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Low compression unlike anything i've seen
So at the beginning of the summer i finally got my winter build done.
CP pistons 9.0:1(85.5 coated top and skirt) Manley Turbo Tuff Rods ACL race bearings GSC intake and exhaust valves GSC valve guides GSC Beehive springs 5041 ported head ARP 625+ head studs torqued to 100 oem head gasket just a quick background i snapped my timing belt last november and bent 6 valves. so i decided it was time to build. about a couple weeks after i got the car done one of my bolts in my tensioner broke and the timing belt slacked. drilled out the bolt cleaned it and replaced with a new one. timing never jumped so figured maybe i got lucky. about 5000 miles later the idle starts getting rough and blue smoke started coming out the exhaust until the car warmed up. so i decided to do a compression test. CYL 1 30psi CYL 2 205 CYL 3 200 CYL 4 210 HMMMMMM.... Leak down test result CYL 1 80% CYL 2 5% CYL 3 5% CYL 4 5% so ok i have low compression cylinder 1 during leak down i can hear air coming out my intake and exhaust BAD VALVE?? i looked at the pistons and cylinder 1 is dry 2-3 wet cylinder 4 dry but spark plug was white (running lean) also during leak down i looked to see if i was getting any air in my coolant by watching for bubbles, nothing seen aslo never lost any coolant either. the only thing i kept losing was oil which i figure cause my block has more crankcase pressure i was losing it that way but not leaning towards that anymore. i pulled the head and there is nothing visible as far as bent valves but lots of carbon buildup. pulled the cams installed a spark plug in cylinder 1 filled it with water and waiting on results. so far no leak after 30 min left it over night and about to check it again today when i get out of work. i will also upload some pictures. visual inspection of head gasket looked good as well. any ideas besides just carbon buildup blocking the valves from closing? also not to sure if my pistons are installed correctly kind of look backwards will upload pic as well. so any thoughts? |
Lifter/s bottoming out/collapsed, keeping valve/s open ever so slighty?
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I did buy the GSC zero lift to tick but new parts don't always mean they are good I'll look into it thanks for the input
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What fuel are you running? Is the car tuned? That all looks thoroughly gunked up for only 5k miles.
Was the installed height of the valve measured? the GSC lifters are sensitive to the installed height of the valve being correct. They can cause valve to hang open if it's not correct. But that doesn't account for the smoking and all that gunk. Who built the motor? Improperly installed or damaged oil control rings will not cause a compression issue, but they can cause a motor to smoke. |
The car is on 93 pump and is tuned I had the block built by a local shop who has done good work on evos in the area. The head was done by a separate local shop who design heads for top fuel cars. The lifters however were bleed and installed by me. I didn't take into account of the lifter height.
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that is a whole lot of crap on the valves, how do the valve seals look? Did the intake manifold look like it had oil collecting in it at all? Those compression / leak down numbres look terrible, you should fill the intake and exhaust chambers of the head with alcohol and see if it leaks past the valves. What did the head gasket look like?
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FYI, Air has smaller molecules than water. Go get it pressure checked.
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Head gasket looked good no burn marks checked the head and it's still flat valves are making a good seal upon further investigation. Once the is cleaned going to put the head back on the car it's no cams and conduct another leak down test to check the rings as well as if there is something we are not seeing with the valves
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Thank you mobster for the advice checked into the valves staying open and 2 of them on the intake side are leaking as far as everything being gunked up come to find out my injectors are no where near healthy and I'm losing oil through my valve cover cap and pcv thanks for everyone's help :beer:
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I would check the rings for sure. check the valve seals too.
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I'm going to change the valve seals for good measure the rings however I see no score marks on the cylinder walls I did a second leak down test with no cams in and I was at 5% is it worth it if it passes leakdown?
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I would go over everything again.. just to make sure everythings good and you dont have to worry about it.
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If you had leak down out of valves.
A you weren't on true dtc. B the valve seals,guides,seat need to be inspected. Not visually but by a machine shop. |
to work properly the GSC zero tick lifters need valve stem projection to be inside oem limits.
I had this same problem with my engine and GSC lifters. |
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