621 replies to this topic

[Pie]

looks like a lego mans hair or helmet lmao

Unlucky mate, but im sure after our discussion on msn earlier, you will see sence and scrap the 1071. Go on, buy them hamsters lol

[alexcrosse]

is the top of the piston still flat? or a lil bend? doesnt look like anything to do with cylinder pressure unless its bent... weird! U do any running in in the end?

Bad luck mate, was a really nice lump.

[Tom Booth]

Unlucky Dan Sounded like a good engine!

On a random note, wheres your hazard switch from dude? A google search brought nothing up

[timbo]

Ball Bags mate! Are you gonna keep the 1071?

I hope this doesn't happen to mine once it's built.

[JetBLICK]

The pistons still flat i think, its got marks on it where its hit the head, but i think thats most likely because of it wobbling in the bore. Bromsgrove engine's said it wasn't to do with high compression due to the fact the top half of the piston is fine. They mentioned that the con-rod stretch could have lead to all the pistions just kissing the head, which would take out the bearings, but i dont think theres any marks tho on the other 3 pistons. Tis definatly weird

The motor was run in on the rollers, then i took it fairly easy for a week or so with occasional moments of ragging the tits off it. Should have been fine, it was due an oil change, previously when i changed the oil inbetween the countless trips to the rollers, nothing showed up... so i'm pretty stumped as to what happened.


The hazard switch was from Auto Electric Supplies


Hope yours goes better timbo, i think this was a freak accident, if i find out what the cause was i'll let you know so you dont make the same mistake. I will be keeping the 1071, but its gonna be a bit different next time, even more speshul, and built to be bomb-proof!

[alexcrosse]

thought so, wouldnt make sense to go there. Get a large bore in there lol

[mini93]

it is a large bore just short stroke!

[Sleepy Stu]

Heh sorry to hear about your engine dude however i think i may have an idea as to your special, bombproof engine

Im sure i have spyed you on another forum enquiring about the same conversion that i am going to be doing to my new engine!!!

[JetBLICK]

Duno about that yet stew it was just an idea i had, but doing that goes against the whole idea of making it bombproof, we'll see tho.

Edited by JetBLICK, 01 April 2008 - 08:29 PM.

[Deathrow]

Sorry to hear this chap, seems like such a waste of hard earned cash now . I hope you have better luck with your next motor.

[mini13]

Hmmm,

It looks to me that those pistons are (were!) of the sloted variety, ie rather than gols being drilled to clear the oil from the bottom ring there is a slot which weakens the piston significantly. These slotted pistons when used with high rpm =BANG!

Well, heres a little update for you.... Its all gone tits up!

I was driving along the other week and the motor started clonking... we pulled over straight away, to cut a long story short i left it on my drive at uni and didnt drive it, then towed it home a few days later. We got the motor out and found this... one knackard piston..




I'll get pictures of them tomorrow but the big end bearings where also destroyed. The crank however looked okay. Turns out it wasnt I went to the engineers today to have it polished and we noticed a great big ridge in the crank... with the big ends being on 60thou, this means its game over.

We dont have a clue what went wrong, it apears that the broken piston had hit the head, which is understandable because it was flapping about without its skirt on. What i dont understand tho is how the big ends are so trashed, but the mains are immaculate. Its evedent from the mains bearings that there was a little oil contamination, but this could just as easily happened after the big ends got trashed. Gutted as i am, theres sod all i can do about it now anyway, the crank is effectively scrap.

6 weeks it lasted... it was an awesome 6 weeks, but im dissapointed after taking so much effort to make sure it was all correct, that it let go so soon.

Never-the-less, i have a backup plan and the 1071 will be back one day, stronger than ever before

[mini93]

could be right! so if so conclusive evedence that slots are a bad idea rather than just hear-say

[retroracer1380]

could be right! so if so conclusive evedence that slots are a bad idea rather than just hear-say

The reason why the piston has broken is from hitting the cylinder head nothing to do with the slots, there is bad markings on the crown to show this il have to do sum pics for dan as i currently have his trophy lol!

[mini13]

Sounds a it chicken and egg,

Why has the piston hit the head?????

I'd bet because the piston has broken ad then been able to hit the head.

[JetBLICK]

Tis a bit chicken and egg, its hard to figure out what went first really. I wouldnt say slots are necessarily bad, they are perfectly fine in many peoples motors, and these pistons where given a hard time. I was warned that long periods above 8/8500rpm was their limmit, and occasionally i did go above that, but never for an extended period, only really went over 8k in first.

Need to see the other pistons to determine whether they where all hitting the head, which would explain why it happened - which so far is the most reasonable explanation. The engineers said that every 1000rpm accounts for 3thou conrod stretch. If you work this out at 9000rpm max...

9x3=27 + the 12thou my pistons sit above the block face = 39thou

And i believe that the compressed thickness of a head gasket is around 33thou? if it is, then its plain to see what happened.

Whats not plain to see tho, is how this motor ever ran with its previous owner. It would have been interesting actually to see what it was like if i'd have just left it alone and plonked it all straight on a gearbox and took it for a drive. From what i've learned so far... it shouldnt have worked