1973 Sportsroof Compression Test

[timsweet]

I finally got around to doing the compression test on my '73's - 1972 351 Cleveland.

Right side

Cylinder 1 - 130

Cylinder 2 - 35, 25, 60, 90

Cylinder 3 - 140

Cylinder 4 - 135

Left side

Cylinder 5 - 160

Cylinder 6 - 155

Cylinder 7 - 160

Cylinder 8 - 140

Burnt valve on #2 maybe? I did not do a wet test.

Tim

Tucson, AZ

 

[Don C]

I wouldn't expect a burned valve to vary that much. Are you burning oil, visible smoke? Any signs of blow-by when you take the oil filler cap off? Try putting some air pressure in that cylinder with it at the top of the compression stroke, if it's a burned valve (or valve not closing) you'll hear it in the exhaust pipe or carburetor.

 

[will e]

Might be a warped head or blown head gasket. How does the car run? Does it overheat quickly?

Whatever it is, looks like you are going to have to pull the head.

 

[timsweet]

Might be a warped head or blown head gasket. How does the car run? Does it overheat quickly?

Whatever it is, looks like you are going to have to pull the head.

No doesn't over heat at all. Drove it home at 70 miles/h on the interstate. Starts and runs - idles rough, wants to stall while in drive.

Blown head gasket - not sure if that would impact only one cylinder? Maybe?

I am going to have to pull the heads.

Anyone know if these were open or closed chambers? Might want to order a re-man'ed set.

Tim

 

[Jeff73Mach1]

If 73-they are open chamber.

Have your own gone through and rebuilt by someone reputable and local. Unless you have a bad core. Even then I have a pair of bare heads that are buildable and OC heads are fairly inexpensive,

 

[timsweet]

If 73-they are open chamber.

Have your own gone through and rebuilt by someone reputable and local. Unless you have a bad core. Even then I have a pair of bare heads that are buildable and OC heads are fairly inexpensive,

Engine is a '72. Mostly likely open as well?

 

[Jeff73Mach1]

Not sure, I think both were available in 72.

The problem with buying heads ready to go is they usually aren't done with the higher quality parts and often are "just" good enough to bolt on and run for a while (Ie the length of the warranty) before you notice problems.

Bronze valve guides, stainless 1 piece valves with good quality MATCHING retainers and a proper 3 angle valve job should be done at a minimum. Springs should be matched to cam and set up to proper height and have the pressure checked.

Hardened seats are an option, but some folks run without them (myself included) either because they are cheap-or concerned about the proximity of the water jacket and don't want to risk a seat falling out at some point. If driving daily, I'd probably get hardened seats, under 5K a year, probably not

 

[will e]

Do you know if they are 4v or 2v heads? There is a casting code on the corner. All 2v are open.

 

[OMS]

72 are open chamber

+ 1 with Jeff - rebuild yours if possible

Don

 

[timsweet]

Do you know if they are 4v or 2v heads? There is a casting code on the corner. All 2v are open.

They are 2v.

Thanks

Tim

 

[timsweet]

Not sure, I think both were available in 72.

The problem with buying heads ready to go is they usually aren't done with the higher quality parts and often are "just" good enough to bolt on and run for a while (Ie the length of the warranty) before you notice problems.

Bronze valve guides, stainless 1 piece valves with good quality MATCHING retainers and a proper 3 angle valve job should be done at a minimum. Springs should be matched to cam and set up to proper height and have the pressure checked.

Hardened seats are an option, but some folks run without them (myself included) either because they are cheap-or concerned about the proximity of the water jacket and don't want to risk a seat falling out at some point. If driving daily, I'd probably get hardened seats, under 5K a year, probably not

That would be a good build!!!

Thanks

tim

 

[timsweet]

Here's a couple links to my blog with test videos.

1973 Mustang - Project SportsRoof - Compression Test Part I

http://wp.me/p2YxYx-4CY

1973 Mustang - Project SportsRoof - Compression Test Part II

http://wp.me/p2YxYx-4D4

 

[MeZapU]

I would try a leakdown test before pulling anything apart. It will further identify any issues you might be having.