RE: The Complete Saito Notes by Bill Robison
Quieting ramps again
As near as I can tell, the later engines all have the quieting ramps. If your FA-100 has an early code date it may not.
I suspect the late engines I've found without ramps were assembled with earlier cams. All the replacement cams I've gotten, even for older engines, had them.
A quick note. Back in the timings chart I posted, the FA-72 and FA-80 use the same part number cam, the FA-120 and the FA-150 also use the same part number. In theory I should have gotten the same timings from each engine pair. Production tolerances make them a little different. OK, so maybe measurement error had an influence too.
If you look at the cam out of the engine, inspect the leading edge of the lobe, where it starts opening the valve. You might see what looks like a hard line on the face of the cam, usually about 90 degrees from the peak of the lobe. That is where the ramp is staying at the same height momentarily after taking up the clearance in the valve train. If you see the line it almost definitely is a quieting ramp, but not seeing the line does not mean there is no ramp. The only way to be sure is get out your degree wheel and dial gauge.
Experiment. Set the valves to 0.0005" and see how it runs. Check high and low rpm. Then reset to 0.0015-0.002" and try it again. Then use whichever pleases you more. Don't worry about burning a valve or a piston strike. Wont happen. If the valves are too tight, standing open, the engine wont run or will run so poorly you'll shut it down yourself.
Loose valves now tightened
Immediate difference? Maybe a little more power and faster rpm gain, possibly a slightly rougher idle.
Long term gain is much lower cam wear, it eliminates the hammering of the tappet and the rest of the valve gear. For maximum benefit use a castor blend oil in your fuel.
On your engine, with the inlet clearance opening 0.005" in that time I'd check the clearance at least one every weekend to be sure it's not opening again. It may be you've already taken a chunk out of the inlet lobe of the cam. Keeping the clearance down will, along with the castor, slow the wear down.
Don't be concerned, if it's done it's done. Just plan on a cam inspection and possible replacement when you do the bearings next time.
Lash change with temperature
On the older ABC Saitos the valve seats were bronze, they did wear, but a very small amount. Later engines with the AAC cylinders do not have any measurable seat wear - the seat is the same hard chrome of the cylinder plating. The only AAC seats I've seen damaged were by people who insisted on lapping their valves, the chrome was damaged, it flaked off. Repair is a new cylinder, the seat can not be serviced.
The valves are interchangeable from intake to exhaust, I suspect they are austenitic or a similar steel alloy, they just about do no wear on the face. If the engine is run a lot with loose clearance the ends of the stems will wear very slightly, the major damage is to the top of the retainer groove - it will mushroom slightly and wont pull out of the guide until the ridge is cut away.
The small and mid block Saitos use steel push rods, combined with the aluminum cylinder and heat the clearance does open as the engine warms up. Very hard to maintain the temperatures to check, but as nearly as I can determine the increase is a little under 0.001" when hot. The big block engines use steel tipped aluminum push rods, they open less than 1/2 of one thousandth inch. Again, as nearly as I can measure.