e30 m10 build - first steps

[jwetering]

Hello - This is a cross post from 2002faq, but they suggested I come here.


I posted there because I am committed to building an m10 powered early e30 for the street. I'm keeping the m10, not because it's the smartest or cheapest thing to do, but because that's what I want to do. I've read all of the threads talking about alternative engine choices - but I'm determined to keep it old school. Twin carbs, hot cam, header, minimal interior, chrome bumpers. I will be adding lightness wherever possible. Looking for 150 hp in a 2000 pound car.


Some background - I'm 52 years old, I built a Datsun motor in high school and I've worked every nut and bolt of about 35 cars since then. Mostly a 911 and 996 Porsche guy, but there have been bmw's as well.


I am looking for initial thoughts on my engine plan, and especially carb jetting recommendations.


I have collected a number of parts already - here is the plan:

1) stock e30 case - the one in my car has done 185k kilometres. I assume it is good but the PO ran it without coolant and cracked the head...am I deluding myself ?

2) The stock head is cracked as stated. I have a replacement head that has been refinished and (I assume) decked and I have two handfuls of valves. The new head has new seats installed and they've been ground but they haven't been ground to a specific set of valves that I can tell. Thoughts? Can I get away with just lapping-in the best set of valves I have ?

3) Will install a 2 litre crank in my e30 block. I have a line on a 1976 short block for $100 - I plan to use the crank and maybe the rods but scrap the block. I will buy new rod and bearing cap bolts.

4) I have a set of new JE 10.5:1 pistons with wrist pins. They are 89 mm so if my cylinders are oval or otherwise out of spec I will need a new case. Assuming the cylinders measure out ok....can I get away with a good honing ?

5) I picked up a pair of well used 40 DCOE. I will rebuild them. Looking for jets and venturi recommendations for my 2 litre 10.5:1 m10 build. That's the main reason for this posting.

6) I have a 4.10 LSD differential....whoohoo.

7) I have an e46 ZHP steering rack. I am thinking about running this without the hydraulic pump - ie in manual. Is this a dumb idea for the street ?

I will keep this thread updates as I move along - it will be slow going but it should be interesting.

Thanks

Jasper

[thebutterson]

Hey Jasper, fellow M10 E30 and 996 owner here

You're best off getting engine advice from the 2002 guys and anything else E30 answered here.

I depowered my stock steering rack. It's fine while once I'm moving at a decent speed, but parking maneuvers are annoying. I imagine that using a quicker rack would be much more annoying. People have said good things about using the nonpowered Z4 rack though, you should look there if getting rid of power steering is a priority. This is on my "to do" list.

The 2002 block will not work without custom mounts, so your idea not to use it is good. I think BMW made improvements to the block stiffness over the years also.

Ireland engineering sells pistons that you pick the diameter, head, and compression ratio. You may want to check there if your current pistons don't work.

[SkiFree]

Welcome to R3v Jasper, I am a 2002 guy and an editor on the FAQ (AceAndrew over there). I also managed product development/production at IE for several years.

1) Assume everything is broken (given your experience, you know the drill). There are a lot of good/helpful 2002 guys in Vancouver that can help. Hayward Performance (for engine work) is a good one that I can remember off the top of my head.

2) Depends, that's not a question any of us can answer without having it in our hands. Hopefully the head is the same type as the cracked one (i.e. the type is cast between the 3/4 intake ports. Assuming your new one also has injector ports [which will need to be plugged going to carbs], its going to be the same.).

3) Cool, just a tip. ARP M10 rod bolts might still be cheaper than new OEM bolts. If that short block comes with an oil pump, hang onto it.

4) I say no. I don't like new forged pistons only made for the stock bore, when I was supplying pistons this was always a recipe for increased blow-by and early wear. Especially when you are talking 10.5:1. If those pistons are made from 2618 those issues are exasperated. (JE offers both 4032 and 2618 if I recall correctly).

Also, 10.5 is pretty dang high, even with 93octane. If you ditch these pistons (which I would), i'd recommend speccing a set of 4032-alloy pistons for 9.5-9.75:1 comp., 90mm bore, and if you can.... 144mm S14 rods. The extra 9mm in rod length really helps in adding some mid-range torque where the M10 is typically weak. I believe VAC, Ken Blasko, and Andy Dikeos all are familiar in speccing this setup at this point.

5) I'll check my notes and get back to you with a good baseline jetting.

6) Niiicceee

7) Herp Derp - no idea.

[jwetering]

Hey Jasper, fellow M10 E30 and 996 owner here

You're best off getting engine advice from the 2002 guys and anything else E30 answered here.

I depowered my stock steering rack. It's fine while once I'm moving at a decent speed, but parking maneuvers are annoying. I imagine that using a quicker rack would be much more annoying. People have said good things about using the nonpowered Z4 rack though, you should look there if getting rid of power steering is a priority. This is on my "to do" list.

The 2002 block will not work without custom mounts, so your idea not to use it is good. I think BMW made improvements to the block stiffness over the years also.

Ireland engineering sells pistons that you pick the diameter, head, and compression ratio. You may want to check there if your current pistons don't work.

Thanks for that - I bought the e46 zhp rack after having no luck at all looking for a Z3 or Z4 rack. You've confirmed my suspicion that the faster rack would be a bit of a bear around town without hydraulic assistance. At the end of the day - the rack is designed to be powered after all.


Regarding pistons - This set of pistons fell into my lap for a great price so I snatched them up. They're actually higher compression than I would have preferred but for the price I couldn't pass them up. The trick now will be finding a block to work with them....back asswards to how the process is supposed to work I know, but that's where we're at.


Will keep everyone posted - and shout out to the 996 for being a hugely under appreciated car.


Cheers

[jwetering]

Welcome to R3v Jasper, I am a 2002 guy and an editor on the FAQ (AceAndrew over there). I also managed product development/production at IE for several years.

1) Assume everything is broken (given your experience, you know the drill). There are a lot of good/helpful 2002 guys in Vancouver that can help. Hayward Performance (for engine work) is a good one that I can remember off the top of my head.

2) Depends, that's not a question any of us can answer without having it in our hands. Hopefully the head is the same type as the cracked one (i.e. the type is cast between the 3/4 intake ports. Assuming your new one also has injector ports [which will need to be plugged going to carbs], its going to be the same.).

3) Cool, just a tip. ARP M10 rod bolts might still be cheaper than new OEM bolts. If that short block comes with an oil pump, hang onto it.

4) I say no. I don't like new forged pistons only made for the stock bore, when I was supplying pistons this was always a recipe for increased blow-by and early wear. Especially when you are talking 10.5:1. If those pistons are made from 2618 those issues are exasperated. (JE offers both 4032 and 2618 if I recall correctly).

Also, 10.5 is pretty dang high, even with 93octane. If you ditch these pistons (which I would), i'd recommend speccing a set of 4032-alloy pistons for 9.5-9.75:1 comp., 90mm bore, and if you can.... 144mm S14 rods. The extra 9mm in rod length really helps in adding some mid-range torque where the M10 is typically weak. I believe VAC, Ken Blasko, and Andy Dikeos all are familiar in speccing this setup at this point.

5) I'll check my notes and get back to you with a good baseline jetting.

6) Niiicceee

7) Herp Derp - no idea.

Wow - you sound like my new best friend ! Thanks for the great insight.


The story on the pistons confirms the concerns I had both from both the compression ratio perspective and the bore. I will let the case inspection determine my next move but fully respect that if I end up using them I may regret it on one level or another.


The head came from a e30 m10 - so hopefully the casting is good .


Wasn't planning to but stock bolts so I'm good there - finding S14 rods for a decent rate may be tough......but will definitely look for them.


Lastly - I have made prelim contact with the 2002 guys already through the FAQ - looking forward to meeting the guys who have been there.

[jwetering]

So - to keep it interesting - here are two photos of the BMW k75s I built this year. I like them to operate as well as possible but look a bit scruffy. This is partly because that's how I like to spend my limited funds, but also because pretty things make me uncomfortable.


The e30 will be similarly flavoured - but at least will have paint.