97 Etc N* Head Gasket Project

[zonie77]

Ranger, the cast iron blocks held up but the aluminum radiator hose necks corroded pretty fast!

[97Concours1]

How come there has never ever been a Northstar taken apart with a bad head gasket, which still has ALL good threads? I'll say it again, never a bad head gasket, with NO bad threads. They ALWAYS have some bad threads too! If the gasket goes first, wouldn't we be seeing cases of bad gaskets with all good threads?

To solve this for good, I think we need a new show called - CSI Northstar!... LOL

[zonie77]

I know there has been at least one a few years ago. That's the one that pulled the threads on the last bolt, final torquing. I believe there have been a few others that asked about the necessity of inserts.

I can see why this "syndrome" exists. Due to the design, free standing cylinders, you get a leak into the water jacket under load. It still runs well, doesn't put coolant in the oil, and only overheats under load. It takes a while to diagnose and when you hear the cost takes even longer to commit to fixing. This gives the depleted coolant a chance to corrode the threads. Less than perfect casting, porosity, and smaller than optimum bolt sizes all contribute.

The point is initial failure is not obvious and does not get repaired in a timely manner.

[tateos]

I think zonie is right. The left bank was the one that let go, and had a w really bad and 2 kinda bad holes. The right bank appeared to be still holding, but had 7-8 with bad threads. Also, why is it that good holes are always dry, and the bad holes are always wet or at least slimy? I think because it is the gasket that goes first. I'm still not sure why coolant, even if a little degraded, should cause such metal degradation, except maybe the combustion gases are a catalyst.

[zonie77]

The dexcool loses any protection when old, the older green still offered the silica coating.

The heat from combustion gases definitely would speed up the chemical reaction. Was it double for every 10 degree centigrade rise? That sounds too extreme...hmmm.maybe someone with a better memory will chime in.

[tateos]

On both banks, one pair of cylinders shows evidence of leakage between adjacent cylinders, and on the left bank, I think it broke through to the coolant passage. Although all the entire bottom side of both head gaskets is pretty deterioted and rusty, notice the difference in the areas where the two fire rings are really close. On the photo on the right, you can see the line of each combustion chamber and the area in between the cylinders. On the photo on the left, you should be able to see the difference.

[97Concours1]

This is probably a good point to mention that the little "burr" at the top of the cylinder liner has a purpose and should not be removed.

Head location dowel removal: I used a slide hammer. I drilled a hole crossways through the dowel and also though the end of a slide hammer shaft. Put the shaft in the dowel and then put a pin in the cross drilled holes. The dowel can then be driven out with little or no damage.

Also, Lisle makes a nice 10mm hex drive with a 1/2 in drive, just for head bolts.

[tateos]

97Concours1:

Thanks for info on the Lisle tool. I suppose the 3/8" drive Craftsman tool will work if it got me this far, but that is good to know if I do have a problem. So you did not have to replace the dowels? If anyone did, and knows the part#, please let me know.

[ramdge]

I believe the part number for the dowel pin is
GM PART # 3522352 .

I believe they are like $7 dollars each.

[tateos]

Thanks ramdge. Assuming that is the correct #, GM Parts Direct shows the following:

3522352

MSRP $7.02

Our Price $4.16

[97Concours1]

I wound up replacing two of the four dowels because I didn't use the slide hammer on two of them. After destroying two, I decided to try to find a better way to get them out. One thing about the using the slide hammer; drill the cross hole close to the block, but don't let the drill bit hit the block. If the cross hole is too close to the top of the dowel, it will tear out when you use the slide hammer on it.

Yes, 3522352 is the part # I bought too. Dealer had them for $6.88 each.

Also, if you are changing the rear main seal, I found them at Advance Auto for $17 each. This was the new design version too. I couldn't find them anywhere else nearly that cheap.

I couldn't find the part # for the Lisle 10mm head bolt socket (for reference). Lisle's Torque Angle Meter works great too for torquing the head bolts (P/N 28100). Thats another thing. Head bolt torquing. The new specs are 30 Ft-Lbs, 70 deg, 60 deg, 60 deg. There was some talk about only going 45 deg on the last pass. If I did another one, I'd think about only going 45 deg. The end of the last pass gets kind of scary.

[tateos]

Didn't get too much done this weekend - the wife came back from being in Boston for 19 days, so I had a LOT of house cleaning to do before she got here!

I didn't "destroy" the dowels - just mangled them. I was able to grind them smooth enough to re-insert, so I may be able to re-use them. I'll test fit them and if there is any problem, I'll just get new ones. I will tap the bottom row of the left bank with the block out of the cradle, since otherwise the tap handle will interfere with the trans and exhaust. I guess I could rig up some kind of extension, but since I am pulling the block to change the oil pan and rear main seal, there is not a problem.

I plan to use the old head bolts inserted into the new inserts to left the engine off and back onto the cradle. Not sure where else to lift from...anyone think there is any problem with that?

97Concours1 - I plan to replace EVERY seal and gasket I can while this engine is out of the car, so I plan to buy the entire FELPRO cylinder head and block gasket sets and also new cylinder head bolts from Rock Auto. What is scary about tightening the bolts - were you afraid they would snap? Afraid the threads in the block will let go? Besides, would 15 degrees make that much difference?

[97Concours1]

Originally Posted by tateos

I plan to use the old head bolts inserted into the new inserts to left the engine off and back onto the cradle. Not sure where else to lift from...anyone think there is any problem with that?

That's what I did too. I put a long socket on the head bolt first and actually tightened the head bolt against the block ("sandwiching" the flat steel link of the engine lifting chain against the block).

Originally Posted by tateos

97Concours1 - What is scary about tightening the bolts - were you afraid they would snap? Afraid the threads in the block will let go? Besides, would 15 degrees make that much difference?

The bolts are getting expotentially tighter on that last pass. It just seemed like overkill to me at times. I don't want to talk anyone into stopping at 45 degrees though. There was talk on this forum that a mechanic stopped at 45 degrees on ones he did, but there was no long term report that this was a good thing to do.

Threads letting go? If they where the original aluminum threads I'd be very concerned, but with the Norm's inserts I wasn't.

[dhm37]

I have used Norm's inserts on two engines now, after using the Timeserts on the first job. With Timeserts, two of the inserts seemed to give on that last pass. But with Norm's, I actually broke a headbolt when I got lost in the count on a hole, and over tightened - a lot. It was fun getting the bolt drilled so I could get it out, but the insert was solid. I would not want to back off of the last torque cycle for fear if lifting threads in the engine.

Might be an interesting test for someone to try - using old block and torque four or five bolts to spec, and then see how much more they can take until threads pull or bolts snap. From a sample of one, I have seen the bolt snap first, and I was probably 70 degrees past spec.

[tateos]

dhm37 - thanks for the info and also for alerting me to be careful not to lose track of where I am in the tightening sequence. I think I will write it down as I do it.