Cowboi

If i have a std zetec bottom end and a set of c20let pistons and i want to put them together. do i just take them both to a machinest and ask him to bore the block to suit?

do i have to tell him how much clearence i want or will he know the tolerances and just do it?

how about pistons rings... shoudl i change them first or does he do everything from the actual piston?

sorry for all the questions but its the first time ive had anything machines tbh.


also can any one reccomend a good place in east lodnon or essex way?

im not far from burton and know they do it. are they good?


Cheers guys

reality

You have a PM

Cowboi

artfulmatt

Standard tolerance for the LET piston is 1.5 thou - can't see this changing though as they are in the zetec block....

Rings - leave them off until all his work is complete...unless u get them too fit them

Cowboi

artfulmatt is auto vaux the best place to get rings for the pistons?

cheers for the tolerance mate! i'll pass it on when i get it machined.

Garage19

What rods are you using? If they are zetec rods, you are aware you will have to have them modified as well?

ON-UJAH

Rings from Vx are very expensive!!

Ask the place where you go to get you suitable rings, they should fit them (which involves filing) for you.

Cowboi

it was the zetec rods i was hoping to use. im only looking for about 250bhp. so i think the std rods with arp rod bolts should be ok.

i am aware that i need to somehow use the let gudgen pin with the zetec rod. so i guessed something is going to need modifying.

any ideas how hard it is?

ON-UJAH

Take it to the machine cshop. The Zetec pin needs presing out, and the little ends machined to accept the LET pin.

Check prices for all this work - a set of ZT rods, pistons and rings can be had from USA, for maybe only 150 quid more. Thats forged pistons and H-beam rods BTW, plug and play.

reality

Yeah, if you like them to be the wrong length. The American zetec has a different length rod.

Rolls

iTrader: (2)

and a different piston height to account for that ......

Anonymous

What sort of power are you intending to run?

The piston to bore clearance should be increased if they pistons are likely to get worked really hard (ie lots of heat)

I would go for 2 thou for a moderate build, 3 thou if its something really lairy, and 3.5 thou if you are using nitrous.

Cowboi

only looking for about 250.

i can do small machineing at work as we've got lathes and mills etc here.
but im not boreing out a block.

pressing out the zetec pin aint a problem.

i think i'll get the block, strip it down. take the pistons off the rods.

then take the let pistons, the let pin, the zetec rods and the block down to the machine shop. tell him i want 2 thou clearence and the pistons mounted on the rods.

does anyone think thats not the best way to do?

Anonymous

Sounds like the best way for me, but i would go 2.5 thou just to be on the same side probably, better to have a tiny bit of piston slap when cold than to seize a piston in the bore

make sure you check the ovality and taper on the bore, its amazingly common for machninist to hone a block not straight!

Cowboi

cheers chip

have you heard of zetec rods giving up with only 250bhp being thrown at them?

im going to use arp rod bolts but im just a bit worried about paying to have the block done and then loseing a rod.

Anonymous

i know lots about the let pistons but i dont know enough about the zetec rods to comment, sorry

TurboBlower

Ive been making enquiries into this myself using the states products,

even though the rods are longer and the piston deck being taller, using acombination of machining 1mm of the deck height and using a suitably sized copper plate from ferriday, i think the c.r can be corrected to run some reasonable boost.

Whats your opinions on this peeps v.intrested... I know a lot of peeps think that de-comp plates are a waste of time but ive heard people using them and running 30PSI of boost so surely they must be strong enough

Regards - Adi

Cowboi

dont worry mate i wouldnt of made u repair my engine if a rod broke when running 250bhp.

i've just heard mixed things. some people have said anything over 250 is risky. and others say they should take 280-300.

cheers again for the advice. as soon as i source a block i'll be down the machinest and i'll post up how mounting the pistons go.

reality

Eh.. no real point in doing that when you can just machine the piston crown to compensate.. If I remember correctly, the American rod length was about half way between our silver top and black top zetecs..

TurboBlower

Ive been advised from JE that you could safely take 1mm of the deck height but wouldn't advise anymore,

I believe the rods supplied by eagle are 1mm longer than rods found in UK Blocks???

Correct me if im wrong ?? as im unsure about this myself

Thanx - Adi

Garage19

Right, if you use the both the rods and the pistons from the states (designed for a black top engine) in your silver top you will not have to do any further machining.
In the black top engines the rods are longer but the deck height of the piston is shorter to compensate. So if you use a matching rod/piston combo from the same engine you will be ok.

As for the zetec rods, I'm not sure of their limit. The ARP rod bolts you have added are a wise investment, but only really if you want to rev your engine harder. The extra forces / cylinder pressures will create a different type of rod failure than the stronger rod bolts are designed to combat. With extra revs, the rods will typically fail just under the little end or by snapping a rod bolt from being pulled apart at the top/bottom of the stroke. The extra force that your turbo conversion will create on the rods will tend to lead to the rod failing under compression or bending.

reality

Not actually true. The n/a zetec in the states has a lower compression ratio than ours (for emissions and potentially to make it non-inteference). Also, i've never seen a zetec piston in the states that gives you lower than say 8.5:1 (based on the stock CR of 9.5:1). So you will need to machine the piston still if you want to be remotely proper.

I think you mean "compression height", not "deck height"

Anonymous

Reality, whats the difference in height of the yank and uk blocks, measured from the bearing tunnel to the face?

reality

As far as i'm aware, the block deck height is the same. The yanks only get the black top zetec (they get another engine called a zetec that we don't get too). They basically run a slightly shorter rod to drop the compression ratio from our 10:1 to their 9.5:1 (or whatever the exact figures are, don't have them handy right now).

Regarding the yank pistons, JE or whoever, not sure you'll be able to get say -20cc's from them or whatever is necessary to drop it enough (say 7.5:1)..

TurboBlower

Garage 19 PM sent M8y

TurboBlower

All Good Info this Guys Thanx and Keep It Up

I'll reveal what im going to use shortly so your opinions would be greatly appreciated !!!

Regards - Adi

Anonymous

at 86mm, its 6cc per mm roughly, so you wouldnt need to machine much off to lower the CR a lot.

The standard LET pitsons can easily lose 5cc if you have a decent machinist.

reality

Chip, yes but I was talking about the American 8.5:1 pistons.. not C20LET ones..

Anonymous

If they are JE then they are probably a 6mm crown and the same will apply

Garage19

Reality, have you got the rod legnths of the UK and US spec ones? Would be good to know the exact difference. I would have thought they would have made such a small CR change with a different gasket rather than pay the new design / tooling / manufactuer costs of shorter rods?

Yes, its compression height you smart arse but the yanks refer to it as deck height!

Anonymous

I always say "deck height" for where the pistons sit in the block

reality

deck height is exactly that chip...

Garage19.. I do at home.. as I said above it's approx half-way between our silver and black top rods..

Garage19

Ok, well we all know what we are talking about, the height between the "wrist pin" (yank stylee) and the piston crown.

You are right on the cc/mm chip. 86mm bore gives 5.8 cc per mm.

The engine i just built measured 8:1 CR using yank pistons, but then they weren't JEs.

Garage19

To get that drop in CR i reckon the yank rods would have to be approx 0.65mm shorter.

Anonymous

pretty small beer then really, running a 2mm gasket would sort that
(ie 2mm as opposed to 1.3 standard i mean, not 2mm more)

Garage19

I think the early UK zetecs have a gasket with a crush thickness of 1.6mm and the later zetecs with the MLS gaskets have a crushed thickness of only 0.5mm.

reality

Okay chaps..

From what I've been able to scavenge from the available Farndon and Eagle info..

UK Silver Top 136.14 mm
US Black Top 139.27 mm
UK Black Top 140.72 mm

+1.45mm US Black <> UK Black
+3.13mm US Black <> UK Silver

So the US rods are 3.13mm longer than our silver top ones.. that would give a C20LET piston a positive deck height

TurboBlower

Right Then

Wondering if you could give us some advise and confirm if i would require maching work carrying out?? the following links are of the pistons and rods im considering using:

http://cgi.ebay.com/ebaymotors/EAGLE...6459QQtcZphoto

&

http://cgi.ebay.com/ebaymotors/JE-PI...5541QQtcZphoto

Hope those links work !!!!

I'll be fitting them to the Later Zetec Block the one without the DOHC stamped on the Rocker.

CheeRs Guys - Adi

TurboBlower

Oooopsss Forgot to say Cowboi SORRY for Hi-Jackin your thread but hopefully this is good info. for you to

reality

The silver top zetec came with both 'DOHC' and 'Zetec' on the cam cover.. you can't go by that.. unless you mean the zetec as in the focus, with the black plastic cam cover with 'zetec' on it.. you're best to specify a year

Oh and I can't get to ebay at work