I agree. I was just surprised that the other poster said 150+ on a used engine, when specs are 120-150.

 

and what are flyers???

 

so my average is 116.5 psi. and my lowest two cylinders are #3 at 85lbs n 6 i think at 115. at 90% they should be no lower than 105psi and no higher than 110% at 128psi or so. thanks fellas. good info. and bub i think your right. this girls a 97. not 2011. shes seen her days even with 116k

 

It's called a "leakdown tester," and it's readily available.

If the rings are worn, nothing will help but replacing them. There's no "cure in a can," it don't exist. Either the rings have lost spring tension, or they've worn to the point where they can't seal against the bores. Either way, you're going to have to get into the engine...

I've not used Seafoam to clean the crankcase - I usually either run MMO for a maintenance clean, or replace one quart of engine oil with a quart of ATF (Type F if I can find it, Dexron if I can't - Type F has a higher detergent content, and it also makes a good hand cleaner...) and run it for not more than a week.

In either case, drain while hot.

 

Oh yes I would, lol.

 

hahaha. been there done that huh. there had to be pounds of old BS stuck in that thing. clogged two oil filters and the first about caused complete motor failure. so i pulled the valve cover and scooped the rest out with a spoon! lol. And thanks. but i understand a trash ring means bad motor. or at least rebuild. and theres no point in getting that far in without doing it all, and right, or possibly a 4.6 stroker upgrade! <<<Anyone heard of pricing on these?

 

I worked for a Ford dealer back 30-some years ago. The 302's were notorious for that. 70-80K and those old LTD's were wheezing like the geezers who drove them, lol.

The leakdown test is your best bet, as mentioned. Sometimes you luck out and a good ring-soak breaks them loose. I've used GM top engine cleaner for that instead of MMO. If you do that, change the oil....

 

not burning oil and that low of compression....hmm...that favors the cylinder head being the problem just by that alone. as everyone has stated the leakdown is your next test. still. i can't help but wonder if you did the compression test correctly. you need to turn the engine over at least 6 revolutions on each cylinder to get accurate peak numbers. also, if you had any grime in cyl3 the tester itself could have not sealed. the leakdown will help pinpoint this. the most typical way people have low compression in only one cylinder is either

1. fractured ringland. real popular in forced induction and or high compression engines

2. chipped valve of heavy build up that prevents sealing completely.

i suppose it's possible that a HG could be leaking but that often lets you know in other ways such as boiling coolant and or the milkshake radiator

 

i did the test three times. engine warm and let his a good 8 revs till it Quit building pressure. i got the same readings within a lb or two on each cylinder in each test. only thing is that i may not have had throttle plate closed. didnt know it would make a difference.

 

Do bear in mind that the oil control function uses a separate ring from the compression seals - you can have failed/failing compression rings, but have good oil control; and vice versa. It's uncommon, but I've seen it happen.

 

Sorry - marksman's term.

A "flyer" is a data point that doesn't fit the set. Say you take five shots at 200 yards; you get four in the X ring and one in the eight. The one in the eight ring is the "flyer."

Say you get compression readings of 120/115/60/100/110/125. The "60" is the flyer, you set it aside while you're calculating your average.

120+115+100+110+125=570; 570/5 = 114. 114x90%=102.6, 114x110%=125.4

Anything outside the range of 102.6-125.4psig can be considered "suspect" and warrant further investigation. The 60psig reading is obviously off, the 100psig reading warrants further investigation. Based on those readings, I'd do the leakdown test on #3 and #4, just to identify the faults (a failed/failing cylinder head gasket may cause both low readings, but it may not be. Ergo, check both and verify.)

Does this make sense now? It's pretty much the de facto standard for interpreting and responding to compression test results - if the readings are consistently low (say all <100psig!) you're going to need a general overhaul and shouldn't bother checking individual cylinders. If it's just a cylinder or two, then you do the deeper check.

 

thank you very much guys!!! im a little younger (24) and just never had a chance to do any of this growing up. Im no mechanic, but you guys got me addicted. It all makes plenty of sense, and now that i know ill make this a by the book operation. sorry fellas, but cash is tight till i get paid. Will update when i get the "leakdown tester"! And if i get some time today, i intend of re-running my compression test since i have thoroughly bathed the rings with Marvel. Also i stripped her down last night. took most all the trim and fender flares off! thinking about starting to cut and fold the fenders!!! and def. at least am reshaping and repairing my flares, then bedlining or painting. Any reccomendations? Will update with pics ECT

 

Light bar i fab'd up drunk last night.

 

pics of my beauty!

 

just a lil more of my baby