So my 8RT runs good, but puts on a pretty good smoke show out of the passenger side exhaust. Pulled plugs several times, and number 4 is always the culprit: wet, oily plug. Today, I did a compression test to see what kind of numbers it would put out. I did the test after letting the motor run for 15/20 minutes to get it warm. Then pulled all the plugs, and propped the throttle all the way open. Gave the motor 3 turns for each cylinder test. Here were the results dry: 1- 78 2- 77 3- 80 4- 15 5- 82 6- 78 7- 78 8- 80 I realize that these numbers are still pretty low, but what is the normal pressure an 8RT should put out?? I tried squirting oil in each cylinder, but it really didn't bump the numbers much at all (except for number 4 that went up 5-10 lbs). I'm sure I'll get some crap for this... But could I get away with just rings on number 4? Don't want to go down that slipper slope of doing rings, rod bearings, main bearings, etc. for a motor that'll see pretty few miles a year...
It may be the rings and/or the piston. Also, if your luck is really bad, a burned valve. Can you just 'recondition' one cylinder? Sure, why not. Easier and cheaper than an overhaul.......but is only a relatively short term solution.......but if it gets you by for now......that's the way to go. Ray
I'm sure you can do that as long as there is not a lot of wear on the cylinder. If once you open it up and ther is not a lot of wear, hone the cylinder with a ball hone to get the a cross hatch back in there and then get a good set of soft moly rings so the seat easy and fast. The problem just might be you have a week oil ring, so replacing those rings will help. It for sure wont hurt anything and I'm sure you're not the first or last to do it.
seems most of the time it's a burnt xhaust valve - I have had luck getting a new valve and lapping it in....pull a head and look....it's not all ways the rings....
Generally speaking, when all cylinders are low then it's rings or cylinder wear. When one or more cylinders are low then it's a valve problem. That squirt of oil in each cylinder didn't do much for the numbers. So, that along with the numbers before and after the oil indicate a valve problem. Personally, if it we my engine with those test results I would do a complete valve job. And, (smiling) not that much more work to re-ring it while it's apart. And, while you have the rod bearings out...it never stops!!Keep us updated on what you find.
I'd have to think that they should be about 110 psi according to this. http://www.vanpeltsales.com/FH_web/flathead_tuneup49-53_239-255.htm personally I'd pull the head and see what I am facing. A set of cast rings and gaskets wouldn't cost all that much and you can probably find a deal somewhere on the bearings. Even though you don't seem to drive it much having an engine that you know the condition of and can rely on is worth more than a little bit. Plus if they run better they get driven more.
Why not look for a better-condition (flathead) engine? They're out there, people pull them for SBC's and such. Cheaper than a full-on rebuild. With the numbers you've got, the cylinders have to be really worn, and the valves in serious need of work. You would drop at least a couple hundred on gaskets and stuff, and not likely it will buy you much. You can't put lipstick on a pig...
Well, today I pulled the head and dropped the pan. There wasn't a whole lot of ridge at the top, and the piston popped right out. I'm definately going to need a new piston though... Will share some pictures tomorrow. The cylinder wall has little cross-hatching left, but doesn't have any serious scoring on it. No burnt valves. Just real quick I measured the top of the piston and it came out 3 and 1/8"... Is that standard bore??
I have several flatheads .My street motors test at 110 to 120 lbs. my race motors pump 130 to 150 lbs. when you spin it over, pull all the spark plugs and throttle open.spin it til the needle stops moving.
Oh , also try another gauge .I've had some bad gauges. Once a air gauge problem(tire) and another time a valve spring tester. Grump stops in our pit and said " check your checker!" We had a bad spring tester!
I'm guessing I just measured in the wrong place and it's really 3 and 3/16" then? Will have to get a mic and see to be safe though...
If there are no markings on the piston crown, they're standard. Sounds like you may be able to improve things pretty cheaply!
That's what I'm hoping! Looks like I can buy an individual piston, a single set of rings, and just one head gasket for around $70 right through NAPA. BTW, I understand where you were coming from about buying another used motor- but running ones are pretty scare (or expensive!) and I don't really want to go out and buy another junkyard motor just to take a chance and hope it's better then my current one...
If the block isn't cracked all to hell, it's worth a ring job. You will probably have to buy a full set anyway, might as well use them.
I followed this method, and the piston came back as 3.188" - STD bore right? There were some signs of copper showing through the rod bearings though on the pistons I ended up pulling out... Should I be worried about the crank condition? Will have to mic it of course, just wanted to know if I should be prepared for some bad news on it...
Std piston is correct. I Would be very tempted to put in new rod bearings, to me that is the most critical part of a engine. Even if the crank is alittle worn if it had decent OP new bearings will make OP better yet.
I'm intending to do all the rod bearings and rings on the whole motor now... Pulled the number 1 piston and it also had broken rings, so now I guess I might as well do them all! I'm guessing it's safe to say that the crank hasn't ever been ground right? Being standard bore, and plus all the rod bearings were marked Ford...
If you can, mike all the rod journals. If they are are tiny bit undersize from wear, you may be able to use .001" or .002" undersize bearings. They USED to be available ...... Ray
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