Piston ring gaps with woosner

[ben_p]

Hi got my pistons the other day in STD size (82.7mm) the rings are 83.0mm.

How do you shorten a ring by 0.3mm? Machine shop?

Also what size should the ring gap be? I take it you fit the ring and piston into the liner then use a tiny feela (sp) guage to measure to gap between the two ends?

For all 5?

I know they have to be set at differnt angles when installed ( I have the order of these on a manual)

 

[stan*]

Its Wossner, not woosner!!!!

You use a piston ring filer, and feeler gauge. You need to install them to determine the ammount removed, 83mm is the diameter, not the circumference.

One of the most satisfying jobs when building an engine.

Takes alot (ALOT) of practice to do it right. This area is make or break when trying to optimise for power making. Make sure the ends are square and burr free.

As for gaps, the general rule of thumb is 0.004" per inch of bore for the compression ring, and 0.005" per inch of bore for the second ring.

 

[mas]

What's 82.7 in inches, what ring gap for compression rings 1 and 2? Ben

 

[BenR]

long and short is......dont do it yourself ben lol.

Its not hard at all, but really isnt something you'll want to bother with.

 

[ben_p]

ok, cool, phew even lol

Will the machine shop set them for me?

 

[BenR]

They should do.

 

[stan*]

I'd be suprised if they would to be honest. Worth asking though.

As for it not being hard, thats relative, it would be very hard for a first timer to get them right.

 

[ben_p]

I'm taking the whole block to the guy to do all the clearences etc, I'm thinking of using him just just build the whole BE! Im struggling for space, lack of experience with BEs and he owes me a favor so it wont be expensive!

If he builds Aston Martin engines i'm sure he will manage my crappy renault one. lol.

 

[ben_p]

FARk 423 wont run with the pistons, there 0.5mm more lift at tdc! 422 it is!

 

[stan*]

You will have more clearance around tdc with the high comp pistons...

On an F7R its about 8mm with high comps, and about 3-3.5mm with standard!

Are you sure you wont have enough clearance..

Besides, you could just back the timing off slightly.

 

[BenR]

How do you know?

L@TDC is not an indicator of piston/valve clearance. The 25 deg before and after tdc is where you'll most likely clip a valve, but if you dont measure, you wont know.

 

[ben_p]

Matt at QEP said the 422s are just just off hitting. So 0.5mm will clip the pistons with the 30 deg before and after TDC.

I cant mill the Wossners i dont think! (well it seems like too much work and cost)

My s**tty postman pat ruler will on measure mm's! So i cant measure it!

I dont want it to be too peaky too! Farking joke this engine building shizzle. Even selling houses is more fun!

 

[Fred@BTM]

you're just plucking s**t out of thin air here ben, make a decision!

 

[BenR]

Its not a linear 0.5mm fore and aft tdc, it could well mash then to f**k.

However, without measuring on your actual pistons, I'd find it hard or near impossible to give advice on such tolerance issues over the net.

If you dont measure, you dont know.

This whole idea of you (especially you) 'slinging' an engine together is going to end in tears. I havent seen you measure one thing yet! lol

 

[ben_p]

meh, measuring is for gays! stabbing in the dark ftw!

the machine shop is doing all that shizzle. Im just buying s**t (the fun bit) Other people have used 422s with woosners and it worked! Just no one has used 423s!

 

[ben_p]

you're just plucking s**t out of thin air here ben, make a decision!

LOL rephrase that to.

You're just assessing you options, I like that in you! do your due diligence before you order!

 

[stan*]

How do you know?

L@TDC is not an indicator of piston/valve clearance. The 25 deg before and after tdc is where you'll most likely clip a valve, but if you dont measure, you wont know.

I never said it was, what I said was from experience, with forged pistons, you have about 8mm of clearance at TDC.

Also based on experience is that fact that whilst lift accln is high around tdc, on the cams he is talking about i dont think its anywhere near enough to cause issues around tdc.

yes, you are right the only way to know for sure is to measure...hence why i said ^^^ as a guidline.

 

[broster@JAM-Sport]

ben, you need to get the engine dummy built up then check for clearances, then look at machining the pistons if need be to suit the cams, then cc it again to check the static compression.

building a decent power engine is alot more involved than people think.

 

[BenR]

I never said it was, what I said was from experience, with forged pistons, you have about 8mm of clearance at TDC.

Also based on experience is that fact that whilst lift accln is high around tdc, on the cams he is talking about i dont think its anywhere near enough to cause issues around tdc.

yes, you are right the only way to know for sure is to measure...hence why i said ^^^ as a guidline.

Not you ya twonk!

BEN!

 

[stan*]

LMAO!!

 

[MATT BLACK]

Ben.........the best thing you can do to shorten your ring is stop getting bummed of blokes.

Remember what happened last time - go 1.8T my son