Guestimates...

[4x4_e30]

The thing in common is a head that flows atleast ~200CFM through the whole intake tract (not just a bare head) a well matched combination with proper inlet and exhaust tuning and huge lobes on the cam. These are fully built race engines

I don’t agree with low lift and midlift importance blanket statement, it doesn’t make any sense to make blanket statements when there are camshafts ranging from 10mm lift to 14.5mm lift and duration 250 to 330degrees. It depends on the application and the cam.

i feel the importance of flow needs to be based on the cam specs and to account for peak piston speed ( peak flow demand) and the cam lift where the port air speeds are highest and the port chokes. If you do some basic analysis of piston speed vs crank angle and cam lift versus crank angle it will become apparent that mid and high lift on a performance m20 stoker with decent cam will delay choke and make more power at higher rpm more effectively. With a stock cam the importance shifts to flow at lower lifts IMO.

No M20 has a pentroof chamber at all, the M50, S50 i.e 4V cylinder head etc have pentroof chambers. The most powerful M20 that is publically known uses the 885 semi hemi design with its angled squish band so if you think this is bad you need to take a step back for a bit as it seems to work well.

The 731 is similar but the squish pad is flat and the chamber ends up a little smaller making it slightly easier to get higher CR. The advantage in the 731 chamber is being able to use a flat top piston successfully retain squish and being able to set up the squish clearance easier. There is no evidence that it is better for making power over the 885 chamber.

My point about low to mid lift came from this thread:

http://www.e30tech.com/forum/showthread.php?t=117701

I'm going off of what e21jps and TK have built as far as chamber shape go, which M20 build are you talking about?

Edit- Oh damn, the TK build is a semi hemi. I feel incredibly stupid now.

[digger]

Lol.....

Problem with low lift flow is reversion. Getting good low lift flow makes it flow better in reverse which is not a good compromise IMO when you need to operate at low rpm and part throttle.

its similar to adding more cam seat duration which gives more topend at the expense of bottom end. There is often better BFYB with mid and highlift flow but it depends on what cam is used

[Bullhead]

Op I will also add something to what others have said. I have only had my E30 for a short while but I have raced sbc powered cars on the 1/8th and 1/4 mile. There are only 4 things that build power.
1) Displacement, there is (almost) no substitute for this. Cubic inches, examples but not limited too: Larger pistons, larger crank, larger rods.
2) Forced Induction, this comes in 2 common forms. A supercharger (roots or belt driven accessory type) or a turbo which uses the exhaust gases to spin the turbine. Both force air into the engine at a much greater rate than it could consume or "inhale" on it's own.
3) NOS or other Nitrous Oxide brand. When NOS is heated it splits into Nitrogen and Oxygen thus creating more O2 for your fuel mixture then allowing you to use more fuel which creates more hp.
4) Tuning, just as it says. A tune up, custom chip, custom fuel mapping etc..

These are it, pick one. I will warn you though displacement can get expensive.

[Sykohtic]

hp is going to be governed by the induction flow mostly and the head and cam shaft are most important aspect given you have a proper intake listed on your spec sheet. you should be able to make your target

A considerable addition to the parts list I've considered is upsizing the valves. What's your opinion on this? Would it be worth doing since I'll already be taking the head off/apart to do all the work on it? I've heard people say that in most cases in NA builds its kinda pointless to upsize the exhaust valves because they can already flow enough gas as they are, and I read that on a thread on here somewhere... (I'll track it down if I can). Theres a chemistry formula I could use to actually calculate the approximate volume of gas produced by the combustion (if I had ideal air-fuel ratio that is), and then I guess after for a relative approximation I'd just have to calculate the cfm of the exhaust valve, and then basically compare the figures to see if it was enough cfm, but who wants to actually do that when someone with experience who knows better can help me out?

Basically the principal that inspired me to try and go NA was forced induction itself. I guess I sort of thought to myself that well, since I figure my engine is due to be rebuild anyway after all the trauma its been through, If I turbo-ed or SuperC-ed, I'd end up spending all that money rebuilding the engine to factory spec, then the cost to turbo or SuperC. By that point, I could just go NA stroker for nearly the same price point as a rebuild to spec, still end up with a near-totally fresh better than stock engine, and be a little different. More expensive overall? Quite likely because of everything I wanna do, but logical to me.

[digger]

oversize valves work but the porter needs to know what he is doing to get them to work. you don't just add them and expect results.

you can get the stock exhaust valve size to flow plenty so IMO you want something like 44/36 rather than 43/37

[Sykohtic]

oversize valves work but the porter needs to know what he is doing to get them to work. you don't just add them and expect results.

you can get the stock exhaust valve size to flow plenty so IMO you want something like 44/36 rather than 43/37

Alright cool. I'm looking around NC for a place to do professional head-work, for when the time comes. I know about a race shop or two around the state, not sure that they really need to specialize in BMW, but while it ain't gon be cheap, I want it right.

[digger]

Alright cool. I'm looking around NC for a place to do professional head-work, for when the time comes. I know about a race shop or two around the state, not sure that they really need to specialize in BMW, but while it ain't gon be cheap, I want it right.

id look for a place with good reputation and speak to them. they don't need to be a BMW specialist. if they dont ask the right questions then best to avoid

[Sykohtic]

id look for a place with good reputation and speak to them. they don't need to be a BMW specialist. if they dont ask the right questions then best to avoid

What are a few examples of some crucial questions I should listen for? Basically some of the finer points mentioned in this thread?

[digger]

What are a few examples of some crucial questions I should listen for? Basically some of the finer points mentioned in this thread?

application.
engine size (bore and stroke)
rpm
compression
cam specs

if they don't ask info about these then they probably wont give you what you need.

[Sykohtic]

application.
engine size (bore and stroke)
rpm
compression
cam specs

if they don't ask info about these then they probably wont give you what you need.

Awesome stuff, I'll be on the prowl and the listen. Thanks for all your help!

[LJ851]

Keep posting here or do a build thread when you build, a shop/person that can build a head/combo that makes power is worth knowing about.

[ForcedFirebird]

oversize valves work but the porter needs to know what he is doing to get them to work. you don't just add them and expect results.

BTDT

Just plugging in larger valves will actually hurt the flow. OP, make sure whoever you pick to port the heads has a flow bench and can give you before and after numbers, otherwise they are just shooting in the dark.

[Sykohtic]

Keep posting here or do a build thread when you build, a shop/person that can build a head/combo that makes power is worth knowing about.

I definitely plan on a full build thread if I can manage it. I agree totally, and also wanna include things like the ITB install and rigging and the exhaust setup. If possible, I thought potentially about doing a sort of Mighty Car Mods thing and do my thread in videos, since I enjoy doing that sort of thing.

[Sykohtic]

BTDT

Just plugging in larger valves will actually hurt the flow. OP, make sure whoever you pick to port the heads has a flow bench and can give you before and after numbers, otherwise they are just shooting in the dark.

Understood. I was planning on having whoever does it take the valve ports and expand (not sure if expand is the right word) them out an extra Xmm to match the additional Xmm of valve diameter there'll be, so the person who does it is gonna have to have all the right stuff. I'm probably gonna start my search with this shop I saw in I think it was Concord, NC, and see what sort of leads I get from them and a couple of mechanics that have laid hands on my car before lol

[Sykohtic]

So I thought I'd continue posting here for a little as decisions develop and I have new ideas.

After reading some of the posts above, I did a little research. I might go ahead and add the extra effort into having the car rigged to adjust itself to fuel mixture so I can run pump gas and e85 in mixture.

Nothing in the course of the build has changed, all that you see above will be done. I honestly saw a MCM video on thier 11 second Subaru RS Wagon build about doing this with e85, and kinda just decided that well, if it's actually possible, and the engine can take it, why not just do the little extra bit to make the car capable of running e85 of I want it to, and then just add 93 on top of it when I don't? I still want it running over 300 wheel on pump gas, but why not add the potential for more power over top of that?

I assume a standalone will be capable of handling such a task, as it's gonna probably have to be able to adjust cam timing on the fly to cope with changing mixtures of e85.

This is just a whimsical thought. I kinda do wanna do this, but its probably gonna be one of those things where as long as its relatively easy to accomplish with a few additions and extra tuning once that bridge is ready to cross.