Rebuilt engine no compression

Ok although the terminology of how you describe getting to TDC may not be in the same context as I asked , were going to assume that you are in fact at TDC..............with the Rocker arms off .........you rotate motor and feel compression coming by your finger and your watching the push rods moving and then when you approach TDC as evidence by Compression push, visual look at piston & the marks on the Timing cover you stop.........

You could say that the push-rods are to long but really it is more than likely the increase in Lift generated by your new Camshaft that is causing the increase in travel to the Push Rods................that is why they sell shims ( Jegs / Crane ) that you mentioned above that go under your rocker stands to move them up and not allow the extra lift to pump up your lifters early..............Two ways to fix that: Get some adjustable push rods in the length you need........Those once installed have to be adjusted. Or put the shims under the rocker stand............that's why I was asking what the difference in lift is between your old Cam and the new one. That measurement will help you decide on which shim would be needed................

But first I would call the cam manufacture where the cam came from and tell them what you are experiencing and ask them to provide or suggest a solution.

 

Yes, I have thought about the adjustable pushrods to get a measurement for my setup. The cam isn't anything special....it's only .433 lift which isn't too much over stock. I guess I will figure out which route to go.

 

I don't know on the Jeep, but valves must well close and if not of course no compression.

Better to start withe the less complex problem and check valve position.

Of course check the spark plugs, they must be well in position, with some good oil on them or special grease soem people will tell you the best, well cleaned.

Afterwards, it is more complex. Difficult to see. It is a pro job, need tools.

 

On the adjustable push-rods you could use them as a check method or as sixteen individuals........most push-rod manufactures will make them to length and if they tell you no I can tell you who will.........I checked your old cam specs.on the stock cam and it has a .266 lobe. Take that times the rocker ratio of 1.6 and you should have about .426 lift at the valve with a 111 degree center line. And like you have mentioned I did check your Comp 252 Cam and with a 1.6 Rocker you are correct it has about .433 of lift at the valve with a 110 degree center line.

So with a difference of only .007 thousands at the valve that may not be enough to really matter to get both valves to start to open as you say they do when clamping on the overhead...........In fact on the compression and power stroke neither valve should be anywhere near close to being open, the event for the exhaust valve opening is at least 50-60 degrees of crank rotation away..............

On your Timing gear set do you remember if there was any options there via an offset key to advance or retard the Cam Timing? Did you or anyone else degree that cam in?......off of TDC on #1 with a positive stop or dial indicator? There is a chance that the cam is not installed correctly..........meaning that perhaps the cam timing event is not correct to the crankshaft timing.............

Are you sure you were up at TDC on #1 on the firing stroke or could you have been on the exhaust stroke.............from what your telling me with both valves open at TDC it sounds more like your 180 degrees off and checking it on the exhaust stroke. In this event the exhaust valve is still open and starting to close while the Intake is starting to open.........called Overlap...........Rotate the motor 360 degrees and check it again. Once there pull your Distributor cap and see where the rotor points.

 

Well, I believe I've come to the realization that my cam timing may be off. I will start the front timing cover tear down when I get time to do so. It sucks when you are sure of yourself and have assembled many engines in the past without issue. I will start from square one.

 

Did you recheck...............TDC on the firing stroke as I mentioned? I really think your off 180 degrees...................send me a PM if you want with a contact number and I'll try and help you.

 

I was thinking about it and now believe I was referencing an incorrect mark on damper when I initially located TDC. I'll just tear timing cover off and recheck. That way I'll know for sure.

 

The damper is outside of the cover and would need to come off prior to getting the timing cover off........... referencing TDC there is of no value until you get the two gears inside in the proper alignment.............without knowing what timing set you have the norm would be aligning the two "0" Zero's together..........meaning the one on the Camshaft positioned at 6:00 o'clock ( Down )and the small gear on the Crankshaft at 12:00 o'clock ( Up ) But do check your timing set for the correct instructions relative to the set you purchased as some sets do allow for variable timing by different key-way positions on the Crank gear............

This will get the Camshaft and Crankshaft in the proper relationship to each other in regards to valve and piston timing only...........once done then put the cover back on along with the vibration damper and turn the motor over to find true TDC which can be accomplished by watching the valve action at the rockers as mentioned above , or ..............( intake valve only on #1 cylinder opens and close's and the next time in rotation back to "0" on the front damper should be near TDC and where it fires #1) Once the damper is at O or a few degrees before TDC , then the distributor is dropped in so that it is correctly orientated for clearance for the vacuum advance or other obstacles. Since the motor is now on number one.....The cap should be wired correctly to where the rotor is pointing which again should be #1 and then to each plug in the correct firing order and rotation ( if the distributor is already in then just rewire the cap or verify that the rotor is pointed to the correct cylinder)..........fire it up, put a timing light on it and drive it!

 

I appreciate the help my friend....I understand you are trying to help me out and being as detailed as you can, but I know how cams, cranks, timing covers etc go together and what needs to go on and come off in what order. Like I stated previously, I lined the cloyes double roller timing set up with the zero degree keyway set up on crank at 12 o clock and cam sprocket dot set at 6 o clock. I believe my error was when I temp fit my timing cover to eyeball the dampers zero timing indicator ( or so I thought ) IE TDC of number one piston.
I then proceeded to install timing set thinking all was good based on the wrong mark I used. Being I have never messed with an AMC, I thought there was something I was missing since it wasn't starting after I assembled it hence the reason I posted here. I am certain now that I had crank location wrong to begin with not knowing it. This is why I said I will just take front timing cover off and double check crank position in reference to TDC and cam alignment.

 

I will let you know what I find when I get to it.....probably won't be for a while. Have been working a lot of hours at work.

 

10-4...............And report back when you figure it out.........were all interested!

 

Since your engine was able to build compression without the rockers installed, that tells you the crank to cam timing is off. You will get it going after corrected alignment of gears.

 

Or, something is keeping the valves open.

A leak down test would tell the tale.

 

Well without the rockers, the only thing that would keep valves open are broken springs or bent valve stems and that didn't seem to be the case since he said he could see the springs compressing.

 

I'll get it figured out....I get into those brain fart and hey stupid moments every once in a while. I do appreciate the feed back though. I was so certain I had the timing sprockets aligned correctly with proper crank alignment, but I do believe the TDC is off compared to cam timing.

 

I lined the cloyes double roller timing set up with the zero degree keyway set up on crank at 12 o clock and cam sprocket dot set at 6 o clock. I believe my error was when I temp fit my timing cover to eyeball the dampers zero timing indicator ( or so I thought ) IE TDC of number one piston.
I then proceeded to install timing set thinking all was good based on the wrong mark I used.


Are you certain you needed to line a keyway up instead of a dot on each gear? BTDT on a small block Chevy once...wasn't very good. (I could be completely off base here but worth asking anyhow)

 

I either mistyped or you misread....My cloyes crank sprocket has three slots cut into it. One for advance, zero and retard...I lined slot on crank key way at zero. Dots are a seperate item between crank and cam tdc.

 

I haven't posted in a while, but will hopefully have a chance to tear timing cover off engine and double check the cam to crank timing comib g up.

 

Just a thought here.. I would call comps and ask them if after you install the cam and timing gear straight up, do you need to spin the motor 360* before installing the dist. This was the case with my SBC the winter before last, apparently comp changed the way they marked the timing marks on the gears "BUT" did not make the changes in their directions, and when you align the timing marks straight up, you are actually setting the engine 180* out and need to spin the motor 360* (cam turns half of crank) to bring it back to TDC. they left the instructions the same for ease of installation but left out that you need to turn the motor one revolution after you install the gears. After I spun the motor over 360* and dropped the dizy back in, the engine fired and ran great. I read this is on chevys but I was reading on a chevy site so I don't know if the change in the gear markings is on all makes. I called comp and they varrified it for me.