broken ring land = lame!!

[280zex]

ok well I got realy lucky with my blo thru holley/turbo Z L28. Looks like all that happened is the 2nd ring land on piston number 3 broke off. This did not cause any further problems other than loss of cylinder compression. The cylinder wall is a bit funky but I can hone that out. The shop that did the .5mm over bore and piston upgrade SAID they used forged pistons, now I know they didnt. I have no way of getting them to fix the issue. Thats what I get for trusting a shop to do work I should have done myself.

 

On a side note: The flywheel bolts came loose again!! I even used new bolts and red lock tite. Aparently my engine does not like the boost I was feeding it.

 

I realy did get lucky this time that the engine didnt eat itself with a broken piston. Time to loose the turbo and go back to just being happy with a Z that runs, without the extra HP;-(

[78zstyle]

You don't have a receipt that shows you were charged for forged pistons?

[280zex]

You don't have a receipt that shows you were charged for forged pistons?

yes I keep all my receipts. the shop in question couldnt stay in business in this economy. They do have a shop in Portland,OR tho. I called them and aparently there was some shady things going on in the shop here in Seattle so they closed up. Figures.

[Noddle]

On a side note: The flywheel bolts came loose again!! I even used new bolts and red lock tite. Aparently my engine does not like the boost I was feeding it.

 

I had a Ford 250 X-Flow that did the same thing, give it high rpm and the blots came lose, It did this 3 times in all,

 

the fix was to replace the flywheel and bolts..

 

NIgel

Edited July 30, 2012 by Noddle

[Zmanco]

Aparently my engine does not like the boost I was feeding it.

Are you sure that the land didn't break due to detonation? How much boost are you running?

[randy 77zt]

Here is where electronics (efi) come in.The ability to retard the ignition timing under boost.I run. my turbo at 20 btdc at anything after 5 lbs boost.A distributor set up for this engine would need a vacuem can that could pull about a 12 degree timing swing(difference between cruise and on boost).If the car is tuned on a dyno the dyno operator usually installs some kind on knock sensing on the engine-there is a sweet spot the tuner looks for.Forged pistons are not a crutch for poor tuning.Oem turbo pistons will work at 16-18 lbs boost if the engine is tuned correctly.Usually at highway speeds an most engines are set up to run at 32-36 btdc degrees timing .Say you had the car set up for 22 btdc under boost.the vacuem can on the dizzy would add the 10 degres under cruise.If the dizzy was set for 8 degrees centrifical advance+14 degrees initial that would give you 32 total at cruise + retard at boost.+ on a holly 4 bbl that is on a boosted motor usually the power valve is referenced to boost

 

 

[280zex]

The damage wasnt due to poor tuning. The holley carb I built works perfect with the turbo. My problem is that I paid a shop for upgrades and machine work that wasn't done correctly. I USED to be friends with the people who did the work, I trusted them and got screwed over. Just a life lesson: if you can do something for yourself then do it, don't trust somebody else to do it.

 

I know the parts I purchased and the parts installed are not them. I didnt think to check the lower end parts after I got it back from the shop that did the work. MY MISTAKE. THEY WERE FRIENDS. oh well. atleast the block is ok! I'm just going to order some ITM 86.5mm turbo pistons and rings and rebuild the lower end myself. I just gota get a press for the wrist pins, no big deal. Hone out the cylinders. Probibly should get new bearings while I'm at it, just to be shure everythings fresh.

 

note to self: NTA = never trust anybody ;-(

[280zex]

I had a Ford 250 X-Flow that did the same thing, give it high rpm and the blots came lose, It did this 3 times in all,

 

the fix was to replace the flywheel and bolts..

 

NIgel

Ya thanks Nigel, I think too many RPM's was the main issue.....

[Zmanco]

The damage wasnt due to poor tuning. The holley carb I built works perfect with the turbo. My problem is that I paid a shop for upgrades and machine work that wasn't done correctly.

 

You seem convinced that the failure of the ring land was not due to detonation and could only be avoided by using forged pistons. Please explain how you can you be so sure.

 

I'll ask a second time: how much boost are you running? As a point of reference, I'm running the equivalent of 15 psi at sea level with cast pistons and have no issues with rings and lands. I also run Megasquirt and retard timing a few deg at the torque peak as well as utilize a knock sensor to pull timing further when that's not enough (e.g. 90+ deg days at the track).

 

If you don't solve the underlying problem, you're going to repeat history. As Randy 77zt said "Forged pistons are not a crutch for poor tuning." Based on your brief description of the setup, experience suggests that's the likely root cause of the failure.

[NewZed]

I live in the Portland area. Who's the shady shop?

 

Seems like three things going on here -

 

- maybe a shady or just incompetent shop. If it's the same owners why can't you deal with the Portland people now?

 

- maybe a tuning issue. Will cast pistons automatically break above whatever boost you're running? Or is it an assumption.

 

- maybe a cast vs. forged piston issue. Are you assuming the pistons are cast, not forged, because they broke or have you confirmed it by some other method?

 

I'd like to learn something here, especially the local shop to avoid if you're positive they scammed you on the pistons. Since you have receipts, it should be easy to show.

 

If the Portland shop is on the level,they should cover the mistakes of their Seattle shop. What's the rest of the story?

[Mack]

and what do yo have your timing set at? I am sorry, but a blow through holley carb in this day and age is kind of primitive, especially with options available that could give you full standalone control for under $1000. Building a forged engine then running a blwo through turbo set up seems kind of contradictory.

[280zex]

I live in the Portland area. Who's the shady shop?

 

Seems like three things going on here -

 

- maybe a shady or just incompetent shop. If it's the same owners why can't you deal with the Portland people now?

 

- maybe a tuning issue. Will cast pistons automatically break above whatever boost you're running? Or is it an assumption.

 

- maybe a cast vs. forged piston issue. Are you assuming the pistons are cast, not forged, because they broke or have you confirmed it by some other method?

 

I'd like to learn something here, especially the local shop to avoid if you're positive they scammed you on the pistons. Since you have receipts, it should be easy to show.

 

If the Portland shop is on the level,they should cover the mistakes of their Seattle shop. What's the rest of the story?

The pistons I bought were wiseco forged 86.5mm turbo pistons. The pistons I just pulled are??? I will take some pic's and post them here later. I also got a kameari(sp?) crank, and that is not the crank in my block. I will not say what shop did this until I get some resolve from the Portland main shop. Problem is that the work I had done was several years ago and I didn't have an issue until now, so kinda hard to prove things on my end. The tune on my car is/was solid. The engine issues I face was from too many RPM's, not too much boost. My setup was suposedly built to withstand 9k rpm's, but seings how the work I got was shoddy my engine broke. I have one guy in Portland supoda come here this weekend to inspect things and look at my receipts. I should have taken pic's but I didn't...oops..

[280zex]

and what do yo have your timing set at? I am sorry, but a blow through holley carb in this day and age is kind of primitive, especially with options available that could give you full standalone control for under $1000. Building a forged engine then running a blwo through turbo set up seems kind of contradictory.

Try reading up on the subject. blo thru is old skool yes, but puts out the power at less than half the cost...

[Pyro]

If the rings don't have enough gap then the piston will come apart like that also. And turbo engines need more end gap than NA's do.

 

Forged pistons are not required for a turbo. And forged pistons will also break, just not as quickly as casted.

 

A turbo setup with no ignition control will do best if you just lock out the ignition. With stock boost (7-8 psi) and 93 octane: I use 28 degrees with 7.4:1cr, 23 degrees with 8.3:1cr, or 17 degrees with 8.8:1cr.

 

Do you have an O2 sensor in the exhaust? Even a simple 1 wire used with a volt meter will indicate the mixture on boost.

[Tony D]

"The shop that did the .5mm over bore and piston upgrade SAID they used forged pistons, now I know they didnt."

I'll echo that, how do you know KNOW? Weisco is pretty plain to see. Forged pistons DO break, and the #1 reason for land breakage in turbo cars is detonation.

Forged may not be needed for turbo, but it is if you want it to live beyond 7500rpms.

I'm suspicious of this whole post seeing things like 'ran for a few years till I had this problem' statement. Sounds to me like someone is upset their engine broke and just hasn't grasped that you can use the best parts on the face of the planet and if one thing, one time, doesn't work....it won't save ANYTHING from going "Boom!"

[HowlerMonkey]

I'd wait for the pics of the pistons before assuming.

[Mack]

Try reading up on the subject. blo thru is old skool yes, but puts out the power at less than half the cost...

 

I have read up on the subject and from what I have read, I don't think I would ever attempt it unless I was running webers or mikunis or some other IR side draft set up. A lot of the older barrel manifolds produced for the L series engines had problems delivering consistent mixtures to each cylinder, especially the end ones according to what I have researched, not to mention fuel puddling issues. There are people pushing the stock short blocks to over 400rwhp, and that's with cast pistons, but with EFI. I am still trying to wrap my head around buying a completely forged lower end, with a Kameri crankshaft and then going "old skool" with what some would argue is the most important part of the engine.

 

I too will be anxiously awaiting pics.

 

Megasquirt ain't that hard.

[letitsnow]

There are TONS of very fast blow through turbo v8's. The carb isn't the problem. Even if the manifold doesn't distribute evenly, I would expect that the air fuel ratio of the affected cylinders wouldn't change much because the fuel is mixed with the air before it's distributed, that is, unless the manifold is REALLY bad and fuel is coming out of suspension.

[Leon]

There are TONS of very fast blow through turbo v8's. The carb isn't the problem. Even if the manifold doesn't distribute evenly, I would expect that the air fuel ratio of the affected cylinders wouldn't change much because the fuel is mixed with the air before it's distributed, that is, unless the manifold is REALLY bad and fuel is coming out of suspension.

There will always be fuel out of suspension, it is called the "Tau layer", and it will contribute to an uneven mixture. A V8 (downdraft, central manifold) does not compare to the L6 (sidedraft), your analogy is not applicable.

 

Uneven runners also screw up the resonance tuning effect and may add some extra vibration due to power variations between cylinders.

 

FWIW...

[Zmanco]

Isn't the main issue that without an ECU it's not possible to optimize spark across the rev range, adjust mixtures at a variety of engine conditions, etc? Nothing wrong with going old skool, but to Mack's point, seems strange to spend so much on a premium bottom end and not take advantage of optimizing fuel and spark to get the most out of the motor.