Zero Compression on new Cam and head install

[dlafont]

I just did a compression check on number 1 so that I could dial in the cam sensor and it appears I have zero compression on this cylinder. Other cylinders look fine. I know that this engine was good before I put the new GN1 heads and roller Cam, roller rockers and double sprocket timing chain. I just primed the oil however I set zero lash when the engine was still on the stand.

I know that worst case zero compression can mean a hole in the piston, block, heads, etc however I'm pretty sure this is not the case.. Could this be caused by a miss-adjusted rocker which is keeping the intake open during compression stroke? The rings would have to be *really* damaged/worn for zero compression correct?

I'm going to pull the valve cover tonight and see what the lash is like any try and debug but I though I would get some consensus on this.

Any other thoughts come to mind?

Also... What is the best process to make sure that the hydraulic lifters are filled when setting zero lash? Or does this matter?

Thanks,

D

 

[SPOOLFOOL2]

Hyd or solid lifters?

Check lash/ preload first. If that doesn't fix it, do a leak down, or just hook some air up to the spark plug hole and listen to where the air goes. You want to do it while you've still got the valve cover(s) off. Could be a bent or stuck valve. If it were rings or a hole in the pistons, the plug would be oily and you'd have massive blowby puking all over the outside of your engine.

good luck. Let us know how it goes.

Mike B.

 

[bison]

Take the rockers off and see if you have any pressure cranking it

 

[dlafont]

Thanks for the input... I'll try and I'll let you guys know.

 

[dlafont]

Good news so far..

Pulled valve cover and backed off rocker bolts on both #1 intake and exhaust until no tension. Turned the crank by hand and now #1 has compression. Looks like I have the pre-load/lash incorrectly adjusted.
Looks like I adjusted the original lash when the lifters were completely collapsed so when I primed with oil and cranked for the first time they pumped up and and must have kept the valve open.

D

 

[dlafont]

Well.... Here is an update to the issue.. I have found the root of the problem.

Apparently my Pedestal Mount Scorpion Roller Rockers are interfering with my nice Kenne Belle Valve covers and keeping the valves open on number 1 and number 5. I havent checked the passenger side however I suspect the same problem..

Has anybody had this problem with the Scorpion Roller Rockers?

Can I just clearance the rockers and valve cover? Those Scorpion Rockers are pretty fat.. Would it hurt them if I take a little material off where they are interfering with the cover? It doesn't appear that they are interfering by too much.

D

 

[bison]

Well.... Here is an update to the issue.. I have found the root of the problem.

Apparently my Pedestal Mount Scorpion Roller Rockers are interfering with my nice Kenne Belle Valve covers and keeping the valves open on number 1 and number 5. I havent checked the passenger side however I suspect the same problem..

Has anybody had this problem with the Scorpion Roller Rockers?

Can I just clearance the rockers and valve cover? Those Scorpion Rockers are pretty fat.. Would it hurt them if I take a little material off where they are interfering with the cover? It doesn't appear that they are interfering by too much.

D

Use spacers under the covers

 

[SPOOLFOOL2]

Spacers.

RJC makes nice ones. Where on the rocker is it rubbing?

 

[dlafont]

I have tried spacers however once I put them on I don't have enough room to put the covers on the passenger side. I still have my heater/AC box and there is no room between that and the Valve cover to allow me to tighten the passenger side valve cover bolt with the spacers on. Without the spacers there is just a little room to do it but barely.

D

 

[dlafont]

They appear to be interfering around the inside of the valve cover bosses (channels) for the bolts.

I could remove some of the material in the valve cover but not sure how much material I can take out with these valve covers.

D

 

[SPOOLFOOL2]

If it's just light rubbing, take a little off the valve cover, and a little off the rockers. If you don't have a hight problem, then you don't need spacers.

 

[dlafont]

Yes.. It just looks like light rubbing on the inside of the valve cover bosses. There is no height issues with this valve cover.

Thanks for your help..

D