: Won't start - Inconsistent compression



mehansen50
01-11-05, 09:27 PM
:banghead: Recently rebuilt a Northstar 4.6. Timeserted, new rings, sufaced the heads and a professional shop cleaned and seated the old valves - checked all ways and everything fine. When putting it together my buddy put the water pump pulley on backwards and bottom line we broke the camshaft. Got a brand new cam - the intake of course - replaced and retimed. The timing is right on checked several times but the engine wont start. Compression test on the back head shows all the conmpression ratings at approx. 150#'s. The front bank is very inconsistent. Sometimes it shows 150 on each of them and then 20#'s the next time I check. Could it be that when I took off the cam and replaced, that the lifters filled and are not allowing the valves to close? The comporession inconsistency is only on the front bank. Any ideas how to isolate the problem or if it is the lifters, a there a reasonable way to fix that possibility? any help really appreciated. Thanks Mark 1996 STS engine #9 type

BeelzeBob
01-11-05, 10:43 PM
Sounds like it has a cam out of time.....

How are you checking it???

You can do a quick check by using a dial indicator in the number one spark plug hole (right front corner) to set the engine to TDC. Take the cam covers off. All the cams should be sitting so that the timing pins are at 12:00 RELATIVE TO THE CAM COVER SEALING SURFACE. Also, check the cam sprockets. Each sprocket can be used on either the intake or exhaust cams....BUT....the correct slot must be used in the sprocket. Each timing slot is labeled RI and RE (right exhaust and right intake) for example so if the sprocket is on the exhaust cam you must use the RE slot and the RI for the intake cam. Same on the left side. The LH and RH sprockets are on the correct sides, right??

The lifters will not stay "pumped up" that long...LOL. That is not the problem.


See the attached post http://www.cadillacforums.com/forums/showthread.php?t=27965

mehansen50
01-12-05, 06:39 PM
Thank you - you were right - the LE pin was on the bottom rather than the top - rotated the cam 180 degrees and bang - on the first turn - Thanks for the idea Mark

BeelzeBob
01-12-05, 11:02 PM
Cool....darned those pesky timing pins....LOL