96 3100 Rods

[JohnnyReb]

I did buisness with a well known machine shop for over 20 yrs without a single problem. Two years ago the owner retired and hired a manager. The guy he hired was the manager of a local Autozone. Not one single problem in 20 yrs and thousands of dollars, everything from class 8 diesel engines to my Kohler mower engine. Now a new manager. My first problem was with a head job. Dropped them off with specific instructions to check for cracks and call me if there was a problem. These were Olds 307 Y heads and I just wanted them checked, didn't want to dump any money into them if they were bad. A week later they called while I was gone so I had my wife pick them up. She picked them up and paid my $480.00 bill. Idiots did guides, valves, surface, springs, couple seats and replaced some valves. I let it go, figuring after all those years problem free I'd give em this one. Next I have a 552 forged crank, needs checked and turned. Get the call its done. Go to pick it up and they have a 442, cast, two-piece seal crank in the bag. I say WTF, not mine, not paying and you better find my crank. Now these idiots are sending me a monthly bill and threatening to send it to a collection agency. So yea, mark your parts and make sure they note the casting numbers and any important information on your drop off slip. I now take my stuff to Ohio Crank, at first they thought I was crazy asking for castin #'s, date code and serial numbers if there were any when droppin off parts.

[jp_grasshopper_007]

right-on, we have a rod heater that heats the pin end. then you can push the pin in by hand.

[ForcedFirebird]

I'm not saying dry ice (or cooling metal) won't shrink it. If you have press fit pistons the pin is pressed in the rod not the piston. In that case dry ice will do nothing. The pin and rod will be the same temp.

Any piston you have press or float the pin is not pressed in the piston.

Correct. Cool only the pin, sorry if there is confusion, I'm talking about installation. You can heat the big end of the rod for removal, but even without heating and the right fixture, they can be pressed in and out room temp.

[bszopi]

Try using the MACRO feature on your camera. I can't see anything in those pictures but blurs.

[94GPGTP]

heres the pictures of the cracked heads..

[jp_grasshopper_007]

It's worked in the past for my machining mentor.

Cooling the metal will decrease it's size.

I'm not saying dry ice (or cooling metal) won't shrink it. If you have press fit pistons the pin is pressed in the rod not the piston. In that case dry ice will do nothing. The pin and rod will be the same temp.

Any piston you have press or float the pin is not pressed in the piston.

[94GPGTP]

Between the valve seats and between the spark plug and the valve seat. I think its from overheating...due to bad LIM gaskets.

thats where my heads are cracked.. i remember the auto parts store telling me that thats where they are cracked..

[ForcedFirebird]

The pins should be stuck in the rod not the piston, dry ice isn't going to do anything.

It's worked in the past for my machining mentor.

Cooling the metal will decrease it's size.

[jp_grasshopper_007]

Taylor is right, heating/cooling parts makes the job a no-brainer. Dipping the wristpins in dry ice for about an hour will make them practically fall in without any force. Aluminum is going to expand with heat much faster then the steel pins, and they should come out fairly easy with the proper tools.

The pins should be stuck in the rod not the piston, dry ice isn't going to do anything. How a shop is going to "mushroom" the wrist pin I have no idea. They will have to pressed out, that could damage the pin (maring the outside surface) but more than often not so bad it can't be reinstalled in a stock eng. As far as not knowing if the shop is fucking you or not, don't take your shit there. If you can't trust them don't use them. But, those heads crack, in those spots. See em all the time. LIM gasket leaks for a long time, eng over heats, blows head gasket.

[SappySE107]

Between the valve seats and between the spark plug and the valve seat. I think its from overheating...due to bad LIM gaskets.

[ForcedFirebird]

I have had heads with cracks and seen them at the machine shop. Its more common than I thought.

Really? Although you have seen far more 60* head then me, I'm sure.

Is there a potential weak spot the is common, or multiple areas of concern?

[SappySE107]

I have had heads with cracks and seen them at the machine shop. Its more common than I thought.

[ForcedFirebird]

I somewhat agree on the cracks. I also have not found any cracks on any of the 60* heads I have encountered, although I have found many cracks on aluminum heads in general (all of them overheats).

Yeah, there are a lot of crooks in the biz, but people like me just hope that doing good business will create more in the long run. Sucks, but it does happen in every business category.

Taylor is right, heating/cooling parts makes the job a no-brainer. Dipping the wristpins in dry ice for about an hour will make them practically fall in without any force. Aluminum is going to expand with heat much faster then the steel pins, and they should come out fairly easy with the proper tools.

I have the cores I can send out anytime if you are going to take them local.

[3100 MPFI]

I just mentioned that in the short few years I have been working on these engines, I have NEVER seen a head crack. I have seen them WARP, but not CRACK.

I also mentioned that when I take parts to a machine shop, I write down my casting numbers, and then I make a small engraving on them (in an exposed area like the side of the head) of a symbol that will NEVER be seen coming from GM (gotta love the double-male symbol for GAY).

I also mentioned that I have not heard of a piston mushrooming trying to get the wrist pin out. I have had some pistons swapped out before and got the old ones back just fine. Them saying that strikes me that they are trying to press the pins out without heating them up first (or however they do it). I got a full set swapped out, and the stock ones were not mushroomed in the slightest (camaro pistons on 3100 connecting rods with the 3100 pins).

[SappySE107]

Doesn't have to cause a problem to be cracked. If its not all the way through, you wouldn't know. Vans have more problems with this on the rear head but anything is possible.