Topic: compression question for the experts

[Redline it]

ok so i checked ign timing and it's ok, tried the running the starter in the dark to see about strays, seen none. the plugs are firing nice. took the valve cover off, it and the breather tube cover came apart with no stuck gasket. also i put the "T" mark exactly in line with #1 before taking the cover off. the condition of the upper cam bearings are spotless of any scores. one bottom left closest to the gear, is it the thrust bearing, has a couple of light scratches on the head side. the cam looks normally weird with the polished lobe tip and then following around it has 2 distinct polish marks close together like the rocker bounces type marks. i didn't check the lobe height the cam gear is exactly lined up with the head so cam is timed right to that degree.

sitting in that position, the cam has a little play in it rolling it forward and backward by the gear, and the chain gets loose in both directions, i didn't remove the cam yet, i can't see if the tensioner bolt moves or if the chain has rubbed on the pivot or case. i changed oil just before doing this work and had the oil covered for a few days and checked for steel and aluminum particles there were none, i loosened the lock bolt/nut on the chain adjuster, then removed the adjuster bolt cap, i haven't got the tensioner to move from what i can tell. the chain stays the same. but the cam turned the crank a small degree. that's ok isn't it, with the valves all closed isn't it? from initial checks the head isn't loose, since i'm taking it off, i don't have to super careful other that wiring the chain up and trying not to drop the scupper into the bottom and nothing over a 2lb sledge hitting softly on the fins to get it off right? jk, the last time one head wouldn't budge so i got a grade stake or lath the length of the rear head width placed it under the fins, seriously and used another short piece as a wedge tapping it and it popped off. it's possible the c-chain adjuster is stuck. things are going even slower than i normally go, i fell straight onto a narrow brick wall and ribs that landed perfectly on the edge, are broke or separated, i heard crunch, no pops of snaps, still crunches when i bend over. 

[Redline it]

if any of you are around right about now, do i absolutely have to remove the cam chain tensioner holder and the tensioner slipper and the cam chain "guide" before taking the head off, and why. and the chain tensioner bottom damper if it comes out of its seating area does it fall off pretty easy? will a magnet hold it on it's way out? thank you.

[Redline it]

Maybe your head is not torqued down properly.

hey mike, you might have a point, i hope you seen mixed in the compilations of check-offs that i mentioned that head was torqued sufficient. that test was with a 3/8 ratchet held 1/2 way into the handle with a good full thumb on the socket and the last 2 little fingers first knuckle in as the indicatorsk, shooting for the feel of any loose nuts, figuring 10 to 15ft lbs wouldn't be much to cover. and all checked out, then. tonight i was gonna take the head off, so i dug out an old craftsman beam wrench, 3/8 drive to put it back together with. but just a hunch i figured what the heck, i'll give it a go around once shootin for 1/2 way to 25ft pounds. the first 4 in the center held up and the 5 nut, the rear tall "special nut" and around what i can see as just under 10ft lbs it gave a snap and turned like some bolts do in advancing sequences, as opposed to others tightening smoothly, so took note and kept on going and the special nut on the right side rear also did the same only smooth turing (less than the left side, i kept going the rest were ok, so going back to the loose one i gently gave it some additional turn force to get it close to 14ft lbs and it felt ok as it was getting close to 14 it did the same type of a snap turn, which kind of sucked immediately, the other felt ok as it snugged up to the 14ish spot. to find out if the one on the left is doing something funky i put the socket on it and it's at the starting point of looseness going out of the gate. so pretty much put it to bed under the sheet. i've never seen any "special" treatment in head assembly when putting the "special nuts"  on while tightening to torque specs. they were both loose enough especially on the left intake side to qualify my judgement to think they could be leaking. since running this motor starting a few years ago, i run it hard, and plugs i've never been able to get hardly any color on the insulator. it's not blister white but it's always been way cleaner of a light grey than i'd like it to be. all four, as matter of fact. and specifically according to Normal appearance in the plug lineups, it's right on that. the advance right at the curve of the negative twang and the first or second thread and no more has the color. of course all the past internet checks for plug chops all i find is the guy that his website of plug chops for hp or blown motor drag racing is thoroughly detailed, and tonights searches are all bring up "white" "bad." as if it's trying to say something. so i might as well, continue on and take the head off. 

[dave500]

even if a torque wrench is off calibration at least it gets em all the same which is important.

[Redline it]

even if a torque wrench is off calibration at least it gets em all the same which is important.

yes it would, but what do you think is going on the "special nut" snapping forward, with a distinct "snap" it did it 2 times the second time didn't get as tight as the first time, which was pretty far less equal than the other nuts to start with. take it off and check it out? i have 2 more  motors  sitting around with the heads off, parts all packaged,maybe i'll look at those,  but i don'r remember anything super different about the stud threads on those, they're the ones with the oil holes i think running through them. the way i always understood torque after i learned it wasn't so much aimed at just tightening by torquing the heck out of a bolt or nut, but more of the level protection to not strip the threads of the fastener, that came with age. now looking ahead such as the head cover and it being a 5 to 8 ft lbs torque spec and then seeing the "note" that "torque differences of each bolt should be within 1.5 ft lbs is gonna be hard to learn. and would  it  start in stages say of like aiming for the first set in the range of 3ft lbs then 4 then  5? isn't that finger tight to begin with. digital would be my only hope in feeling that difference. i should design a break away toothpick torque wrench using toothpicks, and nobody even think about stealing that future pattend pending idea. delta rider, how'd we make it this far without that toothpick torque wrench?

[HondaMan]

No need to remove the cam chain tensioner parts for top-end removal. Just use a long, thin screwdriver and loosen the chain's adjuster, then gently (but firmly!) push the tensioner back and re-set the little bolt to hold it out of the way (makes the chain looser). Then the sprocket comes off the cam and the cam and sprocket slip out of the top end. Leave the tensioner "preloaded" until you put it back together.

One thing about the smallest Fours: if someone installed new pistons and rings and the original cylinder clearance-to-piston was more than 0.0010" with fresh bore, it will wear quickly. The 350F and 400F (and especially the 250F) require TIGHT bores, like 0.0004"-0.0008" maximum. If they start out at 0.0010" or more, they will wear out within 10,000 miles, if even that much. That's how I end up getting many of them for yet-another rebuild.

[Redline it]

No need to remove the cam chain tensioner parts for top-end removal. Just use a long, thin screwdriver and loosen the chain's adjuster, then gently (but firmly!) push the tensioner back and re-set the little bolt to hold it out of the way (makes the chain looser). Then the sprocket comes off the cam and the cam and sprocket slip out of the top end. Leave the tensioner "preloaded" until you put it back together.

One thing about the smallest Fours: if someone installed new pistons and rings and the original cylinder clearance-to-piston was more than 0.0010" with fresh bore, it will wear quickly. The 350F and 400F (and especially the 250F) require TIGHT bores, like 0.0004"-0.0008" maximum. If they start out at 0.0010" or more, they will wear out within 10,000 miles, if even that much. That's how I end up getting many of them for yet-another rebuild.

I appreciate that, before i got this message i took the tensioner push rod cap off and then tried to get an effect from applying pressure to the top of the push rod and can't see a change in the slack, there's a lot of slack too on the tensioner side, so i took out the lock bolt to see if there's divot from overtightening the lock bolt. there's only a very small mark, the bolt itself looks fine, with no mushrooming end at all. i loosed the tensioner holder and removed it together with it's insert. i loosened 1 sprocket bolt and that was as far as i got. i'll put the holder back (i don't think the chain has fallen off the crank gear)then  push the tensioner back,with the long thin scr dvr, applying pressure on the plunger,)  then in that position i'll set the lock bolt  to hold it there. 

yesterday i did come across your reply to someone's 350 smoking on piston to bore clearance on fresh bore. to bring the info to the machine shop so they don't use the briggs and stratton clearances, which they probably would, and instead bore to .0004 final clearance and the info about the oil passage oring increase size of .2 to .4mm thicker to allow for thicker aftermarket head gasket, or mill the cylinder past the oring recess (which i wouldn't want to do.) i got my eyes open, thanks again.

[Redline it]

No need to remove the cam chain tensioner parts for top-end removal. Just use a long, thin screwdriver and loosen the chain's adjuster, then gently (but firmly!) push the tensioner back and re-set the little bolt to hold it out of the way (makes the chain looser). Then the sprocket comes off the cam and the cam and sprocket slip out of the top end. Leave the tensioner "preloaded" until you put it back together.

One thing about the smallest Fours: if someone installed new pistons and rings and the original cylinder clearance-to-piston was more than 0.0010" with fresh bore, it will wear quickly. The 350F and 400F (and especially the 250F) require TIGHT bores, like 0.0004"-0.0008" maximum. If they start out at 0.0010" or more, they will wear out within 10,000 miles, if even that much.

That's how I end up getting many of them for yet-another rebuild.

am i reading this right? so you're still building motors? if so is just 750s? i got a couple more motors that are benched because of a worn standard bore, crosshatch is polished. the .0004 to was it .0008 clearance, is that including the 466 kit or does he have his own clearance specs.

the toss up of not cutting all the meat out to 466 bore size is the .010 or .025 over piston availability and prices vs the extra passes to get to 2.060 or whatever it is, comes out almost the same in price either way.

one question i'd have is: would the 30,000 mile bottom ends handle the new top end without more than jetting? and a new clutch maybe. that was the plan on one of them.

i seen an ebay deal of .25 over pistons pins and rings for 595. that be gambling to buy that and find out the .025 wouldn't be enough to get a clean bore.