t56, 3.55 gears i think.

Both ran with similar conditions and both SAE numbers.

Everyone says c heads are better for low-mid range but it seems like the b's are better. So is there something in the tune? Cams? intakes?
I already bought a '98 mark vii complete motor. Im looking for 700 rwhp. Should i just forge the bottom end and clean up the heads, get '98 intake cams, imrc delete, boost the hell out of it and call it the day?

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Is all in how you blend the parts.

The quickest mod motor on the track run b heads..

Out of the box the c head is a better option on a street car.
But if you spend the money on the heads
& send them to the right company,with the right combo the b head will out perform the c head

 

Thats what Im trying to understand, what would be a better combo. Ive been away from the mod motor scene 9 years and trying to play catch up again with knowledge. Im willing to spend the money where it needs to be spent, but im not trying to get the "best on the market" parts if they are not needed. The car will be more of a weekend fun car, 75% street and 25% drag. To live up to the abuse, I know ill pay out for a good bottom end, rings seals, bearings, etc. Not sure if I should look for a cobra crank and h beams from a terminator with aftermarket pistons or just buy mmr 900 rotating assembly. Once again the heads, I already have the B's that came with it, do I sell them and get some mach or aviator heads? Or just throw some guides and springs? Ive read tons of info, thats why I thought I was sold on the c heads, but seeing these 2 dynos, im second guessing myself.

The dynos are virtually identical up to 3500 rpm's, so I dont see the loss of low end from what other people say and what I was afraid of. Any help on what may be the best route for me?

 

The question is :
Do you have another car to drive around?

 

Yes, I have 2 reliable dailys, and I have my 88 stang that will be running here very shortly, just deciding if I should get a clutch and sell it or keep it but buy a converter and stick in the 4r70w that is built for it thats siting in the garage.

 

What I meant by this 4v new edge will be 75% street, is that I plan to drive it mostly on the weekends, and when it is being driven, majority will be on the street for those days. Not sure if you understood that or not.

 

Then go with the c head...

 

What else would you recommend? My original plan was 99 cobra manifold and 98 cobra intake cams. I heard the mach intakes have a little less top end than the cobras.

 

Either combo will work. Both have been proven at huge power and streetability. The c's will result in a better low-midrange, and in turn spool all things being equal so my opinion would be to use the c heads with 96-98 cobra intake cams or 99-01 cobra intake cams if using stock cams. The C heads are just a better design and wont leave anything on the table up top either. Every combo is different and the combos listed above are a perfect example. The smaller turbo will spool faster all things equal. Also cam timing and the tune make a huge difference. I think you are seeing the results of a combination of differences more than the heads. My car has 03 heads, 98 intake cams, and a ported mach 1 intake. So far I'm very happy with my parts selection. To be fair I'm still on lower boost working some bugs out. Since you said you already have the b heads I might consider that route as it will work well also.

 

https://www.theturboforums.com/threads/364532-ported-B-heads Food for thought !

 

i like the b- heads but seems like there are more intake options for the c heads, unless you do an expensive sheet metal intake.

 

Those heads in that link are crazy!!!! A little too much for me , lol. R Snake, I think you migut be right about the spool time. I was just talking to the guy, hes actually my bro inlaw, and he has mentioned how his turbo is way too small for his car which may have added to the dyno showing nearly the same low end power, which im still stunned at how similar they are up to 3500. Im not going with any sheet metal intakes, seems like all of them lose a lot of low end power. I honestly like the look of the c head cobra intake better, but I feel fine with the b intake. Looks are not a big thing as far as these intakes. The b route seems easier since I already have the heads, but not sure cost and ease of finding anything just yet either.

 

I say stick to the b heads.. The low end power lose is not that noticeable. Mine seem fine.. There cheap I paid 200$ for mine that were allready machined. I then Had the Exh ported and the intakes cleaned up. I run stock 97 cobra cams. Just run a flat top piston and you will never notice the low in power lose.. Lol.

 

1slo, I dont supose yiu have your dyno? I am going to run 10:1 compression and e85

 

Cars never been on the rollers. I street tune the car myself. I go to track to dial in timing. I don't understand what the dyno graph is going to show you. Every setup is going to he diff.

 

I was just looking to see the low end people are scared of losing with b heads. Thats why I started this thread, to maybe see some more since it seems like turbo size doesnt matter at low end much. I was also debating on runing myself since ive had a book that pretty much lays is all out for you, and do's and don' ts

 

I have no low end loss really , it pulls pretty strong from a stop plus my twins spool fast. Now with the 3:08s it's spooling at about 1900 - 1950 and my comp is only like 8.9.1 B,s or good street heads, mines a street car.

 

Comments like this ^ make me want twins.. I won't see full boost till 4600 in low gear. Footbraking to 3000rpm.

 

WOW! 4600? What size turbo and down pipe do you run?

 

I meant that when not in boost at all it still runs and pulls good , but a built 4V should pull pretty good. I would venture to say it probably makes 400 to 420 N/A with those heads. But with the twins and the small exhaust housings it spools to fast almost, lol as soon as the tires break its at full boost, giving a lot of thought to a better boost controller , AMS 500 or the other new one that just came out so I can ramp it in and get it to hook although it is a lot better with the new tires than it was with the 17" D Rs they had no side wall and these 295/55/15 are biting a lot better.