Stock piston question

[434nova]

How far in the hole are the stock pistons on a 109 motor? 10 thousands , 20, thousands? Also what is the stock deck height on a 109? Thanks

 

[earlbrown]

The one's I've measured hovered around .055" in the hole. Add another .025" for a 14 bolt block.

Deck height typically measures around 9.522 but it varies block to block (and all four corners sometimes)

 

[434nova]

Why are they so deep in the hole from the factory? Wouldnt that kill the quench of the motor? Or is bot that important on a turbo motor.

 

[No disintegrations]

They did it to lower the compression ratio. The old way of thinking and 250 HP was enough anyway for the time.

 

[earlbrown]

Because the architecture is based on a plain ole POS V6. That's why I ended up decking the crap out of my 4.1 (then having to design forged pistons that can just be moved up in the bore.)

There's no quench distance when you start off that far down. One you go past .060" all the benefits are long gone. Plus the stock heads have VERY little quench pad sticking into the bore. With a 4.1, it helps a little with the extra .100ish" of radius moving the bore out.

 

[GNVAIR]

I had JE do a custom set for mine. I have them at 0 deck. I am using head gasket thickness to set the deck clearance. I measured the combustion chamber CC's and adjusted the dish volume to arrive at the compression ratio I was shooting for.

 

[Ernie GN]

I had JE do a custom set for mine. I have them at 0 deck. I am using head gasket thickness to set the deck clearance. I measured the combustion chamber CC's and adjusted the dish volume to arrive at the compression ratio I was shooting for.

Roughly how much is a set of custom pistons?

 

[GNVAIR]

I seem to remember it was $700. I got them through my machinist so I can't remember the exact amount.

 

[Ernie GN]

I seem to remember it was $700. I got them through my machinist so I can't remember the exact amount.

How long ago was it

Thanks in advance

 

[Turbo6inKY]

Roughly how much is a set of custom pistons?

My custom Carillos came out at just under a grand once the wrist pins, rings, and spirolocks were added in. And that was last month. And I got a hefty Xmas discount.

These engines are getting stupid expensive to rebuild.

 

[GNVAIR]

Early this past fall. That was with the wrist pins and locks. No rings.

 

[Ernie GN]

My custom Carillos came out at just under a grand once the wrist pins, rings, and spirolocks were added in. And that was last month. And I got a hefty Xmas discount.

These engines are getting stupid expensive to rebuild.

Dam, I could possibly have to order a set to.
There goes my beer $ haha

I have hopefully one more question.
I still need to call gn1 and find out but maybe you know something.
So those rotating assembly kits they sell with crankshaft, rods, pistons and rings.
Do They let you choose the piston compression Height and piston dome cc?

Or do you have to adjust your compression ratio using the gasket?

I imagine not everybody has exactly the same deck height and cc in the heads

 

[turbo89]

They did it to lower the compression ratio. The old way of thinking and 250 HP was enough anyway for the time.

This X 2 ... factory could care less about leaving a bit on the table

 

[~JM~]

Because the architecture is based on a plain ole POS V6....

Wasn't it originally a V-8 with the front two cylinders lopped off?

 

[Turbo6inKY]

Wasn't it originally a V-8 with the front two cylinders lopped off?

No, the V6 was its own design. Buick repurposed the front cover for both engines, but the V6 is not a the Buick V8 with two cylinders lopped out.

 

[~JM~]

No, the V6 was its own design. Buick repurposed the front cover for both engines, but the V6 is not a the Buick V8 with two cylinders lopped out.

Think they used the aluminum block 215 V-8

 

[Ernie GN]

Wasn't it originally a V-8 with the front two cylinders lopped off?

I know Chevy did that with the v6 4.3 engine.
It’s a v8 5.7 cut down

 

[GNVAIR]

The original Buick 198 cubic inch V6 that was introduced in 1962 (of which all of the rear drive Buick V6 engines come from) was a derivative of the all aluminum 215 V8. The original V6 was an odd fire design with opposing cylinders having their connecting rods sharing the same crank pin. Buick replacing the 215 with the iron 300 cubic inch V8 which also shared the same architecture.
Buick updated the V6 engine many times over the years. Starting in 1977 they designed an even fire crankshaft for it but kept the same off center bore spacing as the odd fire engines.
So technically the rear drive V6 and the Buick small V8 family are related and the original odd fire V6 was a V8 minus 2 cylinders but did have its own unique bore and stroke.

 

[~JM~]

I had a 225 Dauntless in my '68 CJ-5.

It was a great combination!

 

[bison]

They are approximately .060” in. I measured one out years ago and it was like 7.999:1 CR. Someone else could have measured 8.0001. I’d be curious to see what happens if you simply run a flat top with a lower compression height at the same CR. My guess is that very little would change the way most are running them.


Sent from my iPhone using Tapatalk