Some of you may remember previous posts where I was telling of my low temperature problems. The motor only shows 160 degrees at cruising from 20-65 mph, irregardless of how long it has been running, with an ambient of 90 degrees plus. Cruising temp will be 150-160 at lower ambients. Accuracy of gauge and thermostat has been verified, and the temps are with the electric fan turned off.
I have thought that the reason was one or a combination of four issues: 1. Aluminum intake, water pump, and timing cover, 2. excessive coolant bypassing thermostat, 3. Low compression, 4. Big *** four row radiator.
Recently I have been playing with an online calculator for figuring cranking compression, and it shows a chamber temperature of 357 degrees when plugging in values of the current motor! When putting in values for the new motor, the chamber temps go up to 424 degrees F.
Is this an Ah Ha moment .
It looks like numbers close to a stock 292 produce chamber temps of 420 degrees.


Here is the calculator: http://not2fast.wryday.com/turbo/com...pressure.shtml

Mike

 

What thermostat are ya running 46?

 

It is a Robert Shaw brass 180 degree.

 

I'm with you. It don't make sense. As the thermo should not open till the coolant in the engine reaches 180*. Which means that The engine is not getting there.
so it has to be bypassing somewhere I would think. I would try another thermostat even if this one checks out. What else could it be? I am not sure I buy the cooler combustion theory.

 

Fair enough Arctic . So I have one doubter, and I guess that was where I was going. Does it make sense or not?

 

It makes sense to me that yer thermo is not closing all the way. May have something holding it open and the water is circulating to fast to get hot. Maybe to much RTV? I have done that myself. I read or was taught in Auto school that 160* is the best temp to keep down corrosion and gunk build up in the cooling system. But it ain't enough heat for me. But mandatory on a salt water cooled engine. I have also seen where the heater hose's where on the wrong side of the thermo and letting the water bypass and not get hot. Just a thought.

 

The thermostat is a modified Robert Shaw from Stewart Components. I have been reading a forum they now have, and found that the modified units are drilled for coolant bypass even when closed. So that bypass plus the regular bypass is too much. They said on the forum that there are nonmodifed units available but not listed. The next thermostat installation will be the fourth!

Nevertheless, the chamber temperatures I mentioned at top caught my attention. The cranking pressure calculator makes me wonder how many guys have or are going to put performance cams in relatively low compression motors, and have poor results, i.e. sluggish low end, poor mileage, etc. It also gives some strong cranking pressure numbers for the old Y's using stock cams, in support of the Y's torque reputation.

Funny how taking a look at one motor parameter can send a person off in another direction, solving a completely different old issue.

This addition to my learning curve has given me one more appreciation. That being how badly I was screwed by the machine shop that did my current motor back in 1994. Come on, 312 rods in a 292, two different models of heads, a CR of 7.5:1 (which is generously overstated) with a 270 degree cam, 11 new pushrods and 5 original 1956 pushrods, springs not strong enough for cam, and no telling what else will eventually be uncovered once the motor is replaced. Luckily at least I caught the head mismatch before leaving Kansas, but the rest wasnt fully discovered until 2003 when returning to completion of the project in a state far away.