Head Rebuild (possible upgrades) questions

[Cabriolet]

for those who says I am a retard:

http://speedtalk.com/forum/viewtopic.php?f=1&t=8652

at the end of the conclusion:
'I calculate the following for the '200', '731' and '885' respectively:93m/s, 76m/s and 77 m/s the last two are lower than I had expected'
If you want power, you will need gas velocity:)
dialoge end...

OMG just get out. you know just enough to get into trouble.

you know the velocity is higher because it is overly restricted.
While velocity important for torque, this is only a small factor. the restricted air flow of the 200 head cannot be over come. and is VERY evident when you get you 40mph. Go ahead and mod the crap out of you eta show us the dyno numbers and your 1/4 mile time. and ill show you how far behind you are.
an 885 head on a 2.9L can make 250-270 wheel HP NA. you will find you cannot hit 200whp with that 200 head.

and as your chart show. after VL passes 4, the 885 head is what you want

[digger]

for those who says I am a retard:

http://speedtalk.com/forum/viewtopic.php?f=1&t=8652

at the end of the conclusion:
'I calculate the following for the '200', '731' and '885' respectively:93m/s, 76m/s and 77 m/s the last two are lower than I had expected'
If you want power, you will need gas velocity:)
dialoge end...

its too much work to be practical to start with a 200 head, instead start with a 731 which still has a small port but out of the box its better than 200.

there is a relationship between flow, cross sectional area and velocity. the thing moving air in the engine as opposed to a flow bench is the exhaust and piston motion which creates pressure differential. simply using the smallest port irrespective of other engine parameters may not be the best thing.

still the B25 pistons dont work with 200 or 731 without removing material not adding it.
if you are welding the chambers you would want to know what you are doing you can easy stuff up the combustion efficiency. sometimes what looks and sounds right doesnt work so without extensive testing its a stab in the dark

the only combustion chambers that should be symmetrical are really 4v pent roofs the best 2V chambers are not really symmetrical.

if i wanted the most power with a 100% stock b25 bottom end i would start with a 200 head, modify the chamber like the 885 to match the psiton and fit oversizes valves and do a nice port job. would work well but would be alot of work and $$$ i would be better off with a bigger engine + 885 worked over......

show us some results if it works, people wont think you are smoking some plant matter if you back up what you say.....

[Hobbit]

At first I use a B20 engine, not a B25.
I haven't measure my car yet, I will if I have time.
Inlet ports are related to the inlet valves, that is absolutely true, 731's port a bit larger than the 200.

My welded up chamber... (If my english is right, and it is called like that).
And the final result:

And it works
All the mods costs about 250$ converted from the currency of my country. :) And the post asked for a cheap mod, so I shared my experiences. I didn't know that I am going to be 'retarded' with a working project that nobody tried before :)
My port:

[digger]

that wont fit on the OP's block......you say it works where is the dyno graph?

[henryki]

Well after seeing where things went with this thread, and that since I'm still in college i have plenty of time to make my E30 much more powerful once I graduate, my dad was telling me that I should just have it rebuilt to stock, and he'll help me out a bit with the rebuild cost (gotta love living at home some times). But he wants to keep it stock for the mean time while I'm still in college so that I don't go "mod crazy" and lose focus of school. And knowing me with how its been already with this car, once upgrade power on this M20, the progression of things will be like this.

1. Cam + a little head work - cool! more power! car goes faster I'm a bad ass 8)
(a few speeding tickets later)
2. Cam is cool but want MORE POWWWWEER as Jeremy Clarkson would say, Upgrade to turbo
3. run out of money after turbo build
4. debt builds up
5. max credit cards out can't even pay for gas
6. look at turbo E30 sit on the street with no money to pay for gas
7. beg parents for gas money and to let me drive anything. even the god damn astro van (friends call it the rape shuttle)
8. eventually end up driving the rape shuttle to school
9. have to sell turbo E30 to pay for credit card debt.
10. stuck with driving the rape shuttle and distant memories of a turbo E30

I DON'T WANT TO LOSE MY E30 JUST YET!!!















:jk: I'm not that bad with my money, but yeah my dad basically said, focus on school not your car and during the summer I can do whatever the hell it is I want with working full time, but for now focus on school get good grades and land more scholarships.

[dwight]

Good Advice........