Top ring gap

 

"You came here with a blown up engine and the correct theory of PTW issue"

You are right.

I brought engine block and pistons to machine shop to measure wall clearance after engine blown up.

They said it is 0.101 mm.

Should I argue with machine shop?


"PTW issue is something you are denying"

What purpose I deny your answer?

I come here to find what cause the problem.

My mechanic said it is wall clearance.

But according to machine shop wall clearance is fine.


"You cannot measure ring gap with a caliper"
"You have to use feeler gauges"

I mentioned I dont have the feeler gauge.

I use caliper just to show.

It is better I stop this discussion.

No need to argue further.

Thanks for all your answers.

 

in mm..

you cant measure the PTW now with the worn pistons..

 

If the PTW is CURRENTLY .101mm that measurement means nothing as everything has been eaten up. Well it does mean something, that the PTW was too tight because there is easily .1mm of wear pictured...

 

OP, 0.101mm is the piston to wall clearance after your engine used the piston as a boring tool. This is literally the "black death" treatment people talk about when your PTW is set too tight (or cylinders are completely egg'd out of shape). If when you installed the piston rings, they rotated freely on the piston (ringland clearance was good), then the machine shop is just trying to save themselves the blame. Remember to always check their work for future engine builds to prevent mistakes like this from occurring. Subtract piston diameter measured just below the wrist pin from the cylinder bore diameter. Those pistons are of high quality and would have had similar measurements.

One thing I would also double check is the main bearing and rod bearing clearances. If the machine shop skimped on the PTW measurement, everything else is a crapshoot.

 

It makes sense that when you finally got it hot enough to fully expand the piston, thats when the problem surfaced.

Oil temperature can rise very slowly in some cars, especially OEM turbo w/ cast piston, used as a daily driver. The cast piston does not expand much when fully warmed which is why it is a good piston for low temperatures, and there is often supplemental oil cooling involved.

The forged piston on the other hand is designed with it's fully warmed temperature in mind. So if you start an engine with cold oil and cold piston, it should not be run hard until it fully warms up. But sometimes the piston oil cooling effect is so good it can take quite a while to fully warm, 20-40 minutes is not uncommon. And if the engine is kept at low rpms (driving in traffic) the piston might never fully warm up and expand in the bore as intended.

Sometimes a forged piston needs 'laps' to fully warm up, where it gradually expands as power output is increased. Blow by should decrease as the oil thins out and temperature rises, this can be seen on both oil pressure gauge and crankcase pressure gauges.

 

Thanks Pal215 and KingTal0n.

I see some responses in my inbox.


Let me make it clear.

"Wall clearance is 0.101 mm based on machine shop"

It is measured using intact piston to all cylinder walls using digital micrometer and analog dial bore gauge.


Wiseco sent email to me yesterday.

They told me how to measure piston wall clearance.

They will give feedback on 22-04-2019 after I sent some detail pictures.

I will bring engine block and pistons next week to different machine shop after getting information from Wiseco.


Notice piston pointed by yellow arrow.

This is the only piston which is still in good shape.

 

The cylinders are now worn. Due to the issue you have, it is impossible to determine what PTW once was.

 

I brought engine block to be measured at different machine shop based on Wiseco information.

Clearance is ±0.10 mm for all cylinders based on piston #1 (intact piston).

The rest 0.16 mm piston #2, 0.20 mm piston #3, 0.28 mm piston #4 (all worm pistons).

Engine fail might be caused by piston wall clearance.

But I still in doubt based on measurement.

Anyway I appreciate all your input.

 

That shop just wasted your money and I’m sorry about your mishap. Next time just get a new oem shortblock
and call it a day, dealing with some of these shops is a waste of time and they never
like to take blame for their mistakes.

 

Its the same story in every car clique. Chevy, Toyota, Nissan, Ford, Mitsu... etc... @(#*@# machine shop $#!Ts on everybody

I like so many others now use completely original engines 02+ from chevy for daily drivers now because they dont need any machine work (no down time, no mistakes) and support 500-1000rwhp with oem internals

 

Seconded, I'm not entirely surprised when people sell their project cars for a new leased car or a 3-5 year old sports car nowadays. These performance shops all tend to be fly by night operations (3-5 year longevity sometimes less) that tend to simply not give a **** about customers after the check clears and if you don't have the time/space/tools to do everything yourself you're entirely at their mercy (sometimes even if you do: look at OP, no one has $50,000 in machine shop equipment that'll be used once every 5 years at most). You just after a certain point run out of patience and get tired.

And I bet OPs **** machine work will be blamed on a bad tune or similar.

 

"Next time just get a new oem shortblock"

I might have driven the car if I stayed stock with just piggyback tuning.

I raced this EVO on street for years without problem.

Not even engine bearing failure.

Thanks again friends.

 

I was not aware that any none exotic oem engine could support 1000rwhp.

You don't need all those tools, you just need to check their work and assemble the engine yourself. If the machine shop messed up a PTW measurement too small, you can take the block back for them to cut more material The tools required for engine assembly cost much less than one might think. I think people just give up too easily because learning this stuff is not easy and can be nerve racking.

There is nothing wrong with what your intentions were. They just were not executed properly. I wish you luck on your next built.

 

"They just were not executed properly. I wish you luck on your next built"

Have not decided what to do for next, maybe back to stock.

To import those parts from US is quite expensive (shipping cost, high import tax).

I can get complete used EVO block and head from Malaysia cheaper than price of pistons.

Buying parts from Indonesia or Singapore even costs more.