Does anyone know what year they stopped putting the boss on the intake? I ask because I have a 73, but the heads are not 73's. The repair manual I have shows the boss for the O-ring (to mate with the boss on the intake manifold), but the heads that are on it don't have it, they are just flat, no inner ring. I know up to at least 75, they had the boss.


From the fitment chart, it shows 73 up to 79 will fit, but they are clearly not the same heads. so what do they mean by fitment? Bolt pattern location? Do they use the same valves? Springs? The valve guides in it right now don't have the flange that a 73 head valve guide does. The free length of the inner and outer springs are different as well. And the lower spring collars on a 73 are stepped, mine are not. It's just a washer that has an OD smaller than the ID of the outer spring. The valve guides also have seals, which 73s dont'. So if the heads are interchangeable what's up with the internals being so different?


Is there any info to be gained from the casting number? Casting numbers are 16682-71E and 16684-71E. The 2, 4 difference just refers to which head it is (front, rear), correct?


How do you tell the difference between 72-early 73 heads, and late 73 up? I ask because there's an auction (http://cgi.ebay.com/ebaymotors/ws/eB...S%252BI%252BSS) for 72-early 73 heads, and they look identical to the heads I have except for the intake boss. Granted I don't know bolt pattern dimensions and fire ring diameter. But the casting number is the same except for the letter on the end. What does a difference in the letter correlate to? I found a set of heads on ebay with the boss I need, but the casting number ends with "BB"

This leads to another question of distinguishing between 900 and 1000cc heads, because I have found anything definitive. Or were 900cc motors only used up to a certain year, then upgraded to 1000cc.[/align][/align]Thanks in advance[/align]

 

Last 900cc engine made was 1971. First 1000cc engine made was 1972.
The earlier Sportsters used round O rings at the intake manifold/head position and later seals were not O rings, but rather things that looked like flat rubber bands, for lack of a better term.
I do not know which year this happened, but some of the members here do.
It is possible you have an early manifold and later model heads, so the 2 shapes do not match each other. This is the way I understood your description of what you have anyway.
If that is correct, then the easy way to fix this is find the correct intake maniflod to match your heads and buy a new pair of seals.

 

You could just buy rubberband type intake seals and not worry about it. They make adaptor rings that fit over the lip of the o-ring type so that you can use the rubberband type seals. Not a big issue

 

piniongear-

thanks for the reply. Yes, you understood my description correctly. The issue I have is that I have a 73, and I want to have the correct heads for that year ideally, but since heads are quite expensive, even for an old beat up set, I could like with the heads I have. My question is this, are there any fundamental differences between pre 79 heads and 79 and up, aside from the intake bosses? I ask because I have the AMF repair manual for 70-73 sportsters, with all the specs for valve spring length, installed height, blah blah blah, and would like to install the proper year components in my 79+ heads. The lower collars installed right now are just washers, and the OD of the washer is smaller than the ID of the outer spring, so only the inner spring sits on the washer. The 73 heads have a depression around the valve guides for the stepped collar, but the heads I have do not have this depression. Basically is there any danger of using the correct internals for a '73 in a '79 head.

Also, is there any information to be gained from casting #s? or are they part #s? Mine are 16682-71E and 16684-71E. The 2, 4 difference just refers to which head it is (front, rear), correct? What does the 71 mean? And what does the letter mean?

 

Topdong1....
The casting numbers ending with 71E do not mean much to me. HD always ended casting numbers with a (dash) and a 2 digit number. This number indicated the last year a change was made to the casting. For example, you find a lot of casting numbers on 1960 and early 1970 Sportsters that end with '-52'. This means that particular part is basically the same as the part was for the 1952 K Model. If 1966 comes around and a design change is required, then the new part would end in '-66' and all of the following parts would follow with this ending until another change was made.
So that would indicate the heads were off a 1971......BUT, I am not certain of that, so I do not apply what I have just described to your heads.
1971 was the last yead of the 900cc engine.
1972 was the first 1000cc engine.
The bolt pattern on the cylinder base was different between the 2 engines, but were the heads different, and did they have different bolt patterns as well? Of that I am not sure. So, you have stumped me there. The diameter of the cylinders and the diameter of the heads at the gasket surface on your machine should measure about the same. The 1000cc engine (3.188 inch bore) had a bore 3/16 inch larger than the 900cc (3 inch bore). Beyond that, I cannot tell you what other differences they may have.
My so-called knowledge is limited to before 1974 as I have said many times here. 1979 was an odd ball machine but the engine was pretty much the same. Of course I know little about anything made in 1980 and newer.
Just keep researching and you will get the answers you are looking for..........pg

 

I had my old Mikuni out this morning taking some shots for another member and thought to take one of the manifold edge where it meets the head on my 1971.
The pencil points to the flat area where the O ring goes on the intake manifold. The head will have a like flat on it.for the other half of the O ring.
The larger flat is of course where the clamp band sits. The head has a matching shape. Your later heads may not have that shape...........pg


[IMG]local://upfiles/8331/343273B6980C4C4095C336C79E12AE26.jpg[/IMG]

 

The intake manifold I have has the boss for the O-Ring type seal, but the cylinder head itself does not. So I know I don't have the right heads.

So my question is, if the intake manifold port is different between 78 and below and 79 and up, then what else about these heads are different. For instance, the valve guide on a 73 has a flange around it that sits against the top side of the head, The valve guide I have does not have this flange. The lower collars are different as well, because the the cylinder heads differ as to which surface the collar sits on. The 73 has a depression around the valve guide for the collar to sit in, but the heads I have do not.So this is the kind of information I'm after, the differences.

The differences are important because I'd like to use the correct internals for a 73, so that my repair manual will be useful when checking things like spring free length, valve guide to valve clearances, etc. And I can always buy the matching intake manifold to use the rubber band style seals.

From what parts I've seen on ebay, and I know the people selling the stuff may not know anything about it, other than casting numbers, BUT...I have seen alleged heads from a 72-early 73, a 74, and a 75, and the casting numbers are the same except for the letter at the end. Some have B, others have BB, and others have E. Any idea how these letters correlate to specific model years?


I appreciate all your help

 

The differences are important because I'd like to use the correct internals for a 73, so that my repair manual will be useful when checking things like spring free length, valve guide to valve clearances, etc. And I can always buy the matching intake manifold to use the rubber band style seals.

I hear what you are saying, but you have the heads that you have and that is not going to change. You have to use the springs... etc, that go with the heads. You cannot mix 1973 'internals' with 1979 heads if there are the differences you noted.
Find yourself a 1979 manual and copy the page(s) that differ from your 1973 model. It becomes an addendum to your manual. Get a manifold to match your heads and you are goo to go.......pg

 

I'm a tinkerer to a fault, and I have the time and patience to do it. My point is that it canwork, assuming everything checks out

the valve guides clearances now are good, exhaust is a little tight though. The outer springs in it are 1/8 inchlonger than the springs for a 73, but sit directly on the casting. The addition of the stepped collar and outer spring from a 73 takes care of that 1/8 inch, but I'm not sure it will give me the correct installed seat pressures.Could anyone with a 79+ repair manual please look that information up for me?

Anyone with a 79+ happen to have valve part #'s? Inner and Outerspring wire diameters would be the icing on the cake

 

If anyone has a parts books for 79 up, and would scan the pages about the cylinder heads, I'd really appreciate it.