The Ford Barn

bonanza7369 · 03-29-2016, 01:16 PM

what should the compression reading be on a 292 Yblock. cranking with the starter cold engine, all plugs out.

wbedwards · 03-29-2016, 01:25 PM

Book says minimum at cranking speed should be 160. Having said that, I have the 361fe says the minimum is 180 and I am running 75% of that with no problems.

darrell · 03-29-2016, 06:10 PM

it depends on what heads your using and a few other things.

Ole Don · 03-29-2016, 06:33 PM

If they are all similar, it may run on for years with less that 100. Look for big drop from one to the next, that's trouble.

Kahuna · 03-29-2016, 11:14 PM

As mentioned, depends on the engine:
Is it stock? Modified? Cam change?
All these items affect the compression test & readings
I have a very big cam in an engine and the compression
readings are in the 105# range.
Also, Carb butterflies should be wide open when cranking

dmsfrr · 03-30-2016, 11:16 AM

Sponsored Links (Register now to hide all advertisements)

Depending on the condition of the engine and stock/aftermarket parts variables...
anything above 110, as long as all readings are within 10% of each other.

.

bonanza7369 · 03-30-2016, 01:37 PM

Thanks guys mine are all about 120

Sid · 10-26-2016, 04:28 PM

Ford somewhat embellished on their compression ratios. I have seen fresh 292's barely go over 140 put back to stock. Also factory head gasket was a shim.Most head gaskets today are just shy of .050 thick. Basically try to stay within about 10% on the lowest to the highest reading. As long as you are 110lbs. or more just drive it like you stole it.

Kurt in NJ · 10-31-2016, 08:34 PM

And you have to check the calibration of the gauge---4 different gauges, 4 different readings,25lb spread on the last ones I checked,2 the same read different) the ones with the longest hoses read lowest, the flexible hose swelled with each compression stroke (the gauge I use has steel corded hose)

What I find more important that the highest reading you get is how even, and how much on the first --2nd pump, you have to remember the engine running only gets 1 compression cycle, if you don't make 75% of the total on the first or 2nd full pump there are compression losses that there shouldn't be, and if there is much of a difference between cylinders you can't have it as smooth as it could be

03-29-2016, 01:16 PM	#1
bonanza7369 Member Join Date: Sep 2015 Posts: 38	compression what should the compression reading be on a 292 Yblock. cranking with the starter cold engine, all plugs out.

03-29-2016, 01:25 PM	#2
wbedwards Senior Member Join Date: Jan 2015 Location: Birmingham, Al. Posts: 339	Re: compression Book says minimum at cranking speed should be 160. Having said that, I have the 361fe says the minimum is 180 and I am running 75% of that with no problems. Last edited by wbedwards; 03-29-2016 at 08:56 PM.

03-29-2016, 06:10 PM	#3
darrell Senior Member Join Date: Dec 2010 Location: p.e.i. Posts: 1,060	Re: compression it depends on what heads your using and a few other things.

03-29-2016, 06:33 PM	#4
Ole Don Senior Member Join Date: May 2010 Location: St. Michael, Minnesota Posts: 1,713	Re: compression If they are all similar, it may run on for years with less that 100. Look for big drop from one to the next, that's trouble.

03-29-2016, 11:14 PM	#5
Kahuna Senior Member Join Date: May 2010 Location: NorCal Posts: 2,617	Re: compression As mentioned, depends on the engine: Is it stock? Modified? Cam change? All these items affect the compression test & readings I have a very big cam in an engine and the compression readings are in the 105# range. Also, Carb butterflies should be wide open when cranking

03-30-2016, 11:16 AM	#6
dmsfrr Senior Member Join Date: Aug 2012 Location: Abq, NM Posts: 3,607	Re: compression Sponsored Links (Register now to hide all advertisements) Depending on the condition of the engine and stock/aftermarket parts variables... anything above 110, as long as all readings are within 10% of each other. . Last edited by dmsfrr; 03-30-2016 at 04:22 PM.

03-30-2016, 01:37 PM	#7
bonanza7369 Member Join Date: Sep 2015 Posts: 38	Re: compression Thanks guys mine are all about 120

10-26-2016, 04:28 PM	#8
Sid Senior Member Join Date: May 2010 Location: Rathdrum Idaho Posts: 737	Re: compression Ford somewhat embellished on their compression ratios. I have seen fresh 292's barely go over 140 put back to stock. Also factory head gasket was a shim.Most head gaskets today are just shy of .050 thick. Basically try to stay within about 10% on the lowest to the highest reading. As long as you are 110lbs. or more just drive it like you stole it.

10-31-2016, 08:34 PM	#9
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,159	Re: compression And you have to check the calibration of the gauge---4 different gauges, 4 different readings,25lb spread on the last ones I checked,2 the same read different) the ones with the longest hoses read lowest, the flexible hose swelled with each compression stroke (the gauge I use has steel corded hose) What I find more important that the highest reading you get is how even, and how much on the first --2nd pump, you have to remember the engine running only gets 1 compression cycle, if you don't make 75% of the total on the first or 2nd full pump there are compression losses that there shouldn't be, and if there is much of a difference between cylinders you can't have it as smooth as it could be Last edited by Kurt in NJ; 10-31-2016 at 08:50 PM.