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1963 PV544 rat rod

Thanks! I found a single piston on eBay: http://www.ebay.com/itm/Volvo-Brand...r_Truck_Parts_Accessories&hash=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...:oogle:
 
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.
 
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?
 
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.
 
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.
 
B21FT pistons.


240TurboPistons1.jpg
 
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.
 
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.
 
Gratuitous pic of flaky piston:
P5202490_zps8296cdeb.jpg

It started near an oil control hole, but didn't propagate from it. There's clean metal (even if not much) between the edge of the hole and the cracked off chunk. It doesn't even look like it was moving around much - the way the second ring ran through it kept it pretty much in place and out of trouble. Other than letting some compression sneak on by.

Here are the weird marks on the rods - on the metal underneath the bearings. There are no wear marks on the bearings, but they're only 20K miles old. But the marks here are weird. They're on the thinnest section of the rod, where it tapers down near the head of the rod bolts. I'm not sure if this is an indication of bad things to come/almost happened, or if it's just some sort of machining artifact from when they were made. But it's made me a bit nervous about these rods slinging the B21 pistons around at high rates of speed.
P5202489_zps0fb90edd.jpg

P5202486_zpsb8b693cd.jpg
 
Dimensionally they're exactly the same (vs. the 6 bolt B20 rods, the 8-bolt B20 rods are the same as B21 rods.

But they're lighter, and a bit weaker. The big end 'ring' is much thinner between the stem of the rod and the rod bolts.
 
6/8 bolt refers to flywheel mounting flange?

So all of these rods would work on all crankshafts (B18, B20, & B21)?

B20 8 bolt -b21are the same as I am aware of

B18 -b20 6 bolt crank are in their own group I'm guessing?

Gathering info as at the end of summer I'm gonna tear into my 75' b20, interested to see what corners can be cut.
 
Yeah, I worded that awkwardly. The B18 and 6-bolt B20 rods are dimensionally the same, although the B18 rods are lighter and weaker.

They changes the bottom end bearing sizes for the 8-bolt B20's. The 8-bolt B20 rods are dimensionally the same as B21 rods. basically Volvo redesigned the bottom end of the motor a few years before they redesigned the top end for the B21.


I bought a set of B20E rods. I'll have the same thing done with the wrist pins as I had done with the B18 rods - press out the brass bushing, and ream it lightly for an interference fit on the 24mm wristpins.
 
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aww. I was hoping you'd dropped in some of john's goodies. on an NA mill that kind of weight savings would be huge
 
I didn't want to spend $$$$ on the old thing.

If I was going to spend $$$$ on it I'd probably put a TDi engine/Toyota pickup trans in it.
 
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