OlBlue

Hi everyone!

Ol Blue, blew....her head gasket at cylinders 2 and 5. The Service Manual says flatness of deck and head to be .0004 inches in a 2" diamter......my feeler gauges certainly don't go that thin!

Would you folks with experience please tell me what you find as acceptable flatness?

TIA

Here's a pic of the gasket at cylinder #2

Ryan

I can't help on the specs but I am curious as to what kind of boost you've been running at.

OlBlue

Al and Piers said not over 40 on their PDR-40, so It's always been set at 39psi. This is with a home-made, adjustable boost elbow and read from an Autometer 60psi gauge.

I did hit 40 at Diesel Thunder dyno, that was once and several months ago. Typically, I run with the box off where max boost is 32psi.

Don M

First the ETH is just gonna blow the OEM gasket easier than the ETC. Compression ratio is the reason. A major part of it anyway.

My suggestion is to go ahead and go back with a stock gasket and use a single o-ring in the head.

Surface finished is paramount and the entire warpage should not exceed .002 from side to side and .006 from end to end.

The manual is also correct in its specs of .0004 per 2 inches.

The reason is head gasket unloading can occur and even in the smallest amount will eventually cause a failure.

I wrote a head gasket paper last year for Copper gaskets and I will attach a few paragraphs from it to help you in the block/head preparation below:


Constant thermal expansion and contraction, localized heating of the combustion seal area, and cylinder head movement are a few of the examples that can lead to brinelling. Brinelling leaves the surface of the head and deck with high and low spots that can cause localized uneven clamp load being applied to the new gasket. We all know that when any gasket is unloaded it won’t seal. Unloading the combustion sealing ring as little as .001" can create trouble! The loss of load will show up as the engine cools down and the head shrinks back, but the gasket doesn’t follow the indentation. Upon restarting the engine COLD, leakage can occur. This cycle eventually leads to gasket failure. Brinelling also causes a localized hardening of the area affected up to a depth of .015” in some cases.

All brinell marks must be machined out.

2. Engine block overall flatness should be a maximum from end to end of .076mm or (.003 inches) Side to side flatness should be .0508mm or (.002 inches). Visual inspection should find no dips or imperfections present.
Cylinder head overall flatness should be a maximum of .152mm or (.006 inches). Side to side flatness should be a maximum of .0508mm or (.002 inches).

3. If the block or head condition warrants resurfacing you must be careful the shop you chose can properly perform the task. The surface finish must be 16-30 RMS or 0.4-0.7 Ra or roughness average. This will produce a very smooth finish to aid in even gasket loading when torque is applied to the fasteners. Somewhere between higher levels of performance expected from the engine, longer durability and tear down windows, and plain old pride exists a logical reason to give thought to proper cylinder head and block preparation.

Don~

OlBlue

Don,

Thank you for the info and taking the time for to type out a great reply.

thumper 549

You probly know this ...its a good idea to replace your head bolts too. when you bolt her back to gather make sure both decks are supper clean and lightly lube your bolts, dip and wipe? worked for me so far.

OlBlue

Thanks Thumper 549! It never hurts to be reminded, especially in my case

A .020 over gasket would drop compression from 17:1 to 16.98:1. Would the extra thickness in the gasket metal make it rigid enough to seal worse against the block deck and head if they are within .002", .003" and .006" parameters, but I have no way of measuring the .0004" parameter?

It doesn't look like I can get the head o-ringed around here.

TIA
Rob

thumper 549

do they sell a thicker head gskt. for a isb?? I asked around here and the ans was no from cummind n.w. .... To my knowledge so far the only option is changing the deck ht. of the block or diff grade pistons..but i live in the boondox where the most up to date info is not current.
Can you mill that head to get the kinks out??
g.b.

J.R. Adkins

[quote author=thumper 549 link=board=4;threadid=22698;start=0#msg213155 date=1069622133]
do they sell a thicker head gskt. for a isb?? I asked around here and the ans was no from cummind n.w. .... To my knowledge so far the only option is changing the deck ht. of the block or diff grade pistons..but i live in the boondox where the most up to date info is not current.
Can you mill that head to get the kinks out??
g.b.
[/quote]

Sir you can mill the head. Just make sure you take off as lil as need.

PDR sells a thicker 12v moddefied HG to fit the ISB's

Hope that helps.

J.R.