327i build advice

nando · 07-18-2011, 04:35 AM

you need a B25 manifold, at least. the ports match up nicely with the 731 head.

chrisbmwe30 · 07-18-2011, 02:24 AM

what about the option of port and polishing the head o size valves mild cam say a 272/284 to open it up a bit. use my current 320i manifold with a 325i throttle body.
will this stop it flattening out at 5500? i would like to got to 6500.
what will hapen after 5500 with a 731 head? no increase in power?

thanks for your advice so far!

ps my engine number is 25453826
anyway to find out if it is the early block with the higher compression ratio?
and am i right in thinking higher compression means more power?

chrisbmwe30 · 07-18-2011, 01:28 AM

I am newbto understanding Cr s what should I aimto achieve if using the 731. I can get a decent amount of headwirk done for the same price as getting all 885 bits. Would o size valves port polish and a cam 272:284 nit to big cam help it breath better to get what I need put of the striker?

digger · 07-18-2011, 12:56 AM

Originally posted by acolella76

many m20 strokers that have 200whp+ are easily street-able so I don't know where you're getting that information. I also don't know why you think that the 731 head is going to stop the engine from falling flat after 5k rpm. The drop off is due to the horrible rod ratio, and besides, the 731 doesn't flow as well as the 885 head so if anything it is going to drop off even worse. The only 'benefit' IMO is not having a change in the static compression ratio, but its definitely not something worth spending a fortune over.

a stock/stockish 731 head on a stroker wont make much topend, they just don't flow or even enough port velocity to make up for it. Even a stock 885 on a stroker doesn't make for topend screamer without some pretty decent cam thrown in. Then the intake manifold becomes a problem due to the skinny runners. The rod ratio has little impact on performance more so on the durability of the engine.

A 2.7/2.8L with decent CR (9-10:1) and decent head (stock 885 or modded 731) mild cam 270ish with free flowing exhaust will do what the OP wants. If you want more performance on a budget then strip that sucker of the dead weight.

chrisbmwe30 · 07-18-2011, 12:12 AM

I would like to 885 but its expensive in Australia especially need manifold etc too. But I have heard with 885 valves will hit pistons?

StereoInstaller1 · 07-17-2011, 10:14 PM

Guys, do remember that the OP is in Auzzie-trail-ya

acolella76 · 07-17-2011, 09:53 PM

Originally posted by pantelones

huh?

anyways...

well, if your on the quest for low end torque, then i think you need more displacement. a fully built, barely street-able m20 can put down 200 to the wheels. you really just need to do more research. i am about to do the same exact build (eta m20b27+731 head), but my goal is to retain 25mpg highway and have a higher revving motor that doesnt fall flat after 5000rpm. ill post a few links that i have found very helpful

http://www.e30tech.com/forum/showthread.php?t=75938

http://www.r3vlimited.com/board/showthread.php?t=200342&highlight=2.7+885+head

http://www.r3vlimited.com/board/showthread.php?t=100939&highlight=m20b27+885+head

http://www.e30zone.net/e30zonewiki/i...Building_a_2.7

many m20 strokers that have 200whp+ are easily street-able so I don't know where you're getting that information. I also don't know why you think that the 731 head is going to stop the engine from falling flat after 5k rpm. The drop off is due to the horrible rod ratio, and besides, the 731 doesn't flow as well as the 885 head so if anything it is going to drop off even worse. The only 'benefit' IMO is not having a change in the static compression ratio, but its definitely not something worth spending a fortune over.

StereoInstaller1 · 07-17-2011, 09:50 PM

Originally posted by chrisbmwe30

Ok so its my first post on here I feel like I have read every m20 thread on here and still am confused so looking for some solid advice.
I have a standard 325e bottom end and a 320 for the top end. I am looking to give my car more torque especially after driving the 320 around. In the future i will use the car for towing and will use it to carve up the hills on thee weekends for sure.
I'm hoping to put new rings bearing gaskets and seals on the button end. And use the 320's 731 head with possibly minor port and polish over size valves and a mild streetable cam that won't kill my fuel economy at the same time. I'll run Miller war chip with new air flow sensor to match. Unsure whether to out bigger injectors to match displacement increase??
Will this car pull good keeping bottom end standard but rebuilt?? Not keen on putting 325 bits in and mixing and matching etc if i can avoid it.
Not going to turbo it either.
Any suggestions would be sweet!
Thanks in advance.

See if you can find an 885 head, the ports are MUCH bigger. The 731 will start to cause diminished flow about about 5500RPM while the 885 will support plenty of air all the way to 7500RPM.

pantelones · 07-17-2011, 09:44 PM

Originally posted by matt0300

To make a sets u need a 88 eta bottom end and a 885 head otherwise ur just gonna spend a lot of money for not much gain. Just buy an eta and chip it.

huh?

anyways...

well, if your on the quest for low end torque, then i think you need more displacement. a fully built, barely street-able m20 can put down 200 to the wheels. you really just need to do more research. i am about to do the same exact build (eta m20b27+731 head), but my goal is to retain 25mpg highway and have a higher revving motor that doesnt fall flat after 5000rpm. ill post a few links that i have found very helpful

http://www.e30tech.com/forum/showthread.php?t=75938

http://www.r3vlimited.com/board/showthread.php?t=200342&highlight=2.7+885+head

http://www.r3vlimited.com/board/showthread.php?t=100939&highlight=m20b27+885+head

Page not found - E30 Zone

http://www.e30zone.net/e30zonewiki/index.php/Building_a_2.7