Hello, am working on an m20 and noticed when id crank the engine with my torque wrench it turns over smoothly about half way and then stops, wont continue without some actual force. I then checked my timing and the tdc marks were off. I took off the belt, carefully adjusted the sprokets so both cam and crank were at tdc, put the belt on, tensioned it up, decided to crank it with the wrench to make sure everything was alright. Cranked half way smooth then stopped, I then cranked it backwards to the tdc marks and they were again like an inch off?! Could someone help me out and hopefully explain why this thing keeps "untiming" itself when the engine turns.
-
-
I'm thinking key on crankshaft gear or pin on camshaft gear is missing or damaged. -
I dont know if its possible, but maybe your cam gear is on backwards. One side has a pin sticking out that goes into the camshaft itself.Comment
-
I hope you already know this...but crank rotates 2 full turns for a single cam rotation. Did you make sure that crank was at TDC for cyl1 when setting the cam mark?
In any even, there is no way both marks can gt out of alignment if they were set correctly to begin with....unless your belt jumped when rotating backwardsComment
-
Alright so heres my guess of what happened, diving in deep tomorrow.. When i first put on the belt it was probably a few teeth off and then I think I put the harmonic balancer on without aligning it with the other two tdc marks, because im a dumbass. So then when trying to get the timing back on I aligned the cam tdc with the most likely off tdc line on the harmonic balancer. Tomorrow im taking the balancer off, timing belt, checking my cam gear, maybe pulling the head if its too fucked haha. Will let you guys know what I encounterComment
-
Also curious about the outcome of this. Let us know man!@BaggedMWComment
-
Alright heres what happened. Took of the balancer, actually looked like it was on right. Lined up the two tdcs and put on the belt, could then turn the engine smoothly about 50% of the cam gear before something hit and it cant turn anymore. I checked several times to make sure it wasnt any teeth off. This was pretty difficult because for some reason, when the crank is at tdc it puts maybe 1-2 teeth of slack on the top of the cam, it then picks up the slack normally once rotated maybe 10-15° past tdc. So i ended up aligning the cam tdc with a made up line slightly counterclockwise of the cranks tdc mark to account for the slack stuff. Same thing tho, rotates about halfway then hits a wall. Pulling off the valvecover this afternoon and am gonna see if I can find anything wrong.. Really dont wanna pull the head again haha. Let me know if you guys think of anythingComment
-
Possible solution? Just took off the vakve cover and nothing seemed wrong there, I couldnt figure out what the M20 valves are all supposed to look like at tdc so if anyone knows or has a picture of that that would be great. Then for the fuck of it at this point i tried aligning the crank tdc with the other line on the cam. I have a pretty cheap aftermarket adjustable cam so you can retard/advance timing, i adsumed the line was for that. But after careful aligning them my engine will now turn all the way over with only one small bump of maybe 5ish ft pounds of torque.Also if anyone know which direction that little T thing for the distributor on the cam gear is supposed to be facing that would be grea t, got a hunch mines wrong, yay. Heres a pic of my cam, belt on, no aligned on anything right now sorry but this is with using the other cam line
Comment
-
i would pull the head and make sure some of the the valves aren't bent, after all that's gone on id be surprised if there weren't any.
also if you arent already crank it over with no spark plugs in89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...
new build thread http://www.r3vlimited.com/board/showthread.php?t=317505
Comment
-
This may seem too obvious but are you sure youre actually hitting something and not getting compression resistanceSeat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com
https://www.r3vlimited.com/board/sho...86#post4944786
Alice the Time Capsule
http://www.r3vlimited.com/board/showthread.php?t=360504
87 Zinno Cabrio barn find 98k and still smells like a barn. Build thread http://www.r3vlimited.com/board/show...20#post3455220Comment
-
Compress the tensioner and tighten the bolt to keep it back. Put the belt on the crank first and pull up tight. Then wrap it around the oil pump, the the cam, making sure the right side of the belt is very tight. Then go around the cam while keeping it tight on the crank and slip it on the tensioner last.
I actually back the crank up one belt tooth so that as I put the belt over the tensioner, I turn the crank up to TDC. Then before releasing the tensioner, rotate the engine and make sure the cam lines back up.
Also, this. When a piston is on it's compression stroke, you will have resistance. Take the plugs out and see if there's change.Originally posted by digger View PostComment
-
At TDC the two rockers for cyl 1 will have play because the valves will be closed. Are the threads holding in your tensioner stripped. If they don't lock in then everytime you spin it backwards the slack will get you out of time. Why are you even spinning it backwards?Comment
-
You didn't answer the question. Are you certain that your crank is in TDC for cyl #1? How did you verify that. Just because TDC marks on the crank aligned, it doesn't mean TDC for cyl #1.Originally posted by RoarinE21 View Post
Also as someone mentioned, there should be no slack if your tensioner was set correctly. You could experience some slack when not being careful in rotating it CCW but it will go back to normal once you get it going in CW direction.
"made up TDC line for slack" etc is a very wrong approach when dealing with TB and interference engines. They do not forgive.
The correct approach is to find true TDC for cyl#1 with a piston stop, install degree wheel and zero it out based on found TDC (disregard factory mark). Install head with cam at TDC for cyl 1. Install TB and set the tension, lock the tensioner. Install dial indicator on the rockers and verify that valve timing is where it needs to be based on the degree wheel on the crank. Adjust the cam gear (if adjustable) accordingly. If not adjustable, decide if you can live with what you get out of stock cam gear. If not, get an adjustable cam gear.
Based you your description of events, I would strongly recommend to pul the head and verify that valves didn't meet pistons. I know it sucks...Comment
-
Maybe once you get the belt on right you should do a leakdown test instead of directly going to pull the head. You have a small chance you didn't bend a valve but it's worth a shot if it means you don't have to pull the head.Comment
-
Was planning to do just that! its a project engine so I haven't started it yet (only hand cranked), plus I have double head gaskets for lower compression because boost, but that should also allow for more valve clearance.Originally posted by vtechnik View Post
Also for the slack people, it was only when I was setting the belt but then it quickly goes away once your crank it clockwise.
So today I took out the spark plugs and was also browsing pictures of m20 cam gears at TDC online, specifically was looking at how that little metal thing for the distributor is sittinf/facing. I then set my cam using that stratedgy to some random tooth on the gear. First I notcied both the rockers for cyl 1 were movable so that was a good sign, I the put on the belt and it cranks all the way beautifully no problem, what the fuck. Do you guys think its just some stupid chinese gear they messed up the lines on? It has the pin on the back like the normal cam gear so its sitting properly on the cam, then im pretty sure the distributor thingy is sitting in there right because theres that little divot thingy in the ring it goes into. Had an extra one of the aftermarket gears so I took some pics. Thankyou guys! Please keep up the feedback I think were figuring it out!!
Any other ways to confirm my valves are at tdc?Comment
Comment