To rebuild or not rebuild, that's the question!

[markjohnson]

On the subject of these 1972 casting LS-6's, I have one and have seen several others so there are definitly a number of them out there. Mine is also gang stamped TO610CRR with no VIN #. The block is a #289 block, not the #512, and has a F-7-72 casting date. Even the cylinder heads are 1972 castings with the rectagular port/closed chamber configuration. This motor has never been apart until I purchased it and verified what it was. Don't forget that motor has factory forged pistons and they tend to burn a little until they warm up to operating temp. It's a hot rod, they require more maintenence than a regular car. If you feel that you have to rebuild that motor, just use a good Fel-Pro permatorque head gasket and you'll be fine. NO WAY would I ever attempt to deck that motor and have the machine shop forget to stop the grinder, answer the phone, pass on to another machinist, and lose those numbers on the front. It doesn't need it. Bad things do happen. Too risky.

[budnate]

[ QUOTE ]
One quart in 500 miles is nothing I would worry about. It's not your daily driver. I would leave it alone. I sure wouldn't bore it. 24000 miles it should not need a bore.

[/ QUOTE ]

thats what I was thinking, take a afternoon and replace the rubber valve seals under the springs and set the valves bet that cures about 80% of the oil usage.

[Mr70]

Mark
Is your #289 Block a two bolt main block?
Many Cars got this from 1972 +,rated anywhere from 215HP-270HP.
But mainly I refer to this as a 72-78 Truck Motor.

[markjohnson]

Most of the #289 blocks I've come across are two bolts, but I've pulled the pan and it is a factory four bolt main, steel crank, 7/16 rod engine. Even the heads are 1972 #291's with the #569 aluminum pancake intake manifold. The camshaft is even stamped the correct number as a stock LS-6 camshaft. I would almost bet that tirebird's LS-6 is also a #289 block. Like I said, I've seen a few of these 1972 LS-6's and can only conclude that Tonowanda ran a batch of these for whatever reason. The normal LS-6 crate engine that everyone knows came with rectangular port/open chamber heads and lower compression. By the way, this has ran 11.80@112 with headers,through the mufflers, on BFG drag radials.

[olredalert]

Tirebird,

------Can you give us your reasoning for using Mobil 1???
------I had an oil consumption and lifter noise problem with the crate 502 in my Suburban with Mobil 1. A very good local engine builder told me to switch to 15/40 good quality regular oil. This quieted down the lifters a ton and cut my oil usage in half. Oh yah, I have just over 130,000 miles on the motor now, and it uses a quart per thou. It has also surprized a few 5-liter Mustangs and gets right around 17 miles to the gallon without trailer. Thats about 2 miles to the gallon better than the 454 I took out. There was quite a bit of computer re-programming involved in getting this mileage figure.........Bill S

[markjohnson]

Upon re-reading this thread the "215-270HP truck motor" comment almost comes across as insulting. General Motors saw fit to produce and stamp these '72 produced engines as 1970 LS6 CRR emgines and that's what they are and always be. It is a real LS6. Tirebirds' is a real LS6. I'd like for someone to show me a truck motor that comes with rectangular port heads and a solid lifter camshaft. Alan Colvin has even looked into these several years ago and could not explain the engine suffix. If anything, it's much more rare than the common #512 1970 block.

[tirebird]

Wow you guys are great. First, Mark you, of course, win the bet. It is a #289 block 4-bolt block. However, because of the TransAm hood scoop, it has an aluminum Corvette intake manifold, #3963589.

I, like many of you, would love to solve the mystery of my and probably dozen of other #289 4 bolt engines with #291 heads. Even Alvin Colvin, the author of "Chevrolet by the Numbers", had a correction on his website for his Chevy bible regarding the #289, ” Some blocks have 4-bolt mains...several 4-bolt main blocks have been found."

Why did the Tonowanda plant use this block for warranty replacements and not the #512? It's an intellectual exercise that has no practical application. But, like all mysteries, it would be fun to know the answer.

Bill, you ask a good question. I've always used Mobil 1 in all my previous cars; a 63 Stingray and a 69 Z28 with a DZ302. I think it's the best oil to control wear, to keep the engine clean, and to prevent damage during high engine speeds and/or with high temperatures. I've seen high mileage, even abused engines taken apart that used Mobil 1 during their lifetime and was impressed with how little wear they've suffered. And, wear is what, most of all, I want to prevent with this rare block and heads.

Now, even with that said, the engine builder echoed what I've heard from other experts, that the Mobil 1 is so slippery it may be the reason so many people have oil consumption problems, with oil slipping past the oil control rings and the valve seals and guides. But, other than consumption issues and, of course the expense, I don't think I'm damaging my engine by using Mobil 1.

I've replaced the valve seals and I've decided that may be the extent of my rebuilding. If I do any work on the car this winter, it will be only to the heads for valve guides, hardened seats, and a general stuff. Thanks again everyone.

John

[SamLBInj]

I use synthetic oil in all my new vehicles, work trucks, harleys, ect How many are using it in there muscle cars?
Also, is that Slick 50 still around, I remember in the commercial a bunch of white coat scientist guys all used regular oil and one guy was a using a quart of this stuff, They all drained the oil and let the motors run, all siezed except for the slick 50... Im pretty sure it was slick 50, could have been something else, anyone remember?

[markjohnson]

If you go ahead with the head rebuild this winter, please make replacing those heavy two piece welded valves your first priority along with good retainers and keepers. These motors were notorious for breaking/dropping valves and this usually wipes out an entire motor. This is especially true on 4-speed cars with Ronnie Sox/Dave Strickler wannabes, but a great idea on all these old performance big blocks. Even the cheapest Manley valves are a vast improvement in performance and reliability. This is something I need to get around to also. By the way, we probably have the same intake. It is the #569 aluminum low-rise pancake manifold. I know you have the shaker hood on your 'Bird, but if you could fit the earlier GM aluminum hi-rise on the motor, it's worth quite a bit more power. Worth the effort.

[bigchevydaddy]

On Mobil 1 --

My work truck has had Mobil 1 since new. Recently found a broken head bolt, and pulled both heads to replace all head bolts and inspect. Was very surprised to see on this 90K- mile engine that there was no ridge in any of the cylinders and the original hone marks were still visible on the cylinder walls. Can't argue with no wear. BCD.