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While I'd been dragging a kicking and screaming 851 through the Jenny Craig program, a whispered doubt had become a shout in my head: if the engine builder had put the engine together without sorting the cam timing, would he have done the same with the squish (piston to cylinder head clearance, measured at TDC).
Brad Black gives a good explanation of squish and an example of optimising it here:
Given the disappointing dyno result I wondered if I had a similar issue to what he experienced above, with too much squish losing me valuable compression and performance.
It's not difficult to measure/adjust, just time consuming at this stage of the game as you have to disassemble the top end of the engine, place wax, solder or some other malleable measurable material in various spots on the piston, put it back together with properly torqued head gaskets, and turn the engine over. Then you have to pull it apart again to measure the thickness of the now squashed (is that why it's called "squish"?) wax/solder. Somewhere close to 0.9mm is generally accepted as optimal, allowing for rod stretch at high rpm.
To make adjustments there are a variety of base gasket thicknesses available (they are called gaskets but are really just shim material) which you mix and match to fit between the base of the cylinders and crank case, effectively raising or lowering the cylinder head against the piston position.
So I hit pause on the weight loss program and set about more invasive surgery: the heads had to come off.
Not so long thereafter this pretty much sums up my hopes and dreams:
When I found myself looking at this:
It is pretty obvious where the piston is actually contacting both the cylinder head and exhaust valves.
Mirrored on the cylinder head:
I went from shocked, to stunned, and in about half a second I was absolutely raging! I mean I'd paid hard earned money for professional expertise and the fcuker didn't even bother to check the squish?! On what he knew was going to be a race engine? GAAAAAAH! I just couldn't comprehend it.
After a series of disappointments that was the last straw for me, fcuk the "professionals". I didn't need them to screw things up on my behalf and then charge me for the priviledge, I was quite capable of screwing things up myself, for cheaper. So from now on if at all possible I'd just have a crack at whatever it was myself, if I screwed it up at least I'd learn something from it.
After I'd calmed down, or at least stopped hurling things around the shed, I set about measuring the squish as it stood:
I couldn't believe it, I mean a slight error would have been kinda/sorta/almost understandable, but this was no error, a vital check hadn't even been on the guy's radar. I had to literally talk myself off the ledge, with another "toddler at the supermarket" type tanty about to erupt.......
.....but the fact the cams still rotated smoothly meant the valves weren't bent, and the piston seemed to be marked rather than damaged. Checking the horizontal cylinder found an identical situation. It was ugly, very ugly, but could have been a whole lot worse.
How much worse? I had found a company in the Netherlands, Carmo Electronics, who could burn a custom eprom for me, allowing a bike with a single injector per throttle body Strada induction system to rev like a dual injector per throttle body SP...or more importantly like the 748R the heads/cams came off (748R makes peak power at 11500rpm, Strada is limited to 10000rpm). So I got them to burn a 916 Strada P8 ECU (single injector per TB) eprom with an 11500rpm rev limit.
I was really impressed with Carmo Electronics, who offer a range of electronic services:
The eprom had actually arrived but the stars hadn't aligned for me to plug it in and get it on the dyno again....I break out in a sweat just thinking about how that would have turned out....
The 0.16mm squish measured above was with a single 0.4mm base gasket fitted. Knowing that 0.16mm squish resulted in juuuust making contact, with the stronger aftermarket H-beam Ti rods fitted and the fact I won't be revving it to 13000rpm, I was comfortable aiming for the lower side of 0.9mm - 0.85mm, so:
0.85mm (squish needed) - 0.16mm (squish existing) = 0.69mm (extra gaskets required).
The gaskets aren't available in a great range of thicknesses but as luck would have it 0.3mm is one of the options, so 2 x 0.4mm, plus 1 x 0.3mm would be pretty much spot on, giving me an almost perfect 0.86mm.
I'd always been a little intrigued with performance coatings, so, trying to salvage some good from the bad, I dropped the pistons off at Competition and Industrial Coatings for some TLC: ceramic coated crowns to reflect heat and moly coated skirts for reduced friction.
Then I ordered the gaskets, pushed it into a dark (naughty!) corner of the shed and pretended the bloody thing didn't exist.
