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Dr Evil
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Discussion Starter · #1 ·
I searched for a while and found no similar sounding issue on threads, being a novice I'm sure I posted this wrongly, but.

My 1.9 had 60psi in all cylinders, strangely enough it ran "ok". Showed 66 bhp on my dynolicious iPhone dyno app.
I have a weber, header and medium hot hydraulic iskendarian cam.

having rebuilt dozens of motors in my past, I rebuilt it using a reputable local machine shop, did 2.0 pistons and the large valves, new cam chain and sprockets, and it started and ran "ok". new parts everywhere, except the cam and lifters, they had only 1000miles on them.
I still have 60 psi compression check numbers again, same in all cylinders.
400 miles break in, no change. 70 Bhp on iPhone app. And it feels like about 70 Bhp, 0-60 in 17 sec.

The cam is timed right, tdc and the dot when #4 is at tdc is exactly where it should be next to the groove on the shelf as viewed thought the centerline of the sprocket, woodruff key straight up on crank snout.
This motor should be making twice as much Bhp.

The low compression number befuddles me. I checked the compression gauge against a second air gauge, even borrowed a second compression gauge, same results. Replaced the starter thinking it was cranking slow, even removed the carb to ensure unimpeded air flow. Rebuilt the carb, added large bore exhaust, new plugs wires and cap/rotor. No change.

I know that quite a bit of cam over lap can keep the exhaust valve open later, but that's way too much change. Other web sites talk about huge cams causing 120ish psi artificially low numbers due to overlap.

I am absolutely stumped. I guess a possibility is a bad from the factory cam, but that seems quite odd. Next step is to loosen up the hyd tappets in the hopes they are too tight, but the hyd function should even out a small difference in adjustment. All 4 cylinders being identical kinda rules out a bad lobe on #1.
I can check total lift and compare w the cam specs ( haven't done that yet), performing a cam degree event in the car would be tough I'd think, I really don't want to pull it all out again.

Anyone else had similar issues? Brilliant thoughts? What am I missing here? I will even accept jeers if it will help.

Help!
 

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...

I know that quite a bit of cam over lap can keep the exhaust valve open later, but that's way too much change. Other web sites talk about huge cams causing 120ish psi artificially low numbers due to overlap...
Overlap is the wrong cycle.
The engine is exhausting during this time.

The compression cycle is after the Intake valve closes.
Now this effects compression!

I searched for a while and found no similar sounding issue on threads, being a novice I'm sure I posted this wrongly, but.

My 1.9 had 60psi in all cylinders, strangely enough it ran "ok".
I still have 60 psi compression check numbers again, same in all cylinders...
Bull****!
 

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Bikini Inspector
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5,774 Posts
did you stagger the rings when installing?

cylinders bored to proper diameter?

my first hunch was rockers were too tight. id start loosening them alot and checking again and/or leakdown test.

was your head decked or block? perhaps cam timing is way off now due to rebuild
 

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Über Genius
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9,536 Posts
My guess, since it's an across the board reduction in psi, is that you thought TDC on #4 was when the ball on the flywheel lined up with the pointer on the block.

If I were a backyard mechanic with relatively rudimentary knowledge of Opel CIH engines, I'd advance the cam gear one tooth and check pressure again.
 

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I'd look into doing a leak down test of each cylinder.

How are the valve guides? Any work done there and if not, why not?

Compression test will tell you that you have a problem but the cylinder leak down test will pinpoint the problem area.

Later model 1.9's have a history of cylinder head cracks so keep that in mind, too.
 

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Also if the valve adjustments are set tight with a decked block and head TDC relationship on the crank to the valve settings cam changes a bit and will cause you to adjust the valves in a off position to TDC lines on the crank. Ron
 

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Opel Tinkerer and Rescuer
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If you decide to move the gear a tooth.. I came up with a way to do it that does not require a TON of work.

BUT requires the special Kent Moore J Tool to be made and used, as you will bend back the ledge the cam sits on and has the pointer on.

Info here:

http://www.opelgt.com/forums/6a-engine-mechanical/15024-opel-1-9-valve-timing-checking-tool.html

and Gary shows his home made one here:

http://www.opelgt.com/forums/6e-tune-up/26490-tuning-unknown-2.html#post238961

I then take a big screwdriver/small crow bar and wedge it down between the cam sprock and cam.. then lightly flatten the cam sprocket holder down.

With it out of the way and the tensioners out of the side.. you can drop the chain and move it around and around to get what you need.

I also use some nail polish, to mark where the chain is in relation to the sprocket. So when I get it around I know I moved one tooth.

I think I posted pictures somewhere around here showing the method.
 

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Dr Evil
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Discussion Starter · #10 ·
I am 70% sure I used the ball on the flywheel for initial timing, so I am making a tdc tool out of an old spark plug and will verify tdc and cam timing based on tdc. If that's the fault I guess the cam is retarded the amount the ball and tdc differ, I sure hope that's the answer.
I will oil the floor of the garage and set the lifters while running also.
Has anyone done hat before? Is it accurate? I plan to use a dial indicator, but don't know the error in the method... 1-2 degrees?
 

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I can't imagine your cam timing being soooo far off as to being the cause of your low cylinder pressure probleme, although it's certainly a good thing that you double check it.

I'm really surprised you have such low numbers!
I have a fresh 2L with big valves and an or-66 cam. This motor has zero miles and has never ran! I can hang crack 40psi using a powerbar of the front bolt pulley on the crank. Even before I rebuilt it my original Low compression 40 year old motor had 140-130-125-140psi.
I don't understand how a new broken in motor can have those low no#?:confused:
One or more things must be contributing to the problem.
 

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Kalifornia Kid
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551 Posts
Befuddled

Have to admit,...those numbers are low. Being you double checked the numbers with a second and third compression tester, and the fact you cranked the engine with the carb. off (ie. wide open throttle) I'll assume you tested correctly.

With that said, I'll go with what everyone else said about the cam timing. I would also perform a leak-down check to verify your valves are completely closing and the rings are sealing properly.

The cam spec. you listed with 2.0L flat top piston should be reading around 150 psi per cylinder. Which is what my engine read (all be it my cam was even bigger and made those psi numbers).
 

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Dr Evil
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Discussion Starter · #14 ·
Tdc check

OK,
Tdc check complete, the ball embedded in the flywheel, woodruff key straight up and a spark plug hole tdc/ dial indicator all show the dot on the cam sprocket to be perfectly aligned as viewed through the center of the cam sprocket at #4 on the compression stroke and of course #1 mirroring #4 at tdc.
I know some folks say the ball in the flywheel isn't tdc, but as far as my car goes, it sure seems that it is. I cannot figure anyway to screw that up during assembly. I bought a 1970 GM Opel manual and page60-42 section 61-5 b,8 note says the ball mark is tdc also, but in a round about way. I'll stand by for someone to convince me otherwise, seems dumb to time an engine to 0 degrees tdc, so I see their argument.

I will now reassemble and start, warm it up and remove the rocker cover and loosen the rockers until they clack, tighten 1/4 turn. And borrow a third compression checker just to rule out two consecutive bad ones,... Kinda doubt that as an issue,...but I am out of ideas on that front.
I haven't considered it until now, but I wonder if I was sold solid tappets instead of hydraulics,... Should be easy to check by removing one and seeing if it has an oil hole and some "give". ???
Unless there's some smarter way to compare the two. I've never had a car w solid tappets, or at least never disassembled it if it did.

I can't keep from coming back to the cam is ground incorrectly or I am so blindly and completely wrong about something that I just don't see it. If there was a good diagnostic opel mechanic around I'd pay for his opinion, but there just isn't one that I am aware (Ridgecrest is in the middle of nowhere - Death Valley).

Anyone aware of a good opel mechanic in Bakersfield Ca or maybe Las Vegas?
 

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Bikini Inspector
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5,774 Posts
hydraulic will have a thin metal collar around the top, which you can tell is seperate from base, also a hyd will pinch down(unless pumped up)

will also have holes in side, like you said. you can tell it is more than one piece period. solid is one dense piece for sure.

ball on pointer would fail Compression that bad is if cam timing is way off, bad cam, tight lifters, or broken rings, bad head gasket etc

did you try with a squirt of oil too? did you ever answer id rings were staggered? doubt it would be that

head bolts torqued properly?
 

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Super Moderator
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ball on pointer would fail Compression that bad is if cam timing is way off, bad cam, tight lifters, or broken rings, bad head gasket etc
How bad is blow by?

... did you ever answer id rings were staggered? doubt it would be that...
Smokey Yunick says the rings rotate so it doesn't matter whether they are staggered or not. I tend to believe he knew what he was talking about. :yup:

Harold
 

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Bikini Inspector
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How bad is blow by?

Smokey Yunick says the rings rotate so it doesn't matter whether they are staggered or not. I tend to believe he knew what he was talking about. :yup:

Harold
I remember reading that link you or someone provided and I agree, but I bet some inexperienced people install rings all the same way.

Wagertons issue sure is confusing, just grasping at straws. is it possible it was bored out too much? or ring gap is too large?

were the ring ends filed?
 

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Dr Evil
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48 Posts
Discussion Starter · #18 ·
Rings/blow by

I had the speed shop install the lower end, they allowed me to pop out the pistons of the old motor in their shop and they said the PO had not installed the rings correctly and we discussed it. Since they bored it and refit the 2.0 pistons I would say its terribly unlikely they did it wrong.
Also, no blow by, there isn't any gas coming out of the valve cover to speak of. I've had a motor fired after 40 years inactivity (tractor) and know what blow by looks feels and sounds like ( that motor had 80-100 psi compression check after firing up, but it was a tractor and not a performance car so all I cared was that it ran.

Squirted oil into cylinder and rechecked compression, didn't change any numbers, which points to valves or valves not opening at right times.

"If" the cam were ground wrong, that would explain low compression, valves not closing at right time, as would bad cam timing ( eliminated I think).
Bad valves, they're all new large valves and they were cut in and seated, I'd think some might leak but not all.

I keep coming back to the cam
 
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