Engine conversion do i go for 2.5 or 2.7? - With pics of 2.3

[tomson]

Alpina claimed 237bhp for their C2

Really? I though they claimed 210bhp?

[oakey]

Alpina claimed 237bhp for their C2

Really? I though they claimed 210bhp?

Correct tomson.

A 2.7 built with (early 325i pistons?) or custom pistons and 885 head with eta crank will make 200bhp with equal torque.
My old 2.7 with the above setup made over 200bhp when it was on its last legs.

With head work and cam etc 220bhp is fairly easily achieved.

[--alpina--]

Alpina claimed 237bhp for their C2

Really? I though they claimed 210bhp?

Correct tomson.

A 2.7 built with (early 325i pistons?) or custom pistons and 885 head with eta crank will make 200bhp with equal torque.
My old 2.7 with the above setup made over 200bhp when it was on its last legs.

With head work and cam etc 220bhp is fairly easily achieved.

How comes daimlerman achieved only 178.3 BHP and with a Miller maf on his 2.7?

and also if a 2.7 home built engine has say 170 bhp with massive amount of torque and another home built engine 200 bhp with less torque the output would be that the 170 bhp engine will have more power? is this correct is what your saying?


j
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[oakey]

^ no.
There are different ways of building a 2.7 that all vary in how much power they produce. As daimlerman is using a 2 litre cyl head he is not making as much hp as others.
Have a read through the 2.7 engine building sticky in the engine swaps section dude.

[reggid]

there is only a certain amount of torque a 2.7L can make, the power is determined by what rpm the torque is made.

The 'real' upper limit of torque for a really really good 2.7L is approx 225-230 lb-ft. But the difference between a 170bhp 2.7 and a 270bhp 2.7 is you need to make the 230lb-ft @ 6200rpm for 270bhp but you only need to make 230lb-ft @ 3900rpm for 170bhp.

If you want a high hp 2.7L you need to make it so it can breath and make more torque at higher rpms and this requires some of or all of a hotter cam, headwork, 6 branch, exhaust, good CR, proper tuning, short length bigger bore intake manifold etc etc depending on how high you want the hp to go.

In aiming for more high rpm torque you end up losing some from the lowend with most mods and therein lies the reason for a 2.7L or larger (the added cc will offset the lost lowend).

A high compression M20 using the 885 head with a mild cam is the best of both worlds solution IMO for both low rpm torque and high rpm torque.

[tomson]

[quote="--alpina--"]How comes daimlerman achieved only 178.3 BHP and with a Miller maf on his 2.7?[quote]

Because despite what he say's an 885 head will always be better than a 731 head despite what you do to it! Which head did BMW use when they produced the super ETA? Thats right the 885 head

[reggid]

How comes daimlerman achieved only 178.3 BHP and with a Miller maf on his 2.7?

Because despite what he say's an 885 head will always be better than a 731 head despite what you do to it! Which head did BMW use when they produced the super ETA? Thats right the 885 head

but what was the purpose of the SETA and is that also what we want out of our engines?

[daimlerman]

IMO the best comprimise is a 731 head with 325 valves and a 323 cam.I have all of these bits in my treasure store for future use!! IMO,the 885 head works best with it's matching pistons,but this then opens up the worm can marked vernier pulley with all the extra machining work involved to deck the block accuritely to get the compression ratio to a decent level.The OP was asking for advice on a budget build,he appears to already own the bits he needs to build a 2.7 to give similar or better results than my effort.Bedore I built my motor I considered very carefully exactly what I required from it,living/working/playing in the Lincolnshire/Norfolk area we are not blessed with motorways,most of my motoring is on single carriageway roads with overtaking oppotunitys limited to gaps in the oncoming traffic,so I required effortless,instant grunt every time I stuck my right boot down.I have achieved this,as the graph shows.My wife also drives the car,she requires that it starts and runs properly at low,city,speeds without showing any tendency to be 'difficult'.I also require good fuel economy as the car is expected to cover 15000 plus miles a year.I consider that my effort is almost perfect,when I can get my spare head built with bigger valves and my 323 cam it will be interesting to see if my theory is correct. However,bearing in mind my requirements,my current project is to restore a LHD engineless touring to RHD and fit an M50....

[--alpina--]

everyone says that the 323i cam was the factories roughest!! so why dont they fit the 323 cam in the 885 head?, back in 1991 i fitted a 325 cam in my old E21 323i and noticed a big difference also the engine itself came from an E30 as th orignal engine snuffed it!! so i opted to put the 325 cam as i had to take the head of due to head gasket sp i thought let me change the cam as i got it free and new.


ok my car is a 2.7, bottom block 325, crank 525e, conrods 525e and the pistons are from the earlier 1981 which had a high comp piston as you can see the middle is slightly concaved and i slapped an 885 head on it which worked well and was buil in 1990. few months later engine blew so i had another 2.7 block i was building was also the same spec but using the 325 rods and pistons and the piston crown sat a few mill above the block level so that the head and pistons were very near.. this had alot of torque what i remember but the 0-60 didnt feel it had what the previous engine had, so 10 years later i decided to whip the pistons out and get the right pistons needed which Les Stannard advise me to use... am happy but i know somewhere some how i can squeeze some more horses i have throttlebodies on there also but i think i need a decent head to give me that extra that im hungry for then i reckon im happy enough......

so all in all, i need a 731 (323 head) ported inlet and outlet and bigger valves ? if so how much BHP would i get from that and also what cam is good .. i currently have a schrick 284` sorry for the questions!!! what price for the head work stated would roughly cost!!

Cheers guys for your replies, appreciated!!


j

[tomson]

so all in all, i need a 731 (323 head) ported inlet and outlet and bigger valves ?

IMO this will be yield less power than the 885 head.

BMW, Alpina, Hartge etc all used the 885 head in their 2.7 hybrid's, albeit with custom pistons.

The bigger power 2.7's that have been home built have all used the 885 head too. The fact that the ETA pistons are flat topped and more suited to the combustion chamber of the 731 head is outweighed by the 885 head having more all round capabilities IMO!

[--alpina--]

Ok, to achieve say approx 200bhp or little more.. what do you say a good 2.7 build be? what bits....




cheers


j

[tomson]

http://www.e30zone.net/e30zonewiki/inde ... ding_a_2.7

The third option in the above link along with a decent brand 6 branch, BBTB and lairy cam at the least....