All LT1s have '327' stamped into the side, near the oil filter adaptor I believe

 

Could I see that while its in the car or do the engine have to be out to see.

 

A super quick way to tell an L99 from an LT1 is that the L99 uses a smaller alternator. An LT1 alternator will not fit into the smaller bracket so you can always just get an alternator from a parts place for an Impala and see if it fits on the engine in question. If it's too big to fit then the engine is an L99.

At least that's my experience when dealing with these little 4.3 engines

 

im not sure but i bought a 95 caprice wagon and it has a LT1 WITH a small alternator.and my son had a a 9c1 with a 4.3 and it had a large alternator. i was wondering why the wagon had a small alternator.

 

What kind of car did it come out of?

 

Some dont have the oil cooler, mine didnt.

As it was said before, look for the "327" casting in the block.

 

Look on the block where it meets the trans bellhousing, right behind the driver's side head. It should say "5.7 LG" there, if I remember correctly.

Like this:

 

Both the 4.3 and the 5.7 have "327" cast into the lower sides of the block, at least on the ones I've seen. The only real way to tell is to look behind the drivers side head like the picture in the previous post. If it says 4.3l, then it's an L99. If it says 5.7l, then it's an LT1. To just go by an alternator case size is to assume that no previous owner swapped in the best that he could afford at the time........

There's one guy in my state who keeps popping up at a Spring car show with "Southern" 9C1's with LT1's that have later turned out to be L99's once the number on the back pad of the engine block was checked. Just because the SPID label shows an LT1 doesn't mean it actually is..........

Jim

 

First off "LT1" is just an engine type. I came in either 5.7 or 4.3 liter versions.
Second: Alternators is no way of knowing. I have seen them go both ways on both engines.
Third: "327" was the casting for both engines.
Fourth: 5.7 engines came without out oil coolers. It was a merchandise option for the 9C1 for the police departments. It was to help them sell. Personally they were not needed. Roadmasters came with out oil coolers. At one time you could by the oil filter adapter without the cooler provisions. GM discontinued those but I have one brand new.
The only way to tell is on the back side of the engine by transmission bell housing.
If you put a 4.3 & 5.7 side by side you could not tell them apart except by looking at the backside where it is stamped.

 

First off "LT1" is just an engine type. I came in either 5.7 or 4.3 liter versions.

LT1 is a code for a specific engine model, a 5.7 liter engine. Either a 2 or 4 bolt main, iron or aluminum head but always 5.7 liters.

The 4.3 is NOT an LT1, it's the L99. Agreed it's built on the same platform but that doesnt make it an LT1.

 

Well the engine is already sitting in the car so I guess I have to see if the 5.7 pcm starts that babe up or if the 4.3 one will I'm just crossing my fingers. But for the alternator statment I'm swapping mmy l99 for this socalled lt1 and my l99 alt was a big 140 amp.

 

I have never had an L99, so I'm not sure. but wouldn't either PCM start the car. But if it was the wrong one, it would just run like Sh*t?

Does an L99 have 588 cast into the side?

 

Yes the L99 says 588 in one of the places the LT1 says 327 but it also says 327 in another spot, too much chance for confusion.

Far as the pcm thing, an L99 pcm absolutely will start a LT1 and vice versa.

 

I admit I was wrong on the first sentence, & as for the "327" I have seen on it on both the 4.3 & 5.7. If I am wrong everywhere else correct me.

 

My lt1 wagon uses the smaller 105 amp alternator but it also has crank windows, manual seats and no options. My L99 sedan had the 105 alt and it had the majority of the options. Power windows,keyless entry, leather(not that leather takes electricity) etc.

My lt1 wagon also doesn't have any oil cooler. it uses both sides of the radiator as a trans cooler.

 

You can try everything from checking the vin, spid, looking for dual exhaust, but Dwayne pointed out the absolute best way to tell. Pull the head and look at the size of the bores. It's obvious which is which once the heads come off. For a junkyard motor it wouldn't be a bad idea to replace head gaskets and such anyway.

 

I would not pull heads to check this, most folks wont be able to see the roughly 1/8" difference anyway unless they had two to compare side by side.

Maybe the easiest way to tell on a smashed up junkyard car when you can't see under the cowl or behind the head would be to pull a valve cover and check the head casting number BUT the heads can be bolted on the wrong block and run.

 

im not sure but i bought a 95 caprice wagon and it has a LT1 WITH a small alternator

94-96 non-tow pack wagons got the small alternator.

 

Then why did my 94 non-tow package complete with 2.56s, fixxed antenna, single power seat, the crappy tape deck(as opposed to the nicer one) etc. point being low option, get the big alternator.

People draw conclusions from seeing a single car, it doesn't work.

 

Then why did my 94 non-tow package complete with 2.56s, fixxed antenna, single power seat, the crappy tape deck(as opposed to the nicer one) etc. point being low option, get the big alternator.

Because your car was OPTIONED with the larger alternator. Go look at your SPID.

 

And yet Dwayne's wagon was a non tow-package car that could be optioned with a larger alternator when the non tow package cars --per your statement-- only came with smaller alternators unless they could possibly be optioned with the larger alternator which would make your statement truly false or possibly falsly true.
Which is it? Is Dwayne right, or are you wrong? Please keep in mind that picking either choice will only succeed in making you right about being wrong.......and coincidentally will make Dwayne right about you being wrong. And yet Dwayne is never right on this Forum.......Ahhh the paradox continues.

Got a headache yet?



I can type it slower for you..........

 

You can go ahead and type slower if you like. With 100 posts since you joined up, I'm sure that you haven't offered any real help to the forum.

 

it's ok, the good ole boy network can talk smack all they want, they're not here to help anyone, that's not why they joined.

 

After reading all the crap in this thread,
I am more confused than a blind lesbian in a tuna cannery...

 

Post count has nothing to do with knowledge level. That man's cam only 9C1 ran close to what the "well done" strokers did in St. Louis a couple years back. Like within .2-3 of trailered stroker cars.

...yawn... why don't you two take your bromance over to the misk where it belongs?

V8killer, you are cracking me up!

Hey, supermod... lock up this waste of space...

 

^^^^^^^^^^^^

That time of the month AGAIN?

 

The real shame is that after losing a ton of data and cumulative experience on this Forum, bad information is still being put out there even though most senior members with overly inflated post counts ought to know better. Rather than speculate on possible ways to determine whether the OP had an LT1, I drew from first-hand experience much like you did. Correct?
Then I checked my facts using HP Books "How to rebuild small-block chevy LT1/LT4 engines" which also stated that the only sure way to tell them apart short of measuring the bore was to check the casting behind the driver's side head and made my post.

What facts are you using to back up "all non tow-pack wagons came with small alternators"?

While it might be a fact that the one you owned had a small alternator, that doesn't mean that they all did. And yet you said that "all non tow-pack wagons came with small alternators". Then you said that SOME could be optioned with the larger alternator, which invalidated your previous statement. One of those two statements proves you to be wrong. That's not something that anybody should hold against you as long as you're capable of learning. So are you?

Jim

 

Jim, why are you wasting your (and everyone else's) time with semantics? In case you missed it while you were typing slow, here is what I said:

94-96 non-tow pack wagons got the small alternator.

It doesn't say ALL, as you have mis-quoted me above. Could I expand on that and make it "94-96 non-tow pack wagons got the small alternator as standard, with the 140 amp alternator as optional"? Sure, and you could, as could Dwayne, or hundreds of our other members. I was trying to be helpful, and I get ganged up on by two ITGs. Spare me.

Stop being a jerk. This is my last post on this thread, so feel free to type whatever you like about me, slowly.

Jason.

 

Back on point.

This only applies to '94-'96 b-bodies
If the engine is still in the car then:
Check the vin/spid for the LT1 coding
Check for factory dual exhuast
Check for an 8.5" rear-end
If it's a 9c1 then the rear should be 8.5" with disks regardless of the engine so be careful
If it's a wagon then it got the LT1 regardless of anything

Any of this is contingent on the engine being original though. If there's a chance that it was swapped out at some point then pull the head and measure the bore so that you don't buy an engine you don't want. If it saves you buying the wrong engine and not knowing until it's already in your car, then taking time to pull a head is not that big of a deal. You could always measure the stroke instead

Bore & Stroke (in.)
L99 = 3.74 x 3.00
LT1 = 4.00 x 3.48

 

Should've gotten a engine out of 94-96 RMS/Fleetwood

They all came with LT1s

 

Should of gotten one from a corvette or F-body & you would really have one or steal your neighbors.