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Got the time this evening to remove the pistons and crank, and everything went well:
Pistons were all in good shape, and I was easily able to gently remove them from the bores.
All the crank journals are in excellent shape, and can spin the crank over a couple of times
Everything was going GREAT, and then I wiped off the bores for a closer inspection.. I noticed a nick at the bottom of cylinder #7, and after closer inspection found a small crack! Take a look and let me know what y'all think, looks like I may have to sleeve this cylinder:
This is pretty disappointing, but it sounds like it can be saved and isn't that big of a deal. I'm hoping for the best and getting the engine to the block shop this week to see what they say!
Dissapointing!
Chipped cylinder,a crack and copper bearing showing. Hmmm...
Could be a sign of a rod / bearing problem in the past.
Maybe something else is bent. But sleeve is no big deal.
Best to have your local machine shop inspect everything to see if OK.
It should have eight forged rods with pink marks. And they should be straight. Crank too.
Dissapointing!
Chipped cylinder,a crack and copper bearing showing. Hmmm...
Could be a sign of a rod / bearing problem in the past.
Maybe something else is bent. But sleeve is no big deal.
Best to have your local machine shop inspect everything to see if OK.
It should have eight forged rods with pink marks. And they should be straight. Crank too.
Considering the engine was rebuilt and doesn't have the LT-1 crank anymore, rod problem was my assumption. But after talking to some engine builders this evening, apparently that cylinder get's damage at that exact spot in an SBC from two things commonly: 1) factory machining of the distributor , 2) when being bored, the bore caught the lip and damaged it.
Where would these "pink" marks be? How can I tell if they're stock forged rods?
I did not notice before that you no longer have the LT-1 crank.
When I looked closely at the pic in post #422 I could tell.
You reported a 3932442, which unfortunately is just a standard cast crank.
It could be out of a 305 or any garden variety 350.
If I were you I would consider finding a forged crank if you want to spin it past 6000 rpm very often.
The forged cranks are at least 36% stronger, or more.
That is the real "heart" of an LT-1.
Here is a list: http://www.jimsperformance.com/cranks.html
And here is a pic of how to tell them apart by a quick look. Just look for the wide parting line.:
The rods are much less special. They were basically just standard chevy rods that were magnufluxed, and given a pink stripe on the middle of the rod to tell them apart. Anyf 50 year old rod at this point should be magnufluxed and checked for straightness anyway at this point, if you are going to run it hard. And with ARP bolts added you will be good for 7000. The factory rod bolts were the weakest link. They sometimes let go around 7000. The ARPs won't.
Question: I can tell you have a 4 bolt block. But do you even still have the correct dated coded and pad stamped block that would have been original to the car?
Many of these hi-po motors were raced, til they broke, back in the day.
I did not notice before that you no longer have the LT-1 crank.
When I looked closely at the pic in post #422 I could tell.
You reported a 3932442, which unfortunately is just a standard cast crank.
It could be out of a 305 or any garden variety 350.
If I were you I would consider finding a forged crank if you want to spin it past 6000 rpm very often.
The forged cranks are at least 36% stronger, or more.
That is the real "heart" of an LT-1.
Here is a list: http://www.jimsperformance.com/cranks.html
And here is a pic of how to tell them apart by a quick look. Just look for the wide parting line.:
The rods are much less special. They were basically just standard chevy rods that were magnufluxed, and given a pink stripe on the middle of the rod to tell them apart. Anyf 50 year old rod at this point should be magnufluxed and checked for straightness anyway at this point, if you are going to run it hard. And with ARP bolts added you will be good for 7000. The factory rod bolts were the weakest link. They sometimes let go around 7000. The ARPs won't.
Question: I can tell you have a 4 bolt block. But do you even still have the correct dated coded and pad stamped block that would have been original to the car?
Many of these hi-po motors were raced, til they broke, back in the day.
Leigh,
Keen eye as always! I have confirmed that it's a run of the mill cast crank, but I won't be replacing the crank or the rotating assembly since it's in great condition. The block and pad are all correct numbers , and match the VIN. It's all posted on page 1 I believe on this thread. So it seems that the original block was rebuilt, but crank and cam replaced at some point. I have no history on the car, and don't know why some of the weird stuff has been done in the past. They really bastardized an LT-1!
I'm not planning on ever hitting 7000RPM, but definitely be visiting 6500! ARP rod bolts are cheap and easy insurance, i'll add that to the list!
I'm guessing the engine spun a rod bearing badly in the past and killed the crank.
Too bad it's gone. If you do not want to replace it, a cast one "should" be good for 6500 rpm and 500 HP if it is in good shape.
I would still have it magnafluxed for cracks.
I'm guessing the engine spun a rod bearing badly in the past and killed the crank.
Too bad it's gone. If you do not want to replace it, a cast one "should" be good for 6500 rpm and 500 HP if it is in good shape.
I would still have it magnafluxed for cracks.
That was the whole point of the LT-1. It was race ready, so it was as tough as nails on the street.
You picked a pretty healthy cam, which means you will be revving it right to the edge of the safe rpm zone of a cast crank.
With a steel crank you would not have to worry.
There is absolutely nothing wrong with turning a crank .010 under. Most are now.
Without the steel crank, why run the forged pistons? Without the rpm you don't need a 4 bolt main block.
Then it's just a regular chevy 350.
Without the HD forged parts inside, it's just not an LT-1 anymore.
I agree with Leigh.
If you are looking at running this engine up to 6500, one mis step could easily put you at or over 7000.
A forged crank is a little insurance and might just keep you from having to build this engine again.
I spent the additional money on a forged crank and even replaced my numbers matching block with a 4 bolt block just for some piece of mind and savings down the road.
The machine shop doing your work may even have a forged crank they have already checked.
That was the whole point of the LT-1. It was race ready, so it was as tough as nails on the street.
You picked a pretty healthy cam, which means you will be revving it right to the edge of the safe rpm zone of a cast crank.
With a steel crank you would not have to worry.
There is absolutely nothing wrong with turning a crank .010 under. Most are now.
Without the steel crank, why run the forged pistons? Without the rpm you don't need a 4 bolt main block.
Then it's just a regular chevy 350.
Without the HD forged parts inside, it's just not an LT-1 anymore.
Originally Posted by OldCarBum
I agree with Leigh.
If you are looking at running this engine up to 6500, one mis step could easily put you at or over 7000.
A forged crank is a little insurance and might just keep you from having to build this engine again.
I spent the additional money on a forged crank and even replaced my numbers matching block with a 4 bolt block just for some piece of mind and savings down the road.
The machine shop doing your work may even have a forged crank they have already checked.
I here ya, I just can't imagine, nor have I ever heard of a cast iron crank letting go on a mildly built engine with no power adders. I discussed it with my engine builder today, and he didn't think a forged crank was necessary on my build at my power levels and street use. Said need a lot more HP and nitrous/boost to be at risk on that crank.
Dropped my engine off at Womack's Block Shop today and got some good news on the nick/crack at the bottom of my cylinder: He said he's seen that a lot, and it can happen when boring out the engine. He said the two parallel grind marks above it were done by the previous machinist in order to keep the crack from spreading. He said he's going to radius and deburr it, and I'll be good to go. There's no water jackets or cylinder pressure, or ring contact in that area, so a re-sleeve isn't necessary. He also measured my cylinders, and confirmed that they're actually bored out .60 over! So it's a 360in engine! Someone definitely blew it up good once or twice and had to punch it out!
He's doing the following work:
Install new freeze plugs
Install new cam bearings
Hone out cylinders
Inspect and measure out cylinders, inspect/test block
Hot tank block
repair chip at bottom of cylinder
measure out/inspect crank and pistons
He's doing all of this for $275! surprised at the low price from a reputable engine builder! So I'm putting new rings in it, since he recommended we hone it out and change the rings. Also measuring out the crank and making sure I order correct bearings. It'll be nice and fresh, and ready to go next week!
I have a fresh ground forged 350 crank ready to install. I will probably never need it. I can let it go for $250 plus the ride. Send me a PM if you are interested in the details.
I have a fresh ground forged 350 crank ready to install. I will probably never need it. I can let it go for $250 plus the ride. Send me a PM if you are interested in the details.
What's the casting number on it? Is it an LT-1 crank or aftermarket? The LT-1 is an 1182
No 330550 is a cast crank
The LT-1 was an 1182 or a 3931182 etc.
check Jim's list http://www.jimsperformance.com/cranks.html
But there is no significant difference in 350 forged cranks
$250 is a good deal, and already cut!
I’ve never built a sbc so ignore my ignorance.
If this block is already bored 0.60 over how much more can it be bored before the cylinder walls get too thin?
