Are these low compression numbers???...

[Anonymous]

I have a 68 engine in my mustang. Not sure of the head.

But no special cam I am aware of and rest of basic engine is stock.

Let the car warm up real nice today and did compression check on the cylinders. I left the throttle closed and did one cylinder at a time. (stupid me, read I should have the throttle open now).

They came out as follows:

1 125
2 120
3 115 <---- lowest but well within 10% of all
4 125
5 125
6 125

I did not do a wet test as they were all very close to each other. The engine blows no smoke. In fact all I get is a little water out of the tailpipe. Real clean burn. Plugs that came out looked a brownish color, maybe a tad rich in my opinion.

Although the readings are low....they're low altogether. Would they be higher if I held the throttle on the Autoilite 1100 at WOT. Reason I did not do that was concern wrt flooding the cylinders with gas.

Are these readings okay as they are consistent??? I did a search and everyone else had real high numbers (140-180).

Thanks for the help.

Steve-O

 

[jimarlie]

Those numbers are fine on a daily driver. As long as she is running good and not burning oil be happy. IMHO of course.

Jim

 

[rickwrench]

Looks fine to me.
As mentioned, as long as it's not using oil, drive it to death.
Rick(wrench)

 

[MustangSix]

How many miles on the engine?

A streched timing chain can retard your cam timing and lower your cranking compression a little. An easy replacement if the engine is high mileage but otherwise running ok.

 

[Anonymous]

Wish I knew how many miles.

Have no history on the car at all.

Bought it off a guy who had it literally sitting in his garage for 3 years. He knew nothing. He bought it off a guy who restored it (sort of). Of course the guy I bought it from had no idea who had sold it to him 3 years later.

So I discover things as I go. I'm hoping it's a fresh stock rebuild.

Cheers,
Steve-O

 

[Anonymous]

If it has been sitting that long, drive it a while and recheck the compression numbers. They get low if it's been sitting for long periods of time. That's one of the reasons why lawn mowers can be hard to start in the Spring...the rings lose some of the metal-to-metal seal if run a short period after a long rest because of microscopic rust. It wears away after several hundred miles, though, so check again later.

If your engine was rebuilt with a thick head gasket and has low miles, those numbers aren't too bad. Mine went up about 10-14 PSI when I switched from the Victor composite head gasket to the thinner steel FoMoCo gasket, a difference of about .020"..

 

[WhitePony]

Bought it off a guy who had it literally sitting in his garage for 3 years. He knew nothing. He bought it off a guy who restored it (sort of). Of course the guy I bought it from had no idea who had sold it to him 3 years later.

Steve, I have you beat by a long shot. When I bought my vert in late January, it still had 1987 Texas tags on it, and a 1987 inspection sticker. The previous owners let it set for 15 years in the garage before thay did a thing to it. They're in their 70's and finally decided to fix it and start driving it. In the last 2 years it has gone to the paint shop, the tire shop, the brake shop, and the upholstery shop for a new top. Sum total miles driven in that period? About 20.

They had reciepts for everything, and the tires that were put on the car in late 2003 still to this day have the little nubs on the treads that you see on most new tires for the first few miles before they wear away.

The engine pretty much went south on them at the end of all the other work that they had had done, and they put the car up for sale. Other than one small hole in the driver's side floor pan that was rather poorly patched by the people who owned the car before them, the car has NO rust.

So, I ended up with a 17 year garage queen.

Kris