When you shut it off "hot", and 5 minutes later; does the engine crank? If yes it starts right up, then the engine was not hot enough to grab the pistons , nor were the rings butted up. That's a good sign. I have an 11/1, 367 with a 4 speed and my starter gear is 3.09 x3.55= 10.97 which is the same as your 2.66 x4.10= 10.91. This gear hits 2800 at 20 mph, and my car, if I had a mind to, would drive forever at that speed/rpm. In second I am at 30=2570. Your 4.10s would be 30= 2970 in second/2160 in third. IMO not the problem. Oh yeah, I am running a 230/237/110 cam .549/.571 lift. and it idles all day at 14* Idle-Timing/ 700 rpm. And I run 87E10 gas full-time at 180psi with alloy heads. At one time I did have heating issues with the engine locking up at shut-down. I solved that by increasing the skirt clearance and opening up the top ring-gaps. At that time, I also had low-speed heating issues. Here's how I solved those; >Milodon hi-Flo pump which is just a HD pump with an anti-cavitation plate mounted on the impeller. > I installed a 7-blade, all-steel, hi-attack angle clutch-fan with the curved tips; from a 1973 318Dart with A/C > and the 1973 26" rad with it's matching shroud. > and a thermostatic clutch fan from an early 2000s Ford pick-up truck, before they went to the screw on fans. > a hi-flow- Milodon 180* stat. > I restricted my bypass hose and the heater-core is now the primary bypass. And I shut it off for the summer. > My water pump is slightly under-driven, so the fan-belt will stay on at 7000/7200 > I have a 68 Barracuda with a fairly open front grill, and NO A/C. > the engine is getting fresh cold air. Now this is the part you may be lacking; > In my Vacuum-advance distributor, I have a two-stage timing curve. It starts advancing at 1000ish and runs from 14* at idle to 28 at 2800, then slows to all-in at 32/34 at 3200/3400. So on the primary curve, that is .78* per 100 rpm, beginning at 1000rpm. > I run a ported V-can that is able to bring in 22* at 12inches vacuum. >so; in First at 2000rpm/15mph, that is; 2000 less 1000/100 x.78 =8* ;Plus 14; plus 22 = 44* of Cruise-Timing. Second for me @30mph/2600 and that is; 2600 less 1000/100 x .78=12.5*;Plus 14; Plus 22= 48* of Cruise-Timing. Yes 48* IDK if you can run those numbers with iron heads. By IR gun, my system runs between 205*F and 207, no matter what. That big fan, with the T-clutch, takes care of business. Do not pay any attention to certain statements that say this fan sucks 30 horsepower. While it may be true at 6500 when direct-driven, consider this; >if it sucked 30 hp at idle, your engine would not even idle at a normal rpm. > and after 30/35 mph the rad receives enough ram air, that big fan sorta free-wheels. So the fan, primarily, works from idle to 30ish mph. The above is what has worked for me, and I no longer pay any attention to the temperature gauge whatsoever. and >this combo has gone 93 in the Eighth exactly as described, which at 3457 pounds, the Wallace Calculator says is 433 hp. So that Big, really BIG 7-blade fan is staying. BTW-1; that Milodon pump has a 5/8 shaft, turned down to receive the .500 spacers.Mine was new in about year 2000, and is still going. So yeah, delivered in Manitoba, that pump was pricey...... but in the long run, pretty darn cheep. BTW-2; Did I mention that my rad is an ancient 1973 model? It has patches on it's patches.lol. In about 2002 I installed a 7 pound cap, and nothing changed except the patches are now holding, and my hoses are now ancient too. BTW-3 If you run too much Idle-Timing, then the throttles will be too far closed at idle; and so the transfers will not be supplying much fuel. So then, to make it idle, you will have to crank open the mixture screws. Aaaaand then the entire low-speed system will be rich....... and so it can happen that the extra fuel, not having oxygen to react with in the chambers, if it finds some in the headers, will burn there. But if simultaneously, your V-can is not working, or it is not supplying the desperately needed low-speed timing, then the mixture may not even be finished burning at the appropriate time, and so continues burning as the piston is falling, and may even continue burning as it exits into the headers. Of course this will not help the overlap cycle at all. This is why a streeter needs a fully functional and well-tuned Vacuum Advance System. Happy HotRodding.