Piston ring gaps

[worked ssv]

G'day legends
Was just curious I'm fitting new rings to the pistons in my 304 and was curious on the measurments required I've got 3 different measurments, first
The instructions that come with the rings
And second a workshop manual after looking at the how to in the manual it have me the specs required then on the next page the exact same thing but different measurments at first I though it may have been from 1 ring to the next but it's not then I looked back through the instructions that come
With the rings and they're different measurments again I'm confused as hell
If someone could give me the correct measurments would be much appreciate I'm running a 276 cam with flat top pistons cheers guys

 

[EYY]

Just refer to the instructions that came with the rings...

 

[worked ssv]

Yeah that's what I was thinking mate I'm just thinking the workshop manual would be the go but then again that may be based on a fresh motor, my 304 is 30 thou over could this change the measurements?

 

[383 hatch]

General rule of thumb for a street engine is .004" ring gap per inch of bore size. So .016" for 4" bore.

 

[EYY]

Yeah that's what I was thinking mate I'm just thinking the workshop manual would be the go but then again that may be based on a fresh motor, my 304 is 30 thou over could this change the measurements?

No, as long as your rings are .030 over too. Check the rings at the top, middle and bottom of bore to ensure that the bore doesn't have too much taper. Usually if the engine wasn't smoking heaps etc, you can get away with just rings. If you're not getting it bored, run it in really gently. Don't load it up too much like a lot of people suggest.

 

[worked ssv]

Thanks for the advice guys
383 hatch, question mate so all the ring gaps are the same? I noticed by the book ring 1 and 2 are different measurements cheers bud

 

[Wombles]

I think it depends on ring design. Or what the motor is made for.
rings I had for my L67 build gave me 4 different measurements. Think it was strip track and fuel. Top was smaller to middle I think.

 

[383 hatch]

I normally set them both at the same gap (depending on what the motor will be doing), unless the piston manufacturer says otherwise. Some piston manufacturers recommend a bigger gap for the top ring than normal to stop the ring butting together and lifting the crown off the piston. That's normally for hypereutectic or forged pistons though. Standard cast pistons, just set them both at .016". If anything, you could set the top ring a couple of thou bigger than .016" and not cause any dramas. Atleast then you know the rings won't butt together.

 

[EYY]

Some ring kits have one cast and one moly compression ring. That might be why there are different specs?

 

[Decicrate]

Stick with the measurements supplied with the ring set. Also make sure that you do not mix up the 1st and second rings.