What the Hell, Dr. Schrick?

[redlightpete]

So after finally getting my 2.8 together and in the car, I was rewarded with a very disappointing and resolute no start condition. A month of trouble shooting later, I finally took the valve cover off to make sure that at TDC, with the cam sprocket mark aligned with the head, and the rotor pointing in the correct direction (I had already checked that), that the cam lobes were also pointing the correct way. I mean, the cam sprocket only goes on the cam one way, and the rotor mount and rotor only go on one way, so it can't be 180 degrees off, right?


Well, I was somewhat relieved to see that the #1 cam lobes in this all-lined-up situation were in fact holding both valves slightly open; not the recipe for productive combustion. Just to make sure I wasn't having some kind engine theory comprehension failure, I went in the shed and verified that a stock cam, sprocket, and rotor indeed left the cam lobes in the opposite orientation.


At this point, even though I was alone, I expressed my disappointment with Dr. Schrick out loud. Mostly though, I was just glad to have found an obvious explanation for the no start. Eager to validate this obvious solution, I modified an old rotor and installed it the opposite direction with 2 of the 3 screws. Sure enough, it started like I had just turned it off yesterday (not 20 months ago, as was the actual case).


Has anyone else ever seen this?

[digger]

so the cam dowel pin was drilled 180* out? i know one guy who had the engine lunched because the dowel was off

[redlightpete]

The pin bore is more like 184 degrees off. I had set the cam angle based on the valve lift specs at TDC from Schrick, but didn't notice or realize that it was the wrong TDC for the ignition rotor angle. So everything was OK for compression, but the spark timing was completely off. I'm assuming that's the only problem with the cam, but I guess I should check the valve lifts etc. The valve to piston clearances seemed reasonable. It's a 284/272.

[TobyB]

Does your Dr have the Schrick name cast into the blank,

or is it the 'new' generic AVL marking?

The M10 Schquick is now much less sexy than it used to be...

One wonders about QC on these things from Eastern Europe...

t

[ForcedFirebird]

Spark timing will still be correct (should be), as the rotor has a large contact point and the ECU will tell it how many degrees in relation to TDC at the crank (CPS).

The 4° might be ground into the cam, but another way to make the engine run 180° out is to move the plug wires around to compensate. When I was a kid, I did this a few times on my own vehicles when inadvertently setting a distributor to #1 on the exhaust stroke. Granted this was on a small block Chevys and once in my 520 Datsun, but it's all the same.

[digger]

The pin bore is more like 184 degrees off. I had set the cam angle based on the valve lift specs at TDC from Schrick, but didn't notice or realize that it was the wrong TDC for the ignition rotor angle. So everything was OK for compression, but the spark timing was completely off. I'm assuming that's the only problem with the cam, but I guess I should check the valve lifts etc. The valve to piston clearances seemed reasonable. It's a 284/272.

Don't use lift at tdc to time the cam. It's not a robust method on a m20

[redlightpete]

Don't use lift at tdc to time the cam. It's not a robust method on a m20

How should the cam be timed?

And FF, I'll have to check whether the spark plug wires can be swapped and still reach the cap. I also wanted to keep the solution near the problem, but that might not be useful.

[redlightpete]

TobyB, I remember that the cam had a rectangular marking cast into the blank, but I don't remember the marking in the end.

[digger]

How should the cam be timed?

And FF, I'll have to check whether the spark plug wires can be swapped and still reach the cap. I also wanted to keep the solution near the problem, but that might not be useful.

by the middle (average) of opening and closing points to put the lobe in the correct centreline. for example find crank angle that valve opens 1mm and the crank angle that its closing back to 1mm. the middle of those two should be 110 ATDC or whatever schrick says. you can be off many degrees just using lift at TDC, the profile never seems to 100% match the catalog/camcard specs due to the variable rocker ratio and subtle differences in installed height, rocker brand etc etc. from what ive seen schrick are the best in terms of matching their claims except drilling the pin position it seems

[zaq123]

crazy...184' off?

I guess good thing it was 180.... Can only image what you would call Dr. Schrick for bent valves

Doing a lot of valve clearance checks on dirt bikes (do it before every ride), I got a habit to actually glance on the lobe orientations when putting the motor in TDC. Basically, quick glance at lobes and their symmetrical roughly 8 o'clock EX and 4 o'clock IN position (for M20 engine) tells me that the cyl in question is in TDC on the compression stroke.

my thumper is different, 10 an 2 o'clock

[ForcedFirebird]

And FF, I'll have to check whether the spark plug wires can be swapped and still reach the cap.

Swap them at the cap, leave them on the plugs ;)

[rav320uk]

It will be 180 degree off, it's well known that Schrick cams are like this.
One guy here did what you did, and found the same result, but only after he totalled his engine, rebuilt it, turned the cam 180 degrees and all was well.
He went back to Schrick, who denied any responsibility, saying he should have checked the timing properly.

[mrsleeve]

How should the cam be timed?

And FF, I'll have to check whether the spark plug wires can be swapped and still reach the cap. I also wanted to keep the solution near the problem, but that might not be useful.

what does wire length matter change the order on the cap not at the plug

[zaq123]

It will be 180 degree off, it's well known that Schrick cams are like this.
One guy here did what you did, and found the same result, but only after he totalled his engine, rebuilt it, turned the cam 180 degrees and all was well.
He went back to Schrick, who denied any responsibility, saying he should have checked the timing properly.

I don't think 180 flipped cam can destroy your engine when rotated by hand or cranked with the starter. It will just reverse comp to exhaust stroke for that cyl. It won't start unless you reverse wiring order completely, than it should work as normal. No?
New mark on cam gear?