Rebuild?
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Joined: Jan 2005
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From: Douglas, Georgia
get a compression tester and check it whenever you do a tuneup.
while your at it, go to autozone and read thier lil 'when to rebuild' chapter. it sums it up nicely.
I wouldn't bother rebuilding a 300/6 until it really needs it, like burning massive amounts of oil. I would say 'when it runs bad' but I tend to think my truck likes to run badly, it's done it for 8years :-)
while your at it, go to autozone and read thier lil 'when to rebuild' chapter. it sums it up nicely.
I wouldn't bother rebuilding a 300/6 until it really needs it, like burning massive amounts of oil. I would say 'when it runs bad' but I tend to think my truck likes to run badly, it's done it for 8years :-)
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Posting Guru
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From: Cincinnati Ohio
Where can I get a compression checker, and what would the price range? I think since I have the money right now Im going to go ahead and rebuild it. What all should I get to do a rebuild, I also plan on putting a one size over stock cam in it. Can The rebuild happen with the motor still in the truck? What special tools should I look at for doing a rebuild?
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Joined: Mar 2002
Posts: 3,545
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From: Coal Region
if ur asking where to find a compression testor id steer clear of rebuilding an engine. sure u can mickey mouse it and throw in guesstimated sized bearings and such and it may run or u can have it done right and know it'll last 200,000 +...
also, no the motor cant be rebuilt in the truck...
special tools?
-cam bearing tool
-dial bore guages
-mirometers
-bore and honing equipment
-milling machine
-valve grinder...
just to name a few so the moral of the story is...pull the motor and tear it down the a long block. send it to a machine shop and have them take care of the hard work. have it sent back and re-assemble it urself.
also, no the motor cant be rebuilt in the truck...
special tools?
-cam bearing tool
-dial bore guages
-mirometers
-bore and honing equipment
-milling machine
-valve grinder...
just to name a few so the moral of the story is...pull the motor and tear it down the a long block. send it to a machine shop and have them take care of the hard work. have it sent back and re-assemble it urself.
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Joined: Jul 2005
Posts: 258
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From: Black Hills South Dakota
Any good parts store will have several compression checkers to choose from. Thread-in ones are more certain in their readings but rubber tip ones are quick and easy. Pull all the plugs and run the engine for several spins to get a good reading. All cylinders should be within 20 pounds or so of each other, they don't need to match exactly, but one or more reading quite low indicate a problem. Higher overall is better, hard to say what a "normal" reading for an older motor should be. 60-80 pounds maybe? Shoot some oil in low-reading cylinders and see if the reading improves. If it does, it means bad rings or scored cylinder. Low pressure can also be bad gaskets or valves, other problems as well. Squirting oil in the cylinder wouldn't affect these things as much.
It's good to take and write down readings as the motor wears. That way, you'll notice a drop in compression or some other problem before it becomes serious.
When you rebuild, lots of parts need fairly exact measurements so the proper thickness bearings can be ordered to compensate for wear. The engine has to be removed, torn down and closely inspected to do this, then you order the rebuild kit. The block may need inspected for cracks or defects, flushed and cleaned, etc. and at the least the cylinders would need honing. Cam, crank, block, pistons, everything needs a good lookover. If the block needs rebored, you'll possibly also need oversized pistons and rings to match.
For the 300-6, people seem to prefer an "RV" cam, one optimized for a recreational vehicle. What gets changed in cams that affects performance is how far the cam opens the intake and exhaust valves, exactly when that happens and for how long the valves stay open.
Buy a Haynes or Chilton manual beforehand and read it through a couple times. Optikal's right, if you mess up and install too tight or loose of bearings or make a mistake, the rebuild may not last, may damage the crank, block or other parts and at the least might have problems running right. It's relatively simple stuff if you have the tools and some experience or at least a lot of care and attention to cleanliness and details, but there's many things that need doing, and doing correctly to adjust for your motor's relative amount of internal wear.
Rough-running can be from many things. Compression is just one of them, but if that's the main issue, try a heavier weight oil and it may help a weak motor live a little longer.
If you're thinking that just because it's old and original, it's probably bad, that's not always true. If it runs good, not leaking or burning a lot of oil, good mileage and power still, and you change the oil and filters regularly, there's really no reason to suspect it needs a rebuild at any particular time. If you often skip an oil change and it's black and gooey, the motor's all covered in dirt and oil, smokes and runs rough, well, maybe then, yes, it would help!
-Ed
It's good to take and write down readings as the motor wears. That way, you'll notice a drop in compression or some other problem before it becomes serious.
When you rebuild, lots of parts need fairly exact measurements so the proper thickness bearings can be ordered to compensate for wear. The engine has to be removed, torn down and closely inspected to do this, then you order the rebuild kit. The block may need inspected for cracks or defects, flushed and cleaned, etc. and at the least the cylinders would need honing. Cam, crank, block, pistons, everything needs a good lookover. If the block needs rebored, you'll possibly also need oversized pistons and rings to match.
For the 300-6, people seem to prefer an "RV" cam, one optimized for a recreational vehicle. What gets changed in cams that affects performance is how far the cam opens the intake and exhaust valves, exactly when that happens and for how long the valves stay open.
Buy a Haynes or Chilton manual beforehand and read it through a couple times. Optikal's right, if you mess up and install too tight or loose of bearings or make a mistake, the rebuild may not last, may damage the crank, block or other parts and at the least might have problems running right. It's relatively simple stuff if you have the tools and some experience or at least a lot of care and attention to cleanliness and details, but there's many things that need doing, and doing correctly to adjust for your motor's relative amount of internal wear.
Rough-running can be from many things. Compression is just one of them, but if that's the main issue, try a heavier weight oil and it may help a weak motor live a little longer.
If you're thinking that just because it's old and original, it's probably bad, that's not always true. If it runs good, not leaking or burning a lot of oil, good mileage and power still, and you change the oil and filters regularly, there's really no reason to suspect it needs a rebuild at any particular time. If you often skip an oil change and it's black and gooey, the motor's all covered in dirt and oil, smokes and runs rough, well, maybe then, yes, it would help!
-Ed
Last edited by SmokyOlFord; Aug 1, 2005 at 12:12 AM.
Posting Guru
Joined: Jan 2005
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From: Douglas, Georgia
plus this isn't a million dollar engine....
it's one thing to have the time and know-how to rebuild this engine....
I don't rightly have the time, and considering a remanufactured 300/6 costs $1,000-$2,000 with a good warrenty I'd probably go that route.
close tolerances, exact measurements, and questions like 'do I need to take the engine out of the truck to rebuild it' don't all go hand in hand.
there is another fact too.... why rebuild if you do not know what the problem is? a loose vaccum line (and a million other things) can make an engine run badly.
My 300/6 was leaking oil badly and I figured it would need some serious work. I set aside a day or two to diagnose and fix the problem. Ended up being pcv valve wasn't set in the engine (doh). Must have pulled it out once and not stuck it back in. 20second fix, cost nothing, and made me feel fairly stupid for leaking oil for 30,000miles.
dp
it's one thing to have the time and know-how to rebuild this engine....
I don't rightly have the time, and considering a remanufactured 300/6 costs $1,000-$2,000 with a good warrenty I'd probably go that route.
close tolerances, exact measurements, and questions like 'do I need to take the engine out of the truck to rebuild it' don't all go hand in hand.
there is another fact too.... why rebuild if you do not know what the problem is? a loose vaccum line (and a million other things) can make an engine run badly.
My 300/6 was leaking oil badly and I figured it would need some serious work. I set aside a day or two to diagnose and fix the problem. Ended up being pcv valve wasn't set in the engine (doh). Must have pulled it out once and not stuck it back in. 20second fix, cost nothing, and made me feel fairly stupid for leaking oil for 30,000miles.
dp
