11.3cr 360ci on engine-stand

[BigBlockMopar]

The grooves are believed to help prevent detonation.
At first the general idea was the grooves, as the piston comes up to the heads BTDC, provide a 'jet' of fuel mixture from the closed part of the chamber, directed to the sparkplug to increase cylinder swirl and promote fuel burn.
It's now also believed it helps the compression pressure to get into the closed chamber part, again helping combustion.
This is all thought to be mostly beneficial at lower rpms.

 

[qkcuda]

Thanks for the explanation. First time I have seen that done.

 

[BigBlockMopar]

Did a compression test today on the 360. The engine was stone cold, removed the plugs and checked all the cylinders one by one.
I did a second test with the carb wired fully open which I forgot on the first test.
Wanted to do a 'warm' engine test as well but was a little pressed for time.

As can be seen on the cards, holding a (vintage) sturdy angled compression tester firmly against a sparkplughole with one hand while turning and holding the ignition key with the other, makes for some varying numbers over both tests.
I need to fab a screw-in fitting for the tester to be able to get better repeatable readings.

A couple of cylinders made it well into the 11 bar compression pressure (165-174 psi) the second try, which was still on a cold engine.

 

[B3RE]

Cool, and look at You with Your Somender Singh grooves! Curious what kind of power vs efficiency it delivers....keep the updates comin'..........

You beat me to it. I read about that mod many years ago, but never tried it. Would be nice to see some independent before and after testing of Somender's work.

 

[BigBlockMopar]

I've read about and think I have seen some dyno-tests online. The problem with dyno's was that they all start from 2000, 3000 or more rpm, while these mods are thought to be beneficial at the lower rpms, where added swirl can be used in the engine.
At higher rpms there already plenty of things going on that the mods didn't seem to matter much.
I recall reading about a fellow who builds Harley engines that did these mods on all the engines he build and found consistantly his engines didn't really make more power, but did require less fuel to make similar torque/power numbers.

 

[AJ/FormS]

Did a compression test today on the 360. The engine was stone cold, removed the plugs and checked all the cylinders one by one.
I did a second test with the carb wired fully open which I forgot on the first test.
Wanted to do a 'warm' engine test as well but was a little pressed for time.

As can be seen on the cards, holding a (vintage) sturdy angled compression tester firmly against a sparkplughole with one hand while turning and holding the ignition key with the other, makes for some varying numbers over both tests.
I need to fab a screw-in fitting for the tester to be able to get better repeatable readings.

A couple of cylinders made it well into the 11 bar compression pressure (165-174 psi) the second try, which was still on a cold engine.

View attachment 1715105726

I tried one of those push-on testers many years ago, and found it very difficult to keep it on after about 120 psi and nearly impossible after 140.Congrats to you for keeping on to over170!