Does anyone now how to tell an early B20 block, from a 74, from a 75 240 block, once its out of the car, the head is off, crank is out, etc.??????

I am guessing that some of the threaded holes in the 74 and 75 will be metric, but is there an easier way to tell.

Whether there are actual differences between the 74 and 75 blocks is not certain. I am told there are, including cylinder wall thickness, but its one of those things that I will believe when I see it. Thus part of the reason for wanting to be able to identify which is which and not rely on "it came out of a 74 so it must be a 74 block".

Even the year designations can be a little foggy as not all changeovers of all parts occurred on the same dates. Some old parts were used until they ran out and on the older cars, based on chassis number there is even some evidence of earlier cars getting later parts than slighty later cars. This is in accordance with the last in, first out, parts bin theory.

Does anyone actually know the answer?

John
V-performance.com

as for my .02 worth, my 74 block has beefier main caps and as someone mentioned, the drain plug is deeper in the casting and finally, (going from memory here) there is an additional tapped hole on the block. I'll double check in a couple hours. Also, it seems to me that the main cap bolts are metric.

Tremmelle

Just to add to the confusion, or more accurately... add to what we *don't* know about B20 blocks, I just checked the two short blocks I have sitting next to the race car. We'll refer to them as "black" and "red", 'cuz that's what color they are! Since these both have racing history, probably with multiple chassis matings between birth and present, I can offer no history whatsoever as to when they were made or in what vehicle they were originally installed. Anyway....

- Black does *not* have "bridge" castings in the pushrod area of #1 & #4.
- Red *does* have the bridge castings.

- Neither block has any metric threads in any area.
- Both currently have 6 bolt cranks installed.
- Both have the "extra" oil orifice on the right side near the filter.
- If either of the blocks has a date "code", it is just that... a code. No numbers jump out at you as obvious dates.

Incidentally, Black is of exceptionally poor casting quality throughout... as a result, many cast numbers are illegible (see below).

Stamped numbers following the cast "49" on the upper left side:
Black - 8284 2580
Red - 8284 36791

Cast number a couple inches below "49" on upper left side:
Black - 1-1?????6 (might be 1-100896)
Red - 1000197

Cast number behind flywheel (numbers cast in reverse):
Black - B-1??:? (might be B-101:3)
Red - B-101:3

Cast number lower right side, closest to oil filter:
Black - RDG 3A
Red - TDG 12

Cast numbers lower right side, closest to mount:
Black - B J12
Red - B D19

No other discernible differences at this point, but neither have been completely disassembled.

And here's a quicky shot of the "bridge" casting: the #1 cylinder area is shown.

--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5

Gary: Engine number 498284 is a B20F out of a 140 with manual trans and had 125 bhp when it was new.


John: As an aside, I am inclined to believe the chart that I have only covers 6 bolt crank engines.

Cheers, Jim

Its all very interesting!!!!

John
V-performance.com

John,

By far the easiest way to tell is to look at the block like this pic. This specific block is a 6 bolt. The 8-bolt blocks have an extra 'bridge' casted between the walls of cilinder 2 and 3 and the outer side of the block. (hope this makes sense) It's a round bridge basically sitting in between the pushrods of intake/exhaust of both cil. 1 and 2. So in this pic it would be below the coolant hole/passage of cil 1 and 2 (if it would have been an 8-bolt that is)

cheers, ben




--
P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

Ben,

You're talking about the bridge between the pushrods on cylinders 1 and 4? And you're saying that an 8-bolt motor has these on all the cylinders?

I have pictures of the MPPE going together, and it's definitely an 8-bolt from 1974... but it only has those bridges on 1 and 4, not on 2 and 3.

Did I misunderstand what you mean?

Ehm, you are absolutely right dear Phil, it's cil 1 and 4 that has those bridges... I stand corrected. Just replace the 2 and 3 in my previous post for 1 and 4. Also, I must add, I don't know this for a FACT, but all the 8-bolt blocks I (and a lot of people I have talked to) have seen have those bridges, and all the 6-bolts don't.

cheers!
--
P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

Ben, I have two pictures of B20 blocks taken from the top in front of me, both of which I took (I don't have them scanned, sorry). One is a 6-bolt block (date unknown) and one is an 8-bolt (1974), no doubt about either. They both have bridges on 1 and 4, and neither has bridges on 2 and 3.

???

Bugger, there goes my theory. Do you know the date of the 6-bolt block with the bridges? They aparently must have started using the bridges a wee while before the went to metric. Your '6-bolt bridged block' IS metric right? Not excidently a metric block with an older (6-bolt) crank in it??)

ben

The extra stiffening pieces are features of B20E blocks, they also have a counterbored hole where the water drain cock would live near the oil filter, this hole is for the optional oil to water oil cooler available to B20E's & B30E's.

The last of the B20 blocks got metric main bolts which look very pissy & have lighter main caps.

For a simple question you would expect to get a simple answer.
And maybe one that at least two people could agree to.
Now I don't feel so bad for having to ask the question in the first place.
Its surprising what we find we don't know.

Any comment on the fact that the "8 bolt" blocks we tested don't have walls that are any thicker than the 6 bolt blocks tested?

John
V-performance.com

I'd say so far it's looking like they're all the same castings regardless of what crank went into them. I really went through my two sets of detailed pictures and couldn't find any visible differences between 6- and 8-bolt blocks, except for the markings on the bearing caps, which may not be a reliable identifier.

The block we just sonic tested seems to be marginally thicker than the ones you're looking at, but not significantly.

What the minimum thickness needs to be is a different subject, but there are known high-mile 93mm street motors that don't suffer from blowby, and a whole bunch of 92mm kits that don't either. (I did say street motors...)

2centsFWTHIW
When I got my '75 B20 (I pulled it myself from a '75 245) sonic-checked, they weren't real excited by the results and asked that I bring another block. The only other one I had was a '72 or '73 (ID'd by me by the '72-'73 [not '71] D-jet ?time switch? on the back right side + 6-bolt crank).
They liked the results on that one a whole lot less, so they bored the '75.

According to my father I was born not willing to believe what people told me.
So its natural that I have never believed a lot of the gospel about Volvo engines and most of the time this as proved to be a good thing. I usually have to see it to believe it.

Part of the reason for asking this question in the first place is the following
email I received recently from Europe:

Hi
Yes the walls in 75-76 b20 is thiker they are from the 240 series only 75/76 whid M45 gear. Im not sure how thik my walls are. Did just bought that engine from a sweed . But they are 93,98 bore. I got 2* 75/76 mod b20 one hevyely modified and one std engine.Her we say thay not biger bore than 93 on 72-74 block an 92,5 on earlier block
75-76 block 94mm

Brgds
Ken

Of the 5 blocks tested recently, 2 being 8 bolts, the one with the thickest walls would have had a spot high on the thrust side only .935 thick with 92.5 bore.

Shayne, I don't have your block specs handy, but am guessing that it would have been pretty thin with a 94 mm bore.

John
V-performance.com

We (You, Phil and I) had discussed the wall thickness of my particular block before. I think I remember that it was going to be reasonable. No going back now:o)
Bore on mine is 93mm.
Best,
Shayne.

I know that we found that your's was going to be thick enough based on the criteria of at least .125 for a normally aspirated engine, but I recall it as being real close and maybe even under that in spots. Which further raises the question as to whether there are really any blocks that could reasonably be bored to 94 mm.

What I can tell you, and this is not new, is that no one should do anymore than a 90 mm overbore without doing a complete wall thickness check. Most B20 blocks do
not have thick enough walls to bore to 92 mm.

Still open to question is whether there is some identifiable subset of blocks,
75/76 blocks for example, where the majority of blocks are thick enough for a 92 or 93 mm bore.
The basis for the original question was how to identify those blocks with certainty, so I could test some of them to see if this is true.

John
V-performance.com

The last B20 blocks have metric main bolts.

Don't all of the 8 bolt blocks, 74,75 and 76 have metric main cap bolts?

John
V-performance.com

Not here. I've only seen one 8-bolt motor with metric main cap bolts. I guess the 6-bolt crank/rod/piston supply run out before the older blocks did.

The reason for asking the question in the first place was to determine which blocks might be those supposed thick walled late blocks that will accommodate larger bores. Everyone keeps saying that the 74/75 8 bolt blocks have thicker walls.
Well we just tested 5 blocks, 2 of which were 8 bolt blocks based on the cranks that were in them. All five had a thin spot toward the top of one cylinder that was between .150 and .165 thick with a stock bore. For a 92mm bore this spot would be under .100 on most, and there would be numerous spots and whole sides of cylinders under .120 on all. Enough of a problem that we would do an offset bore to get at least an .120 wall for a NA engine and would keep the overbore to .050 on a supercharged engine even with the offset bore.

Am I just getting a thin walled blocks?

John
V-performance.com

On the 8-bolt block currently in progress, we're seeing the thin spots near the tops of the bores, but they are not as thin as you're seeing. At 92mm bore, the thinnest spot would be about .118". I may remember it wrong, but I think the thinnest was forward on #2 cyl.

On mine the rodcap bolts and the bellhousing bolts are 12mm 1.75
where on the 73 they are ½"-13UNC and 7/16"-14UNC.
The type number on the side of the block might be some help although my
info doesn't go that late. It will have the 49 cast on followed by
stamped numbers.
--
George Downs Bartlesville, Heart of the USA!

there is a casting # on the back of the block behind the flywheel. i have a 74' motor ,a 75' motor and a aq130 block that was a 77' i'll check the casting #s for you. it will take me a week or so i'm out of town.

On all 3 B20 blocks I have around (one in the garage, two in cars, all 6 bolts) there is a date cast into the block. on the right side, right above the oil pan flange, below the oil sender. It can be hard to read, especially if it is still in the car.
--
I'm JohnMc, and I approved this message.

On the flat area immediately aft of the motor mount bracket? I've got two 6-bolt motors right now where I can see that number fairly clearly, and neither appears to be a date. ???

I'll take a pic on my bare block when I get home this evening. Maybe it isn't a date, but on all 3 of my motors they all seemed to be valid dates, with the year on 2 of them being '71 and '72 on the 3rd. They were rather indistinct, not really made to be read after being painted/rusted/etc.
--
I'm JohnMc, and I approved this message.

Here's the picture of what I take to be the date on my bare block. It looks as if it says 2 4 70 to me - either 2/4/1970 or 4/2/1970, depending on their MDY preferences. I couldn't get a clear pic of the motor in my PV - but it says 12 3 71 - both make sense as production dates for these B20 6 bolt blocks.
--
I'm JohnMc, and I approved this message.

I checked this on 5 blocks (all b20's) I have say:

-NBG14 53930
-SDG 9 L13 2 (up side down)
-TDG 8
-PGB14 14416
-15 E 75 02 11

So I dont think you could realy tell somthing from this. Although the last one is a B20A from a '75 240 series. Maybe 11-02-1975 / 02-11-1975??

cheers

--
P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

On the 8 bolt block that I keep on the bench for part mockups, on that spot it says
"K 2 F". The F is not on the same line as the K 2 and they are all upside down.

John
V-performance.com

Probably dumb random luck that the numbers on the two blocks I checked looked like dates from the correct time period. It sounds like nobody else has anything there that looks like a date either.
--
I'm JohnMc, and I approved this message.

John:

I can give you the engine numbers off my chart [which I copied off a parts bulletin]. There are only 4 B20F's listed and two are 1800's and two are 140's.

Engine no. 498282, type B20F, bhp 125 [SAE},vehicle 1800e
Engine no. 498283, type B20F, bhp 125 [SAE],vehicle 1800e[BW35]
Engine no. 498284, type B20F, bhp 125 [SAE],vehicle 140
Engine no. 498285, type B20f, bhp 125 [SAE],vehicle 140[BW35]

This should tell you if it is in fact out of a '74 model.
My chart doesn't show any 240's so if your block number is different then it might be a '75 240 block.

Hope this helps.

Cheers, Jim Robinson

Not sure I understand how this tells which ones are from a 74.
Are both of the 140 engine numbers from 74?


John
V-performance.com

John:

My chart does not list the year of the car only the engine type,BHP, and vehicle type. It does not list any 240's so I would say that it does not cover the 75 model year. I am assuming that it covers through model year 1974 but I am not 100 percent certain. I believe I copied the bulletin in the early to mid 80's and figured at the time that it covered all the models up to '74.

The chart has 23 B18 engine numbers,5 B20B,4 B20E,4 B20F,2 B30A and 2 B30F.

Sorry I can't be more specific than that.


Jim

John,

Strictly going from pictures of several projects, the teardrop marking on the main bearing caps is offset toward the distributor side of the block on 8-bolt motors -- at least it is on the one 8-bolt build-up I have pics of, so I don't know if that's universally true (another one is in process, but it's at the machine shop right now). I've never seen that mark not centered on 6-bolt motors.

I'm not aware of having encountered any metric fasteners on the any of the blocks.

Wall thickness on the 8-bolt in the shop would sonic test at around .210" average, if the bore were stock. I have no idea if this is a '74 or a '75, or how to tell them apart. What I've heard is that all the 8-bolt blocks have more meat in the walls, not just the '75, but I have not seen any hard evidence of that either.

ok ...I took a long hard look at a known '75 block, next to a six bolt block. Here are the diferences:

75:
has deep water drain plug casting

has what looks to be a date stamped on oil filter side of block on the bottom. It says: 75 1 22

has a tapped hole on dizzy side of block just to right of the dizzy and up a little. It is plugged. I suspect its a water jacket gauging the size of the plug.

has extra casting between 1 and 4 near the connecting rod opennings

the main cap bolts are metric

main caps are thicker

two tapped holes in a vertical fomation on dizzy side of block, towards the front bottom of engine (just behind timing cover) is metric!

the gears on crank and cam are a different pitch. In other words, I can't interchange timing gears between the early and late blocks, although either will work in either block if you keep the joining pairs together.

and here is a really odd one: the little bolt that holds the clutch folk in one of my bell housing is metric and another is not, though I thought they changed the design of the clutch folk when they went to cable from hydro.?


pre 74:

opposite of above..meaning all listed is either different or doesn't exist.

Tremmelle