115 replies to this topic

[siztenboots]

A 70,000 mile Z20LET is stripped and inspected for damage. Taken from an unseen crashed VX220 there was glass fragments everywhere. The Turbo CHRA was scrap due to the crash G force. Various other parts were salvageable.













oil pickup, timing wheel, balancer shaft drive

[DarrylB]

Cool!

What's the plan for this? Standard rebuild? Simple mods to improve performance? mental overhaul to rival Nev's Nipper?

[Nev]

Wow, looks like a good one. The oil looks nice and clean and hardly any carbon build up (though the sump pan is the best indicator for this). Cylinders are clearly burning evenly and perfectly. Maybe just change the rods and bearing shells for £350 and put it into your car. These engines/cars are a bloody bargain! BTW, I know where you can get 1/2 decent forged rods for £250. Proven to 400 BHP and probably good a for more. Seeing all those pics makes me want to get all oily again myself !

Edited by Nev, 09 November 2011 - 10:41 AM.

[siztenboots]

Wow, looks like a good one. The oil looks nice and clean and hardly any carbon build up (though the sump pan is the best indicator for this).

Cylinders are clearly burning evenly and perfectly. Maybe just change the rods and bearing shells for £350 and put it into your car. These engines/cars are a bloody bargain!

this is sort of the route that I think people would appreciate, leave engine insitu and rebuild it from the bottom without taking off head or turbo.

I'm not sure if the gearbox has to be detached to get to the lower sump after the oil pan is removed. But the idea is whilst removing the balancer shafts , to drop the crank out and then put in arp bolts, optional upgrade rods if going above 360lbf.ft , this would take you to stage4.9+ , pretty much a std engine and wallet friendly.

Ideally get the lot sent to vibration free.

[siztenboots]

BTW, I know where you can get 1/2 decent forged rods for £250. Proven to 400 BHP and probably good a for more.

lithuania bloke (fcp-engineering) , seems to be able to make bespoke anything?

[Nev]

Yes, the Lituanian bloke is the person to buy the rods off. He's sold loads on MigWeb with no reported failures. Both sump pans come off very easily (no need to take gearbox off), so as you say, an easy way for people to make a base engine good for circa 375 to 400 BHP. After that I think the pistons should be changed, which is much more hassle if you decide to rebore as the engine owuld need to come out to go to the machine shop. DuncanVxr did this job (from under the engine) a couple of times I think.

[techieboy]

Blimey, can't believe how clean the piston crowns are after 70k miles. They're properly filthy with carbon build-up on the Z22SE.

[Bargi]

Blimey, can't believe how clean the piston crowns are after 70k miles. They're properly filthy with carbon build-up on the Z22SE.

at 50k mine were cludged up compared to those

[Andrew aka Stuwy]

Blimey, can't believe how clean the piston crowns are after 70k miles. They're properly filthy with carbon build-up on the Z22SE.

at 50k mine were cludged up compared to those

when we had the head off my car the pistons were almost black

can't believe how new that looks

[fiveoclock]

Look like they've had a good old clean to me

[siztenboots]

Look like they've had a good old clean to me

I gave them a hoover to remove the bits of glass that got sucked in, and at best a light wipe over , considering this sat outside for over a year before I could get started on the project.

[techieboy]

Does the Z20LET have an EGR system? I guess that makes a huge difference to the amount of sh!t that gets into the combustion chamber.

[siztenboots]

Does the Z20LET have an EGR system? I guess that makes a huge difference to the amount of sh!t that gets into the combustion chamber.

nope, and its pretty keen to fuel it lean when it can, judging by the LTFT trims

[techieboy]

Does the Z20LET have an EGR system? I guess that makes a huge difference to the amount of sh!t that gets into the combustion chamber.

nope, and its pretty keen to fuel it lean when it can, judging by the LTFT trims

Yep, exact reverse of the Z22SE that seems to over-fuel by default and also by preference.

[Nev]

when we had the head off my car the pistons were almost black

can't believe how new that looks

Fueling isn't the only reason for carbon deposits in the cylinder. Other possible reasons are:

i) 1 or more failing stem seals allowing oil to seap down the valve and thus get burnt.
ii) Turbo seal(s) failing and letting oil into the inlet charge.
iii) Mild HGF allowing oil to seap into 1 or more cylinders.

HTH.

If you have a bore scope and inspect your engine and see loads of carbon on your piston crowns, the first remedial thing you can do is change your oil for some thicker stuff.

Edited by Nev, 09 November 2011 - 03:25 PM.

[out on the bike]

Wow, looks like a good one. The oil looks nice and clean and hardly any carbon build up (though the sump pan is the best indicator for this).

Cylinders are clearly burning evenly and perfectly. Maybe just change the rods and bearing shells for £350 and put it into your car. These engines/cars are a bloody bargain!

this is sort of the route that I think people would appreciate, leave engine insitu and rebuild it from the bottom without taking off head or turbo.

I'm not sure if the gearbox has to be detached to get to the lower sump after the oil pan is removed. But the idea is whilst removing the balancer shafts , to drop the crank out and then put in arp bolts, optional upgrade rods if going above 360lbf.ft , this would take you to stage4.9+ , pretty much a std engine and wallet friendly.

Ideally get the lot sent to vibration free.

This is very interesting as I was thiking of replaceing my engine because after replaceing the head when the valves were leaking I found it still not starting which now looks like bottom end problems as it ate the end of the crank sensor.So now I have seen that should be possable to strip the bottom end down with it in situ I may well have a go at fixing it rather than replaceing it.

[Nev]

Rich, I can't understand what the hell caused your crank sensor to hit anything - it sounds impossible to me, yet it has happened. The only way this could of happened is if the crank moved(!!) or the sensor got pushed in too far.

[Andrew aka Stuwy]

when we had the head off my car the pistons were almost black

can't believe how new that looks

Fueling isn't the only reason for carbon deposits in the cylinder. Other possible reasons are:

i) 1 or more failing stem seals allowing oil to seap down the valve and thus get burnt.
ii) Turbo seal(s) failing and letting oil into the inlet charge.
iii) Mild HGF allowing oil to seap into 1 or more cylinders.

1 and 3 have just been done so if thats the problem its sorted and i dont have a tubby

[siztenboots]

now even when using Z20LEH internals, most people discard standard rods and go aftermarket. Question is, how many then get crank and internals rebalanced?

standard Astra VXR z20leh piston , notice differences to LET pistons above ;
pocket cutouts for inlet cams
larger diameter domed deck profile
dish edge profile



z20leh standard rod (on the left) LEH piston and aftermarket rod (on the right)

[Nev]

Arrow sell a generic C20LET/Z20LET steel crank, its £1800 though. I don't think you need to get the internals balanced myself. The reason I think this is that my engine had no balancing and is silky smooth at high revs. Also, Chris Randal found that he needed to add a lot of weight to his Z20LEx crank to balance it. I don't unserstand some of your english - can you rephrase pls ?