Cranking compression?

Does anyone ever check it? How much do most of you Big block chevy guys like to see???

 

I'm injected on alky BBC (no blower) just did mine, saw 215-220 lbs on all of them. We run approx 14.5 to 1 compression, actual mileage may vary

 

I know you were happy with that, to see just over 2% variance is pretty remarkable. If you don't mind me asking, how many laps were on the engine? And was that hot, warm or cold?

 

Mine is a blown deal, just curious what others see. Mine is 87-90 lbs on each cylinder. My NOS stuff was always 140-160.. Just curious what others seen.. This is COLD...

 

on my blown flat bottom boat 427 pump gas motor 110 on all 8 new motor did it cold..Dave

 

That was after 130 passes on the 1/8th mile tested w/ engine cold

 

Is 200psi cold cranking pressure to much for a blown 355ci small block with about 10lbs of boost?

 

my blown sbc 400. has 120psi cold cranking and running 45lbs of boost.

 

but mighty mouse that is only to the 60 foot...lol...45# of boost you must be using hair gel in that blower...Dave

 

never said i could make it run without blowin the tires off it
thought you use a can of blower gel a race
when gorr sets up a fuel system he wants to know what the cranking psi is. must be something to that.....

 

Cranking Comp.

110lbs on each cyl. 565 bbc, chiefs, 116cl cam, 14/71HH, 20% over. 1850hp.

Thats with used junk and a cast crank. Yes, its still kicking......lmao!!!!

 

I keep my combos above 285lbs on all my cylinders .0r its a big pooch !!
put maybe this boat racing stuff is a little diff?

Harper.

 

boost psi?

dynoed HP?

 

285!!!!.. My god man.. Mine would blow the heads off it..

 

OK so everyone is on the same page what is the actual correct method. Cold/Hot, crank rpm, throttle plates open or closed [Blower motor]?

 

I check mine cold, blades open, 3rd crank. Not right or wrong, just what I have always done, and gets me a baseline for checking between races. Just what I have always done for comparison. But If I seen 285 I would think the rockers had fallen off...

 

cc

Yeah, 285 would send my stuff into orbit. What cam are you running to create such high CC?

 

run a crower dur int 260 & ex 266 & 545 lift int & ex. 114deg lobe sep . 110deg centerline with a 1.70 high ratio rocker
in a bae hemi checking with the main oil line from pump to pan disconnected
48 volt pack & starter @ 600rpm .

 

Although cranking compression numbers for our blown stuff is something I want to do more of...

In my motorcycle engine days we used them quite often. We would open the carb butterfly and crank it over for 3 revolutions, which you could easily recognize as 3 surges on the needle of the gage.

If there is oil in the cylinder you will get a false reading which will read much more than is real.

This summer I hurt a cylinder and was doing a leakdown which leaked only a few %. I was amazed, than quickly realized the damaged piston allowed oil to the top of the rings and I had a false reading. We changed the damaged piston/rings.

 

That camshaft would explain alot of it. Not sure about the oil line being disconnected.. And 600 rpm would also explain it.

Mine is 290-300 ish @ 50 114 lobe in at 116...800 lift in 16volt 3 cranks