batch666
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| posted on 7/11/20 at 09:31 AM |
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Wanted - Conrod & Piston 2L Zetec Blacktop
We did a track day at Blyton in the Tiger GTA in September and managed to spin a big end bearing in the sub 500 mile Zetec 2L crate engine. Looks like
oil starvation/surge was the problem as we were running the unbaffled Tiger era sump and it let go on the long fast left hander.
The crank has now been reground and Raceline sump ordered but struggling to find a replacement conrod (and piston due to the difficulty in swapping
just the conrod) to match the other 3. If I go for aftermarket parts I will have to replace all 4 for silly money and they tend to alter the
compression ratio which will mean remapping?
So if anyone has a Zetec 2L blacktop conrod and standard piston (or set) in good condition that they are willing to exchange for beer tokens or knows
where I might find them, please let me know....
Ian
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steve m
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| posted on 7/11/20 at 10:41 AM |
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If this had been a problem on a basic engine like a xflow or BMC a or b engines, replacing just one conrod and piston would be ok ish
Although i wouldnt do it, and ive rebuilt many many engines
But on a modern zetec, i would replace all four rods, and possibly pistons, but some proper advice from a professional engine rebuilder would be the
next step, and while all this ios still out get the whole lot balanced, crank flywheel clutch etc and rods and pistons
As said, just my opinion !
steve
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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batch666
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| posted on 7/11/20 at 11:58 AM |
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Thanks Steve, all options/info gratefully received.
I would prefer to replace all 4 rods but my understanding is that it is very difficult to replace them without damaging the pistons (even with the
right equipment), OEM conrods are also like rocking horse poo to find. If I have too I will fit a set of aftermarket pistons & rods, if I can find
a set that keeps the same compression ratio and therefore, mapping.
Ian
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big_wasa
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| posted on 7/11/20 at 06:16 PM |
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If you where looking for one from a crate engine I would try the tuners like Raceline, Dunnell and Scholar. Sadly the Zetec is now on the extinction
list.
With them now used in Oval racing 2.0 Zetecs are getting extremely slim pickings.
If you don’t have any better offers I will have a look in the shed. “If” I still have a set they have Done around 80k and you would have to fetch them
from Spalding Lincs. Sorry work means I won’t be able to post.
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steve m
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| posted on 7/11/20 at 08:54 PM |
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how bad was the spun bearing conrod? is it not salvageable ?
Im no expert on Zetecs, but its an engine, and ive never come across an engine that had problems in removing the pistons, nor refitting them
k series were a pain, but easy if you clamp the liners down, also quite a few bike engines required about 8 hands to help, but in the space only two
would fit!
sometimes it just needs some ingenuity in getting it all back together,
My last resort would be to get another engine, and make a very good one from both ?
steve
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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garybee
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| posted on 8/11/20 at 08:14 AM |
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I suspect the difficulty will be in removing the gudgeon pin, not withdrawing the piston/rod from the bore.
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batch666
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| posted on 8/11/20 at 09:05 AM |
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Thanks for the replies.
Yep, its splitting the piston and conrod that's the problem, press and dies needed to remove pin. Damage to the bearing carrier in the conrod is
too severe to "polish out" according to the machine shop that reground the crank.
Used engines (blacktops) are hard to find and are not cheap anymore and I have everything to rebuild mine except the one conrod!
Think I'm going to have to bite the bullet and buy a set of aftermarket pistons and rods if I can find a set that doesn't push up the
compression too much (and break the bank!)
Ian
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big_wasa
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| posted on 8/11/20 at 09:06 AM |
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Yep the gudgeon pin is an interference fit in the rod. The rod is heated until it’s blue. The problem would be heating the rod with out the the
piston. The piston floats on the pin. As your heating the rod the piston will suck the heat. By the time the rod lets the pin go the heat in the pin
will damage the piston.
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paulf
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| posted on 8/11/20 at 08:03 PM |
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I used to work for an engineering company that did a lot of engine work and we often had press fit pistons to remove and refit.We did not heat the
rods but used a hydraulic press and made a dolly to support the piston close to the gudgeon pin and a drift that was a good fit inside the gudgeon pin
and a few thou smaller than the gudgeon pin.Normally the pins would press out relatively easily without damaging the piston but the support had to be
a good fit to the area surrounding the gudgeon pin .
Paul
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steve m
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| posted on 8/11/20 at 11:12 PM |
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All the engines ive ever worked on, had tight gudgen pins, so leaving the pins in the freezer for a few days, and the piston and rods in the sun/oven
never caused an issue, and i cant believe the zetec is any different, its not exactly a race high tolerance engine
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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paulf
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| posted on 10/11/20 at 11:10 PM |
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Older engines had circlips to retain the pins and bushes in the little ends and so the pins were semi floating in the piston and rod.Zetecs and most
other newer engines have the rods an interference fit in the rod and the piston rotates on the rod but with no circlips to retain the rod.
Im not sure why as it doesnt appear to be any benefit apart from maybe to the engine manufacturer when the engines are built and does make it more
difficult to overhaul.
Paul.
#quote:
Originally posted by steve m
All the engines ive ever worked on, had tight gudgen pins, so leaving the pins in the freezer for a few days, and the piston and rods in the sun/oven
never caused an issue, and i cant believe the zetec is any different, its not exactly a race high tolerance engine
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