3B Head Conundrums

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Mar 23, 2021
Hamilton, Ontario
Hello all,

I've gone through a good portion of this forum and haven't found what I'm looking for - but let me know if there is some "please-read-first" that I've missed which explain the nuanced 3B heads and their part numbers. The documentation of my findings are below:

Similar to this thread:
I am also from Canada, and also have a head with a 11111-58010 on it. Mine is from 1982.

From that thread, it was generally accepted that the 11111 = 11101, and the 58010 was interchangeable with 58011, 12, 13 and 14

This also seems to be true in the documentation here:

These are 41mm LARGE exhaust valve heads, with only 4 rocker cover bolts down the middle (as opposed to around the perimeter - which I'll get to in a moment)

You may be quick to say that the "large exhaust valve" indicates it is a "new" 3B head style, as opposed to the "old" style, found here:

These are known as "small valve" heads - and have 4 bolts down the centre to mount the rocker cover. And while the years for these are from 1974-84, and the 58010-14 large valves are from 1980-88, note that A: there is an overlap in years, and B: there is a third newer style which has not been discussed:

These also have a large 41mm exhaust valves, but their rocker cover is bolted in place around the perimeter, and cover years from 1984-96. These are known as 58050 and 58051.

So just be weary when referring to "old" and "new" style heads, or even "small" or "large" valves, because from what I can tell there are at least 3 distinct 3B heads, and getting the wrong one will ruin your day.

1974-1984 - 59025, 59045, 59046, 59105, 59106, 56032, 56033, 56034 - small exhaust valve, rocker cover bolts in centre
1980-1988 - 58010, 58011, 58012, 58013, 58014 - large exhaust valve, rocker cover bolts in centre
1984-1996 - 58050, 58051 - large exhaust valve, rocker cover bolts around perimeter

Let me know if I'm wrong, so I can correct and make it easier for the next poor guy looking for a crack-free head.

Now, to see if I can track down a 58010-14... possibly direct from Chynah. wish me luck.
I had 5 different 3B head laying on the working bench from …10 to …13 and I couldn’t see differences. Heard that it may be internal cooling passage that may differ?

Wonder if the rockers arms assembly is the same from 3B to 3B II ? Is a 3B II head fit the 3B block? Then you have to fab a custom exhaust manifolds and find a cover…

I removed a …10 head from a 1985 block which was repaired. Was welded between valve and all around precups. I believe there was 2L pre cups installed and found 2450 (2L) with dns139 injector nozzle on it. I ran this engine for a summer and it was fine.
I then ask the machine shop to install 3B pre cups on it.
I did ask them to weld (fusion welding) my 1986 …12 head. Between valve.
That another option.
New guide, seat, spring, seal…like new (I think)
One of the reason I'm going through this exercise is to determine if I can source a replacement head from Alibaba. Most, if not all, vendors there refer to "old" and "new" 3B heads. I've seen this same terminology on some online retailers who some would deem to be more legitimate (although they probably just re-sell the Chinese heads for a markup).

Below is a comparison of the valve sizes and their corresponding alleged part numbers. I wouldn't recommend fully depending on this information - I still have yet to confirm if my 58010 = 58014 which is known as the "3B old" head in the chart below. I'll measure mine tonight.

Ive been going through this as well and finally decided to just order the head from cruiser parts, they are getting the small valve heads (from china im sure) and having a machine shop re bore the valves holes for the larger version... and yes you could do that too, just figured that this is a proven path to a trouble free head and i dont have to order from china and find a shop and convince them to re bore the valve holes for my application...
New year, new head chaos!

I'm having a bit of a panic realizing that I've been working on this for OVER A YEAR NOW.

After a lot of humming and hawing, I decided to just dish out the cash and buy a new head from Cruiser Parts. Cost me over $2000 CAD. Shipped with no drama thankfully. I removed an intake and exhaust valve from my old head, and found that the intake fits well... but the exhaust sits proud of the surface.


MEGA annoyed at this, I went back to their website to check which valves are required. On the listing found here:


It states the valves required are:

Intake Valve:
IN size: 46.00*9.0*128.30MM

Exhaust Valve:
EX size: 41.00*9.0*127.80MM

Which are precisely the measurements of my valves. The inner and outer dimensions of the exhaust seat on my old head are 36.28mm and 42.13mm respectively. This fits the 41mm valve nicely. The inner and outer dimensions of the exhaust seat on the new head are 31.85mm and 38.04mm which is clearly too small.







Everything else on this head should be correct: has the valve cover bolt holes down the middle, proper exhaust and intake bolt pattern etc.

I've emailed them; we'll see what happens.
i did not have this problem with the head i ordered from them
My truck is an 86 'large valve' 3b...
i did have the machine shop fit my old valves to the new head and re surface the new head, and they may have recut the exhaust seat but that wasnt told to me... and i think there would have been a charge for this, and there wasnt
Perhaps the machine shop that cruiser parts had recut the seats missed cutting the exhaust side.....

Send them that pic....I'm sure they will respond
update: Cruiser Parts offered a free set of new exhaust valves which would fit, or, a return slip for me to send this head back, and they would ship me a different head with the proper valve seat sizes. I've gone with the latter - I know I'm splitting hairs over 4 mm, but I might as well get the large exhaust valves that came with this BJ.

Looks like they've taken care of the issue. Will update when it gets sorted!

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