350 Cylinder Differences

[steve]

I recently had my 350 cylinders replated, but when they were returned to me, the company who did the work advised that the LH bore was full of tiny pin holes due to the casting being very poor. An opportunity then came up to buy a pair of used cylinders which I took and I thought it would be a good idea to replate the dodgy LH one and use that instead. I was boxing them up to post and for no good reason decided to do a comparison with the original and noticed that there are a number of differences. Take a look at the pictures...

Original re-plated cylinder on the left, replacement on the right - notice on the 4th fin down the 2no cut-outs...


No tubing between the fins...


No holes in the top...


The shaping of the fins is different between the two...


A close up showing the diferent shape of the fins...


I don't have my cylinder heads at the moment, so I can't check to see how they would sit on the replacement cylinders, but the fact that the shape is slightly different, leads me to believe they wouldn't look right.
So, does anyone have any idea what year 350 these cylinders would have come from? I've looked at a good few pictures, but can only see cylinders that are the same as my originals.

Thanks, Steve

[steve]

Not sure why, but the first picture didn't show, so here it is again....

[Bikenstein]

Steve, this subject has been brought up before. I was inclined to think the early cylinders were like yours with the later ones beefed up around the exhaust ports and havin cutouts. One member has said he has cutout cylinders on both his early and late model GTR's. It could still be that those early ones of his have been replaced. If not, I would think, especially because of the difference in the fin shapes that Bridgestone used two different suppliers. I have sets of each with heads so I'll check them tomorrow. I know my 67 number 108 has the cylinders like your original. Maybe someone else can add to this.

[paul]

Which set makes more HORSEPOWER?

[old smokey]

Steve, what interesting timing. I just got my cylinders back from Millenium after being replated.
Price out the door - $551 including state sales tax.
Happy - yes!
Here is the outside of the left cylinder. My left cylinder more closely resembles your reworked one.
Mine has a "O" cast into the base as seen compared to yours where there is no marking.
Mine does not have holes on the top, nor the supporting column between fins.

[old smokey]

Steve,
The instructions which came back from Millenium also talk about porosity in the cylinder bores.
I should scan it, but I'll type what it says....

" You may notice small holes on the surface of your NSC coating. These holes are referred to as porosity. Simply put, porosity is nothing more than gas trapped in the cylinder during the casting process. In the O.E. finishing process these areas of porosity are often masked by the smearing tendencies of aluminum. In other words, it hides the holes by spreading over them. During our re-plating process your cylinder is subjected to various chemicals that remove the thinly smeared aluminum, exposing some air bubbles. When kept at acceptable levels porosity will NOT harm the performance or longevity of your engine but will instead improve the lubrication of your cylinder walls. The NSC coating will not flake or peel, nor will the piston ring wear abnormally at the point of porosity. In our pursuit of both cosmetic and functional perfection in NSC caotings, every step necessary is taken to keep porosity at a minimum. In short, porosity is a cosmetic problem only and will not affect the performance of your motor. Even with porosity, your cylinder is covered under our lifetime warranty against defects in materials and workmanship."

The next photo is an attempt to show some of the porosity I see in my cylinders after replating. Near the top of the photo they are shiny in the photo, lower down they appear as dark specks. So it sounds like you don't necessarily need to find "better" cylinders.

[Bikenstein]

That's very interesting about the poor casting and porosity. I wonder if this is a quality of the older cylinders only. I think your bike is a 67 Smokey, if I recall correctly. I'm sure others who've used Millinium would know more.

[steve]

Appreciate your replies...thanks!
Very interesting to hear what Millenium have said, a couple of others I have spoken to have said similar things too, so I will use both the cylinders I've had replated and see how we go.

Would still be interested to know though how early those two replacement cylinders are...

Steve

[rocketman]

 When rights to the small singles designs were sold and manufacturing began in Taiwan, I wonder if other select parts like cylinders etc may have also been produced there to complete remaining units, possibly at Rockford Motors, or for spares? Just a thought.  Thanks, Mark. 

[moonpup]

Both sets of cylinders on my gold & chrome GTO's have the cut outs and I believe them to be original to the bikes. That would put that cylinder design as early as 1969/70.

[paul]

Sometimes in a manufacturing plant, part are "misplaced", then found and used. So a later complete machine might have earlier parts.

[steve]

Both sets of cylinders on my gold & chrome GTO's have the cut outs and I believe them to be original to the bikes. That would put that cylinder design as early as 1969/70.

Interesting what you said there Moonpup, I would have put the 'cut-out' cylinders as much earlier, I only say that because they don't have the rods between the fins, which I thought would have been a later edition (only guessing here though!). My GTR engine no is 3900 odd with the non cut out fins. I would have thought there would be a batch of bikes with the cut-out type and hoped that someone here would be able to pin point more accurately.

Steve

[moonpup]

Steve, my understanding of the cylinder progression goes something like this.....(from first to last)

1. Had rods and less than beefy exhaust flange
2. Had rods with improved exhaust flange
3. No rods and has cut outs.

When these changes occurred is still open for discussion, as I have absolutely no proof that the order in which I just put them in is the correct one. 

[OldSwartout]

My 350, s/n 4640, has configuration #2 (noise damping rods, beefier exhaust flange, no cutouts).  BTW, those cutouts are for ejection pins in the die, used to hydraulically push the casting out.  The 200 cylinders also have them, the 175's don't.  My guess is that the difference was because of a different supplier making the parts.

[Bikenstein]

Steve, my understanding of the cylinder progression goes something like this.....(from first to last)

1. Had rods and less than beefy exhaust flange
2. Had rods with improved exhaust flange
3. No rods and has cut outs.

When these changes occurred is still open for discussion, as I have absolutely no proof that the order in which I just put them in is the correct one.  

My bike is number 00108, so it more than likely has the first cylinder type. The photo is of the left cylinder which I believe to be original and it not only has the weaker flange and pins, but also has the injection pin cutouts.    

[moonpup]

Well...that sure clears things up      MY head hurts now. 

[Bikenstein]

Sorry bout that Moonpup, pero otra cosita, my right cylinder is a beefed up no pin no cutout one. So since it apparently was replaced at some time, the left one could possibly be a replacement, tambien!    Hope the dentist gave you somethin for pain

[moonpup]

Sorry bout that Moonpup, pero otra cosita, my right cylinder is a beefed up no pin no cutout one. So since it apparently was replaced at some time, the left one could possibly be a replacement, tambien!    Hope the dentist gave you somethin for pain

That sounds like the one old smokey posted a picture of. That makes 5 different configurations as of now.  

(In no particular order)

1. Has rods/weaker exhaust flange/has cutouts
2. Has rods/weaker exhaust flange/no cutouts
3. Has rods/improved exhaust flange/no cutouts
4. No rods/improved exhaust flange/no cutouts
5. No rods/improved exhaust flange/has cutouts.



p.s. no pain, just a good cleaning.

[Bikenstein]

Steve, your guess is as good as mine or anyone elses at this point. I thought I could at least clear up "what came first" until I found I have 2 different cylinders on my 67. Very interesting find though.

[old smokey]

Since both sides on my GTR crankshaft has marks of being disassembled, there's a fair chance both  cylinders could be replacements. Unless a '67 model cylinders were made with having no pins, no cut-outs, and reinforced exhaust flanges.
I'll attach a photo of the right cylinder casting marks. Earlier I posted a picture of the left cylinder having a large "0" cast in at the base. On the right cylinder, there is a small "M" that is stamped into the base of the cylinder.