Timing belt question

[itsonlygeorge]

Simple cam tuning rules for NATURALLY ASPIRATED engines:

* Advancing both cams => more low-RPM power, less high-RPM power
* Retarding both cams => more high-RPM power, less low-RPM power
* Less overlap => more low-RPM power, less high-RPM power
* More overlap => more high-RPM power, less low-RPM power

Retarding the cam gear would change your torque curve for more high-end power at a cost of idle and low end power. Is that correct?

If the cam timing was retarded mechanically, but the ECU timing was advanced with the MarkD chip would that mean a significantly more pronounced "bump" up top? It seemed to pull noticeably harder with the chip around 3500 rpm. If the m20b27 has low end enough to compensate, would it work?

If this was the case, it would explain the rough idle and maybe a sluggishness(?)

[ahlem]

What probably happened is that when you installed the new belt, the slack in the timing belt allowed it to be installed one tooth off. It's always a good idea to put a socket on the crank nut and hand turn the engine over a time or two, reverse the direction to allow slack and then turn it the proper direction again to put tension on and check the alignment. If it's off one tooth, it's not too unusual to have to pull off the belt and reinstall it. All this should happen before you start the car.

[itsonlygeorge]

I checked the t-belt alignment prior to changing it and it had the same alignment. Cam was back a tooth, and crank was lined up.

[itsonlygeorge]

Snapped one of the water pump bolts. Torque wrench was set wrong. Time to order new bolts. Fuck. At least I got it out.

On a related note the PO did not intentionally retard the timing. It may have jumped a tooth when he changed it last or I might have missed something. I will advance the cam gear to TDC once I get new water pump bolts and reinstall the water pump.

[itsonlygeorge]

Fixed timing belt/pump got some replacement bolts from a VW garage nearby. Apparently I snagged some pressure plate bolts with a higher rating... Everything is back together and the car starts and runs. I need more coolant and to bleed the system.

[turbo55]

Good to hear you got it running fine. Make sure the car is idling on an incline (positive) when bleeding, makes it a lot easier.

[itsonlygeorge]

The leak is back. FML. I just noticed it was leaking coolant last night after taking it out for a ride and getting some beers.

Could it be leaking from the bolts! I didn't put sealant on the threads. Is it safe to remove one bolt at a time and sealing the threads?

I used Permatex 51813 Anaerobic Gasket maker. If I have to take the whole fucking thing apart again I am out of gaskets.


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[E30-325iS]

It won't be leaking from the bolts as they go into blind holes. What can happen is that if the bolts are bit too long, they will bottom out before they can put enough pressure on the pump.

[itsonlygeorge]

I went for a drive to NAPA and just checked under the car for the leak. It looks like it is leaking from the smaller hose that runs to the coolant reservoir. The block and pump are dry as a bone. Thank god I don't have to take the whole front apart again.

As soon as it cools I will try reseating the hose and checking for rips or tears before re-bleeding the system.