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Old 08-29-2012, 01:24 AM   #26
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If you got some basic dimensions off those rockers I could probably figure out what domestic application they are from, if any.
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Old 09-06-2012, 11:43 AM   #27
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Cometic big bore HG came in yesterday, bolted it all back together.

And upon first start up now the header is leaking form the center ports? Makes a chuffle, I can feel it. Erg, I'll order two manifold gaskets and double it up.

Drove it to work chuffle and all, no weirdness with the temp gauge this time. Cometic:1 - copper HG: -2. I don't think I'll bother trying to use it a third time.
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Old 04-24-2014, 11:58 AM   #28
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EDIT: Moved this thread to projects and restorations from 'maint and non-perf'. It's not really a great project thread for the PV, but it's all I got.

With the wagon finally getting back together and working well, my #2 pending car issue got a promotion to #1 - the PV's motor.

It's a B20E block, bored to 92mm. It uses some B21FT pistons on B18 rods, with the wrist pin bushings removed and the 24mm B21 wrist pins interference fit (the B18/early B20 engines have 22mm wristpins). It has an R-sport stage 4 head, one of my lucky ebay finds, but in a prior use it was shaved down to a ridiculous degree - that's why I'm using B21Ft pistons - I need the cc's in the dish. It has an Isky W81 cam, old school high rpm cam. Probably something with a more modern lobe shape would work better, but the Isky's are at least cheap. SBC lifters and tubular pushrods pushing a KgTrimning roller rocker setup. It has a pair of DCOE 40's with 36mm chokes on the intake, and a cheap 4:1 header and a 2.25" exhaust on the exhaust. A Crane optical ignition box running an MSD 6A box running an MSD Blaster 2 coil for the zaps.

All in all, it seems to make about 150 hp at the rear wheels, based on the weight and trap speeds in the 1/4 mile. Which is pretty fun in a 2200 lb car.

The motor was built about 20K miles ago, since then I've had a minor issue with cams, with them only lasting about 10K before a lobe goes flat. The lifter/lobes are the weak spot on the B18/20 (other than the fiber timing gear - I have steel Penta/B30 gears). They don't like high rpms, stiffer valve springs, taller cams that much, and in this case it gets plenty of all 3. I rev the piss out of it regularly because it's fun, it has double valve springs, and the cam lift is pretty high plus the roller rockers have a higher ratio, increasing the pressure on the lifters.

But that's not the problem it's currently having. Last spring it started to get a little blowby. And it started to loose a little power. Nothing too bad, but I stopped driving it to make sure I didn't let a small problem turn into a bigger one. But then the wagon had to get rebuilt (tiwce - since I derped out and missed the cracked cylinder wall the first time, oy vey) - and then it needed a new head gasket, all in all, I haven't really had time to take this thing apart, until now.

So I did a compression test. Very clear indication of problems: 160 psi on 1, 2, 4. But only about 80 psi on #3. The plug on #3 looked very slightly different as well, just a little bit sootier.

I obviously should have done a wet test here, bot for no good reason I didn't, I instead whipped the head off.

But instead of seeing clear signs of the cause, it's a bit of a puzzler. The bores on all 4 look great. No signs of lines or rub marks on #3 which would indicate a broken ring. The HG does not show any real obvious signs of leaking, but it's a Cometic MLS, and I sort of think they won't show much unless it's a pretty serious leak. The head seems to show some signs of irregular sealing around the bores - the lines left behind by the Cometic vary as they go around.

The intake valve is also darker on #3, not sure what the problem is there.

At this point, presented with fine looking bores, and a very slightly iffy looking HG, I'm leaning toward leaving the bottom end in place and alone, but I'm starting to regret not doing that wet compression test, to verify that the rings aren't leaking.

As a distant second best shade tree test, I rotated the motor so all 4 pistons were equal height, and filled the cylinders with oil. I'll let that site for a while and see if #3 drains any faster than the others. If they stay the same, I'll just assume that it's OK.

So far, it looks like a very light head skim, a valve job, and a new HG.

It's a treat working on the PV, there are so very few wires and hoses to deal with, the head comes off in about 15 minutes.

Last edited by JohnMc; 04-04-2016 at 07:57 PM..
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Old 04-25-2014, 01:22 AM   #29
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Swap in some beehive valve springs, a lot easier on the rest of the valvetrain. They can work wonders with pushrod engines.
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Old 04-25-2014, 01:39 AM   #30
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Interesting puzzler.

You mentioned you noticed some blowby -- what symptoms? Excess crankcase pressure? Oil consumption? Only could see that being related to HG if the HG blew between the combustion chamber and the pushrods...

Could it have cracked a compression ring? How hard is it to get the pan down in the PV? If it were me, and it weren't too hard, I'd probably want to pop that #3 piston out and see if there's anything happening there that the condition of the bore is not making obvious. Your oil test might show something but if you can get the piston up for a visual, seems like that might give more complete answers.
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Old 04-25-2014, 01:59 AM   #31
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little blowby...compression test....But only about 80 psi on #3. The plug on #3 looked very slightly different...just a little bit sootier.
Any chance compression/oil rings were lined up incorrectly?

If minor cylinder ridge, and if hone marks are still present and decent, I'd just pull three out and inspect...and re-install with new rod bearing.
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Old 04-25-2014, 08:51 AM   #32
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The oil is dropping very, very slowly in all cylinders, but noticeably faster in #3. Looks like I'm going to pull the motor and take the pistons out.

I had just noticed an increase in crankcase vent fumes, I didn't really drive it enough past when I noticed that to see if it was using oil.

I don't think the rings were lined up incorrectly - it's worked perfectly fine for something like 20K miles.

The block has a visible difference where the rings run and the top edge of the bores, but there's not enough of a ridge to feel with a fingertip.

With any luck it will just be a broken ring, if the piston is hosed it seems like I'll have to get a custom set - non-oversized B21FT pistons do not seem to be available anywhere any more.

Last edited by JohnMc; 05-17-2014 at 09:23 PM.. Reason: lol 20K miles,not 20
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Old 05-17-2014, 08:32 PM   #33
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Finally got around to pulling the motor out of the PV.



The head was already off, so I took the pan off and took the piston under suspicion of shens (#3) out. I was expecting to see some broken rings. I was initially confused because all 3 were intact in looked to be in good shape. The ring lands looked good too, no looseness or slop.


Then I looked a little closer and... whoa. Chunk of the piston is split out. It's a weird sort of damage. A 'flake' of the piston is separated, parts of the ring land above ring #2 as still connected, and the #2 ring was keeping this piece in place. Sort of. I've never seen anything quite like that on a piston before.



Well, a little JB weld on the piston and right straight back in it will go!
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Old 05-17-2014, 08:47 PM   #34
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Nah. Some rtv outta do the trick.....whose making b21 pistons these days? Johnv?
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Old 05-17-2014, 09:28 PM   #35
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Looking at those pistons, I don't think they're turbo. They look more like the low compression B21A pistons.


B21FT (pic stolen from jack)



B21A

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Old 05-17-2014, 10:02 PM   #36
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Hmmmm... That does seem to be the case. Maybe my CR has been a little higher than I thought it was? It runs fine on 93 octane though, so I might as well replace them with the same thing.

I guess I need to look for some standard size (92mm) B21A pistons? I wonder it they're any easier to find than the B21FT pistons seem to be.
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Old 05-17-2014, 10:15 PM   #37
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Here you go.

I have +.020" pistons if your block needs to be bored.
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Old 05-17-2014, 10:24 PM   #38
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Thanks! I found a single piston on eBay: http://www.ebay.com/itm/Volvo-Brand-...item27e1916cd1

But it doesn't seem like a very good idea to replace one, although the other's only have ~20K miles on them.

The block looks very good, plus it's an overbored B20 to begin with, I'm not going to touch it. Bearings looked good on the only one I've looked at so far (#3). Lifters all looked good too. Dunno, I'm half tempted to just stick the single new piston in it (after balancing it with the other pistons).
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Old 05-17-2014, 10:40 PM   #39
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Check the other pistons. They may have cracked ring lands too.

If you really do have B18 rods this would be a good time to swap them for some B20 rods. They're thicker where the beam meets the big end, an area where they are known to fail. I suspect you may already have them, since they haven't already broken with the heavier B21 pistons. Can you post a pic of the rod?
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Old 05-17-2014, 10:51 PM   #40
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Changing 1 piston is done all the time. It will make the motor last longer if all the pistons weigh the same, so I suggest sticking with the same brand of piston which appears to be Mahle.
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Old 05-17-2014, 11:51 PM   #41
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Thanks! I found a single piston on eBay: http://www.ebay.com/itm/Volvo-Brand-...item27e1916cd1

But it doesn't seem like a very good idea to replace one, although the other's only have ~20K miles on them.

The block looks very good, plus it's an overbored B20 to begin with, I'm not going to touch it. Bearings looked good on the only one I've looked at so far (#3). Lifters all looked good too. Dunno, I'm half tempted to just stick the single new piston in it (after balancing it with the other pistons).
If your happy with cracking cast pistons---which is exactly what I'd expect on Volvos with those drilled oil returns under the oil ring (as opposed to the T slot design on oh, say OEM Mahle for the Ford V4/V6 fambly where I'd expect to drop the entire top of the piston off from crack propogating from end of oil return slot down to pin bore) then by all means stick just one in.. nothing wrong with that at all and lucky you found one....and an OEM one at that,,

I would kinda confirm what dish depth and diameter your really are and what the new one is..just sorta sayin.

Of course you know what would really wake up a nice n.a. motor like you have, but don't think of saving 450g per hole of ugly useless reciprocating weight...
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Old 05-18-2014, 12:38 AM   #42
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Hmmmm... Maybe my CR has been a little higher than I thought it was?....
A CAT field service engineer I know stated, "By and far the most common cause is detonation. The extreme shock and excessive cylinder pressure spike causes the part of the piston between the piston ring grooves to crack and become detached from the body of the piston. The usual causes of detonation are excessive timing advance, low octane fuel, excessive turbocharger boost, and overheating."

I wonder how the other three pistons look....a knock sensor setup would have eliminated this issue.
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Old 05-18-2014, 08:32 AM   #43
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I'm def. going to take out the other 3 pistons and look at them too, but the compression issues were all on this single piston.

I'm not sure how well a knock sensor would work on a noisy old pushrod motor. There's no sign of detonation damage on the crowns of the piston, no pitting as I've seen on my wagon's last set of pistons (which where def. damaged by detonation).

It's a 6 bolt crank, and it is using B18 rods currently. No issues slinging the B21 pistons around at 7500 rpm with some degree of regularity for 20K miles so far, but perhaps I'm on borrowed time with them by now anyhow.

I had the whole thing balanced to a fine degree when the bottom end was rebuilt about 10 years ago, it was a smooth as silk spinning that fast. Noisy, but smooth.

JohnV - I'm def intrigued by some forged lightweight pistons and presumably longer rods too? But I'm just weighing the cost of slapping a single new piston in there vs. rods and pistons. It's just a hoopty old PV. Slapping a new piston in is just very cheap and quick and easy. As they say - the good is the enemy of the better. How much are we talking for both (PM that if you want)? Would they be 6-bolts sized rods? Could I get the pistons sized so I wouldn't have to touch the block/bores?
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Old 05-18-2014, 08:53 AM   #44
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how well a knock sensor would work on a noisy old pushrod motor.
GM's V-8s small blocks, V-6s, etc., from early eighties onward...I realize these are engines with hydraulic lifters, and timing chains.

Towards last of these posts, 141 and onward, is one possible solution: B280F lacks power, prematurely shifts down
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Old 05-18-2014, 09:02 AM   #45
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That's how someone moved a knock sensor to a quieter place on a B280 to basically disable it. Not sure if that's particularly applicable to a B20 with not a single ECU to be found anywhere.
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Old 05-18-2014, 09:13 AM   #46
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Not sure if that's particularly applicable to a B20 with not a single ECU to be found anywhere.
There are aftermarket knock detectors, with various prices.

DET-1600 DETONATION SENSING MONITOR

Knock Sensor Monitor - Knock Link


On a dyno, it could charted out where its happening.

I think there might be an aftermarket ignition system that will control timing advance when it sees engine knocking...I'd have to scratch around for that system.
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Old 05-18-2014, 01:57 PM   #47
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how well a knock sensor would work on a noisy old pushrod motor.
I'd see what the hot-rod folks are doing...I did come across this system

Delco Electronics Corporation took out a patent in 1993

BACKGROUND OF THE INVENTION

There has been a trend in the U.S. automotive industry toward high performance, high RPM engines which, to achieve maximum performance and efficiency, are operated in the near borderline knock region. Unfortunately, knock detection is more difficult in the noisier environment of an engine at high RPM; and knock control apparatus with noise reduction circuitry designed for lower RPM engines, which can contain envelope detecting analog low pass filters and analog integrators, may introduce phase and group delays which make consistent and accurate knock detection at high RPM difficult.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an engine ignition timing system with knock control better suited for engine operation at high engine speed.
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Old 05-18-2014, 02:14 PM   #48
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B21FT pistons.


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how psi stock cna support?

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Old 05-19-2014, 08:37 AM   #49
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Heh, I tried taking the piston off the rod last night. Room temp, I stuck the rod in a vise (padded) and put a torch on the small end for a little bit, then tried gently tapping it out. It didn't budge a millimeter. So I stuck it in the deep freeze, I'll try the same thing again this evening with it starting off chilled to 0 degrees.
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Old 05-20-2014, 08:12 PM   #50
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I ordered that set of 4 pistons. Mine are Mahle, that single piston was a Mahle, but somehow I just felt a little iffy on replacing one piston. I'll get them balanced to a fine degree and put them in. The whole rest of the engine got a good balancing when it went together last time, it always felt nice and smooth when spinning fast.

I'm just a little paranoid about the rods now. They are def. B18 rods, the rebuild 20K miles ago was prompted when a rod bearing spun. The rod was pretty clean looking, but I didn't want to mess with a possibly scuffed up big end, so I took the rods out of the PV's original '63 B18 and used them. No issues at all so far (obviously, the main issue you'd see is a rod tossed out the side of the block), but I have seen little 'marks' on the big end, under the bearings, right where the thin part is. Maybe it's nothing. Maybe it's.... something flexing a bit here and there? I'm not sure. But I am pondering getting a set of 6-bolt B20 rods and using them this time around.

I don't want to put this back together and feel like I have to take it easy on the motor.
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