M30b35 swap: just a few questions.

[e30addict]

The timing belt in my m20 just went a month before I was suposed to change it so I figured why not swap in an m30. I've been doing some research and I have most of my questions answered, but there are a few things that I need to clarify.

1st: I picked up an m30b35 out of an 88 5-speed 735i. I got the wiring harness and ecu from the car and a getrag 260 from a 535i. This set up should be plug and play as far as pluging the engine harness into the chassis harness in my 87 325is right?

2nd: As I have to take the cam out when the head goes to the machine shop anyway, I figure I might as well put a cam it this thing. I have access to a shop that will regrind any cam profile that I want for about what a reground cam from any company I've looked into will cost.
So my question is, Does anyone have any information as to where I can find the stock cam profile and how much lift I can safely add onto it with close to stock duration without running the valves into the pistons?

3rd: Does keeping the cam duration close to stock and adding more lift make sense? The logic that I'm following tells me that if I keep the duration short(ish) and make the lift higher then I can get more air into the cylinder and bleed off less cylinder pressure and have a torqueier(???) engine when it's all said and done.

Thanks in advance, and I'll start throwing up pics and most likely a few more questions as the project progresses.

[e30addict]

How 'bout just an answer to that first question?

[Miasma]

I am fairly sure it is plug and play, I recall someone using the M20 harness on a M30 swap.

[Doughnut]

If the m30 harness is unmolested I'd use it, using the m20 harness requires a few wires to be extended which isn't such a big deal but it's your call really.

Do yourself a favour and buy a schrick cam for your m30, search alittle bit and you will find threads on people running them with good results. GL!

Just out of interest, how many valves/rockers did you bend/snap when your timing belt went on the m20?!

[E30SPDFRK]

I'm 75% sure that you can use the engine harness that is in your car now and just plug it into the m30. I will be doing this in a few weeks for my friend so I will be able to fully confirm then. What gen 535i did you get the 260 from?


As for the cams, I have no idea. Ireland Engineering sells both a 284 and a 292 regrind though. They say that the 292 needs oversized eccentrics to work but the 284 works with stock parts.

[e30addict]

If the m30 harness is unmolested I'd use it, using the m20 harness requires a few wires to be extended which isn't such a big deal but it's your call really.

Do yourself a favour and buy a schrick cam for your m30, search alittle bit and you will find threads on people running them with good results. GL!

Just out of interest, how many valves/rockers did you bend/snap when your timing belt went on the m20?!

I snapped just one valve, but there was scarring on the tops of all the pistons and a hole in #4.

What gen 535i did you get the 260 from?

I got the 260 out of an e28.

[E30SPDFRK]

I got the 260 out of an e28.

You don't even need to modify anything then. The shifter sticks up in the factory hole and the e30 transmission support bolts right up.

[LowR3V'in]

Ouch, tough luck with the m20.

I used the 325i harness in my b35.
Injector harness too. 100% 325i connectors.

Even using the 325i VR sensor.
Wire's just longer to reach the plug.

[DLag]

Bookmarked* Good info on this thread. Hopefully I will be doing this swap soon..

[yert315]

Ouch, tough luck with the m20.

I used the 325i harness in my b35.
Injector harness too. 100% 325i connectors.

Even using the 325i VR sensor.
Wire's just longer to reach the plug.

same here. I ended up rewiring the entire injector harness though.
what is a VR sensor?

[LowR3V'in]

crank trigger

[yert315]

crank position sensor?

[LowR3V'in]

lol Y E S.

[e30addict]

Alright, here we are 1 year and 5 months later and I'm finally getting around to finishing this thing. Blame college classes and a full time job.

The engine is in and running fine. I have a few questions before I can get this thing on the road before it starts snowing and I have to put it back in the garage for the winter.

I used the engine harness from the 1988 735i and plugged the c101 straight to the chassis side c101 the e30. Car started and runs, no problem. The problem that I am running into is that my tach and temp gauges don't work.

I am a total electrical noob and I'm having a little trouble figuring this out. I have the electrical diagrams for the e30, but not for the 735i. Is there anyone that can tell me how to resolve these issues or start me in the right direction?

[ttrousdell]

no shit it was that easy. no cutting wires or anything. just plug the 735 wire harness right into the c101 connection and she runs?