b35 head on b34

[Justin535turbo]

i'm sure that somewhere it is discussed what exactly needs to be done to a B35 head in order to fit a B34 block. I just can't find it. i've got a DINAN turbo 535is with a B34 in it. it's got a pretty bad headgasket leak so i need to replace the headgasket with an MLS one and get ARP head studs Anyway. i figured while i had it off, i might as well upggrade to the B35 head. So far I know that i will need the B35 intake manifold and the B35 specific head gasket. and I know that my exhaust manifold will work correctly because the exhaust ports are identical (or at least have the same part number stock exhaust manifolds and gaskets). I also know that my compression ratio will go down slightly, which is not objectionable at all on a turbocharged car. i thought i heard a rumor that the B35 head needs a small amount of machine work to fit on the B34...could be bullshit? i might as well get an extra 40(?) horsepower while fixing an oil leak right! has anyone sucessfully done this conversion? thanks!

[Shadow]

Sorry for the noob question, but what compression
ration does this combo give, exactly?

[Brad D.]

7.45:1, down from 8:1. I'm working on getting my CR calculators uploaded to my new server. I should have them up soon.

[Kyle in NO]

B35 bolts right on....you should use the B35 intake too and the timing cover that matches the head. Works great...

[Justin535turbo]

perfect, that's what i was looking for. now just to figure out how much that's going to throw off the engine management based on the b34 head flow...

[Shadow]

that's a perfect ratio for high boostin

Almost wish I had a b34 instead of this b35.

[Brad D.]

I like my 9:1 CR b35 for boosting.

[George]

I like my 9:1 CR b35 for boosting.

+1

No lag and low boost threshold

[Brad D.]

I like my 9:1 CR b35 for boosting.

+1

No lag and low boost threshold

Someone else gets it! 8)

[Shadow]

I like my 9:1 CR b35 for boosting.

You must not be boosting high enough.

[Justin535turbo]

hey bigbronzerim... i used to have a 3.73 lsd in my car and i found that it would barely spool up before it was time to shift into 2nd. so i put a 2.93 lsd in it which is ending up to be to tall for what i want, but i think a 3.25 would be perfect. does yours do the same with that 3.73? it was like driving a damn truck... a god awfull fast truck. but i was constantly shifting.

[Brad D.]

Pretty much. It is too short really. I do love the acceleration though in third and fourth. I think a 3.25 or 3.46 would be a great compromise though.

[Duke]

Pretty much. It is too short really. I do love the acceleration though in third and fourth. I think a 3.25 or 3.46 would be a great compromise though.

I had a 3.25 and was not happy with it. Any boost in 1st and you were at redline....2nd was limited too. Once I installed a 3.07, I was much happier with the drivability of the car and I could actually use that HP in 1st.

[bimmerboy]

I like my 9:1 CR b35 for boosting.

+1

No lag and low boost threshold

Boost threshold isn't affected by CR. A b34 bottom end with b35 head would have the same threshold. It won't be as fast getting to that boost but it's coming at the same RPM

[turbodan]

I like my 9:1 CR b35 for boosting.

+1

No lag and low boost threshold

Boost threshold isn't affected by CR. A b34 bottom end with b35 head would have the same threshold. It won't be as fast getting to that boost but it's coming at the same RPM

No, he had it right.

[Brad D.]

Yup, he had it right. CR affects VE which affects boost threshold.

[Jeremy]

The "right" combination of parts is entirely dependent on goals.

9:1 is great for a perky, responsive motor with quick spools and better transient response, but you'll be limited in the amount of boost you can run on pump gas.

If you want big power, 7.5:1 will support lots and lots of boost (20+ psi) on pump gas, but the turbo will take a little longer to spool.

For me, 10-12psi is plenty to get me in heaps of trouble. Others obviously don't agree. I also preferred my 3.46, but I hardly ever launched the car from a stop. It all depends on your goals and what you want the car to do. There really isn't a universal "best" that fits all needs.

Jeremy

[Justin535turbo]

in actuality, i think i would rather have a 9:1 motor with 8lbs of boost than a 7.5:1 with 15. i like motors that don't feel like they are turbocharged... they just feel like a V-8. like the new 335's, if anyone else has driven one of these cars they know what i am talking about. absolutely no turbo lag, just instantaneous power. it feels like a V-8. but since i will be working with 7.5:1 i'll just have the head decked to get some CR back, run like 12 or 15 lbs of boost and deal with some lag. i don't think it's worth the trouble of a complete engine swap. plus running 12 lbs of boost gets you more street cred . as for the diff, i think i will definately swap to a 3.25. i don't think i'll ever need to do 160 miles an hour to take full advantage of the 2.93. an E28 kind of turns into a brick at about 120 Anyway. i find myself having much more fun blowing the doors off of mustangs and just about anything else at stop lights.

[M. Holtmeier]

I don't know, but my 7.5 cr with 10psi definately does not feel "laggy." I've never been in boosted b35 to make a comparison, but I can vouch for the b34/b35 combo still having a low boost threshhold and a fast spool.

I agree with Jeremy in the fact that any setup won't be universal. I started with a 3.73, went down to a 3.25 and "tried" out a 3.46 that is still in the car because I like the way it drives with that ratio.

Remember, final drive ratios aren't all about top speed. A 2.93 will take advantage of your lower trans gears, helping you off the line.

[Justin535turbo]

that's good to know that your happy with your B34/B35 combo. and also gives me a good guess as to how much power i'll be making. there are differences between the TCD kit you have and the Dinan kit on my car, but the same principals are there. it gives me a close approximation as to what my rwhp should be. cool man. have you ever ran your car on the 1/4? the guy i bought my car from took it a few times and was running 13.9 @100mph. that was with the "no boost in 1st 3.73's". but give some/take some right. I'm curious to see what it does after the b35 head and 3.25.

[M. Holtmeier]

I made it one time last fall. It was maybe 3 weeks before the track closed for the winter. With the 3.46s and a chilly night, I couldn't get any traction. I made 2 passes before having tech. difficulties with a loosening crank nut. The trip was actually to put a little abuse on a just-broken-in clutch and shake the car down for trouble, which worked. I don't know if I'll get a run in at 10psi, I've got over 2k mi. on the rebuild and I'm itching to turn the boost up!

[E30SPDFRK]

So here's a question I haven't seen answered. If a b35 head lowers the compression ratio on a b34, would a b34 head raise the compression when installed on a b35? I saw that the pistons were different, would the valves interfere?

Reason for asking is a friend has a b35 with a trashed head and a new head laying around from a b34.

[Jeremy]

Compression would increase, yes, but overall power would likely decrease. The b35 head flows better than the b34 head in a significant enough way that the compression bump would not result in any increase in power, very very likely the opposite.

I base this assertion largely on the fact that people who have put a b35 head on a stock 10:1 b34 bottom end have noticed an increase in power despite the lower static compression ratio.

Jeremy

[T_C_D]

My experience has shown that the cam has a more significant impact on the boost threshold than the CR.

[Murfinator]

My experience has shown that the cam has a more significant impact on the boost threshold than the CR.

^ Exactly. Rather than half-ass it, just throw a PB cam in a B35 head, flat top forged pistons in a freshened M106 block and B36 throttles FTW? Back that up with a sport transmission and s3.07 and you'll blow the doors off of more than just Mustangs.
Oh, and don't forget a GT35 and tubular exhaust manifold with a cherry on top.

[T_C_D]

My experience has shown that the cam has a more significant impact on the boost threshold than the CR.

^ Exactly. Rather than half-ass it, just throw a PB cam in a B35 head, flat top forged pistons in a freshened M106 block and B36 throttles FTW? Back that up with a sport transmission and s3.07 and you'll blow the doors off of more than just Mustangs.
Oh, and don't forget a GT35 and tubular exhaust manifold with a cherry on top.

I "half-assed" it to a 12.0 at 120mph on street tires in a full weight 535is. A stock b34 motor is plenty good to beat on 99% of all cars. Not every build can be a $20,000 adventure. Most people, including myself, don't have the discretionary funds to do so.

[Murfinator]

That's right Todd, you are Mr. Half-Ass. Who knows where your current project will take you: half GM, half BMW. If you had taken the time to build the drivetrain and tune the car properly you wouldn't need to part it and start over with used domestic parts. The notion you're going to build the car better than the last time is questionable given your track record but I sincerely wish you well. At least you can deduct the project costs on your taxes. It's just a pass-time for me. I'm taking my time enjoying each aspect of the build and doing it right the first time. No rush and no pressure.

Speaking of the business aspects of your build, have you considered how it looks to have abandoned the E34 and now to have abandoned M30-based motors? Why would anyone looking to make good, reliable power drop $2-4k on TCD products when the owner himself has thrown in the towel? With regard to the new direction: how many V8 to E28 swap kits do you think you'll sell, and at what price? I doubt more than a dozen. The lover's of this model either don't have the coin or aren't prone to hybridize their cars with a non-BMW motor. The drag-race use-case for these cars also tends to appeal primarily to the juvenile crowd (no cash). Thinking that boasting a <11 second 1/4 mile will boost sales is a questionable sales tactic given the market. Just sayin'.

T C D wrote:

A stock b34 motor is plenty good to beat on 99% of all cars.

I doubt it, unless the other driver didn't know they were racing. You must mean a stock b34 boosted to at least 1 bar. And how reliable will that be? Not very, especially on a junkyard block with 200k+ miles.

[T_C_D]

Michael,

I knew you were going to be trouble. I knew, I knew it, I knew it. Shame on me for selling you any parts. Thankfully you have decided you are too good for them and are selling them. You should offer buyers the same deal I gave you instead of full retail. FYI, I have learned from the past and you can say whatever crap you want about me and I will NOT respond.

Todd

[Murfinator]

Todd: The TCD parts I'm selling are open to "reasonable offers". If you possess reading comprehension skills you would see I only state what your own website lists the parts for but this does not imply I'm selling them for those prices. No matter, I have several offers out with discounted prices and free shipping. I'm still considering keeping the parts and breaking the 500hp threshold though I have no faith you'd pay the promised $500 for doing so.

[T_C_D]

Todd: The TCD parts I'm selling are open to "reasonable offers". If you possess reading comprehension skills you would see I only state what your own website lists the parts for but this does not imply I'm selling them for those prices. No matter, I have several offers out with discounted prices and free shipping. I'm still considering keeping the parts and breaking the 500hp threshold though I have no faith you'd pay the promised $500 for doing so.

I want to mention that anyone buying new TCD parts from Michael will receive full technical support and warranty like they purchased the parts from me.

$500 store credit certainly will not be awarded to someone that trashes me on the internet.