Never took as offensive, sorry if my explanation seemed that way. SPI’s are beyond a doubt, a great alternative to higher priced oem and Wiseco piston kits. Like I said (and I’m gonna pm You his number for crank servicing), Irondog (Jerry France) uses them in I’d bet over 90% of the sled engines (and ATV engines) where applicable... that’s testimony. As he does this for a living. I’ve known him since fall of 1984, worked for him for a couple years as well in my much younger technician days. Great guy to deal with. ??
I haven’t yet looked closely at latest pics (but I will), the mag cylinder, have that one replated at Millenium, make sure you have a piston assembly first though, ship it with cylinder, WITH recommended piston to wall clearances as well. They will finish the cylinder to within .0001” (1/10,000ths of an inch) of recommended clearances. But they need THE piston for that cylinder in particular, to do so.
The PTO, ship that with piston assy to Jerry (Irondog) along with your crank, jerry can use his diamond hone to true up any small deformities (if any exist), or clean walls properly and crosshatch it to the correct finish (he does all of this kind of work), I kind of egged him on to get started into it back when I worked for him, and when he retired from GM, he then began doing it full time as licensed DBA. He’s very reputable.
As far as ROOT CAUSE of ISSUE......? At this point, it could be anything. I’m beginning to think that MAYBE(??) coolant may have become either partially frozen (or clotted up) in the system, hampering flow? Maybe even bad thermostat?? Remove thermo from rear engine case and take to auto store, should be able to find lower cost match there.
And, I’d at least do a front heat exchanger flow test. It’s a great indicator as to how “healthy” your cooling system is.
Get 5-gal pail, bore hole in very bottom, add plastic inline hose fitting of same ID as the coolant hoses themselves, then a straight piece of same ID Hose to attach pail to exchanger. Pinch hose at closest point to Pail bottom as possible.
Fill pail to the 5-gal mark, using a timer, remove line pinch tool, time how long it takes to drain all 5-gallons, record this, repeat the fill and time procedure 2 more times. Add the times together, divide by 3 for AVG time flow.
Cat recommends no longer than 2 minutes and 45 seconds, and the closer to 2:20-2:30, the better.
If nothing else, this will not only test front exchangers flow rate, it will show if anything such as bad coolant or electrolysis (corrosion buildup) has hampered proper flow.
Flush rest of systems passages really well also. Looking for possible traces of evidence of any of that being clogged partially. In other words, if emitting very high volume of exiting water (showing what appears to be no flow restrictions along any of the way), you can rest assured cooling system will bleed properly when assembling back together (and not trap large pockets of air)
Replace both intakes that you mentioned seeing damage in. Check your reeds petals for damage to them, or the reed blocks seating surfaces (rubber missing, etc...)
Coolant wise, I do prefer a mixture of 60/40 (coolant/water), as this will do an even better job of resisting freezing once temps get (way down there!!), yet cools fine at normal operating temps. Why Cat hasn’t done this with their premix yet baffles me. Polaris does it with good results. Make sure you use coolant for aluminum engines and free of “pulp” contaminants (to avoid clotting)
When bleeding cooling system, the initial filling method does well, but I like to loosen coolant cap, warmup engine, then, using a flashlight to see bubbles that are in the system still, I remove hardware retaking coolant tank from fuel tank, position light UNDERNEATH the coolant tanks UPSIDE DOWN “T”, while watching for larger pockets of air as coolant flows (while occasionally blipping throttle to around 2800-3000 for a few seconds at a time, making coolant move faster to loosen up air pockets that may not be affected by idle speed coolant flow rates. As bubbles replace coolant from within the reservoir), keep adding enough coolant to keep from sucking in anymore air than what may already be in the system. (The reason I leave cap loose)
During the bubble searches, lift left ski into a milk crate for about 20-30 seconds, again, blipping throttle to loosen any air trapped, lower left ski, raise rear of sled off ground a solid 1’ - 1.5’, repeat throttle blipping while watching for excessive bubbles in upside down T at tank. Lower rear, raise rt ski and repeat again, also watching for bubbles of definitive size at the “T”. Remove crate from rt ski. Shut down sled, note coolant level in tank, allow to cool.. check cold coolant level versus hot, ideally, zero difference is the ultimate goal, but rarely does this occur. A variance of less than 3/8” is considered operable and ready to run, anything more than that, needs another bleeding session.
Ideally, IF one can position the coolant tank so that it’s “T” angles the flow direction “downwards” (by slightly tilting tank inwards towards chassis), the air will tend to have harder time BYPASSING the T, and taking nature’s course and going UP into the T instead of slipping past it.
That’s harder to do on the Firecats versus most any other sled of that era though. That’s why I recommend the milk crates and rear hoisting. When right ski is on crate, that alone forces collant to flow DOWNHILL, making air anti-gravitate back into reservoir.
Just be sure cold vs hot is 3/8” or less. You’ll be good.
There’s probably more that I can comment on, I do have some errands to run today though. I’ll be back later.