LT1 casting numbers

[footjoy]

I bought a LT1 with casting number 10125327 which I hope is 350. It also has numbers 527LGSG7 or 5.7LGSG7 maybe those gs are sixs date G186 any help with that middle number would be helpful someone read those to me so I am not sure if it is correct it was on drivers side behind the head.

Thanks Footjoy

[CKJ]

last 3 digits on the block 327 means its a 5.7 350 I can at least tell you that much, the rest i don't have a clue :lol:

[mrcadillac]

all Lt1's are 350's... and they are all the same, except the one that was put in the corvette which was a 4 bolt main. I would not worry about the casting # on the block. Unless your after a #'s matching deal...

If it's an engine outta a B-body, it should have irons heads... and all the iron heads were the same. Alumium heads are a different story. early castings flow less, but are what you want to go all out with porting.. later casting flow more, the same as the irons, but don't have as much room to port.

[72camaross]

all Lt1's are 350's... and they are all the same, except the one that was put in the corvette which was a 4 bolt main. I would not worry about the casting # on the block. Unless your after a #'s matching deal...

If it's an engine outta a B-body, it should have irons heads... and all the iron heads were the same. Alumium heads are a different story. early castings flow less, but are what you want to go all out with porting.. later casting flow more, the same as the irons, but don't have as much room to port.


Well don't forget some of the lt1s put in the big cars could have been 4.3L instead of the 5.7..

[Greg Norris]

all Lt1's are 350's... and they are all the same, except the one that was put in the corvette which was a 4 bolt main. I would not worry about the casting # on the block. Unless your after a #'s matching deal...

If it's an engine outta a B-body, it should have irons heads... and all the iron heads were the same. Alumium heads are a different story. early castings flow less, but are what you want to go all out with porting.. later casting flow more, the same as the irons, but don't have as much room to port.


not exactly...


there are LT1s that are a 265ci that came in the 94 Caprice's instead of the 350ci that came in everything else.

350 - There are two blocks, one with two-bolt mains and one with four-bolt mains. They both have the same 10125327 casting number, so there’s no sure way to know which one you have until you get the pan off. However, if it came out of a Corvette, it should be a four-bolt block, and if it came out of anything else, it was supposed to be a two-bolt. GM used the two-bolt block for everything but the Corvette because it had plenty of strength and it weighed a little bit less. however, there were some straggler 4-bolts that made their way into production f-bodies

265 - There was only one block used for the 265 cid version of the LT1. It’s a 10168588 casting that had the numbers "4.3" cast on the side, too. It’s real easy to spot if the heads are off because of the small 3.74" bore.


however, depending on how you want to look at it. the 4.3L LT1 was also referred to as the L99 (not to be confused with the LS variant bearing the same name)

[KW Baraka]

Well don't forget some of the lt1s put in the big cars could have been 4.3L instead of the 5.7..

not exactly...
there are LT1s that are a 265ci that came in the 94 Caprice's instead of the 350ci that came in everything else.....
Uh........no :P .

All LT1's were 350ci.

The 4.3L engines (265ci) were.....absolutely......NOT......LT1's. They are L99's.

Also.....some 1994 Caprices did come with real LT1's.

Period......end of discussion :cool: .


KW

[mrcadillac]

I did figure out there there were atleast 2 varriants of the LT1 iron heads. the Flow numbers were not much different.

A 265 LT1? RIGHT. That is not commonly "refered to an L99", it IS an L99. just as the 350 right then in trucks, was called an LO5. It's the PRO code for the engine.

All(or almost all) 94-96 caprice sedan's came with the 4.3, UNLESS, it had the Towing package, was a Fleet car & was ordered with the Optional 5.7, had the Impala SS package(:lol:), or was a wagon... All the Fleetwoods, Roadmasters, Caprice wagons, and Impala SS had the same 350 LT1 as each other, for that year.

Still think that not all LT1's were 350's? Even the 70's LT-1 was a 350! Still wanna talk B-body's? I only have 8, 94-96's right now. And a 94 D-body. :D

I still have never driven one with a 4.3. :dontknow:

[KW Baraka]

......I still have never driven one with a 4.3. :dontknow:
And why would you wanna :dontknow: ?!?!?!?!?!?

:P

KW

[CKJ]

Still think that not all LT1's were 350's? Even the 70's LT-1 was a 350!


Apples vs. Oranges

both grow on trees and are fruits but are two different fruits indeed. But i do see where you were going with that.

[mrcadillac]

apples vs oranges, yea. But The 90's LT1 in stock form would give a 70's LT-1 a run for it's money! Given similar setup cars. Now THAT is an impressive feat, considering the 90's LT1 was put into grandma's run of the mill Roadmaster, and Grandpa's Land Barge Fleetwood. and the 70's LT-1 came in what, 1/4 mile destined Camaro's?

[mrcadillac]

And why would you wanna :dontknow: ?!?!?!?!?!?

:P

KW

Just so I knew how much they sucked. I would have to guess... about as much as the 90's Ford 4.6 sucked!

[72camaross]

You guys are right, the 4.3L is an L99. Would any of you know if an LT1 got the numbers "GM 4300G" stamped into the back? And what's the best way of going about finding the number??


I can't find just 4.3 stamped in (unless that's it right there) and I don't see 327 anywhere unless I'm looking in the wrong place. I couldn't see the casting number, probably cuz the block is dirty and needs more engine cleaner and it is still in the car.. I would appreciate the help so I know if a greasy guy screwed me or not...:dontknow:

[CKJ]

If its indeed a LT1 then it should have 327 stamped on both sides of the block right in the middle in about 1" tall letters. Look above your motor mounts for the 327 letters.

[mrcadillac]

http://www.karl-ellwein.org/2005engineprojects/blockpainted.jpg

[KW Baraka]

You guys are right, the 4.3L is an L99.......I couldn't see the casting number, probably cuz the block is dirty.....and it is still in the car......

1. I'm assuming this car is a B-body ;) .

2. If so, does it have a SPID label on the inside of the trunk lid? The SPID is a stick-on paper lable with all option codes for the car. It will have either LT1 or L99 to signify the engine the car came with.

3. The 8th digit in the VIN will also tell you what engin came with the car. If that digit is a 'P', then the car came with a LT1 engine. If that digit is a 'W', then it came with a L99.

Best I can do for ya given the available information........

KW

[72camaross]

Thanks KW,

yes its a b-body, I will get more info tomorrow when I go back to the garage. But something tells me this car was a V6 that was upgraded. I spoke to the guy I bought it from and he had no clue what he was talking about...kept saying it was an lt1 because thats what a magazine said...(the magazine i have and it says all lt1s came with an opti spark..but he thinks nothing else did) so i'll probably have to swallow that i lost that money and start over but I will post for sure what it is.

anyone wanna buy an L99?? lol

[KW Baraka]

......something tells me this car was a V6 that was upgraded.........anyone wanna buy an L99?? lol

The 4.3 L99 is a V8 ;) ........but it's noticeably weaker than the LT1.

Also, L99's have the opti-spark just like the LT1. As a matter of fact, the L99 and LT1 will look EXACTLY alike when you look under the hood. But as Cory's photo shows......if you look at the side of the block (from under the car) and see the "327" stamped there, then you KNOW it's an LT1 :thumbsup:.

Good Luck!!

KW

[72camaross]

jacked the car up, saw 588 on the side of the block... so there is a 94 caprice for sale with an L99 in it haha. But you'll have to replace all the windows... :)

Gonna have to start over to find a power plant for my 68. live and learn I guess.

Thanks for your help guys.

[KW Baraka]

......Thanks for your help guys.

No problem!!!!

Best of luck with your search ;) !

KW

[IMPALADAKID]

Actually, the 4.3 L99 is not bad in a 9c1 with the 3.23 rear ratio. It gets a bit better mpgs, but gives up 60 hp.
On the back of the block, below the head you will also see a 5.7 stamped on the ledge where the transmission mounts