Differences between B18B and B18D

RSready · Jan 29, 2015

I have a B18D which is the original engine in my US-market '67 122S. It is rated at 100 HP (SAE) and 108 LB-FT with 8.7:1 compression, according to vlvworld.com.

I also have a B18 out of US market 142, which I am told was a '67. Am I right to assume that it is a B18B? According to vlvworld, it has 115 HP/112 LB-FT with 10:1 compression.

What makes up for this difference in compression? Is it just a thinner head gasket? What other differences are there between the two? Cam?

aidandebradney28 · Jan 29, 2015

I know about the cam difference, but I would also be interested in seeing the other differences. I have the D cam in my B18, (also a '67 122s), and having driven a B cam B18, there is a noticeable difference.

Phil Singher · Jan 29, 2015

The ONLY difference in any given year is the compression ratio, and that's only because the B head is milled thinner than the D head.

The original D had 8.5:1 compression, while the original B had 9.5:1 compression.

The second generation saw the B cam changed to the slightly more aggressive C (which is still very mild). D compression went to 8.7:1, B to 10.0:1.

The final version of both got the unified intake and exhaust manifold with dual head pipes.

aidandebradney28 · Jan 30, 2015

So, I'm asking a newb question here, would my B18D have a better compression if I put a second gen B head on it? Or is that just a no? And if so, how do I distinguish a 2nd Gen B head?
Sorry I'm just curious.

RSready · Jan 30, 2015

aidandebradney28 said:
So, I'm asking a newb question here, would my B18D would have a better compression if I put a second gen B head on it? Or is that just a no?
Sorry I'm just curious.

That's what I was thinking. Although I think a full rebuild would be in order as I think putting a higher compression head on an older bottom end could put too much strain on it and spin a bearing. I'm no expert though!

Dimitri · Jan 30, 2015

I thought that the difference was only on the head gasket thickness.

No need for rebuilding the bottom end.

Phil, I tried to find the specs of the original cam on the internet, it is hard to come by. Do you have the info? Intake/exhaust duration, lift, overlap. Also, on the internet I found some references that the cam of the B20B was from the factory larger. Not sure if I buy that. But may be the 70's B20's had larger cams. (?)

RSready · Jan 30, 2015

The more I read, the more confused I get haha. So much differing info. Found this though:

http://volvo1800pictures.com/docume.../document/Service_manual_jack/part_2B_engine_B18_B_D/part_2B_engine_B18_B_D.pdf

And for cams:
http://www.1800philes.com/ianr/_superlist_grinds.html

Phil Singher · Jan 30, 2015

The 10.0:1 B head is something like .070" thinner than the 8.7:1 D head. The difference is not in the gasket thickness. They are all the same casting -- you can shave a low compression head and make a high compression head out of it no prob.

The B20B uses a C cam, same as the later B18s. D-jet B20s use the D cam, K-jet the K cam. The D was never used in carbureted engines. Of course, I often use it, but the factory did not.

Don't take the cam superlist data as gospel -- it's a very good attempt, but some the data is off by quite a bit. I measure the D at around 267 degrees valve duration at .016" lash. You'd have to go to something like .009" lash to get 280 degrees out of it. I've never measured a C cam, so I don't know if the data is accurate for that one.

Dimitri · Jan 30, 2015

What about the exhaust? Is it identical?

Even the D cam seems relatively conservative.

Phil Singher · Jan 30, 2015

Both types of exhaust manifold are the same for the B and D engines, although I think the 1800 may have gotten the later setup a few months before the Amazon. The head pipes are the same as well.

The D is pretty similar to the Isky VV71 (iPd Street Performance) except that it has four degrees less overlap, due to wider lobe separation, and makes more torque at the low end.

Dimitri · Jan 31, 2015

Phil Singher said:
Both types of exhaust manifold are the same for the B and D engines, although I think the 1800 may have gotten the later setup a few months before the Amazon. The head pipes are the same as well.

The D is pretty similar to the Isky VV71 (iPd Street Performance) except that it has four degrees less overlap, due to wider lobe separation, and makes more torque at the low end.

When I asked exhaust I did not ask about the manifolds, I was asking about the cam duration and lift ... Thanks

Phil Singher · Jan 31, 2015

Intake and exhaust lobes are the same profile.

saschahewett592 · Feb 25, 2024

Phil Singher said:
The ONLY difference in any given year is the compression ratio, and that's only because the B head is milled thinner than the D head.

The original D had 8.5:1 compression, while the original B had 9.5:1 compression.

The second generation saw the B cam changed to the slightly more aggressive C (which is still very mild). D compression went to 8.7:1, B to 10.0:1.

The final version of both got the unified intake and exhaust manifold with dual head pipes.

hey im struggling to know what b series head i have its apparently a b20z1 block with b18b head its say on the head p75-11 and the date is 01/07/29

Rustinmotion · Feb 25, 2024

This is from Turbobricks, a selection of red block cams measured for lift and duration

Differences between B18B and B18D

RSready

aidandebradney28

Phil Singher

aidandebradney28

RSready

Dimitri

RSready

Phil Singher

Dimitri

Phil Singher

Dimitri

Phil Singher

saschahewett592

Rustinmotion

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