2.7i 731 head build

[cheapshot]

I thought I would start this thread since there are so many opinions and misinformation out there. After doing a lot of reading on this forum and many others, I found so many conflicting opinions and very little first hand experience. Albeit, the first hand accounts that I have read were all very positive about doing this swap. I decided I would chronicle my experience throughout this process. I will include dyno numbers both before and after the swap. I received my head today and dropped it off at the machine shop to be cleaned, checked, resurfaced, and it will also receive a 3 angle valve job. In case you missed it in the title, I will be using a 731 casting head. I plan on gasket matching the ports only. No major porting or polishing. After a long conversation with Mark D, I have almost completely decided to run his 2.7i chip. It is a little pricey, around $300, but it is also plug and play. He did say that the motor would suffer a slight hp loss over a full motronic swap with chip, but only around 2-4 hp. After considering sourcing an 87 harness which I need for my 86 chassis, the proper sensors, pulleys, dme, and a 173 dme chip, plus labor, I figured it would be better to spend a little more on the front end and avoid the headaches and labor associated with the wiring swap. I am still undecided as whether to run the b25 or b23 intake manifold. If anyone has personal experience with either of these, I would be happy to hear your input. The plans right now are to run the b23 cam unless I am able to source a larger cam before the install takes place. I have a good source now on a shrick cam, dual valve springs, b23 manifold, and titanium retainers for a great price, but I am trying to do this as budget conscience as possible without being a cheap bastard. Again, please feel free to chime in over the next few weeks with stories of your personal experience with this setup, or even with the 885 head. I have been in a couple of 2.7i cars and the haters of this setup are completely wrong! They are a freaking blast to drive! Please help me keep this thread as a good source of information to those who are considering doing this swap and not jumbled up with speculation and internet opinions. Thanks in advance for your help and input!

[wakdog]

Im running a 2.7L with 731 head on my racecar...

My motor has 10.2:1 euro pistons, full b25 intake, ported head, b23 cam, extractors and made 160whp@5500rpm while tuning the megasquirt 2 (this was on a dyno called the dream killer - notoriously known for under reading).

All I would need to do to get more out of it would be a bigger cam (such as a 288 schrick) and it should make a decent chunk more power up top.

If you are using a 2.7 eta bottom end, i presume it will have 9:1 pistons and using a 731 head will retain the same compression ratio as a 200 head from an eta as far as im aware.

[cheapshot]

Nice! The guy here that is helping me do this put together one of these with a schrick 288 cam and it made 165 whp on his dyno. He is running 10.5:1 pistons, gasket matched head with I intake, and a stock 173 dme. I am not sure which dyno he has but can find out tonight and let you know. I think you would see much more considering your head is ported. The only difference in the setups would be the engine management and he is running long tube headers which I hear don't really make much of a difference. Realistically I am hoping to get somewhere around 145-150 whp. Stock I will be lucky to make 100 whp.

[digger]

you'll never have a decent topend with a stock head (any of them) and a stock cam on any stroker M20 so if that is one of your goals you need to rethink.

Consider this if you take a stock b25 and stroke it to 2.7L or larger while maintaining everything else the same you will gain hardly any peak hp and the rpm where peak hp is made will drop. this has been shown in all the budget builds. You will gain alot of lowend and midrange which is a good thing but not topend. The problem with most 2.7 builds, is it costs money to get a new cam, rockers, headwork, better induction and exhaust which are need to make topend on a stroker.

I would get a mild schrick cam, new IE HD rockers, new stock valve springs and do atleast a basic port job on the 731 with B25 valves before dropping the head on. Forget about Ti retainers they are not needed and wont have the same durability as the stock steel ones you wont be needing to rev high enough that the lighter valve train.

[etamax]

Just completed a similar swap on my 86 325e..731 head, b23 intake, b25 throttle body, conforti eta chip (5300 rpm redline). Car runs great and pulls much harder above 3000 rpm. Didnt notice a significant loss in bottom end, great upgrade all around. The car is much faster now. Next step is motronic 1.3 swap or mark d 2.7i chip like you said.

Best of luck and keep us posted on progress, especially if you hit the dyno!

[cheapshot]

you'll never have a decent topend with a stock head (any of them) and a stock cam on any stroker M20 so if that is one of your goals you need to rethink.

Consider this if you take a stock b25 and stroke it to 2.7L or larger while maintaining everything else the same you will gain hardly any peak hp and the rpm where peak hp is made will drop. this has been shown in all the budget builds. You will gain alot of lowend and midrange which is a good thing but not topend. The problem with most 2.7 builds, is it costs money to get a new cam, rockers, headwork, better induction and exhaust which are need to make topend on a stroker.

I would get a mild schrick cam, new IE HD rockers, new stock valve springs and do atleast a basic port job on the 731 with B25 valves before dropping the head on. Forget about Ti retainers they are not needed and wont have the same durability as the stock steel ones you wont be needing to rev high enough that the lighter valve train.

Thanks for the information. My goal is not to have a fully built 2.7i maxed out. My goal is to do the swap inexpensive and with available parts. If I can find a cam for the right price I will absolutely run it. The b23 cam is "hotter" than the b25 cam however, just right below a schrick 274. Please correct me if I am wrong about this. I do not plan on revving this thing over 6-6500. It is my daily driver. I love the torque of the eta motor but would like for it to keep pulling above 4500. And before anyone says that chipping it will raise the limiter, I am aware of that and have done it. I am running a mark d chip now. However, the 200 head and cam combo don't seem to produce anymore real power beyond that even though the limit has been raised.

[cheapshot]

Just completed a similar swap on my 86 325e..731 head, b23 intake, b25 throttle body, conforti eta chip (5300 rpm redline). Car runs great and pulls much harder above 3000 rpm. Didnt notice a significant loss in bottom end, great upgrade all around. The car is much faster now. Next step is motronic 1.3 swap or mark d 2.7i chip like you said.

Best of luck and keep us posted on progress, especially if you hit the dyno!

I am assuming that you did as much research as I did and read all of the negative comments, i.e., just get a 325i? Did you think it was a worthwhile mod? Are you still using the 027 dme? I know that once you put the new management system in you are going to see a huge increase! I would also encourage you to call Mark and talk about the chip he has. He is a wealth of information.

[etamax]

Sure, there are quite a few people that haven't taken the time to improve the eta, they would rather buy a 325i instead. It makes sense from a peak horsepower standpoint, but in my mind a well-sorted eta (chip, 3.25 LSD) is much more fun around town than a 325i. As I don't track my car regularly, low-mid range torque is king IMO. I'd put my car against a 325i.

Worthwhile mod? Absolutely, even with a 5300 rpm redline it's worth it IMO. From what I've read, upgrading to M1.3 with a well-sorted chip brings you to 170-180bhp. Here's one example you might have see already:

http://84.45.115.78/e30zonewiki/index.php/Daimlerman's_2.7

Yes, I'm still on the 027 ECU, haven't pulled the trigger on the M1.3 upgrade. Is MarkD's chip designed for the 027 ECU? If so, I might go that route instead.

Like I said, keep us posted on progress. Good luck!

[cheapshot]

It is. Its plug and play just like your current chip. You should give him a call.

[digger]

Thanks for the information. My goal is not to have a fully built 2.7i maxed out. My goal is to do the swap inexpensive and with available parts. If I can find a cam for the right price I will absolutely run it. The b23 cam is "hotter" than the b25 cam however, just right below a schrick 274. Please correct me if I am wrong about this. I do not plan on revving this thing over 6-6500. It is my daily driver. I love the torque of the eta motor but would like for it to keep pulling above 4500. And before anyone says that chipping it will raise the limiter, I am aware of that and have done it. I am running a mark d chip now. However, the 200 head and cam combo don't seem to produce anymore real power beyond that even though the limit has been raised.

Even if you want the same sort of power delivery as the B25 or a hotish one you would need to do what i suggested. If you want a screamer then yuo need everything to work togther and this involves higher CR, properly tuned exhaust and inlet manifolds which add alot to the cost.

See this thread re B25 vs B23 cam. I think the seat to seat duration is larger but the usable duration is not and dont even bother with it IMO. A schrick will be better it will have quicker ramps and more lift and so have more area under the curve per degree of duration.
Schrick only have 272 and 284/272 at that sort of duration unless you get a custom made one. Dbilas have more options in that range.

http://www.e30tech.com/forum/showthread.php?t=108802

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I am running a cam out of an e30 323i which is not addressed in that link. I will see if I can find the link where that one was measured. The results showed it between a b25 and schrick 272.

My goal is not to duplicate the same kind of power delivery as an i. I would like to make it clear that my goal is not to build a "better" engine that an i. I really don't want to take this discussion that direction as this is what always happens when a thread like this is started. This is supposed to be something for eta owners, not a comparison between the b27 and b25.
I wanted to put something together for those of us who have eta's and would like to do something to improve upon what we have.

[digger]

I am running a cam out of an e30 323i which is not addressed in that link. I will see if I can find the link where that one was measured. The results showed it between a b25 and schrick 272.

id be interested to see as i have two b23 cams and neither are particulary special one is from an e21 and the one shown in that thread is also from an e30 1984. Here e30 323i were first available in 1983 so it is an E30 B23 cam that was measured.

if you look at the the curves the B23 has alot more seat to seat duration but only a couple more degrees at 0.05" so the ramp of the b23 is actually slower and the B25 has a bigger lobe. This would mean it actually is closer to the schrick 272 on paper based on duration which is usually quoited closer to the seat figures than the 0.05" by the germans but you have to you have to remember that very little flow occurs at less than 1mm and it is hardly significant and why duration figures can be misleading.

If i had the choice i would use the B25 cam or a B20 cam if stock was only option

[e30trooper]

Need more info. I plan on doing a ful motronic 1.3 swap. Use a b25 head. Get it rebuilt , small pnp, port match gaskets along with intake/stock headers. Reground b25 cam , hd rockers. Ill be using a eta block so plans are to deck the head down so I dont drop comp numbers as much without doing it. All rhis matched up with my gen 3 miller maf kit and 19# tune. Im hoping this should turn some good numbers. This will be for a dd/track toy. I cant wait! Just need to sell my vert off.

[MrNatural]

Here's my .02....I've done a bit of this for my '87 eta. I got a euro 320 head (same casting as eta 200) with a 260 degree cam and dual valve springs about five or six years ago (Couldn't find a 731) had it decked and valves ground slapped it on with a 3.25 lsd and it ran pretty good, quick take off and pulled pretty hard to about 70 but nothing extreme. Finally got around to the motronic 1.3 upgrade and all the i stuff...wow! It's like a different car. I haven't dyno'd it but it pulls very hard. When you guys do the ecu upgrade you'll see the results. No need to to chip the eta computer (I've done that) it's not that big of a gain compared to the 173 ecu.

[e30leigh]

this is all very interesting.

sorry for the ignorance. but the 731 head are they off the 320's?

im asking as im building a motor. its a 2.5 turbo. kinda off topic. not to steal away from this. but i was going to run an 885 head. but might rethink if they 731 is ment to be higher flowing?
i assume thats the reason behind using this head? am i right in thinking they can be found on 320's? i think i have both an 885 and 731 sitting on the bench at work.

thanks for the help. and good luck with your build man. sounds very interesting.