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Opeler
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759 Posts
Discussion Starter #122 (Edited)
You've got at least 25% disparity on your compression. Holy schitt. My 2.5 engine had 185 on #1 and 205-220 on the other 3. I had a headgasket leak due to an insufficiently milled head/block. I would suggest lossening your valves 1/2-1 turn on those 2 low cylinders and do the compression test again to see if their numbers go up.

Its a little odd that 1 and 3 are the same and 2 and 4 are the same basic measurements. If 2 +3 were the same and 1+4 were the same, I might say it has to do with that stroke or something of the such
I called the guy that built my motor today. I’ve driven it less than 15 miles since I last saw him, which was almost 4 years ago. I filled him in on all the things that I’ve gone through since I saw him last and where things are now. He wants to check the motor out. He’s planning to make a house call either late next week or early the following.

Basic stuff BUT, be sure throttle plates are held open when testing.
Thanks, I didn’t have the throttle opened up at all. What would that do to change the procedure?
 

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Registered
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1,808 Posts
Your supposed to have your throttle plates wide open to permit each cylinders maximum gulp of air per crank....your trying to build max cylinder pressure after all.....
 

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Opel Rallier since 1977
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1,454 Posts
Yes, open the throttles. But I typically only see 5 psi increase but that is not with dual DCOE's.

One area where you can see large variations in cranking pressures with hydrualic lifters is when some of the lifters won't hold up properly... i.e., one or more more lifters collapse or partially collapse. When this happens, then the valve lift on that particular lifter is low, and if on an the intake valve, it closes too soon; this builds abnormally high cranking pressure and gives false high readings. Seen this more than once. I'm presently having some fits with rebuilt hydraulics from OGTS.

Has there been any loud tapping from the engine, in the valve cover area? Where were the lifters that are now in the engine sourced from for the new cam?

Next suspect area is cam lobes going flat. Not a pleasant prospect but one that has to be considered.

A leakdown test would be useful to find any valve or ring seal issues.
 

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Opel Key Master
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4,951 Posts
Another thing is with 15 total miles on a newly built engine, I just don’t think you have gotten enough break in time to be worried about compression. I want to see at least 100 miles of driving in one stint, before I would think the rings have had a chance to settle in. I know you have had a bunch of issues and couldn’t really run it, but if it will drive halfway decent, I would get some seat time in it to make sure everything is fully broke in
 

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Opeler
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759 Posts
Discussion Starter #126
Another thing is with 15 total miles on a newly built engine, I just don’t think you have gotten enough break in time to be worried about compression. I want to see at least 100 miles of driving in one stint, before I would think the rings have had a chance to settle in. I know you have had a bunch of issues and couldn’t really run it, but if it will drive halfway decent, I would get some seat time in it to make sure everything is fully broke in
After the initial break-in, I drove it about ~75 miles before I started experiencing a stumble when I tried to leave a stoplight. After that, I could barely get it to idle. At that time, the motor builder came out and did an inspection and said all looked good, it was probably carb or vacuum related. At that point is when life got nuts and we moved 3 times, including building a house and switching jobs a couple times too. The car basically went in to storage for nearly 4 years. In the last 7 months is when I’ve finally started doing anything with it again. I drove it out of my driveway last month twice, totaling ~15 miles, which was the first time it has left a driveway under its own power in 4 years. I feel confident enough in it to drive it....it starts fairly easily, idles strong and smoothly and didn’t exhibit any issues when I’ve driven it, aside from not having much torque off idle.

The engine builder wants to play it safe and didn’t want me to drive it to his shop, which is why he’s making the house call. So I probably won’t drive it until I get the green light from him.

Eric
 

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Opel Rallier since 1977
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1,454 Posts
Also, make sure the rocker stud adjustments have not backed off and left any rockers loose.

As for compression at 15 miles (And edit to say, now I see there are more)..... unfortunately, there should in no way be this type of variation. Things like rings sticking or valves sticking come to mind, but there just are not enough miles on the engine to have the deposits build up to cause those problems. Maybe the head gasket suggestions....

And edit to add further: If the idle is very smooth and even, then that is encouraging in the valve and lifter department. You could just have some lifters leaking down over night, and then pumping up when the oil pressure comes up. Those where the valves are open and the lifter is under static pressure can leak down when the engine is stopped.
 

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Just Some Dude in Jersey
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14,123 Posts
If you remove your valve cover, you can do a number of tests. You can crank the engine and watch to verify that oil is oozing out of the lifters, starting at #1 and working it's way to #4. While cranking you can also try to get a visual guesstimate of whether any of your lifter buttons are staying collapsed or if certain rocker/lifters don't seem to be moving as much as the others. Take a video of your valves while cranking and put it on YouTube or somewhere. I did this and someone spotted a big problem that I had missed. While you're at it, you could loosen the rocker nuts on one of the 2 low-reading cylinders 1/2 turn each and redo the compression test on that cylinder to see if anything changes. If it does turn out to make a big difference, then I would tell you to re-baseline adjust all your valves.

Are both of your carbs basically adjusted the same way? You don't have a setting on one very different than the other?

Does the car run great, except for loss of torque coming off idle? Once you are going, say, 25mph and you floor it, does it have decent power then? Do you have any stalling or bogging issues at any other time than coming off idle? Does your tranny shift normally, no slippage going around turns, no funny noises? I ask because you may be a little low on fluid. They can slip if the fluid is really low or if the fill tube isn't fully seated, which can allow air to get sucked in and sent to the TC.
 

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Opel Rallier since 1977
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1,454 Posts
Are both of your carbs basically adjusted the same
I was thnking of that, but that would make sense if 1&2 were different than 3&4..... but a cylinder off of each carb is high/low. Trying to think how a DCOE could do that....throttle shafts twisted? I can only think of intake sealing making that kind of effect.

But 30 psi difference? Not what I would expect from just a carb setting or intake sealing difference. I've seen it when the valve action was off on some cylinders....
 
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