i need input on installing index pins into an unpinned piston

[David Luciani]

this question is for the serious engine builder.

i'm re-porting two mc10's i have that were stroked and gully ported back in the day.
they both have decent stroker pistons and the bores are very re-uable as is.

the problem is neither piston was ever pinned even though they were nicely open ported on the 6 transfer ports and the exhaust ports are opened and slightly raised.
i'm kinda surprised they didn't hang a ring like that but they were runners.


my plan was to nine port them but i found both had been gully ported already.

  i prefer nine porting as opposed to making a huge triangle sort of transfer port but i'm working with what i have in hand..


anyway i definitely don't want to run unpinned rings now and would prefer to use the pistons i have already.
i've read how to do pinning before but for the life of me i can't remember where i saw the article.
so either a how to or direction towards a how to install ring indexing pins would be awesome.


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[ted johnson]

We always used plain phonograph needles. Drill in from the side and tap the pin in so it's flush to .010 below the piston wall. You can also come down thru the crown, tap the pin about .06 below the crown and then gently peen the aluminum over the pin to ensure it can never come out. A little red Loctite on the pin can't hurt. Pop and I did dozens of pistons both ways in the old days. You can buy all the plain Victrola needles you want from Amazon. Ted

[David Luciani]

thank you ted!
next question.
is there a better place to pin than the typical positions found on the newer mc91 pistons?
i've made a triangular shaped 7 and 8th port on the first engine block that's wider than i'd like but i am working over old work and had no option.

the second question is has anyone every added exhaust bridge lubrication holes to a mcculloch piston?
that when you add two tiny holes in the piston where it passes over the exhaust bridge to aid cooling an overly thin bridge.
if i was to do this mod i'd need to add four holes total to cool the two bridges..
heres the article i read for the info
wisco piston piston modification link

[url=http://blog.wiseco.com/two-stroke-how-to-relieving-the-exhaust-bridge-and-drilling-lubrication-holes][/url]

[Terry Sullivan]

I'll pretend I am a serious engine builder.

- Do you really need to pin the rings?
I always chamfer the inside of the ports a bit to keep the rings from hanging.
If the Gulley port was done correctly, the rings will not come down that far.
You could do one finger port in the center to get some benefit.

Get that stroker running for next TBO.
Mine melted a plug, so I was sidelined and didn't get to run against Scott.
NEXT YEAR!

t

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[David Luciani]

Terry,
you and me both on the pretending!
the gully ports were done very nicely.
on one i could've just added two small holes above the gully porting to get a slightly better fuel transfer.
at first that was exactly what i did.

going back to the second motor i realized there was no reasonable way to copy that porting in the second motor.
so it was a matter of either matching the big port job i'l need to do on #2 motor or running miss matched motors.

#1 motor is already a full size smaller on the bore sizing so i felt that wasn't an option.
plus i saw how scotts motor ran and i seem to remember he converted a gully port to a full port using triangle sorta shape.

not sure if i'm ok with just chamfering.
though i do try to chamfer the edge on all the ports in any motor i'm grinding on .
if it turns out that a ring hangs it'll make a huge mess in the motor if it doesn't ruin it.

right now chamfering is a real pain to do but i am working out how to afford a new toy that will make it easier.
this is my next big purchase
90 degree nsk attachment
kinda pricey but my whole set up cost alot.
if i didn't already have the nsk hand piece would go with the foredom attachment as that's alot cheaper overall.
but just the nsk asttachment is about the same money or slightly less than buying a 90 degree foredom attachment. using the foredom tool  in general imho  is alot clunkier too.


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[ted johnson]

I will not run any engine with flat top ports without pinning. Side pinning has the advantage of allowing end gaps to not be one above the other. Give the rings an end gap of .015 to .020 larger than the diameter of the phono needle. A VERY slight chamfer is good; too much can screw up port timing. These comments mostly apply to engines with rings .030 thick or thinner. We didn't usually pin rings on engines with thick rings, but it still isn't a bad idea to pin 'tm anyhow. TJ

[Sterling Brundick]

This is a great technical thread but it sure would be wonderful if someone could post pictures or drawings of exactly what you are talking about.  Installing phonograph needles into a piston is something I'd like to see.  And "Gulley" porting too.

[ted johnson]

Sterling, here's a pic of one of my 610 pistons with the ring pin coming down from the crown. Sorry I don't have any showing the little pins coming into the ring groove from the side. Ted

[David Luciani]

i'll get pix going later this week.
#2 motor is just got dycum blue and my story scratch in it so maybe i'll try to do blow by blow on the port mods.
the gully ports are still as found.
scott k. did a thread about ports ages ago but it's in the static copy of the forum.
maybe if scott still has info and pix he'll post them.

[Mike Berg]

Terry,
you and me both on the pretending!
the gully ports were done very nicely.
on one i could've just added two small holes above the gully porting to get a slightly better fuel transfer.
at first that was exactly what i did.

going back to the second motor i realized there was no reasonable way to copy that porting in the second motor.
so it was a matter of either matching the big port job i'l need to do on #2 motor or running miss matched motors.

#1 motor is already a full size smaller on the bore sizing so i felt that wasn't an option.
plus i saw how scotts motor ran and i seem to remember he converted a gully port to a full port using triangle sorta shape.

not sure if i'm ok with just chamfering.
though i do try to chamfer the edge on all the ports in any motor i'm grinding on .
if it turns out that a ring hangs it'll make a huge mess in the motor if it doesn't ruin it.

right now chamfering is a real pain to do but i am working out how to afford a new toy that will make it easier.
this is my next big purchase
90 degree nsk attachment
kinda pricey but my whole set up cost alot.
if i didn't already have the nsk hand piece would go with the foredom attachment as that's alot cheaper overall.
but just the nsk asttachment is about the same money or slightly less than buying a 90 degree foredom attachment. using the foredom tool  in general imho  is alot clunkier too.

 Hi Dave,
I have never installed piston ring pins myself but my  experience in a machine shop tells me it is not a drill press job, too much drill run out enlarging hole size.  Here is how I think it might be done:
drill hole in milling machine part rigidly secure in vise drill undersize maybe .015" in diameter
then using mill ( do not move part in vise ) run a sizer 2 flute end mill type tool Ground to size .010" undersize
this will straighten hole and make it round
lastly, ream hole to size must be press fit for pin, I think pin should be maybe .005" press fit ( maybe heat piston to ease installation )
I have ported a LOT of Mc's and Komets, gulley porting? sounds techy but I don't think it is, best to keep as close to stock shape as possible, but you can raise ports and semi square the inside corners on transfers and square the tops of boost ports ( squared ports MUST have radiused corners ABSOLUTELY NO SHARP CORNERS ).  There is port tool shop in  USA I will try and find it and let you know.

---

this question is for the serious engine builder.

i'm re-porting two mc10's i have that were stroked and gully ported back in the day.
they both have decent stroker pistons and the bores are very re-uable as is.

the problem is neither piston was ever pinned even though they were nicely open ported on the 6 transfer ports and the exhaust ports are opened and slightly raised.
i'm kinda surprised they didn't hang a ring like that but they were runners.


my plan was to nine port them but i found both had been gully ported already.

  i prefer nine porting as opposed to making a huge triangle sort of transfer port but i'm working with what i have in hand..


anyway i definitely don't want to run unpinned rings now and would prefer to use the pistons i have already.
i've read how to do pinning before but for the life of me i can't remember where i saw the article.
so either a how to or direction towards a how to install ring indexing pins would be awesome.


Hi Dave,
The port tool company is CC specialty they have a nice selection of porting tools, as far as cutters go I always buy carbide cutters with diamond cut, I also use the cheap chinese rotary tools with the remote extension but only for the small 1/8" diameter cutters.
Good Luck
Mike
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