New LS with NO COMPRESSION!!
Thread Starter
Teching In
Joined: Jun 2015
Posts: 16
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Originally Posted by bigscoobie
Ok thanks. Motor never fired up just spinning so hopefully no bent valves or piston damage.🤞
I suggest removing all the rockers and letting it sit for a day or two to see if the lifters recover. Then remeasure pushrods.
Thread Starter
Teching In
Joined: Jun 2015
Posts: 16
Likes: 0
Thanks!!!! Quick way to check compression gauge operation put your finger over the spark plug hole have some body turn the engine over if it blows your finger off the hole you have compression! Now to address valves possibly hanging open did you prelude and oil prime the engine! If you didn't your lifters very well could be collapsed! I always pack LS oil pumps with assembly lube and oil bath my lifters for a day or two prior to assembly. As far as cam degree angle it is imperative to do this on LS engines because of the variety of timing sets and the ability to easily put the Crank gear on out of time in the case of some of the sets that are have key way knotches all the way around plus you have adjustable cam gears and advance ground into the cams a lot of the time so you have to pay damn good attention assembling one of these! Also if you are using a leak down that allows you to hook up compressed air and fill the cylinder then getting blow by in the Crank case is understandable especially because your rings haven't been able to seat! But doing a leak down on an engine that has never been fired kinda like pissing in the wind. So follow these steps:
1. Put finger over number one spark plug hole and see if it pushes your finger off.
If not go to step 2
2. Take off all rocker arms set number one down the hole place finger over spark plug hole if finger is pushed off problem is in valvetrain if not it's probably in the shortblock. If it pushes your finger go to step 3.
3. replace rockers leave valve covers off crank engine over until oil reaches all rocker arms. Then back off rockers and crank engine over several more times. Snug down rockers and again finger check number one Cylinder. If still no compression go to step 4.
4. At this point purchase a length checker, remove rockers for number one Cylinder. Measure pushrod length then set tool 0.010 shorter place tool in number one and snug down intake rocker and check for lash the ability to move the push rod up and down if you have no lash rotate the engine watch the rocker open and then close rotate the Crank 1/4 turn from point of closing then recheck lash if no lash note that length back intake off and shorten it again repeat this process until you find the length that gives you lash then go back to the last length and that is the length intake pushrod you need. Repeat these steps on exhaust side and get the right exhaust pushrods make sure you annotate which is which. Once push rod lengths are verified and corrected as needed replace all push rods and rockers spin engine over until oil reaches all rockers. Then repeat step 1. If no compression at this point got to step 5
5. If you are here the problem is in the short block area next is to remove front engine cover and set number one to TDC and. Verify timing marks if timing marks don't line up dot to dot your cam timing is off remove driver side head to degree or if you don't care about doing it right back off your rockers make sure your number one is at TDC and the Crank sprocket dot matches if not mar the tooth that points straight up then match the dot on the cam gear to it so your dots should basically come together with the cam sprocket at 6 and the Crank at 12. If this doesn't resolve the issue then the shortblock needs to come apart.
Hope this helps
1. Put finger over number one spark plug hole and see if it pushes your finger off.
If not go to step 2
2. Take off all rocker arms set number one down the hole place finger over spark plug hole if finger is pushed off problem is in valvetrain if not it's probably in the shortblock. If it pushes your finger go to step 3.
3. replace rockers leave valve covers off crank engine over until oil reaches all rocker arms. Then back off rockers and crank engine over several more times. Snug down rockers and again finger check number one Cylinder. If still no compression go to step 4.
4. At this point purchase a length checker, remove rockers for number one Cylinder. Measure pushrod length then set tool 0.010 shorter place tool in number one and snug down intake rocker and check for lash the ability to move the push rod up and down if you have no lash rotate the engine watch the rocker open and then close rotate the Crank 1/4 turn from point of closing then recheck lash if no lash note that length back intake off and shorten it again repeat this process until you find the length that gives you lash then go back to the last length and that is the length intake pushrod you need. Repeat these steps on exhaust side and get the right exhaust pushrods make sure you annotate which is which. Once push rod lengths are verified and corrected as needed replace all push rods and rockers spin engine over until oil reaches all rockers. Then repeat step 1. If no compression at this point got to step 5
5. If you are here the problem is in the short block area next is to remove front engine cover and set number one to TDC and. Verify timing marks if timing marks don't line up dot to dot your cam timing is off remove driver side head to degree or if you don't care about doing it right back off your rockers make sure your number one is at TDC and the Crank sprocket dot matches if not mar the tooth that points straight up then match the dot on the cam gear to it so your dots should basically come together with the cam sprocket at 6 and the Crank at 12. If this doesn't resolve the issue then the shortblock needs to come apart.
Hope this helps
