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Head upgrade

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86_6series
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Head upgrade

Post by 86_6series » Wed Jun 13, 2018 8:56 pm

1986 CSi stock M30 engine 150,000 miles, Miller MAF and chip. Engine never opened in 32 years.

Blew the head gasket @ Watkins Glen. Ran really great until turn 11.

While I have it repaired, I was thinking of a mild upgrade.

Depending on basic worn out head parts that need replacing, what would be the

recommendations to up the hp for more ump. Not looking for massive rebuild,

just to gain something while I'm in there. I don't know what hp I'm looking for.

Don't want to touch the bottom end at all, Compression was all above 155 last time checked.

No water in the oil, I caught the problem early. So if suggestions could give hp gain, that will help me

make my decision. To go from 182 hp to 200 I would have to do what?

To 220 then it would take this. Or to 240 it would be that, or the best you could do

is this hp and would need these parts as an upgrade. I'll assume I'll have to get a Miller War Chip for the MAF

and program accordingly.

If the B34 head is still good, I'd like to use it. What could I do with it?

If not I guess it would be a B35 head. Or maybe, I'll have to get a B35 head to make upgrade in hp easier.

Complete novice when it comes to this. Upgrading brakes and suspension was easy for me.

This stuff is out of my realm of knowledge.

I'm going to post on Bimmerforums 5 & 6 series as they will also have much more experience than me.

I've searched the posts on this subject and now I'm more confused.

Want to thank you all for any and all input.

Bob V
Last edited by 86_6series on Wed Jun 13, 2018 10:43 pm, edited 1 time in total.

bpoliakoff
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Re: Head upgrade

Post by bpoliakoff » Wed Jun 13, 2018 10:15 pm

Problem is although a B35 head is better because the valves and combustion chambers are larger, it means your compression will drop. Milling the head will cure this. A mild cam will also help. The rest depends on the wear your machinist finds in the cylinder bores etc. A new timing chain and guides may be in order as well as bearings. Don't cheap out and do it right. I had my M90 totally gone through form the bottom end up including new pistons, porting balancing etc and a reground cam. Cost was around $3100-$3200 at one of the best speed machine shops in Phoenix. Of course our labor rates are less then NY. A little shopping goes a long way. Machinist's guess on my engine is an easy 245-250 reliable HP. The removal and install was done by a friend and myself. Put Jody to work!!!
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
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86_6series
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Re: Head upgrade

Post by 86_6series » Wed Jun 13, 2018 10:33 pm

thanks Bert

I'll check out that option. I mean about the total rebuild, not the Jody part.

Nah, just kiddin'. He's checking out options for his rear springs. When he's ready he'll be over for us to

switch them out.

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Re: Head upgrade

Post by bpoliakoff » Thu Jun 14, 2018 2:52 am

Bob

If you don't have any excessive bore wear, you can leave the pistons alone. If your oil pressure for sure has been good leave the oil pump alone. Bearings can be done with the crankshaft in place. Timing chain and guides should be checked carefully. No more thaan a 284 cam. maybe less. I am running a 284 and hope my euro ecu will handle it. Head has to be milled if you go B35 so you don't lose compression 100% for sure, but you will pick up HP. Headers" Not the 2" crap everyone is selling. Those are for a full bore race motor. If you go that way 1 1/2 inch primaries 1 3/8 best for a mildly warmed motor according to Jere Stahl, king of the long tube headers. Actually a pair of the early individual exhaust manifolds will serve you nicely. To bad about Fernando. Between him and Jody you could have an engine that would lose HP instead of making it !!!
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.

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86_6series
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Re: Head upgrade

Post by 86_6series » Thu Jun 14, 2018 11:53 am

Yeah-- very sad about Fernando.

I'm going to take in all the info, digest it for a little--then go with what my pocket can stand.

Thanks Bert

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Re: Head upgrade

Post by GazM3 » Thu Jun 14, 2018 8:14 pm

The m30 has great potential to make a fantastic engine in mildly modified form. Static compression is factory low Comp 8.0:1?

If so you want to raise it as much as possible as aftermarket cams etc won’t work as well. How I raised comp on my m10 was to use the thinnest mls head gasket possible (027thou) and take for memory 30thou off the head. I lifted approx 1.5points so assuming the same looking at starting base of 9.5:1. If u run a higher lift cam u will need to cut in clearance grooves in the factory pistons. How I had this done was use and old head and a dummy valve as a grinding stone that way u can get the cuts perfect.

The other major restriction to making power in the m30 is the restrictive intake manifold. Fortunalty there are a few soultions.

1/ port the original one (with that high pressure paste stuff )
2/ use some glorious dual throat Weber carbs (may not be good for smog laws if they are restrictive and will need some aftermarket control as no maf possible).
3/ install the m88/s38 throttle bodies with adaptor and plenum (to run the Miller maf)

The abrasive porting does work but will yield the least power. With 2 & 3 over 300bhp possible even with moderate 9.5:1 comp!

Good luck.
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Re: Head upgrade

Post by jps635 » Fri Jun 15, 2018 9:17 pm

I’m no expert on this but learn’t a lot from my own rebuild.

The attached pdf will help answer your questions about what you can expect from various levels of investment - a collection of info I come across while researching all this.

Keeping the valve size standard with the M30B34 manifold will yield better torque, which is what I was after for a street engine, while changing to the B35 manifold and using the larger valves will yield more top end, which is likely what you’re after for the track.

I would only use someone experienced to do the head porting, apparently is easy to end up with negative gains if done incorrectly.

See my recent M30B34 rebuild details here. viewtopic.php?f=2&t=29340
I ended up with 210 RWHP, about 250 at the fly., and impressive torque of 375 Nm

I found Carl Bennett at Korman Autoworks - very knowledgeable.
Attachments
High Power M30.pdf
(140.36 KiB) Downloaded 26 times
'85 635csi JPS (RA2-66)

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86_6series
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Re: Head upgrade

Post by 86_6series » Fri Jun 22, 2018 10:54 pm

After digesting the info from the 3 posts here, My e28 and Bimmerforums--I decided to get the Metric Mechanic Sport Head.
I already have Jim's tranny that's an excellent box, I would expect his Sport Head would be the ticket I am looking for.
It's a direct swap because the head is complete. Got his goodies in it from years of experience.

I'll report my findings after the install.

Bob V

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Re: Head upgrade

Post by 86_6series » Thu Jun 28, 2018 5:58 pm

Update on the upgrade---Well, I talked to Todd @ TCD and found out that sport head will be no good with a turbo.

I'm going to cancel the MM sport head and have my head worked to TCD specs to accept his turbo.

I'll get more bang for the buck with the turbo.

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Re: Head upgrade

Post by bpoliakoff » Thu Jun 28, 2018 7:31 pm

Hey

Contact Taylor Marshall on Bimmerforums. He is running a total TCD turbo setup and is making some serious dependable HP. He is in Montreal and left his car with Todd flew down to pick it up when done and has been grinning ever since. Too bad Fernando has left us as he was well acquainted with the car. Stick your hand in your pocket and build a rocket. If you need Taylor's email, send me a pm and I will get it to you. Todd knows what he is doing.
Oh, Jody should be familiar with Taylor's car as well from hanging out with Fernando. But, I don't even want to start telling stories about those two guys !! LOL!!
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.

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86_6series
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Re: Head upgrade

Post by 86_6series » Fri Jun 29, 2018 10:49 am

Bert,

I see Taylor every fall when we meet @ "Idiotfest". I've driven Taylor's car and your right on--it's a rocket ship.

Will chit-chat soon--take care Bert.

Bob V

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Re: Head upgrade

Post by tschultz » Fri Jun 29, 2018 6:27 pm

Turbo is much better band gor the buck IMO. Go low boost setup but it will be difficult to not turn it up.

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Re: Head upgrade

Post by 86_6series » Sat Jun 30, 2018 10:31 pm

Tommy,

I'm with you there. Want to be conservative with 8 to 10 lbs boost.

Somehow I'll have it locked so I won't be tempted!!!

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