23 replies to this topic

[haz]

why would a piston skirt have a slit in it?!

sproket pointed it out that my spitfire pistons have a rather large slit in the skirt in a topic entitled 'deck height' in technical problems section... pictures are in there

taa

[alexcrosse]

on about the holes going through? mmmm all i can think of is cooling, more surface for the oil to get to :S or production reasons? manufacture wise...

dishing out some ideas into the open lol.

[haz]

hmmm i dunno... perhaps something to do with production, although they have been machined to a uniform and deliberate shape

if i knew how to grab a picture out of things iv already uploaded i would

[alexcrosse]

[haz]

[alexcrosse]

apon my research its for oil drainback expansion control.

http://pages.prodigy...kie/index5.html

Kinda an oil circulation technique. And that makes them weaker thing is just his 'oppinion'. I think hepolite would have done their own research LOL!

hope it helps.

Edited by alexcrosse, 26 March 2008 - 11:03 PM.

[haz]

nicely found... i notice he did write something about them weakening the piston

i spose its swings and roundabouts at the end of the day

[mini93]

alex, your always on about people reading the yellow book

holes, slots what ever are for oil drain back to the engine from what has been scraped off by the oil control ring.

slots are easier to machine than holes in sevral locations around the circumfrance, with this tho its making a single point weaker than the surounding area.

with holes there spaces out in a way that gives good strength to the piston

some skirts actualy have a slit right the way to the bottom of the skirt...definaly strange IMO and i believe most other people agree with me on that, slight movment over time in the skirt can cause fatigue failure leading to a piston which has no skirt...and guess where it has ended up

[Sprocket]

The bigest problem with those pistons is that there is little holding the skirt to the crown due to the oil drain slots. They may well be fine in an engine that wont see much above 6k rpm occassionaly, but are some what prone to failure used above this. Fine for a standard production engine, workable in a high performance engine, but for how long?

[alexcrosse]

alex, your always on about people reading the yellow book

lmao, what? i barely ever mention vizzards book, unless im talkin about his grammer, lol. Its really hard to read from where im sat too! since its 150 miles away in sheffiedl so i had to go internet trawling, not sure what ur gettin on at but... hey.

Edited by alexcrosse, 27 March 2008 - 12:05 AM.

[mini93]

i just remember you saying previously (altho not all the time) some of the stuff in the book...anyway, thats not whats in question here

[alexcrosse]

i just remember you saying previously (altho not all the time) some of the stuff in the book...anyway, thats not whats in question here

indeed it isnt mr david, lol. Nah, i am one of the few who doesnt appretiate vizzards book for future reference lol.

[Dan]

It's BigAdam who loves the yellow book.

[haz]

The bigest problem with those pistons is that there is little holding the skirt to the crown due to the oil drain slots. They may well be fine in an engine that wont see much above 6k rpm occassionaly, but are some what prone to failure used above this. Fine for a standard production engine, workable in a high performance engine, but for how long?

These are going into a fairly high spec 1380, CA4 road/rally cam using 1:3:1 roller rockers, 'stage 4' MED head, S-rods, ultralight fly, heavy duty clutch with grey diaphram, wedged X-drilled and nitrided crank, steel centre main, straight cut box... hoping for 90-100bhp at the flywheel

i was told they wouldnt rev too well by a few experienced people, but they also said they're a reliable piston.. u think they wont last?

this is going to be a road going car... so it will from time to time see some revs, but i'll not be screwing the nuts off it every second its running, far from it!

[alexcrosse]

just wondering... but why did you buy these pistons n not go for omega or AE's?