Messages (Become)

On page 8 of this PDF from Metric Mechanic:
http://www.metricmechanic.com/pdf/M42-Engine-Booklet.pdf

You can see the process in a little detail.

Turned out to be a problem with the tensioner - which I stripped and repaired, it works, but there's no reason to use it so will be buying a new one along with a crank pulley bolt.
But at least I can set the cam timing:


The cams are quite mental, cam overlap? Yes it has plenty of that: 4.3mm on the inlet with 3.7mm on exhaust at TDC.

Probably been posted on here before:
https://www.youtube.com/watch?v=Ld7AsVJoRIY#t=313

To get the piston accurately at TDC so that I can measure the piston to deck height the two DTI device is first zeroed on the block deck, these are then pushed to the middle of the cylinder and then the piston sides are pushed to get the dials to read the same - once this is done the piston is sat squarely in the bore. The crank is then turned to find the true TDC, the piston remains square in the bore thanks to ring tension and the small amount that the piston is moved a very small amount.
As the piston generally sits square I can get accurate measurements when I do the valve to crown clearance measurements.

The S50B32 US JE Pistons arrived and were promptly weighed

JE Piston 428.6g
OEM Piston 484.1g
Thats a reduction of 55.6g (1.96oz) per cylinder.

Onto the S50 throttle bodies, the shaft was cut down on the lathe


Then the flat that drives the TPS cut on the mill


And it all bolts together and works nicely


I'm running an electric water pump so a blanking bung was machined out of nylon


Which was sealed with "grey snot", pressed in place, and then held captive with cap heads

Nothing amazing to report on yesterday's work as the job was all about measuring ports and modelling them in a CAD Package, so that we can get the head sent off to Jondel Motorsport for port work while we're machining up the


The ports and throttle bodies have been measured and modeled in a CAD package. The surfaces were then printed onto A3 paper, the holes punched, and the paper copy checked for dimensional accuracy.

The cut out hole on the left is the profile of the port, on the right is the profile of the throttle body.

We can now machine the adaptor plate from the measurements.  If you look closely the ports are about 1.1mm larger than the throttle body, it should be possible to blend this nicely with about 25mm thick aluminium.

I've not done any accurate measuring for about 5 years so I was quite happy with the end result - although it needed a significant amount of input from the Precision engineer who was helping me 

I weighed a rod from my late (Z3) M42 block - it came in at 547.1gm.  This is around the same weight at the Eagle H beam rod (as stated by Eagle).

The Cometic head gasket part number for the 87mm bore is H2197SP2040S, I've been advised to use a marginally larger gasket than the bore hence the 87mm gasket for an intended 86.5mm overbore.