2.8L M20 build - Now with 2.7L!

[acolella76]

I guess that is possible. But it wouldn't start happening at 100 miles, it would start a lot sooner than that. The machine shop showed me that it was over 0,1". Well over that, in fact!

In any event, I forgot to post my findings here. The timing belt skipped quite a bit. The cam gear is turned too far clockwise if the crank is at TDC, so that means it was too advanced, correct? I am taking the head off to make sure I don't have any bent valves, but just wondering if that knocking noise could have been preignition due to it being so far advanced instead of rod knock? Here's to hoping!

[Cinnabar325is]

The distance between the crank and pistons at BDC is about .10".

For a standard M20B25? For a 2.8 stroker as he did (and as I did it) it would depend on how much the machinist shaved off the counterweights. And in my case, the machinist cut it too close and the skirts on 2 pistons just barely skimmed the crank when I turned it by hand on the engine stand. So I got to work with a file on the skirts. Just a little off each where the interference was.

[dinanm3atl]

I believe from talking to Alex he was told it needed to be .08-.1 and his is .15-.2 to guarantee clearance? This is going off memory so I will let him chime in.

[LJ851]

I guess that is possible. But it wouldn't start happening at 100 miles, it would start a lot sooner than that. The machine shop showed me that it was over 0,1". Well over that, in fact!

In any event, I forgot to post my findings here. The timing belt skipped quite a bit. The cam gear is turned too far clockwise if the crank is at TDC, so that means it was too advanced, correct? I am taking the head off to make sure I don't have any bent valves, but just wondering if that knocking noise could have been preignition due to it being so far advanced instead of rod knock? Here's to hoping!

A tenth of an inch should be fine. Cam timing does not cause preignition, only ignition timing does that. That rattle sounds pretty substantial to me, like a rod knock or similar. What were your rod bearing clearances?

[2mAn]

just read the whole thread, was excited at first to see it all come together, but then.... :(

[acolella76]

A tenth of an inch should be fine. Cam timing does not cause preignition, only ignition timing does that. That rattle sounds pretty substantial to me, like a rod knock or similar. What were your rod bearing clearances?

Oh? I thought the cam controlled ignition timing via the rotor. Oh well. Not sure what the clearances were... I think I have them written down somewhere, but I remember the clearance being between 0.03-0.07mm which is what the bentley suggests.

just read the whole thread, was excited at first to see it all come together, but then.... :(

You aren't the only one :(

[LJ851]

Oh? I thought the cam controlled ignition timing via the rotor. Oh well.

The ecu controls ignition timing based on the CPS and a few variables, the rotor on the cam dictates which cylinder fires via it's relation to the cap but has no effect on ignition timing.

[acolella76]

Gotcha. So I guess I should go ahead and try to get that oil pan off huh?

[MR 325]

In any event, I forgot to post my findings here. The timing belt skipped quite a bit. The cam gear is turned too far clockwise if the crank is at TDC, so that means it was too advanced, correct? I am taking the head off to make sure I don't have any bent valves, but just wondering if that knocking noise could have been preignition due to it being so far advanced instead of rod knock? Here's to hoping!

That's a mechanical "bad" noise, not predetination.

What I want to know is how the timing belt "skipped". Bent valves are a likely result.

[acolella76]

What I want to know is how the timing belt "skipped". Bent valves are a likely result.

You and me both!! I am going to check all of the pulleys, replace tensioner and belt AGAIN.

Posted this on e30tech: one of the cylinders had a CR of 90, I'm HOPING it's due to a bent valve not something wrong with the rings.

[acolella76]

Well... shit on my dick. This sucks!



Cylinder 1 and 6 move front to back a little bit, which I THINK is because they might not be torqued enough? Popped the bearings off and they both look normal.

Cylinder 1 bearing:



Clyinder 2 and 5 were a little... worse as you can hear in the video.



As you can see the bearing is razor thin. I need advice... where do I go from here? What caused this?

[5Toes]

Dude. Atleast this is a sort of easy fix

I am postive my car has rod knock now, cause mine started out sounding just like yours!

Then it turned into this. I will pull the oil pan for sure to sell and check my rods too now!

[TurboJake]

Acolella, the two pictures to show the caps are both pictures of cylinder 1, the normal looking one.

Did you plastigauge the bearings when assembling to make sure they were within tolerances?

[acolella76]

Dude. Atleast this is a sort of easy fix

I am postive my car has rod knock now, cause mine started out sounding just like yours!

Then it turned into this. I will pull the oil pan for sure to sell and check my rods too now!

The oil pan is pretty easy to get off, definitely worth a look!

Acolella, the two pictures to show the caps are both pictures of cylinder 1, the normal looking one.

Did you plastigauge the bearings when assembling to make sure they were within tolerances?

Whoops, thanks! Edited.

And no, I did not plastigauge. I just measured bearing inner vs journal outer diameters and used the difference to measure the clearance. I probably should have used plastigauge to double check though.

[5Toes]

Im pulling the engine tomorrow. Going to pull head and pan and all the goodies and make some money!