I would imagine that having the dealer go anywhere near my car for any reason would disrupt it's "harmonious balance"

I agree with the other posters that keeping it clean is super important, but also getting the big lobes in there without shaving or gouging the cam bearings is a biggy. Maybe the fact that these cars are physycally hard to work on causes more mechanics to screw up on the basic stuff. In my experience, no other bike or car that I have ever owned ever got me to say the f word so often as my TA.

 

Couldn't have said it better myself! 4th Gen Fbods are nasty to work on. I swear, everything is a pain in the *** besides changing the oil.

 

dont worry guys... the magazine has convinced me to not swap heads out... Im just going to go a full forged 383 with heads and cam already on it...

Yeah LT1's are a pain in the ***... Worse than TPI's and LS1's.
I wont let the deal touch my car either.... I dont understand how some of those guys are mechanics??? Its ridiculous.

 

I have seen the results of the "mysterious" after heads/cam install bearing problems. Fortunately, both dealers that did the installs were quick enough to bring me the engines right when they noticed oil pressure problems. on tear down, it was obvious that cam bearing 1 was scared pretty badly and scalloping, causing contamination on the oiling system, therefore leading to bearing failure on the rods and mains (no oilfilter in the world has a chance of catching a piece of bearing moving at 300+ FPS.)


My theory is this.... the late model F-body is difficult at best to do a cam swap, miss alignment when first installing the cam, with an AC condensor wrapped around one arm, one hand under the top core support, and playing a game of twister with your toes, easily leads to a damaged cam bearing.


Dennis
Air Flow Development

 

On that note, I have noticed some problems w/ the first/front cam bearing that a lot of people don't when doing a head/cam swap. The top 20% of the bearing is often VERY worn when compared to the rest of the bearing. In fact, in my own vehicle which recieved heads & cam @ 107K miles, the top of the first bearing was so poor we decided to replace it. Apparently the added thrust of the water pump being camshaft-driven causes this, particulary if the water pump's rear seal goes out (as they often do) and causes abnormal play. This theory was further proven to me when I did a cam on a 96 SS that had had an electric water pump put in @ only 22K miles. Even at 96K mi. there was very little wear all the way around the first cam bearing.

 

Anything you want to do major on these motors really requires either to drop the K-member and the whole motor, or to just yank the motor. It's better than risking it and screwing something up. On top of that it's easier to keep the inside of the motor clean in the process.

Bret

 

Personally, I subscribe to the “they’re full of crap” camp on this one, but those of you that are not so sure yet, I’ve got a question for you:
If torquing the head bolts distorts the block skirts badly enough that it’s going to cause a spun bearing, even if you go through a whole rebuild, install new mains… how are you not going to cause the same distortion torquing the heads as part of the rebuild???

While reading MTI’s comments (and all of GMHTP’s recent tech articles) I feel like I can see the words that were written but they’re really saying “pay us for a full rebuild or we’ll toss rtv chunks in your lifter valley, and then you’ll be sorry.” A bit extreme but when was the last time that they published any decent tech anyway?

 

Me too...
Possibly bolt torque plates or heads on it, then line hone it. But some builders even question the torque plate method of honing cylinders, so which way is right?, and why would it whack the whole block out anyway?
I had that magazine for 3 years hoping to see some good tuning articles for EFI, but I really think the average guy on the LT1 Edit list knows more than their whole staff about tuning the F-Body...

 

torque plate, always. for that matter, you should try to get things as close to operating conditions as possible, if you can get them to do the major machining operations while the block is at operating temps...

 

Wouldnt the waterpumps force be towards the bottom of the front cam bearing? The pressure would be downward correct? Unless the fit was somewhat scewed to the top putting it in somewhat of a bind. A cam handle (bought or fabbed ) is a very good tool for cam installation it really gives you a better control when sliding it in. I have actually performed several cam swaps on LT1 cars and classic SBC but never have I had one spin a bearing from it....lol. I agree that you should be clean as possible when doing the swap lots of rags and solvent to clean parts and stuff holes while its apart.

 

Last summer my cat got pluged and my car got pegged in the red. During the winter i put the hotcam + mild ported heads. 200km later 3 mains spun now I have a 383.

one thing i noticed on my new (used) block when they line honed the mains you could tell they were not lined up becuse on one main, one side would be completely honed /shiney while the other side was just touched and the same was true on the next main but oppisite sides.

so if you know the car has never been pegged and i mean pegged in the red you should be allright, but if you know it has I wouldnt bother doing head / cam on it without full rebuild.

these block are probably a lot lighter than old style 350 block hence less webbing and more likely to twist / distort.

 

That statement, especially when widely quoted, requires more qualification and explanation than the magazine provides space for. There are obviously many h/c swaps performed without 'prematurely' spun bearings within 2500 miles, which makes me question the motive or agenda of the folks who say this.

 

great, more input. my only thought is that an LT1 may suffer from thermal distortion in a different way from a gen I or III SBC due to the direction of coolant flow. if that is the case, it would explain why only LT1's would be at risk of this. considering the angle of the head bolts and intake manifold bolts, its obvious that something is being stressed as an intake manifold is tightened. its a matter of what take the brunt of that stress and is it able to handle that stress.

 

I got into a discussion with my mechanic about this kind of stuff a while ago. We were talking about what all I needed to do when my motor went in for a rebuild and he was listing all of the machine work that he knew would be necessary to get everything lined up again.

He figures that the reason for most of the blocks being screwed up (as in, needs lots of machining to align everything again) is the difference in the casting/curing process for the LT1s as opposed to "old school" 350 blocks. He said that back in the day, they would cast a block and then stick it on a shelf for 5 years or so before machining it and using it for production. LT1 blocks were cast and then machined ASAP...they really didn't have time to fully cure before they were put together and stuffed in a car.

Anyone have any input on this? I'm not going to pretend to be an expert, I just thought that theory was interesting and it does seem to make sense.

 

O-neg: I tend to doubt that. Lots of guys doing numbers-matching restorations on older cars search high and low for blocks that have date codes within 3-4 months of the car's manufacture in order to be considered "concours correct". That would indicate to me that the block probably didn't sit around too long before installation in the car, even in the good 'ol days.