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Re: Compression Test Results Posted by CMyles [Email]  (#1126) [Profile/Gallery]
(more from CMyles) on Sat, 16 Jan 2010 13:34:47
In Reply to: Compression Test Results, Rueben44, Sat, 16 Jan 2010 11:58:27 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Reuben44,
Those numbers don't look that bad (what altitude are you at) except of course for cylinder #1. The fact that the reading on #1 is zero wet AND dry tells us that there is a valve stuck open or a hellatious rent in the head gasket. These are "zero clearance" heads meaning that the valves and piston will hit if they are not timed accurately and that's usually what causes bent valves and bent valves will fail to close. At this point I'd pull off the head and go about fixing it. First check it for flatness and cracks, it could have either or both if it has been overheated. A little warping is reasonable to fix, if it has cracks it's best to look for another head (I want the old one). Welding up cracks generally exceeds the cost of a good used head or even a properly rebuilt one. You can get a pretty good idea of whether your head is warped by removing the lifters, replacing the caps and then spinning the cams with your fingers. When a head warps the cams typically bind and are hard to spin, they should spin VERY freely. Torque the cam caps near the center first and feel for an increase in resistance as you torque the other caps working away from center, there should be no increased resistance (put a little oil on there). If that's all good then just check the mating surface with a machinists straight edge and feeler gauges. A discrepancy of over about 0.0025" is considered to need milling. Now I'm gonna catch crap for this but, if it has no cracks and isn't warped, here's what I've done with good success several times: remove the bent valves and install some good used ones. From what I've seen, when these valves get hit the seats, guides and piston don't suffer, just the valve. There's usually a very, very small dent or two on the piston but they won't hurt a thing. Set the head upside down and pour the combustion chambers full of mineral spirits and watch inside the ports to see if it leaks past the valves. if it doesn't (after a while) then install the head with a new gasket and drive it, it will be fine. I KNOW..."Blasphemy" not having a machinist do a complete valve job with new valves and all. I'm just telling you what seems to work and will save you a butt load of money (cause that's the kind of guy I am). By the way, you'll need an "E16" torx socket for the head bolts (1/2" drive) and invest plenty of time in getting the cam timing correct before you run it or you'll be sorry. Good luck
posted by 198.233....
, Sat, 16 Jan 2010 13:34:47 <-- Viewing This Message, Sat, 16 Jan 2010 17:00:48
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