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Old 12-11-2019, 12:25 PM   #51
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If those cam durations are correct, that just makes the problem with the compression tests that much worse. A 207 deg duration is significantly less than a Volvo D or K cam and you should be getting compression test values significantly higher than what you would get for a B20E engine - unless your static compression ratios are completely messed up. With a 2130 cc swept volume, that cam duration and unmodified combustion chamber volumes on a B or E head I would expect that your compression test values should be way above 150 psi.

In your first post, you listed the CR as 9.5:1. Where did that number come from? Was it calculated? With a 2130 cc swept volume the combustion chambers on a B or E head would need to be opened up to get the CR down to that value. My stock E head combustion chamber CCs out at about 45 cc and I am guessing that a B head should be around 50cc. Allowing a very generous 8cc for gasket and quench volume, a 2130 cc swept volume would give a static CR of 11 with an E head and about 10.2 with a B head. 'Correct' quench volumes would nudge those numbers higher. Did you drop the CR by putting a very fat head gasket in or were the combustion chambers reshaped?

I am guessing that the lift of 443 refers to a lift of 0.443" measured at the valve. Volvo D and K cams have 'advertised' lifts of 0.42" with a 1.5 rocker ratio. My brand new D cam had valve lifts that averaged out at 0.404" with freshly reprofiled rockers - Volvo rockers rarely matched the advertised value of 1.5. If you were running stock Volvo valve springs a lift of 0.443" could be bordering on static coil bind at full open and if not, might be running into dynamic bind at higher RPM. I believe that you have larger valves and double valve springs. Did you check for coil bind on the valve springs after the engine was assembled? This problem may be made worse if someone tried to grind your rocker arms to try and nudge up the rocker ratio.

Given the additional evidence, I am more convinced that this is not a tuning issue and that you have some mechanical
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Old 12-11-2019, 12:53 PM   #52
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Yeah, I'd be troubleshooting that compression issue more before pulling the head and cam out.

Have another round of compression testing.
- pull all 4 plugs out so it cranks round and round with some decent cranking RPM
- hold the throttle open while testing
- test 'dry'
- put a small amount of oil in the cylinder (like a tablespoon), crank it around a couple of times, and then test it again

That 'wet' test can help rule out piston ring issues. It makes a temporary better compression seal if the rings are not sealing properly for a variety of reasons (worn out, stuck in their grooves, not bedded in properly, etc). If it jumps up - you need to pull the pistons and see what's going on. If it stays relatively the same, your compression issues lie elsewhere. Still could be the bottom end - things like compression height differences, cracked/holed pistons won't improve with a little oil.

If you can do even a basic shade tree leak down test it would be more informative. Just use an air hose and blow air into the cylinder at TDC (or at least with the valves closed), and then listen to where it's coming back out. If it's coming out of the block, it's something wrong with the piston (or possibly head gasket). If it's coming out of the intake - it's a valve, same with the exhaust. If it's coming out the coolant, it's the HG.

Then once you've gotten that tidbit of information, pull the head off. Eyeball the HG really well, see if there's any indication it was leaking. Maybe do a quick sanity check on the compression height - run the pistons to TDC and measure them vs. the block deck (flat edge and feeler gauges). I'd tend to think it would be a fairly large difference to produce a 30psi swing in compression, but just rule out that some mismatched parts got put in.

Another sort of leak down test that can be performed with the head off - pour a little light oil or even gasoline on top of a 'good' cylinder and to a similar depth in one of the 'suspect' cylinders - and then see how long it takes for that to leak past the rings and down into the oil pan. You can also do a similar shade tree leak test on the valves as well, set it upside down, pour some gas or light oil in the chambers, see if it stays there or leaks into an intake or exhaust port.

At this point, I tend to think the dyno graph is mostly the effects of a weird low-revving cam. But you may have uncovered a somewhat unrelated issue with the compression tests.
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Last edited by JohnMc; 12-11-2019 at 01:36 PM.. Reason: typoes
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Old 12-11-2019, 01:22 PM   #53
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A Cold compression test is a go or nogo test and it passed, it has over 90# so it will fire up.
Get it hot and properly broken in (if not already) and re test hot.
If it was not pushing out oil or showing a lot of blowby, I would not attribute the power loss to ring seal.

While its cold put a degree wheel on it and see where the cam is at, that is most likely where your problem is.
See where the intake valve closes Should be 30 - 50° ABDC, this is what determines the cranking compression #'s.
That will tell you instantly if there is a problem with the cam alignment.
You don't need to pull the head, just hair ball it. A cold lifter will not leak down much, and if you crank the motor a bit for oil pressure they will pump right up.
You are not trying to profile the cam just get an idea of where the intake is closing within 5 or 10° to see if it is a tooth off.
If you have solid lifters no worries, measure it.
If the lifters leak too much you can rotate the motor backwards and watch for movement on the intake and get it within a few degrees.
If it is a tooth off it will be 20° or more off, way early or way late.
If the intake is closing within that span you can look elsewhere for the problem.
To be missing that much power it will be something big.

Have you verified the TDC mark you are using for spark timing is good? Balancers slip, very common.
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Old 12-11-2019, 01:27 PM   #54
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B18/B20's are all solid lifters. There's no oil supply at all on the lifter bores - it's all just oiled from oil dripping down from the rocker shaft.

And they have solid front pulleys too. Of course, they could be bolted on wrong.
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Old 12-11-2019, 01:33 PM   #55
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Last edited by Tfrasca; 12-11-2019 at 01:34 PM.. Reason: JohnMc beat me to it.
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Old 12-11-2019, 01:43 PM   #56
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My point is things have to be verified, maybe someone left the key out of the balancer.

Diagnosis is a logical progression verifying and eliminating factors.
Making any assumptions, it's likely the problem will be passed over.

Solid lifters makes it real easy and you can actually in a hairball fashion profile the cam without removing the head.
With Lobe centers plotted you can determine the separation angle, purty near ID the cam with that data.
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Old 12-11-2019, 01:57 PM   #57
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Everything posted so far has been valid, but i will mention that I have seen wet compression increases from sources other than rings. Particularly poorly seating valves.
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Old 12-11-2019, 10:31 PM   #58
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Old 12-13-2019, 01:58 PM   #59
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Quote:
Originally Posted by oemoilleaks View Post
UPDATE:

I had an hour and was able to do a cold compression test. Results were not good, and I checked on two different gauges.

CYL 1 - 150psi
CYL 2 - 130psi
CYL 3 - 125psi
CYL 4 - 120psi

I also noticed that the VV-71 cam calls for a valve lash of 0.020, set while hot. I don't think I accounted for that lash, so when I get a minute I will warm up the engine, reset the lash, and re-test compression.
Obviously those compression readings are too low. Even at 9.5:1 you should have at least 175psi.

The next step should be a leakdown test which will reveal what is leaking.

FYI, in my copy of the B20 green book, Volvo valve lash setting specs are the same whether the engine is hot or cold. This is because the involved components are either high quality cast iron or steel and they expand and contract at about the same rate.
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Old 12-13-2019, 02:18 PM   #60
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Originally Posted by JohnMc View Post
Yeah, I'd be troubleshooting that compression issue more before pulling the head and cam out.

Have another round of compression testing.
- pull all 4 plugs out so it cranks round and round with some decent cranking RPM
- hold the throttle open while testing
- test 'dry'
- put a small amount of oil in the cylinder (like a tablespoon), crank it around a couple of times, and then test it again

That 'wet' test can help rule out piston ring issues. It makes a temporary better compression seal if the rings are not sealing properly for a variety of reasons (worn out, stuck in their grooves, not bedded in properly, etc). If it jumps up - you need to pull the pistons and see what's going on. If it stays relatively the same, your compression issues lie elsewhere. Still could be the bottom end - things like compression height differences, cracked/holed pistons won't improve with a little oil.

If you can do even a basic shade tree leak down test it would be more informative. Just use an air hose and blow air into the cylinder at TDC (or at least with the valves closed), and then listen to where it's coming back out. If it's coming out of the block, it's something wrong with the piston (or possibly head gasket). If it's coming out of the intake - it's a valve, same with the exhaust. If it's coming out the coolant, it's the HG.

Then once you've gotten that tidbit of information, pull the head off. Eyeball the HG really well, see if there's any indication it was leaking. Maybe do a quick sanity check on the compression height - run the pistons to TDC and measure them vs. the block deck (flat edge and feeler gauges). I'd tend to think it would be a fairly large difference to produce a 30psi swing in compression, but just rule out that some mismatched parts got put in.

Another sort of leak down test that can be performed with the head off - pour a little light oil or even gasoline on top of a 'good' cylinder and to a similar depth in one of the 'suspect' cylinders - and then see how long it takes for that to leak past the rings and down into the oil pan. You can also do a similar shade tree leak test on the valves as well, set it upside down, pour some gas or light oil in the chambers, see if it stays there or leaks into an intake or exhaust port.

At this point, I tend to think the dyno graph is mostly the effects of a weird low-revving cam. But you may have uncovered a somewhat unrelated issue with the compression tests.
I need to do another compression test I think. And I want to reset the lash to .020 before I do it. I've had a busy week so I wasn't able to get anything done, but I will update the tread as soon as I can.
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Old 12-13-2019, 02:46 PM   #61
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Where did you go for the dyno work?
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Old 12-13-2019, 04:22 PM   #62
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Where did you go for the dyno work?
Ed Pink's racing engines.
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Old 12-13-2019, 08:48 PM   #63
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I’ve never seen hot and cold lash come out the same.
Aluminum heads you subtract lash cold, iron heads you add lash cold. It can be small (like .002”) on a smaller engine, but it changes.
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Old 12-14-2019, 12:05 AM   #64
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OK a little update.

I reset the ash to 0.020" cold (because I didn't feel like hot tonight) and then redid the compression test. I think I forgot to open the throttle last time I did the test because we got much more even numbers across the board.

I did the test three times per cylinder and here are the averages

CYL 1 - 143.3 psi
CYL 2 - 147.3 psi
CYL 3 - 145.0 psi
CYL 4 - 141.3 psi

I drove the car around the block and it still felt weak, even around the 5k range.
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Old 12-14-2019, 10:09 AM   #65
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Well, those cam specs sure seem to indicate it's a very low RPM cam.

Those compression numbers are still pretty low, but being even is a good sign. It could still be something wonky with cam timing to drop the numbers down.
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Old 12-14-2019, 01:03 PM   #66
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Here's a link to a dynamic compression calculator that will also estimate cranking psi: http://www.wallaceracing.com/dynamic-cr.php

I found the estimate to be low for my B21FT in Colorado at 5000' elevation (~110psi from calculator, vs. ~130psi actual).

And here's a link to a good Cam Degreeing article: http://www.iskycams.com/cam-degreeing.html
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Old 12-14-2019, 04:45 PM   #67
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Cold compression test? Still low, but at least they are even. I would also suspect cam timing at this point or a pretty lame cam.
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Old 12-14-2019, 07:14 PM   #68
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Here's a link to a dynamic compression calculator that will also estimate cranking psi: http://www.wallaceracing.com/dynamic-cr.php

I found the estimate to be low for my B21FT in Colorado at 5000' elevation (~110psi from calculator, vs. ~130psi actual).

And here's a link to a good Cam Degreeing article: http://www.iskycams.com/cam-degreeing.html
I must be doing something wrong because the calculator is giving me 205psi at 0ft altitude.
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Old 12-19-2019, 03:08 AM   #69
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Interesting topic and I don't really have any more info to add. Sorry to be interested in your pain, but it definitely sounds like you have a small camshaft based on the measurements you gave and the powerband shown, but your cranking compression numbers disagree with it being a small camshaft unless your static compression is actually much lower than you think.

I just played with that calculator and it is also way off for our engine. That being said, trying to enter the actual intake valve close is not easy if you don't have a degree wheel on the car and actually measure it. Using data that I was given by the cam grinder and another number based off of what another forum member measured is showing we would have a cranking compression of 160-180psi depending on what valve close time I enter, but our actual cranking compression is 205-220psi(b230F with approximately 10.8-11:1 static compression and an Enem K13 camshaft).
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Old 12-19-2019, 07:02 PM   #70
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There's an update!

Volvo George was gracious enough to help me understand my problems and figure out what the hell was going on.

Turns out I was way off on my carb settings. 36mm chokes and 4.5 aux venturi were way too big. Too much air was asking for too much fuel and the engine couldn't do anything with either.

He dropped the chokes down to the 32mm I had (but suggests I get 34s) and the Aux Venturi to 3.5s. Then rejetted it a bit to match those settings.. (but suggested I pick up a few things to match the 34s.)

The car really woke TF up. There's power down low and pulls all the way to redline. It feels like it could pull even further, I'm just afraid to find out.

George also suggested I figure out a way to use the vacuum retard with the 123+ distributor to compensate for the DCOE's wanting such a high idle. As well as figuring out a catch can system since the way I had the crank case vent hooked up wasn't optimal for the engine.

There's still more tuning to do, but we at least figured out the culprit!
So my next steps are:

Need 34 choke , 50 f8, f15 emulsions, lightened flywheel, catch can, tinus tuning runners (to have a second vacuum port), 123 distributor with vacuum retard hooked up
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Old 12-19-2019, 08:30 PM   #71
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I tried 36mm chokes back when my motor was closer to stock, and they didn't work very well either. Mostly, you really had to ease into full throttle, if you worked up to it slowly it would work OK, but if you just floored it, it would sputter and bog. It was much happier with the 32's. Until I had more mods on the engine (R-Sport head, better exhaust, cam, etc), then I tried the 36's again and they worked very nicely.
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