Head switch

[Big Daddy Funk]

I recently purchased a basket case of 1100 parts to have some spares. I have a 79 XS 1100 SF that has a wiseco 1196 kit in it with stock exhaust pipes and aftermarket very low restriction mufflers. (no crossover tube). In the basket I found a rebuilt head that had a professional looking port and polish job. I assume that it is a 1980 head because it has the wider valves in it. My question is will this head fit my 79 without any major issues other than rejetting the carbs and shiming the valves to 1980 specs?
I would also assume that the 1980 cams would be used. There were four cams in the box, An intake and exhaust both with the 3H5 cast into them and a intake cam marked ZX and a exhaust cam marked ZJ. I have no idea if either of these cams are the correct ones. Both fit the head and can be adjusted to the proper gap with reshimming.
This web site is great ! It's good to know there are as many people as crazy for these bikes as I am. Thx.

[DiverRay]

The newer head should bolt right on. It WILL give you a LOWER compression ratio, but only by a point or so.(9.2:1 instead of 10.2:1) I would keep the '79 cams in the 80 head, for a start. Cams can be swapped without a lot of problems. I would also check the valve spring tension on the '80 head. It MAY have the better springs, and that will allow for a higher "red line".

[John]

I'd be careful with swapping heads and cams. Just ask trbig what the wrong cams can do to your vacuum readings.

[egsols]

Don`t the older cams have a longer duration then the newer ones. I remember comparing them, I don`t have the specs in front of me but I seem to remember that they also had a slightly different lift as well.

[TopCatGr58]

Hey there FUNK,

Welcome to the site, glad you found us!

Now, with your problems, let's see if we can get your head straight!

It depends on where you want to run the rpms on your machine. IF you like to run it in the lower rpms, and use it more for touring, riding 2 up, hauling a trailer, or just mild mannered revving, then the late head with the early cams is what I remember reading is the ticket. But if you want to run in the higher rpms, then you'll want to use the late head with the later cams, they work better at the higher rpms, but don't provide as much in the lower rpms.

There were some resent posts by our Engine Modder Xtraordinaire Dan Hodges regarding the variety of cams and heads/valve combos that can be used and to what effect.

The early heads have closer shaped domes, so you get more compression, the Wiseco stats of attainable Comp. Ratios were based on the original engine/head design, not the later larger valved heads. But remember, total compression is also controlled by valve duration and timing, and the 80 cams are designed to work with the 80 heads quite well. So...even though I put in the 1179 kit on my 81, whereas stock comp values were supposed to be 142 psi NEW, shortly after breakin, I found 180-185psi, and I'm sure it wasn't due to excessive carbon in the heads.
T.C.

[trbig]

I had always heard that using the 78-79 cams in the later heads made more power, and that's what I ran for a long time. I never could get much of a vacuum reading at all to synch the carbs, but didn't know any different.

Long story short (ish), I put some 3H5 cams (Later model) in the head, and all the sudden I had vacuum to synch the carbs, a smooth idle, and honestly probably MORE than doubled my low end power without sacrificing anything on the top end that I can tell. I wouldn't even think about putting in those early model cams again.

That's just my personal experience with them.. yours may vary?



Tod

[Big Daddy Funk]

Head switch

Very glad to have found this site. I have read through a lot of great info here. I always ride one up to really appreciate what the motorcycle is capable of. Once I get out to the twisties I like to run up to the red line before shifting and I love scraping pegs at night. There seem to be fewer and fewer areas to ride hard in some degree of saftey. Most of my old routes have been taken over by groups of sport riders.
I do believe I would like to use the 1980 cams. My current problem is identify the cams that came with the head. There is a stipped down 1980 engine and a 1979 head as well as numerous other items Everything was disassembled and nothing taged I have no idea if the cams that came in the basket are for a 1980 or a Maxim, or something else.
Now that I know the switch is possible. What I really need to know is How to identify a 1980 cam. Hopefully I have them already. I have left a message for trbig, but open to anyone has any help to add. I will check out the Dan hodges thread. I am gratefull to everyone who replied so far. Thx Rick

[Big Daddy Funk]

Excellent news

Thats really good news, because I have a set of 3H5's Iwish I had found this site a few months ago. Once again thanks everyone so much for your help. Rick

[trbig]

Yeah, they only had two different cams for all these bikes. 2H7, or 3H5. The 2H7's were for the 78 and 79 bikes. What scares me about your posting, is that the cam caps are a mated set with a head. Not a good idea to swap them.
Each one will be stamped to where it goes (I 1-5 and E 1-5) with the arrows all pointing to the right if you were looking at it from behind the intake side. If you get a magnifying glass and look at the cam "bearing" surface, you should be able to see at least some fine lines where a bit of grit has scratched it going through. Try to find the cap with the same scratch marks for that particular location.

Kind of a PITA, but going to be your best bet for longevity of the head.


Tod

[Big Daddy Funk]

Cam caps & porting & polishing

Thx for the tip. I will try to match up the cap scratches to those on the cam. Luckily the 80's head looks recently done and the 79 has been sitting untouched for a while, so there is a visible difference in the cleanliness of the caps. That should help match them up.
I did find that the #4 exhaust valve did not completely close due to slight bend (as if any bent valve is slight) I'm guessing the valve was touched during installation of the head and then removed when it didn't run properly,then given up on. The port and polish looks professional but more metal was removed than I would have done. I will get it flow tested when I get the new exhaust valve ground. Would anyone happen to have numbers on how much flow is workable on this combination without affecting drivability ? I wouldn't like to do all this work and find that the flow is to much and is drowning itself. The valve springs look like new but I haven't measured and tested them yet. Thx Rick

[TopCatGr58]

Hey Funk/Rick,

Check out This thread about Head Porting, and Dan Hodges replies!

The valves get bent not by putting the head on the engine, because until the cams are placed, the valves are all recessed into the head. Once the head is on, and cams are inserted, IF the cam chain isn't properly positioned around the crank...can get stuck BESIDE/BETWEEN the crank sprocket and crank so that with SLOW turnings of the crank, the cams would turn, but once they hit the starter button, the crank would slip/spin and go off time, causing pistons to hit valves=BENT!!! OR...it's on the crank sprocket, but the timing cam tensioner is messed up, doesn't maintain tension, crank sprocket slips a tooth on the chain, out of time, and again, pistons come up too soon before valves close!

If one valve is visibly bent, there may be others. You would be good to turn the head upside down and pour some thin fluid into the head domes...with spark plugs in place, and monitor over a day for leaking!

I had one valve get bent ever so slightly, it would still appear closed, but would not seal, didn't do the fluid test, assembled engine, ZERO comp on that cylinder, pulled head, removed springs, and then spun the valve in the seat and THEN I could see a WOBBLE! Best to do it ONCE!
T.C.

[Big Daddy Funk]

bent valve

I agree absolutely. If that is the only bent valve, I am at a loss as to why only one valve would get touched. Perhaps the valve was not in the head when it got bent, but I don't see any marks on it. The head will be going into the machine shop to grind the replacement valve and put a 3 angle cut on all of them and the seats. I found the bent valve ( looked ok)when I did a quick lap in to clean up the faces before the leak test. The machine shop will be able to pick up anything I missed. My concern right now is how much this head is going to flow with the porting and polishing. I was wondering if anyone has experience with the optimal flow rate for this combination. Thx for the input. It is appreciated. Rick

[bikerphil]

I am at a loss as to why only one valve would get touched.

I've bent just one valve before in a '79 head. I changed out the tensioner and the cam chain was off a tooth. Instead of slowly turning the engine by hand to verify correct timing position, I bumped the starter and heard "clank"! Took her all apart and only #3 exhaust was bent.