2 replies to this topic

[ConnorD42]

Hey guys, I dropped a Race Engineering head into my 1.6 last season since I couldn't afford the whole sha-bang, and was having a conversation with someone about the combination of the lower end and race heads (I overheated a couple years ago to the point that the cylinder head at the time warped 0.017"- stupid coolant caps!) The bottom end that was over heated is the one currently in the car which hasn't been re-ringed, honed, sealed, bearings, etc. where the individual told me that overheated bottom ends in conjunction with a race head tend to make really decent power.

 

Is there any legitimacy to this claim? If so, why? I don't understand the science behind why an overheated motor might have an advantage over one that hasn't been previously?

 

I'm on the fence currently about sending the engine to my builder to check the head (and refresh if needed) as well as build the bottom end. Can't afford an NB at this time, but if anyone with a 1.6 that's went for a full motor; was it worth the cost? Or just stick with the head and junkyard bottom end?

[Jim Drago]

Hey guys, I dropped a Race Engineering head into my 1.6 last season since I couldn't afford the whole sha-bang, and was having a conversation with someone about the combination of the lower end and race heads (I overheated a couple years ago to the point that the cylinder head at the time warped 0.017"- stupid coolant caps!) The bottom end that was over heated is the one currently in the car which hasn't been re-ringed, honed, sealed, bearings, etc. where the individual told me that overheated bottom ends in conjunction with a race head tend to make really decent power.

 

Is there any legitimacy to this claim? If so, why? I don't understand the science behind why an overheated motor might have an advantage over one that hasn't been previously?

 

I'm on the fence currently about sending the engine to my builder to check the head (and refresh if needed) as well as build the bottom end. Can't afford an NB at this time, but if anyone with a 1.6 that's went for a full motor; was it worth the cost? Or just stick with the head and junkyard bottom end?

Wow, no there is ZERO credibility to that claim. 

You should speak to Chris @RE if that is where you bought the head. But if head was over heated to .017, you need to likely go through the bottom as well

[Steve Scheifler]

The “logic” he’s probably relying on is that overheated rings lose their tension (springiness that spreads them against the cylinder wall). Idea being less drag during much of the stroke but still seal well enough under expansion from combustion gasses. Amusingly, one of the old RE cheats (back in the Bob T days) was to install very low tension rings in fresh builds then tell customers to not worry about the crappy leak-down readings on their new $7k engine. It likely did help, a bit, briefly, until the blow-by gunked up the rings making them stick and carbon built up in the combustion chambers. He over did it. A technique that has some value in engines rebuilt every race or two, but probably the second dumbest thing I’ve seen in an SM engine from a “pro” builder.

Anyway, thinking an overheated engine will give the same “benefit” as one intentionally built loose fails to consider that the cylinder bores may be out of round, as well as scored along with the piston skirts, a significant source of drag. You might have spotted that when swapping the head but maybe not if it didn’t run long. They should have been measured then. If the bores are oval things will only get worse. You may get away with it for a long time, or you may not. Without a prior baseline on a local dyno when an engine is healthy it’s difficult to asses the impact, but if you haven’t done a leak-down test you should. If it's acceptable, then run the engine and repeat the test after each event to see if the rings are failing.