No compression can be caused by a few things:
- Bad rings. Unlikely in your situation, and you'd typically see low compression, not zero. And, having rings on two cylinders suddenly die would be pretty surprising.
- Head gasket. Same as above. Also, you typically see low compression on adjacent cylinders, not on two that are not adjacent.
- Valves not closing, possibly due to broken valves, broken valve springs, bad guides, etc. It'd probably be smarter to replace the head then to try and rebuild it in that case. But, having broken components on just two cylinders is unlikely (but certainly not impossible).
- Cams (and therefore valves) are out of sync with the crank due to the timing chain jumping. This is pretty hard to do without, at minimum, trashing the valves. The reason you'd see low compression on cylinders 1 and 3 but not 2 and 4 (or vice versa) is that, if the cam is, say, 90į out of phase, then the valves would be open while the piston is on its compression stroke. The even cylinders are 180į out of phase with the odd cylinders.
In order for that to happen, the timing chain would have to jump - a LOT - or the cam gear would have to come loose, allowing it to rotate without moving the cam sufficiently. If your timing chain is loose enough - I'm guessing due to a bad guide or tensioner - this could happen, but may end with the pistons slapping the valves. That would certainly destroy the valves and probably won't make the pistons happy, either.
In any case, the head is going to have to come off. Just installing a new timing set will not correct the problem.
A replacement LNF will run you about $2400. ATK is a very reliable supplier. Installation isn't difficult if you have the space and tools, but it does take some effort. (Duh.)
Blue-ish 2006 2.4, Werks stage 1 turbo, Borla cat-back, DDM braces, Spec aluminum flywheel, Spec stage 2 clutch, Werks aluminum radiator, some gauges, RKSport hood, Morimoto FX-Rs, GReddy Profec, Norm's fenders
'07 GXP, Werks Big Wheel K04 and tune, Solo catless downpipe, TCE Wilwood 6 piston front brakes, 4-piston rears , stainless brake lines, slotted/drilled rotors, BC Racing BR coilovers, Performance Autowerks intercooler, DDMWorks CAI, charge pipes and braces, RPM rollbar
Last edited by raygun; 08-08-2019 at 02:51 PM.