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early eta engine
Posted: Thu Mar 26, 2009 4:10 pm
by jbh
right I've got the chance to lay my mitts on an early 525e lump... so whats the difference between the early and later one? what do i need to do to build a stroker out of this? will my 325i head work or do i need to use a 320 head ?
Re: early eta engine
Posted: Thu Mar 26, 2009 4:17 pm
by gcs325i
Re: early eta engine
Posted: Thu Mar 26, 2009 4:22 pm
by jbh
hi Gary i have read this but also heard the early eta engine had different pistons and needed extra work for what i could see it doesn't explain on there if there's any different work involved ..
what id like to know is can i lift the standard eta head off throw it in the alloy pile then drop my 325i head or a 320 head on ... i know before any one says ohh your better decking the block... i don't want the extra work i just want to bolt it together
Re: early eta engine
Posted: Thu Mar 26, 2009 4:27 pm
by hongkongfuey
i think one had problems with the core plugs, i maybe wrong about that though,
drop ant a e-mail , he told me about a difference between early and later eta engines
Re: early eta engine
Posted: Thu Mar 26, 2009 4:34 pm
by jbh
hongkongfuey wrote:i think one had problems with the core plugs, i maybe wrong about that though,
drop ant a e-mail , he told me about a difference between early and later eta engines
think ill do that im sure hell be the man to know
Re: early eta engine
Posted: Thu Mar 26, 2009 4:39 pm
by jbh
A lot has been said about Eta pistons being incompatible with the 325i head. Most of it is nonsense as this has been done many times and it works okay. Of course it won't give results quite as good as using the matching 325i pistons but it still has a good compression ratio which is most of the battle won.
Again, depending on which gasket is used and whether the head has been skimmed, using a 325i head on a later 10.2:1 Eta short engine will give a CR of 9.4:1 which is plenty. If you can even find an early 11:1 Eta engine, the CR would be 10:1 which is even better. Because you are using a 325i head, just bolt a 325i inlet manifold straight on.
I converted a 1986 525e Auto to this spec and it was very lively - 0-80 in 21 seconds which is just 1 second slower than an auto 528i which has both 184 bhp and a lower final drive. Then I pulled the engine out and it went into an E30 Touring
got this from the wiki .... could be worth a go not looking for bigger bhp figures more looking for torque
Re: early eta engine
Posted: Thu Mar 26, 2009 5:31 pm
by petrol_1
Be careful if using the early ETA s pistons as the c/r will dependant on head used
BUT LC ETA = 10.2:1 std with a 731/ 200 head WILL PINK on std 95 ron , , does on my daily runner , ,but should be ok on 855 head as 4.5 cc bigger c chamber
and a early HC ETA = 11:1 will pink badly on 95 ron unleaded and possiblie even on 98 ron !!!!,
Re: early eta engine
Posted: Fri Mar 27, 2009 10:26 pm
by cliffybabe
ive got the early bottom end with a 885 325i head its wicked
Re: early eta engine
Posted: Sat Mar 28, 2009 11:07 am
by ed325i
As Ant said in a diffrent post.
Do it right, do it once, and please , don't use ETA pistons they are just too heavy to be worthwhile using.
Re: early eta engine
Posted: Sat Mar 28, 2009 7:29 pm
by eta
Early eta pistons on a 731 head will not work according to A-tech. Pistons hit head. With an 885 head everything will be perfect.
Re: early eta engine
Posted: Sun Mar 29, 2009 1:35 pm
by daimlerman
When I built my 2.7 I placed the head on the block with no gasket,just sat it on the locating dowels.Fitted an old cam belt and turned the engine by hand,with one hand on the back of the head.I could detect movement as the valves opened and closed.Repeated the experiment with a used head gasket and I had clearance.This is one of the reasons I try not to exceed 6000rpm...
I used standard eta pistons and a 731 head with a 325 standard cam.Not mega bhp but plenty of torque.
Re: early eta engine
Posted: Mon Mar 30, 2009 12:24 am
by tomson
cliffybabe wrote:ive got the early bottom end with a 885 325i head its wicked
Me too.
So long as you use an 885 head jbh you will have no issues, just bolt it all together and enjoy it. Dont expect massive power gains come dyno time but its a hell of an improvement over a 325i.
Re: early eta engine
Posted: Fri Aug 27, 2010 12:22 am
by boudy
hi i to have an early eta engine an an 885 head, shal i use my 325i pistons and conrods or will the mash the head? orry if im going over and over with the same problems but want to get it right!!! thanks.
Re: early eta engine
Posted: Fri Aug 27, 2010 12:23 am
by boudy
hi i to have an early eta engine an an 885 head, shal i use my 325i pistons and conrods or will the mash the head? orry if im going over and over with the same problems but want to get it right!!! thanks.
Posted: Fri Aug 27, 2010 7:38 am
by StuBeeDoo
James, FWIW I'd be tempted to leave the 11:1 bottom end as it is and put that big valve 731 on it.
...... Then find yourself an LPG kit. Then there'll be no possibility of detonation while you're enjoying the engine.
Re: early eta engine
Posted: Fri Aug 27, 2010 10:30 am
by m_jermyn
eta wrote:Early eta pistons on a 731 head will not work according to A-tech. Pistons hit head. With an 885 head everything will be perfect.
Thats crap.... Dont hit on mine even with the head shaved and engine decked and also without the head gasket.
Bolted all down and nothing hits at all...
Re: early eta engine
Posted: Fri Aug 27, 2010 1:57 pm
by chu346
petrol_1 wrote:BUT LC ETA = 10.2:1 std with a 731/ 200 head WILL PINK on std 95 ron , , does on my daily runner
Mine didn't pink with either head
Re: early eta engine
Posted: Mon Aug 30, 2010 8:04 pm
by eta
I have run both a 731 head and 885 on a later eta block. Both versions of the engine are fine spinning all the way to 6500 rpm, I don't think clearance is an issue on stock cams. Both varients DID NOT pink on RON 95. A stock eta DOES NOT pink on RON 95 either. It will depend (partly) on the ignition advance you are running. Early eta's have a higher CR as mentioned. I have never ran one so I cannot comment of pinking issues with those, but surely with good quality fuel even 95 it won't pink.
Re: early eta engine
Posted: Mon Aug 30, 2010 8:27 pm
by StuBeeDoo
eta wrote:Early eta's have a higher CR as mentioned. I have never ran one so I cannot comment of pinking issues with those, but surely with good quality fuel even 95 it won't pink.
I can't comment from experience either, but I've read in more place that the reason BMW dropped the CR from 11:1 was that they couldn't dial-out pinking on 95 octane.
petrol_1 wrote:BUT LC ETA = 10.2:1 std with a 731/ 200 head WILL PINK on std 95 ron , , does on my daily runner
Mine doesn't! 
Re: early eta engine
Posted: Mon Aug 30, 2010 9:03 pm
by hongkongfuey
i think turk has one for sale too if anyone else is thinking of one
Re: early eta engine
Posted: Mon Aug 30, 2010 9:23 pm
by turk