Oooops.........
Oooops.........
Ouch! That don't look good mate.
I've bent one in the past too but that was because when a liner cracked it hydroliced and bent it abit. Didn't realise till 6months later when it came apart again for another rebuild
ooh, good effort
Not exactly sure of the reason but believe poss fueling, piston picked up on liner, liner crank, shells, head, etc all good so lucky escape considering the stree needed to bend a 5 rod, piston destroyed and obviously rod but got some spares, scarily the head gasket was perfectly intact....
snap, I have 2 like this (below). GT rod's are much stronger looking than the spindly F4R's I was chancing, so must have taken some doing
The rod has discoloured rainbow style just below piston
looks like the gudgeon pin caused some heat ? crown looks ok, hard to tell in that picture, which might suggest it wasn't a tuning issue. skirt looks hammered - maybe that's poor lube at the gudgeon ? Or maybe it did run lean and the whole thing's expanded and wiped the bore.
due to low oil pressure also? or just were its run leanOriginally Posted by Scoff
depends how the gudgeon pin was fitted. if the end of the rod was heated up with a blow torch, or was the whole lot put in an oven?
The heat at the small end will be from where they were heated to fit the pistons.
Good info, the rods were heated with a torch to fit pins so that would explain the discolouration.
Not exactly sure how it was caused but i feel i may need a slightly larger piston to bore clearence, if it is a lube issue then its a mystery as the rest are perfect? I do intend to fit an additional oil pressure/temp gauge, anyone got one lying around?
Stu, have you considered an under piston spray system? Bending rods is one thing, but it does look like its picked up at the bottom of the skirt, which may suggest its gone dry. Seen this a lot on 2 stroke pistons, to the point where the piston skirt wears razor sharp. Was it the piston on the gear box side by any chance?
You got it, yes gearbox piston. Although if the piston nips up it will always make a mess
Ok but what are the rings like? Other possibility is the rod hasn't coped with the cylinder pressure, bent and then picked up. I suppose its one of them youll not get to the bottom of.You got it, yes gearbox piston. Although if the piston nips up it will always make a mess
Good point, you could well be right, the rings are good, no probs there apart from a deposit of aluminium from the piston on the second ring. One other thing, the rod has tightened on the pin and it is extremely difficult to twist
IMO its a classic on that cylinder. It seems as when you accelarate the oil surges to the back of the block, and the oil is pulled from that crank cap area firstly, which leaves a pocket under that piston. Not sure what oil pressure your running? If all's well in the oil pressure circuit, have you thought about moving the position of the oil return?
Stu a pic to go with your pm. This is from an aircraft engine where oil surge and wrist pin seizing isn't too good:
Could well be the nitrous doing it too, it tends to do things like this.......
Nope. Never heard about something like that
I have just bent my rod on sunday gone
That is serious damage. Do you mind me asking what that sounded like when it happened?
Well when it happened i was on the motorway .... and lights came on and engine half cut out .... On the hard shoulder when i restarted ... the sound was like someone bangin a hammer on the head non-stop .... infact it was the piston smackin the head ..... also bent 2 pushrods in the process ..... what a day !
ranj the pin looks like its been very hot.....
I think thats cos it been rubbing on the liner .... or is there another reason that the pin could get so hot .... the rings are just melted into the piston and the piston itself has deformed .... like a wavy ring you can see ....
spray bars would help... maybe a better piston to wall clearance would help some what. Can of worms yes... its a balance as you cant go to lose as the piston needs to displace its heat some way aswell.... blah im waffling now....
Not sure what did it .... afrs were spot on .. no problems .... so can only think on timing at moment .... or a air leak somewhere .... its the second piston i have melted in 2 weeks ... been trying to set up my gt28r turbo on my engine .... but as you can see not going well at all .....
What boost were you running to do that?
What boost and timing was you at? did it let go on engine shut down...
ranj, I think the piston has melted first in your case, the rod will have bent up as a result.
Here's another thought - where the pistons fitted properly onto the rods ? before you fitted them into your engine did the pistons fall nicely side to side when held by the rod ? If they were stiff then it might suggest that the pistons had distorted while pressing the pins, or maybe the heat from a tight pin caused the problem.
I think you want standard pistons, they'll cause you much less agro.
Was running 20 psi on a gt28r ......
scoff ... the pistons did move freely but the machine shop wasnt sure if con rod was slightly bent ... but when i put it on crank ... it went straight on ... no probs ....
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