m20 power from head mods

[Motox_engineer]

i need to get just a bit more power out of my tech 1 i was planning on buying another head, and re working it with larger valves, porting, cam,lining up the inlet ports to the head and a bigger throttle body mayb. now is there any thing i can do to fueling? what about eprom chip,or a performance fules pressure regulator (FSE boost valve or what ever) i want to rase the rev limit too. oh and ive got a manifold on already and i made a nice gain..

what power do you think i will be looking at?

what valve sises should i go for?

has any one has any joy from chipping?

cheers

[ricey46]

Head work will give you good gains, a chip or remap is a deffo as well, Speak to Ant or the Zone shop about them, there are more folk who do them just can't mind at the mo........
I wouldn't bother with the Fuel Pressure Reg upgrade, a waste of time...

Plenty of folk on here have done this too, they'll prob comment later

[fowler]

Head work will give some more power definately not sufficient gains to be had.
You have an early pre-88 high compression M20-b25 I think the ratio o this engine is in the region of 10.2:1 you can gain some ponies with a chip, Cam , possible exhaust upgrades.
You could prob gain anything from 5hp to 15hp dependant on what work is carried out.
You could go all out. and even free up some ponies by changing you enginemanagement from motronic 1.1 to motronic 1.3 off a Post 88 car. you will need a new wiring harness ect for this mod.
There are plenty of info on here just use the search function.
It depends on how far you would like to go spend etc.
you could even go complete standalone engine management
Give Ant @ ATech a call on 01959-534-718 or email him through the zone

[Motox_engineer]

well ive got a 1987 325i sport, dose any one know the original engine spec for that car?

I think may b changing the car to the later closed loop engine motronic would be a bit long..., how much power would i get?

so will i see a gain from big valves?

I'm goin to build up a head any way with new stem seals etc..

i'm looking for around 200bhp.
The cam i'm going to get is a fast road cat cam and vernier pully

Has any one used bigger throttle bodys or tricked the air flow meter....
or just know any tricks of the ed30 trade?

i'll speak to a tech at some point but just want to know if any one els has any thing?
cheers

[eamo]

all 325s whether sport or standard or whether there post or pre facelift came from factory with 170bhp

[Speedtouch]

Not necessarily: pre-facelifts had the high compression (25 6E) engine which usually gave 170bhp but most facelifts after mid-1988 had the low compression (25 6K) catalyst-prepped mill which only gave around 160bhp.

[daimlerman]

Best gains from this engine come with a capacity increase,have a read of the curent threads on 2.8 conversions. Head work on it's own will see very small gains. Not certain that there is room for bigger valves in a 325 head. An aftermarket cam will improve topend power,at the expense of bottom end torque.

[reggid]

the idea is to make it flow better without increasing the size of ports otherwise you'll lose gas velocity which will reduce cylinder filling at low to mid rpms.

There are some interesting points made here by a guy who has ported M20 heads and says you need to add material to the 325i "885" head (in the right areas obvioulsy) to increase velocity and redirect the flow better around the short size radius in particular and this will increase the flow CFM aswell.

http://www.e30tech.com/forum/showthread ... 523&page=3

Even MarquisRex notes that the 885 port velocities are very low perhaps too low meaning the ports may be too big!

http://www.e30zone.net/modules.php?name ... ic&t=87664

some interesting reading regarding ports, in particular makingthem "smaller"

http://www.mototuneusa.com/think_fast.htm

[Motox_engineer]

ok so i sould be leaving the ports alone and i dont see my self adding material to them. i know alpina use bigger valves in there m20 head mayb i should get the spec for that. i think the best idea is for me to match the ports up to my inlet manifold.

[Jhonno]

there is power to be had from working an M20 head.. Some decent gains with an appropriate management etc, an area often overlooked on the m20

[Gunni]

I´d vote for a bigger engine capacity and leave the head alone, it´ll give you all you want.

[reggid]

ok so i sould be leaving the ports alone and i dont see my self adding material to them. i know alpina use bigger valves in there m20 head mayb i should get the spec for that. i think the best idea is for me to match the ports up to my inlet manifold.

Its alright to remove material just don't fall into the trap of bigger=better and go hogging out the ports the best ports will be the ones that flow the best for the least material removed. Very few people add material as its much more time consuming which = $$$

On their 885 heads Alpina didn't use bigger valves and they didn't do anything overly fancy just a little bigger ports and some smoothing, they do look and feel nice though. At some stage i'll have my cracked Alpina one flow tested and compared to a stock one but thats a little while away yet.