Opinion on this head

[Zyth01]

I just picked up this rebuilt "I" head that I planned on putting on my eta bottom end, eventually planning to boost it. The previous owner of the head said his piston ring blew so he had it completely rebuilt with all new moving parts and had it milled .020 before putting it on a new engine which eventually spun a bearing so he decided to go m50.

So here I am with this new head, I've got a few opinions from people in person (Mostly DSM guys, they'll put anything in their cars though ) and they said it looks like it should work just fine, might have a bit lower compression than the other cylinders but nothing that would seriously effect performance as the head gasket and valve will seal normally, its just a bit dinged up inside.



To me it looks like the machinist already took a bit off and tried to smooth it out, none of the dents seem to go very deep, but all five of the other cylinders look like this:


So, if anyone wants to tell me what they think that'd be great. The new parts that came in the head are worth more than I paid for it all together so I won't be too upset if I have to find a new casting to work with.

[416stroker]

It was pressure tested.

[Zyth01]

Oh, you hadn't mentioned that in PMs. I know you were messaging from a cell phone.

Thanks for the quick reply.

[416stroker]

Your compression will be bumped up quite a bit. So idk If it would be a good for a turbo car due to the fact it was milled.

There was somthing on bimmerforums, that disscused milling the head on a 2.7 "stroker" and said that milling a head .020 would bring the compression back up close to what an I motor was. Idk if it was correct but that's what I did with that head.

[Zyth01]

I'm not all that concerned with what compression ratio it turns out to be, stock "I" would be fine with me. I just wanted the torque from the 2.7 and the high revs of the 2.5 :)

I'll have to check that out though, thanks.

[416stroker]

Ya the motor pulled real good . I trust the machine shop that did the work they have done a few of my motors and I know a lot of people at sac race way that run there motors.

[Aptyp]

1. that looks like it was sand/media blasted or something like that.
2. I would never put that head on my car, I don't care how it was tested. Those imperfections will become cracks.

3. I top on e bottom drops compression. When you mill it, you bringing it back up to what I engine suppose to be. I compression is lower that E compression.

4. How long was it on the running car this way? Seeing how clean those scratch marks are not very long. Since when are valves not movable parts? They look like they weren't replaced.

My verdict: I'd pitch you another head, but I just sold both of the ones I had. Start looking for another one, unless you plan to rebuild your engine again.

Here's a pic of clean head:


Here's a pic of blasted head:


You won't see missing metal there.

[Aptyp]

Double posted, for some reason it happens at night.

[416stroker]

1.Ya the head was bead blasted .
2.valves were replaced the stock valves had mushroomed stems. Still have them in a box .
3. The last motor I built the head was on for around a month or more before I blew it up
4. Also the head wouldn't crack there there is way to much aluminium behind the dings.

If you think the marks in coumbustion chamber are from that. Your nuts. If you want to see a pistion with a broken ring land ill gladly show you that there was dings in the number 5 cylinder from that and it then crossed over to the number 2 cylinder to ding that one up a lill.

[Madhatter]

problem is, things like that are going to cause hot spots which will lead to pinging. Carbon will get trapped in them and it definately will heat up, so you will probably run into issues down the track when they fill up.

The other side to it is the chamber has been enlargened, so that cylinder is going to be down on compression a little, so it might run a little rich and you might notice a bit of a drop in power.

What does the seat look like if the chamber is like that? im tipping its (or was) pretty hacked out too. Was the seat replaced or just machined?

The other poster is right too btw, chips and dents are spots fissures form, its one of the reasons for shotpeening things like rods to remove all points of weakness. Those dents are effectively a stress point which will be more prone to developing cracks, even just from expansion and contraction, but when you throw a load of heat at them, it could potentially cause problems.

There is quite a lot of carbon build up on the head though, how many km's were on it since it was damaged if the valves were replaced?

Unless you got it for free or you have no other option, id probably look at replacing it too, just from a reliability stand point. At the very least id have my machinist crack and pressure test the head before it went anywhere near a motor.

[Zyth01]

When I bought the head it was completely covered in carbon, so there was no way of knowing there was any damage to it. I might have a machinist crack/pressure test it or I might just take the new parts out and put them into a new casting. Haven't decided yet.

[Aptyp]

I'll get pics of an engine that was taken apart after a few months of use. Valves don't look that bad, and that head that you see cleaned and not blasted in the pic, had 100k miles on it, and all of stuff came after an hour of soaking in throttle body fluid.

Stuff on that head won't come off unless you scrub.

[Madhatter]

if it was totally covered in carbon, either someones been running way rich or its done more kms than claimed. I just hope someone didnt take to the chamber with a dremel or die grinder to clean it up and sell it off. If the previous owner said it was crack tested and it arrived like that, its a straight out lie or its been back running on a vehicle. Its difficult to even do a pressure test properly with that much carbon on it, it tends to plug problems. If the above is done its usually hot tanked and comes back totally clean.

[TS87325IS]

I wouldn't use it unless absolutly necesary .

[h82crash]

A difference in compression from those dings? Theoretically or under laboratory conditions, yeah by fractions if a psi. Real world, no way. Even IF the rings in all 6 cylinders were perfectly seated you wouldn't be able to measure the difference. Your probably ok with hot spots too. The sharp edge on the dome opposite the sparkplug is more likely to be a hot spot. If you find another head for cheap then run that if it eases your mind. There are other forums that are exclusive to engine rebuilding. Ask them.