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There's something I don't get after measuring a stock B20E head:
Fact: A stock B20 has a bore of 88.91mm. With a stroke of 80.00mm it adds up to a total of 1986cc. The so called big bore B20 should have a bore of 92.10mm to fit the B21 pistons. With a stroke of again 80.00mm this adds up to 2130cc.
Common knowledge: If you would bore a B20 to 92.10mm you should also work on the head so the combustion chambre will match the bigger bore (92.10 in stead of 88.91mm).
Case: I am planning on building such a 'big bore B20'. I have a stock '73 B20E head (deck height 84.9mm) and a '74 8-bolt B20 block.
Now, the thing that strickes me is that the diameter of the (for as far I know) stock B20E head is 92mm.
Questions:
So:
-Does that mean that a stock B20E has a mushroom-shaped combustion cambre?
-Does that mean I shouldn't do anything to the combustion chambre as it is?
Or:
-Would a big bore B20 also prefer a mushroom-shaped combustion chambre?
-Would a larger CC only be for the benefit of unshrouding the valves?*
*the head now has 44mm intakes, 35mm exhaust. I'm keeping stock size intake valves, but larger exhausts.
I think I once measured an B20A-head, and think it had a CC diameter of just 88.91mm (can anyone confirm on that?). So what's the story with these E-heads?
Thanks a lot in advance! Cheers, Ben
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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B20A/B heads have 90mm chambers. B20E/F heads have 92mm chambers. Why Volvo did that no one has been able to explain to me.
Don't enlarge the diameter. If it's an E head, you may need to reduce the compression ratio, as it will go up quite a bit due to the increased swept area from the big bore. Simply continue the curve further into the straight side away from the spark plug to increase chamber volume. Please do NOT use a thicker head gasket.
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The last year of the B20B was offered in the US only on the 145. That year the 144/142 was a B20F/E. The B20B head of that year was a 92mm combustion chamber and had the larger valves, which iirc are 45 mm intake, not 44mm. It also was the only year that the cast manifold did not have the secondary throttle plates in the manifold and had a very short intake path.
This head was a great addition to a modifeid B20F block and use the old SU HS6's to produce a 200 hp high rev motor, capable of nearly 8k rpm.
I owned one for 18 yrs in a '68 144s. A Trans Am runner.
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'89 245 Sportwagon, '04 V70 2.5T Sportwagon
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The last year of the B20B was offered in the US only on the 145. That year the 144/142 was a B20F/E. The B20B head of that year was a 92mm combustion chamber and had the larger valves
Were there carbureted '74 140s sold in the U.S.? We see this head on carbureted '75 240s from Canada, but they were never sold without injection in the U.S.
which iirc are 45 mm intake, not 44mm.
No, they were still 44mm -- the earlier B heads had 42mm intakes.
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"This head was a great addition to a modifeid B20F block and use the old SU HS6's to produce a 200 hp high rev motor, capable of nearly 8k rpm."
What 'modifications' can be done to a block? Decked and different camshaft? Or also a larger bore?
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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I purchased a 'used' B20B from an old timer and retired Volvo master mechanic, that had his own inde shop in CT in the late '70s. I needed a good motor for fitting in a '68 144 that came with a B18 and auto tranny.
He said "It'll cost ya though" He showed me a 1" thick stack of reciepts, ALL from Volvo, ALL R-Sport parts, 1" main bearings, very important for a high rev motor,+.060 overbore, custom crank, lightened drilled hollow lifters and high strenght pushrods, ported head, dual valve springs, R grind cam, alloy pistons, rods, dual sump pump, the list went on, and on.
It was 'used' for 4k miles, built for a customer that wanted to have his son get into Volvo's. The son slammed it into the wall at Thompson Speedway at 140 mph, was almost killed, and the father wanted to clean house of all the residuals of their efforts. I walked off with the engine, taking the mechanics word for it without as much as testing the compression, for a sum of $250.
btw, after the break-in period, maybe ~125k miles on the engine and a M410 OD tranny I got out of the paper for $50, I drove cross country and actually passed a Trans Am, going uphill in the Wasach Mtns of Utah, going 120. I also had the full R-sport suspension on it. It did a 1/4 in the high 13's.
RIP after 384k miles and 18 yrs of driving like a bat outta hell.
As far as I know, the only, and last carb head with the larger valves sold in the US was the '72 145.
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'89 245 Sportwagon, '04 V70 2.5T Sportwagon
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As far as I know, the only, and last carb head with the larger valves sold in the US was the '72 145.
That's what I thought, but it had the regular 42mm intake valves (and 90mm chambers). Only the '74 and '75 carb heads, which were not sold in the U.S., had 44mm intakes.
Not that it matters. Most of the R-sport heads had larger valves than that anyway. I'm using 46mm intakes and 38.5mm exhausts in one of those late carb heads (that's as big as you can go without the valves touching each other). Sorry for the out-of-focus pic...
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I should also mention that it had 12:1 compression and ran beautifully on airplane fuel. I used to stop at airports and fill a 5 gal can and mix with the street available CAM2 gas which was 102 octane leaded.
Sounded like a piper cub on take-off.
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'89 245 Sportwagon, '04 V70 2.5T Sportwagon
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"B20A/B heads have 90mm chambers. B20E/F heads have 92mm chambers. Why Volvo did that no one has been able to explain to me."
That sounds pretty odd to me aswell. I guess to give the larger valves more clearance?
And hang on, if an E/F-head is 92mm in diameter, the gasket should be too. So I just measured two B20 gaskets. One is 91,4mm the other 91,8. Maybe it would be possible to just use a standard gasket (if the block bores precisely match the gasket bores). I mean if you could use a 'normal' gasket on a standard block with a 92mm head, why not with a 92mm block and 92mm head? It results in the same gasket contact area.
Also, I reviewed my calcs, since I always asumed the gasket bore the same as the cilinder bore. I 'backwards calculated' the CC volume of a stock E-head from stock figures (with 0,8mm gasket): it gives me 47,0cc.
Using an E-head as it is on a 92,10mm bore block and a (stock) 91,8mm diameter and 0,8mm thick gasket would give a ratio of 1:11,2. A little high, but not extreme here in western Europe. Maybe take of some sharp edges in the CC and the ratio will drop to 1:11,0 which is quite nice.
Hmm, gives me some stuff to think about...
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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Very interesting. I should measure that B20E headgasket that has been hanging around in my garage for years. I've been buying those special '92mm big bore' gaskets from Sweden each time my head needed to come off, and this time around I have decided to get a copper gasket made (with 92.5mm bores) so I don't have to scramble for a rare BB one each time. But if a stock B20E/F gasket would work...
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I'm JohnMc, and I approved this message.
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I have 3 gaskets that I got on ebay for $5 that measure 3 5/8" bore which
I am planning to use on my next big bore job. That would make the bore 0.003"
smaller than the gasket IF they line up.
Elring P/N of these gaskets is 192.163.
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George Downs, Bartlesville, Oklahoma, Central US
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3 gaskets for $5 sounds like a good deal...
But wouldn't 3 5/8" make 92.075 mm? (1 inch = 2.54 cm right?) Which is also less then the 92.10 bore of a B21 / 2130cc block.
[EDIT] I checked: 1 inch is 2.54000508001016 cm...[/EDIT]
What are your thoughts on the pistons hitting the gasket at high rpm's?
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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I don't do millimeters if I can avoid it but the last I checked the
2130cc bore is 3.622" which is 0.003" smaller than 3 5/8", not considering
significant digits, accuracy of measurements, etc. When I get the chance
I will see how the piston crown fits into the bore of the gasket.
Since the crown of the piston is smaller than the bore (smaller than the
skirt, which is also smaller than the bore) I imagine it will be OK.
Big deal is if it is bored concentrically with the gasket....
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George Downs, Bartlesville, Oklahoma, Central US
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Volvo specs for B21 is 92.10 mm wich is 3,62598" being 3 5/8". If you by any chance have a B21 piston lying around, I'd be eager to know what the piston crown diameter turns out to be.
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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Oh. I think mine is are an even 92mm which is 0.004" smaller.
The pistons I have are IPD big bore pistons for the 6 bolt engine.
I'll mike them and let you know. Probably not today.
Where is ".tk"??
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George Downs, Bartlesville, Oklahoma, Central US
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George, I think I might have lied. I always thought the B21 bore was 92.10mm and 2130cc. However I couldn't get that verified. On the internet I found some site saying the B21 is 'only' 2127cc which would "stroke" with the 92,00 mm bore you found...
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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Is that the difference between the bore (92.10mm) and the pistons size (92mm)?
At long last I've given up on getting a cam or B20 big bore parts from KgTrimning, so I've just ordered parts from various other sources to get my engine back together. I'm going to fetch the set of rods out of my PV's original B18 and have a machine shop ream them for an interference fit with the 24mm wristpins and use a set of standard B21 pistons. And instead of a KG-19 cam (out of stock for at least two months) I'm going to try an Isky VV-81. I'm also just getting a copper headgasket to avoid future scrambles for a big bore headgasket every time I need to pull the head off.
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I'm JohnMc, and I approved this message.
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Is that the difference between the bore (92.10mm) and the pistons size (92mm)?
You mean the dif in 2127 or 2130cc? Yep it is. 92.10mm bore and 80.00mm stroke gives 2131cc. 90.00mm bore and 80.00mm stroke gives 2127cc.
Or do you mean that perhaps the cilinder bore of a 21 will be 92.10mm and the piston diameter will be 92.00mm?
Would it perhaps be possible to just round of the top edges of the piston (or cut a 'step' in it) so it will not hit the gasket even at high rpm?
cheers, ben
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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I'll mike them and let you know
Ok, thanks in advance!
About ".tk" : check www.dot.tk , it's just a free url which links an other url. The url of my site is actually http://home.wanadoo.nl/j.w.flierman ...
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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On a balanced, blueprinted motor with corrected, shot-peened rods -- everything really straight and accurate and strong -- we allow for .030" (.76 mm) "stretch" at very high RPM.
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I measured the piston to deck clearance to be 0,55mm (0.022"). So considering 0.76mm stretch (0.030"). The piston would rise 0.26mm out of the block (0.010").
Considering the top of the piston is a bit smaller then the skirt, and since the very top edge of the piston is a bit rounded of, I think a B20E gasket might actually work.
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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The two gaskets I just measured were both B20A gaskets (2mm thick). I thought maybe the 0,8mm thick B20E gasket might even be slightly larger in diameter and be usable. I'd be interested what your B20E gasket diameter turns out to be.
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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Alas, I went to the garage and it was a B20B gasket, not a B20E. It was larger around that I would have thought still, at 90.98mm. Not big enough for a big bore engine though. I'm going to go ahead and get a copper gasket this time so I don't have to get one each time the head comes off from now on, but I'd still be interested in finding out if a B20E one would work.
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I'm JohnMc, and I approved this message.
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This may be already known and sound obvious or whatever, but from what i'm hearing, you're going to be using 92mm pistons with a headgasket that's less than 92mm, so if your head's been decked(i don't know how much, or if the pistons will come out of the top of the block, but just in case) you might run into problems squeezing a 92mm piston through an almost 92mm gasket...
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Kyle - '68 Volvo 142 w/71 b20b and m40...
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Yeah, I know, although the pistons normally stay under the deck/block. Not sure what happens when revving it to 6000 rpm though. It's stuff like this I'm am hoping to find out.
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)
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I'll try to remember to measure my stock F head tonight.
I recently did some work on my 'race' head, and did need to widen the combustion chambers to match the 92mm bore. I'm not sure of the provenance of that head - it doesn't have injector ports or a cold start valve fitting up front. It has bigger that 'E' spec intakes and exhausts, with double valve springs and what appears to be plenty of port work. It had been shaved an extreme amount to about 12, 12.5:1 and I had to remove a lot of material in the chamber to get the cc's back to a reasonable amount for a street car.
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I'm JohnMc, and I approved this message.
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