Engine rebuild...piston protrusion

[Nickmix]

I am in the process of rebuilding the engine in my 03 jetta tdi. My block is back from the machine shop where they had to rebore due to a scratch in cylinder 2 and deck to true it up. I have assembled the block with asv pistons (+.5mm) to check the piston protrusion (multiple times)and these are the measurements I got:

Cylinder 1 =
.0345" .0355"
.0345" .035"
.035" .0355"

Cylinder 2 =
.0355" .036"
.036" .0365"
.036" .036"

Cylinder 3 =
.034" .036"
.034" .0355"
.034" .036"

Cylinder 4 =
.0365" .035"
.0355" .0345"
.0355" .0355"

All measurements were taken on the centerline of the wrist pins using a Starrett dial indicator, magnetic deck bridge and machined 123 blocks.
My question is do I really need to take it back to the machine shop or leave it be? If I take it back then there is a small chance they could overshoot. If it does need to go back how much should be taken off? I know the one hole head gasket spec (which I was shooting for) is .0358" - .0394"
I just don't want any issues like hard starting...etc.

 

[Fix_Until_Broke]

Nick - I wouldn't mess with it. Put a 1 hole head gasket in and advance your cam 1 flywheel tooth and it'll start just fine.

Rough numbers are 0.001" of piston protrusion = 0.1 point of compression ratio

See my "where to stop" thread for a bunch of boring details, but the above is what I'd do.

 

[Nickmix]

Nick - I wouldn't mess with it. Put a 1 hole head gasket in and advance your cam 1 flywheel tooth and it'll start just fine.

Rough numbers are 0.001" of piston protrusion = 0.1 point of compression ratio

See my "where to stop" thread for a bunch of boring details, but the above is what I'd do.

I will probably just go with the 1 hole gasket. I have actually read through your "where to stop" thread several times. What are your thoughts now on the ceramic piston coating and sputter bearings. I have gone back and forth on both of those for a while. I am only looking for around 200 horsepower.

 

[smelly621]

Can't recall if the asv pistons have the upgraded oil cooling galleys or if you need PD pistons for that? I'd prioritize that over coating myself. Sputter bearings were a "might as well" upgrade when doing a rebuild since the cost wasn't much more than regular ones.

Isn't 200hp about the safe limit on the stock ALH rods?

 

[Nickmix]

Can't recall if the asv pistons have the upgraded oil cooling galleys or if you need PD pistons for that? I'd prioritize that over coating myself. Sputter bearings were a "might as well" upgrade when doing a rebuild since the cost wasn't much more than regular ones.

Isn't 200hp about the safe limit on the stock ALH rods?

The ASV pistons I bought do have the upgraded oil cooling galleys.
I have read conflicting levels for what the stock rods will take but generally 180-200hp depending on the tune and how it is driven. I have already purchased forged rods for some headroom and future upgrades.

 

[IndigoBlueWagon]

I can say from experience that 180-200 HP is beyond the strength of stock rods, if you in fact use all the power.

 

[Nickmix]

Also one of the reasons I was considering ceramic coatings (other than performance reasons) is it would put me closer in the ballpark of a 1 hole head gasket. Cerakote says the coating adds .001" and Swain tech cays .002" or .003" depending on which coating you go with. Still might not be worth the cost though.

 

[smelly621]

Just checking, but did you get the matching oil squirters for the block side of things that line up with the hole in the new pistons?

Think you're totally fine as is on the piston protrusion and starting isn't going to be an issue

 

[Nickmix]

Just checking, but did you get the matching oil squirters for the block side of things that line up with the hole in the new pistons?

Think you're totally fine as is on the piston protrusion and starting isn't going to be an issue

I have installed the squirters but not lined them up yet.

 

[Fix_Until_Broke]

I will probably just go with the 1 hole gasket. I have actually read through your "where to stop" thread several times. What are your thoughts now on the ceramic piston coating and sputter bearings. I have gone back and forth on both of those for a while. I am only looking for around 200 horsepower.

Regarding piston coatings and sputter bearings...it's one of those things that if they're doing their job, you won't know it . Coming up on 190k miles since the rebuild and it hasn't blown up or broken yet so, they have not done any harm. Have not pulled the head to look at the pistons.

I think it depends a lot on what you intend to do with the car. The occasional interstate on-ramp run through the gears kind of thing, probably not worth the extra time/$$ invested. If you're going to be doing track days with extended full throttle operation or heavy trailer towing at interstate speeds (and expect it to live...), then it's probably good insurance.

Rods are way more concerned about torque than HP - Many of the "all stock internals" running 200+HP are presumably doing so with a big turbo and at high RPM (>3000). If you're a torque junkie like me and rarely ever get to 3000 RPM, then you need to invest in rods/pistons/bearings/coatings in my opinion.

 

[IndigoBlueWagon]

Jeff at Rocketchip once told me that three things bend rods: fuel, timing (revs) and boost. I ran a 6000 RPM tune for 120K miles with moderate fueling (PP520s and 11mm pump) and boost (26 PSI). Rods were bent when my guru tore the engine down, but not by a huge amount, and it still ran great. And I did a lot of track days with that setup.

 

[PakProtector]

Reliability is relative...but statistically the engine needs more rod and big end bearing when you graduate to ARL/BHW power levels at a comparable torque profile. Is no darned way VW just went with heavier, stronger bits for shoots and giggles.

Douglas

 

[[486]]

I think it depends a lot on what you intend to do with the car. The occasional interstate on-ramp run through the gears kind of thing, probably not worth the extra time/$$ invested. If you're going to be doing track days with extended full throttle operation or heavy trailer towing at interstate speeds (and expect it to live...), then it's probably good insurance.

yup, gonna be trying out the cerakote one pretty soon, just busted my second set of rings in 8k miles
restrictive fuel filter causing a loss of timing advance, alongside not monitoring EGTs for a 70 mi freeway trip was enough to butt the top ring and bust it twice now

short duration severe abuse ain't too much concern, sustained abuse is where the weak constitution of these engines shines through

 

[Nickmix]

yup, gonna be trying out the cerakote one pretty soon, just busted my second set of rings in 8k miles
restrictive fuel filter causing a loss of timing advance, alongside not monitoring EGTs for a 70 mi freeway trip was enough to butt the top ring and bust it twice now

short duration severe abuse ain't too much concern, sustained abuse is where the weak constitution of these engines shines through

What was your ring gap set to? I am also thinking about a diy cerakote job to my pistons.

 

[[486]]

What was your ring gap set to? I am also thinking about a diy cerakote job to my pistons.

oh, "stock plus 350k miles", so... "still too tight"
gonna hone the bores out a couple thousandths with the lisle rigid hone and see what it looks like after that, I opened up my golf to .004" piston/wall and the rings on that worked out to an acceptable gap way back then...