For the sake of discussion imagine two identical 350 engines. The only difference is a 6 inch rod and a 1 point increase in compression. Say from 9.5 to 10.5 SCR. The high comp engine has increased cooling of water, oil, ATF and fuel. Say a 20* reduction in temps all around.
Looking at some of the sharp edges on the piston, they get smoothed too.

Question is: Will the high comp engine handle the increase in SCR and how much more Hp/Tq would it put out?

If we gain 1% in engine efficiency for every 10* reduction of air temps.
What do we gain w/cooler fluids?
I notice racers wrap and insulate everything.

JMHO

R

 

I think that you might be confusing air inlet temp and power gain with thermal efficiency of water and oil temps.

I am a firm believer in 192 or 195 high flow thermostats and keeping my oil temp gauge in the 200 - 210 range. My oil gets hotter under load and then returns to about 200 when i let of or just cruising.

This kind of explains cr and power increase. My two Vette engines are 11.2 and 11.7 static compression. this is allowable with bigger cam duration.

http://victorylibrary.com/brit/compression-c.htm

 

George: I understand that pressure can be reduced by using a higher duration cam.
I was thinking along the lines of same cam same heads. I notice that when SCR is raised, overheating often follows.
I was thinking of solutions to allow more SCR and more power.
I'm thinking of ATF & Oil coolers, insulating everything.
Going from 9.5 to 10.5 should be good for 20 hp on a 350?
Any thoughts?

 

The graph I posted shows a 3.4% gain from 9.5 to 10.5
Power = BTU It takes X amount of HP to maintain a constant speed on level ground for your vette. free power from a compression gain requires less throttle opening to cruise.

Only at increased throttle openings will heat become a problem. I own a Dodge dualy as my tow vehicle. Ram 3500 I use an edge power chip so I can add hundreds of HP and Foot pounds of TQ with My Gale banks turbo induction system on the fly. The problem with power and a load is that I have to watch my exhaust temp gauge because it can go over 1100 degrees very easy. So you have to turn the computer down on power levels and take you foot out of it on mountain roads.

 

So are we assuming that the cam is ideal for the 9.5 CR set up then changing CR to 10.5? Could run you into trouble with too much cylinder pressure.
10.5 CR is going to want a different cam spec than a 9.5 CR engine.
The increase in CR without running into detonation will depend on several factors. Intake charge temp is a big one as it cylinder temps and load on the engine at a specific RPM.

Power increase has to do with intake charge temps rather than oil, water, trans temps and exhaust temps. However if coolant and lubricant temps result in a lower intake charge temp then more power can result.
If you can bump the CR and still keep cylinder pressure manageable then it will result in more power.
A 6 inch rod dwells longer at TDC. This could present a problem if you're on the edge of to much pressure.
A 6 inch rod also reduces cylinder scuffing and more power is translated to the crank due to it's angular difference vs the 5.7 rod.
A 6 inch rod also see's higher piston speeds and may limit the RPM unless steps are taken to insure that the ring package, piston material and con rod material are good for the higher forces/speeds involved.
A higher CR may be worth much more than the simple math implies if the associated cam and intake are appropriate for the greater RPM a higher CR can achieve with a better cam.
A reduction in intake temp may also be worth much more than simple math implies if it allows for ideal timing and better thermal efficiency for the engine allowing for ideal mixture as well.

 

Sorry: I never mentioned that the engines were the usual 300 hp replacement.
BTW: Nothing is optimized!
I read about too may project cars that ran into cooling problems as power and rpm increased.
Then of course alt output must be increased.
I was in a traffic jam coming back from Santa Cruz. A C-5 was alongside. He asked me "How hot are you?"
I told him 205* How about you?"

Almost 230*

I tried real hard not to laugh.
My dual Spals are the bomb.