Duracel79 wrote:If you've got ETA pistons DON'T deck the block otherwise the pistons will poke out the top of the block. Decking is required when using the 325i pistons on 130mm rods and 81mm crank.
Its always best to build an engine with plastercine first, turn over by hand to check all the clearances for cam/valve lift.
Ben
Ok, so is it worth me doing anything do this engine or just run it as is? I'd like a cam...i'd like as much performance as the engine can give me on a budget - but i'm no engine builder and i've read so many different ways of go at it its a bit of a minefield.
1986 E28 M535i - Car stripped to shell ready to be blasted
1981 E21 323i - 2.8 24v on throttle bodies & cams - 3.0 conversion soon.
Eta block undecked
10.2:1 eta pistons + conrods and crank
stock 885 head
stock 325i TB
E30 exhaust manifold, E30 down pipes and Fritz exhaust
I think I have got around 170 hp. Most budget 2.7i builds get this power output.
This engine gives me a CR of 9.35:1. Skimming the head by 0.05 cm will riase the CR to 9.8:1. With this ammount of skim you might get away without needing a vernier pulley. I cannot say what difference raising the CR will make. Not much I suspect as the its not the low compression that causes the pwer gap between basic 2.7i builds and the more expensive builds. The American's remember when they do this conversion get an even lower compression of 8.35:! and they seem to get similar power outputs. There are a few dyno curves on my28 for you to look at. The power difference is down to the choice of cam and pistons. And yes the 320i/520i/323i cam is best stock cam for the M20.
I do wonder what difference uprading the cam would make it will be turboed long before the cam wears out (hopefully). M51 exhaust manifold will fit with an adapter plate and a Volvo V70 turbo is cheap and 280 hp should be doable for about £1500
I will be getting the motronic 1.3 remapped soon with a MAP sensor (no piggyback) as an experiment to see if can be done. So I will know how much I have really got then.
