ZERO compression - what the heck?
 

my 5.7 TPI...

big picture short-n-sweet: years ago i rebuilt the whole engine/tranny. started right up first time, no problems. ran great, except for sucking down the oil all the time. beautiful. so all these years later i decide to rip the top end off and do it all from scratch again. took the heads to the shop for new valve seals (just in case, even tho they weren't the suspect), installed new lifters, rods, and rockers this time cuz apparently there had been an oiling problem from before (that's another story). got everything all set up, valve lash set, etc. then i have no spark. fixed all that, got spark, fuel and power to the injectors. no start. did i say beautiful? cranks all day long but no start, couple of coughs. maybe the dist is 180 out, tried to keep it set up with #1 tdc, but maybe i missed it. so i post about that, get going on checking for that by starting out with the "finger over the hole" check but can't feel anything huffing and puffing. so i put a compression tester on it and low and behold - doesn't even register. so now the big question - what the heck happened??? everything is rotating, so it can't be a timing chain issue... i will say that when i crank it now, it does seem to have a different sound to it than it did before. this problem makes no sense to me and the only thing i can think of is maybe the pushrods being too long, even tho they were the "right" ones...

Re: ZERO compression - what the heck?
 

On all cylinders or just one? Which one?

Re: ZERO compression - what the heck?
 

Loose up the rockers alittle & try again.

Re: ZERO compression - what the heck?
 

Gezzz.I'm chasing you thread to thread.:doh::lol: Here is how to correctly adjust lash.

http://www.enginebuildermag.com/Arti...r_preload.aspx

It is a tech tip from Crane Cams

Re: ZERO compression - what the heck?
 

Did you actually measure pushrods or just guess?

Re: ZERO compression - what the heck?
 

Ok so it was goin through oil, you replaced the valve seals thinking they werent the problem.... so what about the piston rings?

Re: ZERO compression - what the heck?
 

No compression...

1. Valve is open (could be caused by lash, damaged valve seat, broken valve spring...
2. Hole in piston ( caused by spark too advanced, lean mixture under load... something getting sucked into the engine)
3. Seriously damaged piston rings or ring lands.
4. Head gasket isnt sealing at all


If it's just on one cylinder, I would assume some damage. If it's on many cylinders, could be damage or bad valve lash, if it's on all cylinders, you've done something very wrong.

Re: ZERO compression - what the heck?
 

i had run a compression test on all cylinders before i opted to tear it all down, so rings and/or hole(s) in the pistons probly isn't likely... no, i didn't measure the pushrods, i assumed the ones i ordered for my set-up (LT4 hotcam w/1.6 ratio) would be correct since i ordered them to go with that kit. but could be the most likely culprit. and no, i didn't compare them to the ones i had in there the first time. head gaskets not sealing? yea, i would have had to have done something seriously wrong. not saying i did or did not, but after having built the engine from the ground up last time and it ran fine other than the oil consumption issue, a top-end rebuild shouldn't have been to difficult for my skill level... the oil consumption issue was a suspected bad intake seal, but until it runs again, can't confirm or deny. thx for the inputs, i appreciate all. looks like another week in the garage, tho - back to work and school tomorrow!

Re: ZERO compression - what the heck?
 

If the push rods are too long,I would think you would see coil bind too.What is interesting you changed to 1.6 rockers and are now having problems.There is a push rod length checker you can get to determine what is the correct length.Maybe they just by mistake sent you the wrong parts.

Re: ZERO compression - what the heck?
 

Push rod length won't generally cause the valves to hang open.

Which is of course, not the same as saying, you have the right push rod length. (just pre-empting before anybody tries to claim that I said that) Only, that whatever error you do or do not have in your chose length, isn't the cause of the symptom at hand. Might turn out to be the cause of some other symptom, but not likely this one.

About the only thing that will cause that, is setting the rockers too tight.

Re-check your rocker adjustment per the instructions in your other post.

Best push rod checking method, should you get to that point, is an adjustable push rod, a set of "checking" springs (just enough spring to counteract the weight of the valve, basically), and something to make a witness mark on the valve stem. But, fix the rocker adjustment first, then tackle the other potential issue independently.

Re: ZERO compression - what the heck?
 

well, like i said, i assumed... didn't have time to verify any potential difference in rod length last night, maybe some time this week. but anyway, when i did the original rebuild, i went with the 1.6's then, had the heads all done up for that, used the "kit" for the hotcam - springs, etc. no problems til now...

Re: ZERO compression - what the heck?
 

id check the rockers fisrt also.
how did you adjust them?

Re: ZERO compression - what the heck?
 

Or you failed to bolt the flexplate to the crankshaft and the engine isn't even spinning over. Or you failed to install the pistons before closing the engine up!

Just kidding.

You got one or more rocker arms adjusted too far down and holding those valves slightly open, as was said above.

Re: ZERO compression - what the heck?
 

yea, sounds like i got things cranked down too tight with them new lifters... hopefully thursday i can confirm or deny, but it seems to be the general consensus...

Re: ZERO compression - what the heck?
 

You did open the throttle body all the way when you cranked the engine, right? No offense, just being sure, not everyone knows that you have to allow the engine to suck in maximum air without restriction when doing a compression test. Usually, you just hold the pedal to the floor when cranking. No compression on all cylinders and you should be telling us how the engine just whirls over with the starter like you've never seen it before. You should still feel enough compression to blow your finger off the hole without having to open the throttle though.

Re: ZERO compression - update
 

all good - lifters weren't fully pumped up, hence too tight on the rockers. i loosened all of them up all the way then just snugged them finger tight, cycled it, loosen again, cycle for 5-6 cycles. when i got ready to set the lash, i made sure there was no more "slack" in them (unlike the first time). put it all back together, and VAROOM! how hard was that? gotta put another set of wires on cuz 2 of them were bad (high resistance), so once i get them, i can do a good leak check, timing, etc. i didn't let it run long enough to do any of that with the bad wires, so hopefully next weekend we'll be rolling. thanks for all the replies - even the smart-azz ones! :lmao:

Re: ZERO compression - what the heck?
 

It's always good when it's the eeeeezy stuff. ;)