eppoh Posted February 5, 2010 Share Posted February 5, 2010 Following on my previous thread, where the timing belt had been kicked off while driving. I timed the cams, put the belt back on to try it out. The belt keeps jumping a couple teeth. Decided to do a compression test on 1 and 3 cylinders ( easiest to get to right now). I got zero cranking. Took the timing belt off, but not sure I positioned the cam correctly to close the valves. Anyone know how I can set the cam pulley to know that the valves are supposed to be closed on 1 and 3? I am thinking the belt is just too worn out, or maybe one of the cams is offering too much resistance when I crank, causing the belt to skip. Link to comment Share on other sites More sharing options...
idosubaru Posted February 5, 2010 Share Posted February 5, 2010 That stinks. Does the timing tensioner work properly? Have you tried turning the cam over by hand to see if it feels right or not? I'd turn them both over to compare. If something is wrong internally you should feel it. Don't take offense if you're an SAE certified nuclear powered bicycle repair man, I just don't know: Are you sure you're lining the belt up properly, some folks confuse the crank marks. You're familiar with how to do a compression test? Just making sure since some folks don't know and turn it over by hand, etc. Link to comment Share on other sites More sharing options...
eppoh Posted February 6, 2010 Author Share Posted February 6, 2010 Yes, I know how to do a compression test. Done lots of them on airplanes The cams both have one place that is really hard and feels almost 'blocked' when I turn the pulleys by hand, but since I have never turned any before I don't know what it is supposed to feel like. I would imagine if some valves were bent, it would be easier, not harder to turn.. As far as the belt, I am certain it was lined up correctly. There was some concern that the number of teeth between the crank and cams did not agree with the online guides posted here, but I found out that the 2000-2001 impreza 2.2 engines use a different belt than the 98-99- I think it is the same as the 2.5 SOHC. So, before I pull the heads, how can I set those cam pulleys to close both valves on the cylinder to test it? Oh, not sure about the tensioner either, since this is my first one. I know it takes some time and torque on a C clamp to compress it. Haven't seen a spec for extension clearance. Link to comment Share on other sites More sharing options...
idosubaru Posted February 6, 2010 Share Posted February 6, 2010 the cams are extremely hard to turn by hand, so that's normal. if they both felt about the same i'd assume they're working properly. guess you're going for a leak down test? hmm, it's been awhile i forget off the top of my head where to place the cams. that being said, it should just be in the fully relaxed position. in other words....turn it by hand, it gets REALLY tight (that's the valve springs compressing via the cam lobes), then once that let's go...it'll spring really hard - that should be closed. i'd do that and see what mark is close to that point. Link to comment Share on other sites More sharing options...
eppoh Posted February 6, 2010 Author Share Posted February 6, 2010 When I turn the cam pulley, after the cam unloads, there is a rotation of about 30 degrees/ maybe where there is no resistance at all. I was assuming that position is when the flat side of the cam lobes are facing the valve stem and the valves are closed- but I got zero compression cranking I just want to do cranking compression. don't have a regulator to do a leak down with. Link to comment Share on other sites More sharing options...
Qman Posted February 6, 2010 Share Posted February 6, 2010 Bent valves Link to comment Share on other sites More sharing options...
eppoh Posted February 6, 2010 Author Share Posted February 6, 2010 Bent valves That is what I am afraid is true. Apparently this 2000 2.2 is a higher compression than the 98, at 10.0, which means less clearance. Maybe time to start pulling the heads and hope the pistons are okay. I got a quote of 340 dollars for rebuilding the heads with as many valves as are needed. Link to comment Share on other sites More sharing options...
Gloyale Posted February 6, 2010 Share Posted February 6, 2010 \I timed the cams, put the belt back on to try it out. The belt keeps jumping a couple teeth. Decided to do a compression test on 1 and 3 cylinders ( easiest to get to right now). I got zero cranking. Took the timing belt off, but not sure I positioned the cam correctly to close the valves. Anyone know how I can set the cam pulley to know that the valves are supposed to be closed on 1 and 3? You cannot do a compression test without the belt installed. The intake must open, to draw air in, to have anything to compress. Get a new belt and try it. Or at the very least get a decent used belt. the one you have probably already has ripped teeth, which is why it keeps skipping. But for gods sake, don't ever use the starter to crank over the motor with the belt removed or in the wrong position. Link to comment Share on other sites More sharing options...
Qman Posted February 6, 2010 Share Posted February 6, 2010 Doesn't anyone read the vehicle? It is a 2000 Impreza. Spit belt = bent valves. Nothing more to check. Link to comment Share on other sites More sharing options...
eppoh Posted February 6, 2010 Author Share Posted February 6, 2010 Think you are right Qman. Got a belt on it, timed correctly- zero. Heads coming off tomorrow afternoon. Link to comment Share on other sites More sharing options...
eppoh Posted February 19, 2010 Author Share Posted February 19, 2010 Got the right head off. All intake valves bent. All exhaust look okay. it looks like the way the chamber is designed, there is no way for the exhuast valves to contact the pistons. The pistons look okay with only one very minor scratch on one of them. But, I have a question.... What is the purpose of of the two, not one dimple on the lower side of the face of the piston? (see crummy photo) Are these pistons cast for different engines, with intake valves in different places? Since there are only 2 intake valves per cylinder, it seems like one set of "dimples" (probably using wrong term for it) is useful. Will be getting the other head off later. Actually, my 15 year old son is doing wrenching, since my back is screwed up- so it may be a week yet.[/img] Link to comment Share on other sites More sharing options...
bgambino Posted February 19, 2010 Share Posted February 19, 2010 You cannot do a compression test without the belt installed. The intake must open, to draw air in, to have anything to compress. Get a new belt and try it. Or at the very least get a decent used belt. the one you have probably already has ripped teeth, which is why it keeps skipping. But for gods sake, don't ever use the starter to crank over the motor with the belt removed or in the wrong position. Gloyale Can you explain why you said that you cannot do a comp. test without the belt installed? As long as the cams are in a safe spot (relaxed) and you open the throttle plate... What am I missing here thanks Link to comment Share on other sites More sharing options...
naru Posted February 19, 2010 Share Posted February 19, 2010 GloyaleCan you explain why you said that you cannot do a comp. test without the belt installed? As long as the cams are in a safe spot (relaxed) and you open the throttle plate... What am I missing here thanks Valves aren`t moving.Nothing to compress. Link to comment Share on other sites More sharing options...
Gloyale Posted February 19, 2010 Share Posted February 19, 2010 Doesn't anyone read the vehicle? It is a 2000 Impreza. Spit belt = bent valves. Nothing more to check. That isn't always true. All depends where the cams come to rest Link to comment Share on other sites More sharing options...
WoodsWagon Posted February 19, 2010 Share Posted February 19, 2010 GloyaleCan you explain why you said that you cannot do a comp. test without the belt installed? As long as the cams are in a safe spot (relaxed) and you open the throttle plate... What am I missing here thanks You have to have the intake valves opening to let air into the cylinder to compress, then close on the compression stroke. If the cam's are in a relaxed position, the piston will pull a partial vacuum against the closed valves, then come back to atmospheric pressure at TDC, so no pressure will be read on the gauge. A test you can do, which tells you more than a compression test will, is a leakdown test. The basics of it are you hook compressed air up to the cylinder and see where it's escaping. Listen at the throttle body for hissing, listen at the oil fill cap for hissing, and listen at the exhaust ports for hissing. A leakdown tester tool will tell you % of leakdown, but you don't really need that as with bent valves it will be obvious where it's leaking from. Link to comment Share on other sites More sharing options...
eppoh Posted February 19, 2010 Author Share Posted February 19, 2010 (edited) If you have a compression tester with a check valve or just manually open the release, it will allow air into the cylinder through the testers.. But anyway, anyone know why those pistons are forged the way they are? Any while I am here, anyone want to suggest how to surface that block before I re-install the heads. I saw my uncle use a plate of glass with sand paper, back in the 60's on an outboard motor, on the dock. Worked fine- but, maybe not practical here. Edited February 19, 2010 by eppoh Link to comment Share on other sites More sharing options...
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