420a compression frustration

[shaunm]

Previously I posted about this same engine, and it not starting etc etc. I got it, it was running fine until I realized I installed the head gasket upside down. ..whoops. So- replaced it put the head back together- zero compression.

Take the cams out, spin the engine, I get good compression in all cylinders.

cams back in - zero.

Noticed when I put the intake cam in, and the lobes are in the closed position they're still compressing the valve enough to bleed compression. Left the t-belt off and both intake and exhaust lobs in the close valve position - spin the crank - zero compression

If I knock the front cam carrier off an easy 8th inch up I get compression to the #1 but nowhere else. The lobes are off the rockers JUST enough. Obviously I cant loosely install the cams like this and expect to get any mileage out of this engine.

Change the head, and cams - reinstall - same exact problem.

Please help me, what am I missing here.

 

[BLINKY619]

did you bleed the lifters and did you put the timing belt on right

edit: its a 420a not 4g63

 

[shaunm]

Oh sorry - its a 420a. And.. wait bleed lifters?? Clearly this might be my problem, I've never heard of such a thing

 

[Slo2gen]

Yes you still bleed lifters on the 420a, but sounds like you have the timing done wrong. Have any pics of how you had it timed?

 

[Palmetto_TSi]

is the 420a an interference engine?

 

[Slo2gen]

Yes, but he said he had good compression with the cams out. Granted we don't know what "good" compression means. Could have some bent valves, do a leak down test....

 

[Palmetto_TSi]

Noticed when I put the intake cam in, and the lobes are in the closed position they're still compressing the valve enough to bleed compression. Left the t-belt off and both intake and exhaust lobs in the close valve position - spin the crank - zero compression

this was a bad mistake... there is no way all the valves were closed if the cams were in, and he took the timing belt off... could have bent the valves in 2,3 and 4, which would explain why he only has it on number one now...

 

[Shake_Zulla]

In addition to the info already posted I would also check my installation process too. When I experience an epic fail I like to take it apart again and make sure I follow the service manual to the letter and since you have experimented with loosening the bolts on the cams I would take it back apart and follow this procedure to the letter including torque values.
http://az2gnt.net/FSM/2gnt_420a_overhaul.pdf - page 29
Also here is something on timing
2GNT.com - PROPER_TIMING_MARK_ALIGNMENT
make sure that one of your cam gears isn't upside down (happens a lot don't worry) that would explain the 0 compression as well.

Good luck man

 

[shaunm]

Sorry guys, gotta clarify. Timing is dead on - when I installed the cams I made sure the cam was loose so it wouldnt smash the valves. The engine is outside the car, so Im not starter bumping it to compression test. I'm getting by hand turning 60psi (low I know) but I have a bum guage.

The lobes were referring to Cyl 1 only, not the entire row.

I've had to go through learning the timing on this engine MULTIPLE times, and can time this thing w/my eyes shut. Valves arent bent, valves have been lapped. I know the head runs, theres nothign wrong w/that, or the timing.

I did c-clamp the lifters (had no idea they had to bleed) and suspect this is my problem. The lifters are now empty and squeezable. So it shouldnt prop the rocker so high compressing the valve open when the cam is installed. I'll be back at it tomorrow midafternoon, and by sunday hopefully the engine will go back in. I'll update soon.

Thanks all for the quick responses

 

[Shake_Zulla]

In addition to the info already posted I would also check my installation process too. When I experience an epic fail I like to take it apart again and make sure I follow the service manual to the letter and since you have experimented with loosening the bolts on the cams I would take it back apart and follow this procedure to the letter including torque values.
http://az2gnt.net/FSM/2gnt_420a_overhaul.pdf - page 29
Also here is something on timing
2GNT.com - PROPER_TIMING_MARK_ALIGNMENT
make sure that one of your cam gears isn't upside down (happens a lot don't worry) that would explain the 0 compression as well.

Good luck man

Sorry guys, gotta clarify. Timing is dead on - when I installed the cams I made sure the cam was loose so it wouldnt smash the valves. The engine is outside the car, so Im not starter bumping it to compression test. I'm getting by hand turning 60psi (low I know) but I have a bum guage.

The lobes were referring to Cyl 1 only, not the entire row.

I've had to go through learning the timing on this engine MULTIPLE times, and can time this thing w/my eyes shut. Valves arent bent, valves have been lapped. I know the head runs, theres nothign wrong w/that, or the timing.

I did c-clamp the lifters (had no idea they had to bleed) and suspect this is my problem. The lifters are now empty and squeezable. So it shouldnt prop the rocker so high compressing the valve open when the cam is installed. I'll be back at it tomorrow midafternoon, and by sunday hopefully the engine will go back in. I'll update soon.

Thanks all for the quick responses

Just be sure to at least look at that second link I sent you. One of the stock cam gears has TWO TIMING MARKS ON IT and if lined up with the incorrect mark it will give a 0 compression. If you loosened one of the caps then i would redo the whole tightening sequence. Also according to the service manual that I sent you the lash adjusters should have some oil in them making them NOT squeezable. Just FYI man.

 

[shaunm]

Hmmm I'll double check that, but I could swear I've only seen one mark on the cam. Good read too, I appreciate that link. I'll look for the dowel pins as well as the holes pointed north. Man I cant believe I've not seen that link before.

And from everything I read- it seems I've been mistaken on the crank sprocket. Arrows aimed at each other in the link you provided, but the FSM I could have sworn I've read you have to roll the sprocket a half tooth. Am I wrong on this? OR just arrow match, cam match, and be done.

Not sure it matters- too much because I know the computer will compensate for that minor of a change, after the rebuild the engine ran w/the crank arrows off half a tooth. ?? This questions my timing skills now

 

[Shake_Zulla]

Hmmm I'll double check that, but I could swear I've only seen one mark on the cam. Good read too, I appreciate that link. I'll look for the dowel pins as well as the holes pointed north. Man I cant believe I've not seen that link before.

And from everything I read- it seems I've been mistaken on the crank sprocket. Arrows aimed at each other in the link you provided, but the FSM I could have sworn I've read you have to roll the sprocket a half tooth. Am I wrong on this? OR just arrow match, cam match, and be done.

Not sure it matters- too much because I know the computer will compensate for that minor of a change, after the rebuild the engine ran w/the crank arrows off half a tooth. ?? This questions my timing skills now

Line up all the arrows dead on. They might say to roll the sprocket half a tooth to make up for when the slack releases when you pull your pin on the tensioner. All and all after I set the tensioner I rotate the crank untill the marks line up again and see if they line up exactly. It is possible to rotate the assembly and be a tooth off thus making you redo it. I would rather be right on than a tooth off. I have done this with the motor in the car and it is a PITA. Good luck man.

 

[bullettdsm]

Also, be sure that your gears are on correctly. 2.0 should be shown, not 2.4.

MB

 

[shaunm]

Line up all the arrows dead on. They might say to roll the sprocket half a tooth to make up for when the slack releases when you pull your pin on the tensioner. All and all after I set the tensioner I rotate the crank untill the marks line up again and see if they line up exactly. It is possible to rotate the assembly and be a tooth off thus making you redo it. I would rather be right on than a tooth off. I have done this with the motor in the car and it is a PITA. Good luck man.

Oh no.. I will never attempt head swaps, cam swaps, or timing with this engine in the car. I appreciate the help again, we'll see what tomorrow holds

 

[shaunm]

Slo2gen - hit it on the head. Thank you for that suggestion. I took the lifters to a c-clamp and got them back springy. I've never heard of having to do this, but thinking about it, makes sense. Timing I know hands down, I know the holes point north on the shaft, and the (only one tick per shaft on the gear) aim at each other, w/the crank a half tooth of TDC. I've timed this engine literally 20-25 times. Long story short, the car is running, its running great. I the CEL is on, waiting for the scan tool (someone helped themselves to my last one..) and find out who's complaining. Bottom line- lifter bleeding was what the prob was.

 

[Slo2gen]

Well click that little "Resolved" button on here so it helps for future searching!