cloven

Compession Help!!! New HG, correct timing, no bent valves = 0 - 60 - 170 - 170:

Short version:
- a6 block with z6 head.
- compression results:
cyl 1 = 0
cyl 2 = 60
cyl 3 = 170
cyl 4 = 170
- checked timing, all sensors, added oil and still same results.
- replaced with three different "good" z6 head and still same results
Could it be block? Need Help???

Long version:
After a spun rod bearing in my z6, I pulled a d16A6 block from the local junkyard from tboned car. Visually inspected block - no cracks, rods/pistons/cylinder walls all good shape. Was able to turn crank by hand with no issues. Pulled oil pan and all internals checked out good.

Attempt 1:
Mated the block to the original z6 head that spun the rod bearing with new y8 HG and torqued down to specs. Started car and very rough idle. Shut off, checked timing, all sensors, head bolts, then checked compression. Compression results from cylinder 1, 2, 3, 4 were 0, 50, 120, 120 respectively. Added oil to cylinders 1 & 2 and tested again with no change in compression. Took head off, visual inspected HG and found no cracks. Assumed the head had bent valves so I replaced head with another "good" z6 head.

Attempt 2:
Reinstalled everything. I reused the HG and torqued all to specs. Turned engine and same results as first attempt. This time, I let it idle for a while then drove car around block. Engine temps got real hot, almost to the point of overheating. Checked compression and results were: 0 - 50 - 170 - 170. Added oil once again to bad cylinders with no change. Checked timing, sensors, head bolts but found nothing wrong. Could this be a bad HG??? Tore head apart and on to attempt 3.

Attempt 3:
Bought new y8 HG and reinstalled motor with another "good" z6 head I had laying around. Reinstalled everything and results ended up just like the second attempt!!! Drove it around with the terrible idle, engine began to overheat, then parked back in garage. This time I did notice a hissing sound from behind the motor but assumed it may have been just the coolant pipe that I replaced. The original one was corroded so I replaced it with a better coolant pipe and it probably just didn't seal right. Therefore the loss of coolant and causing motor to overheat. Added oil to bad cylinder and still no change in compression: 0 - 60 - 170 - 170.

What the F@ck is wrong??? Could it be that all my heads have bent valves??? All my heads have been used before by me with no issues. I checked them all by rotating the cam gear for tdc for each cylinder and making sure they were all seated properly. I don't have a leakdown tester and not willing to dish it out to and a local shop do a test. I've even adjusted the valves with no change. All compression tests were done at WOT with engine cold and warmed up. Timing was checked a million times. I didn't use a timing light but timing was set with cyl 1 at tdc, cam gear in correct position, and all my timing marks lined appropriately.

Am I missing something??? Process of elimination tells me it's my BLOCK!!! What do I need to check on my block to ensure all is good!!!

Honda Gods - Please help???? Any assistance would be great before I trash this block for another one.

Clo

dude_123

Was the block and head "true" as in was the block and head surface flat and not warped?

srmofo

well you could keep guessing, or you can do a leak down test and get a definitive answer.....IMO though it sounds like valves, although its wierd that the tests keep coming up with the same results with different heads, which would make me start looking into the block.....I would still do a leak down test before I did anything else

cloven

I pulled head off and checked the block for flatness with a straight edge. Surface checks out good. I am stumped!

- rings should be good - I've added oil to cyl 1 and 2 and no change, I've even poured water and checked after a couple of hours and no noticeable difference
- could be bent valves but I've swapped three different "good" heads. Compression stayed the same.
- timing good - rotated crank by hand and all timing marks lined up

I'm isolating issue w/ block. There is no crack in any of my cylinder. What can cause this low compression w/ different heads???

turbo97coupe

just do a leakdown for the answer

bschulz

Leakdown test

eg:R

did you pull out the pistons and check the rings. i say replace the piston ring

mr.sky

rings? busted ringland/s? should be pretty obvious though. After attempt #2 notice any evidence of valve/piston contact on the pistons, set the timing wrong and fusked two heads? Meh, those blocks are cheap just get another one

cloven

there are no signs of valve/piston contact. Pistons look as good as new. I could buy another block but I want to elimate that the block is the issue. New block and still the same issue would mean my heads all screwed up. How can all my heads be bad when they all worked???

Is timing on an a6/z6 different vs just z6? I set piston 1 at tdc, made sure cam on head is at tdc, made sure all timing marks aligned, put on timing belt, rotate crank for tension, then tighten tensioner. Timing stays the same after cranking motor.

I'll be obtaining a complete z6 (head/block) soon however I wanted to diagnose what could be wrong.

91integraLSVTEC

did u find the problem? Because im also having the same problem on vitara setup. its a non interference motor. ive tried 2 known good heads and still no compression in # 4 cylinder.

Scott_Tucker

It's quite possible for the pistons to look fine in the cylinder with the short block still assembled but still be leaking. Just because you added oil to the cylinders and the compression numbers didn't jump up doesn't mean it's not the rings. Things have to be pretty bad for you to get zero on a compression test anyway. The oil test normally only shows you anything if the compression is slightly low. For example if #1 cyl had 120 psi but 2,3, and 4 had 150 putting oil in the cylinders might tell you that the rings in cylinder #1 are leaking if the compression jumps to near where 2,3, and 4 are. But zero compression is a pretty big hole. Considering all the heads ended with similar compression readings I think the heads are not the problem, the short block is.

mr.sky

agreed it must be the block. I had a hole through my piston when my engine dropped a valve and it still had a some compression lol

cloven

Here's an update:

Got a new block. D16y7 block has been rebuilt with less than 5k miles. I checked all my head for bent valves by first rotating cam and and checking if all valves sealed properly. I then removed rocker arm assembly and camshaft and made sure they were seated properly. Well all four head were iffy so I purchase another z6 head. Before putting it on I made sure for no warpage and checked all valves. I looked good so I put it on.

- Z6 head on dy16 block
- correct mix of headbolts
- reused hg w/ copper spray
- z6 cam gear

I put everything on, checked timing multiple times, crossed my fingers and started it up. Rough idle just like before. Let it run for 30 secs, turned it off, and checked compression. Checked cyl 1 and got 0 psi. Quickly checked cyl 3 and got 130psi. What the hell is going on here???

New head, new block, same results... Totally busting my *****. I'll swap a y8 cam gear just to test again but help!!!! Well, having a honda-tech coming over to take a look this weekend but not sure if we'll find something.

cloven

Another update:

My Honda guru comes over to take a look. He didn't see anything wrong so I take off the head and have him watch me put everything back to see if I'm doing anything wrong. This time it's with a y7 block and a newly purchased z6 head.

- We first check for flatness on block - all good
- Put on reused HG that's been used once for startup
- Set tdc on block, set tdc for head
- Put on head, torque everything down according to specs
- Put on timing belt, apply tension to belt, then tighten tensioner
- Manually rotated crank multiple times to check timing - all good
- Connect everything
- Turn motor on, let it prime then start....
- Rough idle again
- With motor running, I pull plug on cyl 1 and no change
- I pull plug on any other cyl and motor starts to die
- I do a compression check - all at 150+ psi on cyl 2,3,4 and 0 psi on cyl 1

I said F@CK and threw gloves off!!!

That was on Saturday. Sunday I get a d15b7 with bad head. Inspect block, all good and I do the same. I follow the same procedure as above and get the same result but wih 170 psi on all three and 0 psi on cyl 1. I'M CURSED BY THE HONDA GODS!!!

Why not just buy a running motor and drop it in??? Well, I like to be difficult and I've spent money on all these parts already. They all look good so why wouldn't it work?

Any explanation of why I'm getting my results is appreciated.

Anyhow, ever heard of a 3 cyl honda - cause I got one....

mouab18c1

iTrader: (5)

WOW thats some crazy shyt! i say turbo the 3 cylinder and make 4 cylinders look bad!! aahahahhaa

Scott_Tucker

You need to put some compressed air in the #1 cylinder to determine where the leak is.

DonF

So what did the leak-down test say? That is what people have been telling you to do.

averyvm

iTrader: (1)

most definately need to do this so that you can isolate the problem

PatrickGSR94

iTrader: (1)

Have you by chance checked to see that the #1 spark plug is getting spark? I know that would not affect the compression readings of the cylinder, but if your distributor and/or wires are bad, you should at least replaces those, too.

Psychoteen101

Maybe you keep forgetting to install #1 spark plug?? lol Do a leakdown test like everyone has been saying.

PatrickGSR94

iTrader: (1)

LOLOLOL that would be a definite [homer voice]D'OH!!!![/homer] moment

jesusc

It may be the piston rings, I had the same problem untill I decided to pull the piston. The piston had a piece broken off so I took off a piston of another motor I had and put everything back together and worked fine.

jr_deleon

iTrader: (1)

Have you done the leak down yet its been a little while got an update (maybe cause of the holidays) or are you still in the same position? As far ar it being the rings i would at the very least expected #1 compression to change since youve been changing blocks after you tried the heads.

This is very interesting nonetheless. i read along as you went through this issue and never threw my 2 cents in. if theres no leak down test done its just going to be a bunch of ideas thrown out there for you to try. The leakdown test would reveal the issue but i would like to know if you checked your ring clearances and did you see if theres anything blocking air going into that cylinder. I mean if theres no air to compress then how can compression exist? i know it sounds crazy but i'm willing to throw that out there as i am thinking out of the box. i mean if all of the other major components checked out fine and different blocks, heads, all in good shape were good what else is left? On all of those z6 heads did you use the same cam for all three or did you use the cam corresponding to each head?
looked into the PCV system either?

Laugh if you wish, but remember crazy things can happen and when they do sometimes getting back to basics on how things work and thinking within that realm box or out of the box can help. Thats just my take

UJLSMoFo

timing marks are different from z6 to a y8 on the cam gear or on the back head covers i cant remeber.

cloven

Issue RESOLVED!!!

- Turns out it was bent valves on all the heads I have - total of six z6 to be exact!!! 4 that I've had on running motors and two bought and said to be good. Anyhow, got my hand on a good condition y8 head, slapped it on by b7 block with a z6 cam gear and runs perfect. Haven't taken the time to do a compression test yet but I would assume it is good.
- And to all that suggested a leakdown test: It was always in the back of my head but I didn't have an air compressor or the leakdown tester and I didn't want to pay for having a leakdown test done.

Anyhow, thanks to all that responded.

Next question - what is the avg cost of getting bent valves replaced?