Valves staying open

[BlueyXJ99]

1999 XJ. New head, new valve train, new timing gears and chain. My problem is at TDC (compression stroke) both of the valves are open. It almost seem like when I torque the rockers down 19ft lbs., the valves tend to stay open. Almost like the lifter(cam followers) are not compressing. I've cycled through each cylinder and used a borescope on each one. None of them are fully closing. What could be the issue. Maybe I'm doing the timing gear wrong. Lined up the two marks on TDC Cylinder 1. Anyone have steps on installing the timing gear correctly? New to XJs. TIA

 

[techno]

Check the timing again. You may have the camshaft timing off by 180* or you are checking the wrong cylinder. At a certain position close to TDC both the intake and exhaust valves are open especially on larger cams that have huge overlap. These are the cams that don't like low RPM idle.

 

[Anak]

Certainly sounds like the cam is not timed correctly.

I would degree it. That would be the surest path.

 

[ChillyB]

YouTube guy had same problem. Was a defective cam. Did you put in a new cam?

Most likely is improper timing but if that checks out then might want to find that video. Look up Dex XJ videos.

 

[techno]

To be sure the cam timing is correct, you need to remove the valve cover and rotate the engine in the normal direction of rotation.
While doing this, look at the valves for both cylinder #@1 and #6.
When the timing mark on the vibration damper begin to come into alignment with the marks on the timing cover one of the two cylinders mentioned will have both valves closed.

This cylinder will be on the compression stroke and ready to fire at TDC (Top Dead Center) plus or minus a few degrees.

The other cylinder will have both intake and exhaust valves rocking/moving. This indicates this cylinder is on the verge of completing the exhaust stroke and at the same time beginning the induction down-stroke.

At this point, the distributor should be inserted with the rotor pointed to the corresponding cylinder on the cap. I am assuming you have a distributor like my 1996 XJ.

These cylinders move up and down together based on the crankshaft profile. 1 and 6; 2 and 5; 3 and 4. what that means is when 1 of these cylinders in on the power stroke TDC, the corresponding cylinder will be completing the exhaust stroke and beginning the intake stroke.

The crankshaft in degrees during which time both valves are open is based on the camshaft profile AKA valve overlap.

 

[techno]

1999 XJ. New head, new valve train, new timing gears and chain. My problem is at TDC (compression stroke) both of the valves are open. It almost seem like when I torque the rockers down 19ft lbs., the valves tend to stay open. Almost like the lifter(cam followers) are not compressing. I've cycled through each cylinder and used a borescope on each one. None of them are fully closing. What could be the issue. Maybe I'm doing the timing gear wrong. Lined up the two marks on TDC Cylinder 1. Anyone have steps on installing the timing gear correctly? New to XJs. TIA

Reading your post again, I begin to wonder is you have installed solid lifters if such a thing exists for the 4.0L. I have not done any head or valve work on my XJ so cannot help you there. The deepest I have dug into my XJ was to replace the timing chain and gears.

Post up some more information, someone will be able to help you.

 

[75SV1]

I'd look at push rod lengths. If you take the push rods out, do the valves remain closed?

 

[BlueyXJ99]

Thanks Techno and 75SV1. A little history on this engine. The engine had a cracked head from overheating. So, I proceeded to purchase a remanufactured head and matched it with existing cracked head. New valve and spring already installed. While going through the engine, I found that it needed new parts like new valve train set, timing chain and gears, oil pump, resealing everything on the engine. Proceeded to replace the timing gears and chain while keeping true position of stock gears. the distributor was never removed by the way. Installed new valve train while checking and matching stock parts removed. The push rods were identical in length, lifters and rockers and rocker saddles were identical. Went through the procedure in installing via Haynes manual ie. timing on TDC cylinder 1 compression stroke and torquing to 19 ft lbs on the rockers while rotating to each cylinder. By inspecting what I have installed and using a borescope on cylinder 1 and 6, both intake and exhaust valves remained open and did not seat properly while rotating. This is also the fact on all cylinders. I did not know what was happening. So I redid every procedure via manual with the same result. My question is, Would the hydraulic lifters be stuck to where it didn't compress out of the box? They were soaking in oil for 5 days before installing. These are TRW brand lifters. I have seen videos that people have gotten stuck hydraulic lifters out of the box. Can this be the case. Any suggestions always appreciated.

 

[Anak]

If indeed none of the valves are closing correctly then pushrod length is something you need to seriously consider.

Research how to measure for correct pushrod length.

 

[BlueyXJ99]

Will do. Thank you

 

[75SV1]

OK, this is what I'd do. And yes, I've been there. Mine was with fixed roller rockers. They take a much shorter push rod.
I'd pull or loosen the spark plugs. Turn the motor with a breaker bar to such. I have heard you can turn by the power steering pulley. If not, then Clockwise on the crankshaft bolt. (others please correct me if that is not correct). I put some oil on the threads of the #1 spark plug. There should be a timing mark on your harmonic balancer. When that nears the TDC mark on the timing cover, you should hear some air passing. Sort of a swoosh. I think I backed out 1/2 to 1 turn of finger tight on the spark plug. That is your compression stroke. Alight the mark on the harmonic balancer with the mark on the Front timing chain cover. Check your Distributor, that the rotor is in the same angle as the #1 spark plug wire terminal. If OK, then:
You will need to take off the Valve cover. Yeah, what fun. Look at the rocker arm for the #1 cylinder. They should be 'horizontal'. Both about the same. So, at compression. Try and turn the push rods. If tight, then your push rods might be to long. The lifters might still be pumped up with oil. If you rotate the crack twice, and stop at a point where the valves are open. Stop and let the lifters bleed down. Could do this earlier actually. With the lifters bleed down and back at TDC, you should be able to push down a bit on the rocker arms. If not, again, probably to long push rods.
OK, what could have caused this. First is your replaced the head. We don't know how much they took off the face of the head. The last few heads I had down, it was about 0.014. Also, that goes for the deck of the engine block. Which I assume you did not take off any there. The next is the head gasket. I think stock is 0.050. They do make 0.042. Actually Cometic will make just about anything. I think 0.027 and up to 0.070. ??? So, say you used a 0.042 and the head was shaved 0.014, there's 0.022.
Now push rods. They do come in different lengths. In stock, I see 9.639 and 9.650. I think there is 0.080 'bleed' distance in a hydraulic lifter. (again, correct me if I'm wrong). So, there might be an issue with new lifters or not.
OK, back to the top at the rocker arms. Loosen if they are tight. I think there are three bolts up there. Try to keep them even tightening them down. Or loosen them in say 1/4 turns. See if that allows the rocker(s) to rotate and you can feel the spring in the lifter. If you tighten them down from where you can just move the push rod up and down no more, then say 1/4 to 1/2 turn on the bolts. The push rod should be able to turn or twist in assembled state. If the rock arm bolts can be turned to tighten, count the turns. I forget what the threads are. 1 divided by the threads. That is the depth of one turn. So, that might tell you how long of a pushrod you'd need.
Hopefully, clearer than mud.