Piston identification

[gsryder]

Okay so I bought a 81 1100 that was rebuilt and parked approx. 12-15 years ago. The PO was not one hundred percent sure but thought that it had a Yosh 1148 kit installed. So I did a little checking and called Yosh R&D in Cali. the casting marks appear to match what they said but that was all the info they could provide, just identifying that they were Yosh pistons.
I need to see if any one can identify them a little better I need to know what compression these are supposed to be for so I can adjust accordingly for a future turbo application.
Also the bore measure 2.905" which if I converted that correctly gets me 73.79mm??? right??? is that the size bore for a 1148???

At the end of the day I need my compression to be as close to 8:1 as I can get. How can I figure my base gasket thickness to achieve this with the info at hand. By the way all else is stock.

Here are some pics

Any help would be greatly appreciated.

 

[Steve]

When you start adding thickness to your gasket, be sure you also install slotted cam sprockets.

Changing the distance from the crank to the cams will affect the cam timing and you will need to correct for that.
You will probably want to optimize your cam timing for pressurized aspiration, anyway.

Yes, there is nothing like horsepressure.

.

 

[gsryder]

Steve could you elaborate a little on the slotted cam sprockets.
I have not heard of this yet??

 

[SqDancerLynn1]

Their are two bolts for the gear that bolts to the cam. If you elongate/slot the bolt holes, it allows you to change the cam timing To ?? 106deg or ???
depends on your intended purpose for the motor. Turbo ?

 

[Nessism]

Those pistons look to be in the 10.5:1 range based on the valve pocket depth.

 

[gsryder]

Does anyone know if the old Yosh pistons were cast or forged?

 

[TeamDar]

That piston is cast. I believe that most if not all yosh pistons of that era were cast.

 

[Steve]

Steve could you elaborate a little on the slotted cam sprockets.
I have not heard of this yet??

SqDancerLynn1 said it about as well as I can:

Their are two bolts for the gear that bolts to the cam. If you elongate/slot the bolt holes, it allows you to change the cam timing ...

Since the cam chain is a rather fixed length, moving the cylinders and head away from the crank with thicker gaskets will rotate the cams a bit, advancing the timing. There are two holes in each sprocket, through which bolts pass to hold them to the cams. By slotting those holes, the relationship of the sprocket on the cam can be adjusted. Also keep in mind that pressurized intake will require different valve timing, so please do your homework.

.

 

[Guest]

I have an extra set if slotted cam sprockets.
Those look like 10/25-1 pistons with the flat center.
The 1075 (stock) have 72mm pistons and the 1166 are 75 so that sounds about right for a 1148.

 

[gs road racer]

You'd be best getting a stock barrel and pistons for your turbo...not enough base gaskets to get that down to 8 to 1. That will cause all sorts of other problems with oil leaks and keeping a bunch of gaskets together where there should be just one. Sell that barrel and pistons, can yosh supply rings for it?

Randy

 

[posplayr]

Steve could you elaborate a little on the slotted cam sprockets.
I have not heard of this yet??

When you try to degree your cams you will figure it out

 

[Guest]

I missed the turbo part
Get turbo pistons

 

[blowerbike]

run it a little below zero deck height to .020 using a copper base gasket.
there are no rules stating that you have to run 8.1 for a turbo application.
i ran an 1168 flat top@ zero deck height.
just around 18PSI and it rock and rolled and lived.
be greedy with the timing and cheap gas and higher boost levels and you'll have a pile of molten crap to take pictures of.
copper head gasket is a maybe depending on boost levels.
o-ringing the top of the liners if you push it.
welded crank of course.
back cut tranny...everybody knows why.
HD cyl. studs is a must.
main studs keeps your cases from pushing apart.
HD backing plate and keep a check on it or straight cut primary's.
i could spend 6 months of your pay...well maybe 3

FYI
if your not familiar with slotted cam sprockets and lobe centers..
do a lot of reading before bolting on instant HP.
you will save a lot cash and headaches.

 

[Guest]

Did you run the oil through the cylinders or block them off and use overhead oiler?
Seems the oil will find a way out with a turbo.

 

[blowerbike]

Did you run the oil through the cylinders or block them off and use overhead oiler?
Seems the oil will find a way out with a turbo.

i have never used a top end oiler.
lil seep.
lil weep.
kept my leather's shiny