Has anybody ever had their GS1100GL (or other 8V) head ported?

[Longitudinal]

I picked up a head to get refreshed for my GS1100GL and swap in when it is finished.

The intake ports look pretty decent. They appear to be designed to promote swirl, which was very popular in the 1970s and early '80s.

The exhaust ports look atrocious. The valve guide bosses are enormous, and that giant hump on the port floor looks like way too much.

Has anybody had their head ported and have results (quantitative or qualitative) to share?

[salty_monk]

Nessism knows a couple of tricks that you can do yourself on that head....

[limeex2]

Yes they are but why change them? If someone does it improperly it could get worse. Unless your doing cams, carbs, pipes ect, your best off spending time, money elsewhere.

[Longitudinal]

Yes they are but why change them? If someone does it improperly it could get worse. Unless your doing cams, carbs, pipes ect, your best off spending time, money elsewhere.

Of course, there are more ways to do it wrong than there are to do it right. But I trust my cylinder head machinist completely.

With that said, the thread I started about cams has convinced me to leave the engine stock with the possible exception of an exhaust.

[Nessism]

The short side radius is sharp and can be smoothed out using a file. And a little pocket porting to clean up machining marks never hurts either. Beyond that, I'd leave it alone.

[Longitudinal]

The short side radius is sharp and can be smoothed out using a file. And a little pocket porting to clean up machining marks never hurts either. Beyond that, I'd leave it alone.

Short side radius on intake or exhaust? or both? Maybe I will pull the valves and touch up the ports a little before I take the head in for a valve job.

[Nessism]

I'd do the port touch up before the valve job. Use your finger and you will feel the sharp edges quite easily. I can't remember if it's exhaust, intake, or both. What I do remember is that a long file reached the sharp edges very nicely. Just under the valve seats there were some sharp edges too. A carbide cutter in a dremel will smooth that over very nicely. This set of cutters from Amazon are very nice - don't be fooled by the cheap price. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

You do not want to polish the ports. You also don't want to change the shape of the port nor remove significant metal; just smooth out the natural shape. A lot of guys hog out metal thinking they are making positive improvement when in fact they are messing up the factory flow.

[headsbikesmopars]

Best way to get to the short side radius safely WITHOUT carbide cutters is to use emery cloth torn into strips 20" to 24" long, and 1/4" - 3/8" wide . 60 grit will work well. With the head upside down on work bench (no valves) pull the abrasive cloth thru the port with an upper motion on chamber side and a straight pull out on carb side . You can radius the SS really easy and fast this way and safely . You want a nice smooth radius with no ridges or 'corners' , air does not like sharp edges. I always counted the 'pulls' in order to keep aluminum removal equal . JUST FYI .

Terry

[Buffalo Bill]

GSXR head job done winter 2019

I had low compression in one cylinder so I decided to fix that last winter. Cleaned and lapped all the valves, replaced oil seals and replaced some worn valves.
As I had it opened I also did some porting and polishing, it only needed it on the exhaust side, intake side looked perfect.
I will be doing the same work on my 82 GS1100G this winter.


Unshrouded the valve ports too. Drop a valve in there first to protect the seats as your grinding.


Did research on porting before starting.
This video was very useful.

[headsbikesmopars]

Some nice work there. Flushing the guides is 4 CFM and doesn't really effect longevity of valve seat .

[Buffalo Bill]

I found this guys videos recently. His slant head 6 engine build is very informative!
Reducing weight by grinding off overbuilt parts and casting flanges, inside and out. Very good concept goals in describing his work on a very crude engine head.

[Longitudinal]

I have been in automotive performance for about twenty years now, and I do understand the principles of cylinder head porting. However, I limit my porting work to reworking manifolds and leave the head work to the guy I have been trusting for almost twenty years. There are many many more ways to screw up a head than there are to help it, and what looks good to me doesn't necessarily look good to gas molecules moving at 2/3 mach.

The head is now in the hands of my machinist. I have instructed him to do only light port cleanup since I don't want to spend a heap of money to make only a small improvement in power that requires me to u[grade carbs anyway.

[Big Jay]

Most of those old rockerarm heads need guides. Also back then they all had small seat throats. They will really wake up if the seat throats are bored, then the ports blended to them. We have probably done more idf these than anyone else.

[GregT]

Most of those old rockerarm heads need guides. Also back then they all had small seat throats. They will really wake up if the seat throats are bored, then the ports blended to them. We have probably done more idf these than anyone else.

I was recently shown a CNC port mill locally. Imported from the US. We looked through the heads that were already pre-programmed into it and one caught my eye.
It was for the late pro-stock Chrysler hemi heads. Valve angles look very close to the GS 8V heads.
I asked if it had a scaling function on the machine- and the answer was yes.
If I ever do another 8V race GS engine I may well go this route - if the customer can afford it.

[Chuck78]

Most of those old rockerarm heads need guides. Also back then they all had small seat throats. They will really wake up if the seat throats are bored, then the ports blended to them. We have probably done more idf these than anyone else.

Hmmm...this sounds tempting! I'm looking for everything I can have done or do myself to make a GS400/425 big bore engine really scream, yet still not such extensive porting or large cam that it's a race-only high-rpm-only engine... I assume the old 8V engines would have the same type of small seat throat issue, and could benefit from some seat throat boring and porting in this same fashion?