Some notes on temps and timing with a 2056, everything else mostly stock. Options

[emerygt350]

I put a set of new pistons and cylinders from AAperfomance on my 1973 GA 2.0 while I was replacing the oil cooler. Cleaned up the engine and had new valves and guides installed. Added a tangerine oil bypass spring thingy and that was all.
Stock engine, ansa muffler, 123dizzy, not Bluetooth, set on advance and my year dizzy.
Ended up with 8.4:1ish compression.

Runs great. No more cleaning burnt oil off my rear valence.

However, it was running much hotter.

Part of this turns out that I was never getting the spark plug on #3 all the way down with my fishing the dd cht ring through the hole in the tin. That was probably a lot of it. However, now that I am getting good heat measurements I was a little bit startled. Makes me wonder what my temps really were before.

I had left the timing from before and it was running at 350 degrees now just puttering around town.

I did replace my fan with two broken vanes for a 'new one'. Of course it's off a bus motor. No marks. I transferred the TDC mark before install.

Checked my timing, it was easily in the 40s. I posted before about adding timing and it cooling off in another thread. That was me being stupid. I was retarding the timing. It has been so long since I messed with the timing on this car I forgot which way it rotated.

Anyway, I can only assume I must have knocked it while working on the motor or the bad rings, valve guides, and dirty heads/pistons might have been fine with that kind of advance. Oil temps were always pretty low. No damage on the pistons or the old valves to indicate detonation.

So that brings me to the topic. I got methodical with it. I double checked my tdc mark and checked the timing. This morning it was about 34 btdc (me mucking with it earlier this week, no gun used). At 34 I couldn't cruise on the highway at Seventy without hitting 370 and nearing 400 on any slight rise. Temps in the 70s. Last night driving home, air temp in the low 60s, 60mph, still skirting 370 on the flats. Never any pinging.

This morning I changed the oil (500 miles since the new rings) I tried again, same temperatures. Came home and set the timing to 27. I can't imagine you could could think that is better than +-2 considering the marks, the methods, and the human involved. For what I am getting at, it actually doesn't matter.

Took it for the drive I always take, through town for a mile, then on the interstate for 4 miles and then through county roads (55) back to the house. About 15 miles total. At 27 degrees advance in the timing the car was still intolerably warm. Same as before. Tried it without the vacuum advance, same result Air temps in the high 60s.

Bumped the timing up to 30 (again +- 2, it's me and my timing gun). Took it for the exact same drive. Ever so slightly cooler cht but still too hot. Removed the vacuum advance and tried again. Same temps. Oil temps have been the same all throughout. The needle hangs just the left of the T on my gauge. I would say that has been far more predictable than before I replaced the cooler and the pistons and cylinders. Before it would run much cooler but under stress jump up faster. Now it's pretty much rock steady. The tangerine oil valve? The oil cooler without leaks? Hard to know.

I tried 27, I tried 30, so I tried 28/29. Wow. Temps have been climbing all day, now the air temp is 88 degrees. In town it went from 330 to 308. Climbing to 320 when getting aggressive but dropping quickly. Took it out on the highway and it was doing 60 at 345 degrees. Hard driving would bring it up to 370 but it would come back down rapidly. I did a 600 foot in 1/2 mile hill climb on a twisty road going full on, redlining 3rd so I was running mostly in fourth, 383 was the max temp but it rapidly fell as I lifted for a corner and when I got to the top it was sitting at 350, dropping to 265 rapidly as I started descending into town (we have hills and twisty roads in abundance).

In conclusion, the crazy thing to me at the moment is how sensitive this thing is to just a couple degrees of timing and that less advance, by only a degree or two, was not a safe place, and just giving it a little more was also not a good place to be. It doesn't really matter what the actual timing is (only the gods know what that is), it's just that there is a very specific spot this engine needs to be in.

Final note: during the last bits of tuning I noticed little change in performance. AFR didn't really change much throughout. It runs a little leaner than I like at feathering throttle cruise (no matter what the timing or advance) but as soon as you put load on it, it is in good places between high 11 and low 12. We have days of 90s coming so it will be interesting to see how it does.

Whew.

P.s. always 93 octane Ethanol goodness.