Nickp
|
| posted on 11/11/13 at 04:38 PM |
|
|
Big end bore measurements?
Rather than paying upto £800 for a set of forged rods for my Monte I've took a punt on some much cheaper H-beam rods from China.
Nooooooooooooooo, I hear you say!!  Well I have anyway.
Instead of just slapping them in and hoping for the best I thought I'd check them using a mates bore gauge. They all seem
'consistent' and are all out of round by 0.02mm, is this acceptable? The Fiat / Lancia spec for the big end bore diameter is 53.89 to
53.91 so ideally they should be 53.90mm. With the 0.02mm out of round each rod measures 53.91 to 53.93, measured at 3 different angles within the
bore. So, is this a pretty good effort by our Oriental cousins or are they a disaster waiting to destroy my newly built engine?
Cheers,
Nick
|
|
|
|
|
snapper
|
| posted on 11/11/13 at 08:15 PM |
|
|
These are best measured with plastiguage on a dummy build as they could true up under torque
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
|
|
|
Nickp
|
| posted on 11/11/13 at 08:49 PM |
|
|
quote:
Originally posted by snapper
These are best measured with plastiguage on a dummy build as they could true up under torque
This is true. I only had them at about half torque as I couldn't clamp them very well in the vice (with cardboard). The straight up measurement
(in line with the rod) was the best one at 53.91mm. The others at about 45deg either way were the ones that were off by 0.02mm.
|
|
|
snapper
|
| posted on 12/11/13 at 07:03 AM |
|
|
Did you fit bearings?
These are also a crush fit and will be marginally bigger than the big end
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
|
|
|
Nickp
|
| posted on 12/11/13 at 07:47 AM |
|
|
quote:
Originally posted by snapper
Did you fit bearings?
These are also a crush fit and will be marginally bigger than the big end
I did trial fit a new pair of bearings and they appear to sit fine. I'm thinking they'll be fine but I had to check as the Chinese
aren't renowned for their QA are they?
|
|
|
dexion7
|
| posted on 12/11/13 at 10:03 PM |
|
|
the big end bore without the shells fitted should be perfect if the rod bolts are torqued (or stretch tested). that is not very good accuracy IMO for
a new rod but may be typical of a used one. cant really see how they could have machined them like that unless the machine they used was worn. check
you have the cap on the right way!
about 4 years ago i bought some chinese rods for my cosworth turbo engine and they were perfect - seen 7800 many times without problems
|
|
|
edthedrummer
|
| posted on 13/11/13 at 08:03 PM |
|
|
As above, check the cap is on correctly, torque the rod up without bearings (carefully nip the big end in a vice, soft jaws of course whilst you
tighten) then check with a bore gauge.
To be honest, 20 microns isnt all that bad, I've measured used con-rods and re-used them that have measured a bit worse than that, albeit not
that much.
I would be interested to see how they measure up after they have been run though!
Good on you for using a bore gauge! If a job is worth doing its worth doing properly!
Ed.
|
|
|
Nickp
|
| posted on 13/11/13 at 09:21 PM |
|
|
Ta for the replies guys. You've got me thinking now and I'm intrigued to see if they get better or worse once fully torqued. I was a bit
wary of damaging them in the vice when clamping so only went to about 1/2 torque (held by hand). I think I'd better borrow the bore gauge again
and have another go. If they get worse I'll be after a refund 
|
|
|
edthedrummer
|
| posted on 13/11/13 at 09:44 PM |
|
|
Don't be shy! As long as you have some aluminium soft jaws in the vice, place the rod upside down (lay the small end to one side of the vice
bed) and tighten. Preferably allow the cap side of the big end to sit above the jaws, that way when you torque the bolts up, if the cap pulls down
further it won't damage itself or give false readings when measured.
You'll need to do it fairly tight to stop the entire assembly wobbling around when you torque it.
Remember the bearing tag cut-out goes to the same side on both the rod and the cap.
Let us know how you get on!
What bolts does it come with? Bolt lube?
|
|
|
Nickp
|
| posted on 13/11/13 at 10:00 PM |
|
|
I'll sort something with the vice and try again, just didn't want to damage them in case I need to return them. Yes the caps were the
right way around They came with ARP bolts and lube. I've got access to a 'yield gauge' when it comes to final install.
|
|
|
edthedrummer
|
| posted on 13/11/13 at 10:02 PM |
|
|
Ooooh a yield gauge!! Can't beat shiny tools!
|
|
|
Nickp
|
| posted on 13/11/13 at 10:05 PM |
|
|
quote:
Originally posted by edthedrummer
Ooooh a yield gauge!! Can't beat shiny tools!
Good to have a mate with all the gear, saves me buying it 
|
|
|
dexion7
|
| posted on 14/11/13 at 11:38 AM |
|
|
I've just used a bore gauge on some new carillo rods to go in a busa motor and the gauge shows no discernible variation in diameter as measured
at various points around the bores of the rods. the gauge reads in .01mm steps but a variation of around .002mm would be detectable were it present.
in other words, as far as the bore gauge is capable of displaying, the bores are perfectly round. they are also all precisely the same diameter across
the four of them too
|
|
|
edthedrummer
|
| posted on 14/11/13 at 08:24 PM |
|
|
quote:
Originally posted by dexion7
I've just used a bore gauge on some new carillo rods to go in a busa motor and the gauge shows no discernible variation in diameter as measured
at various points around the bores of the rods. the gauge reads in .01mm steps but a variation of around .002mm would be detectable were it present.
in other words, as far as the bore gauge is capable of displaying, the bores are perfectly round. they are also all precisely the same diameter across
the four of them too
Pretty much what should be expected from a set of good quality con-rods!
|
|
|
