Educate me on Iron Headed LT1

[Schweet97Z]

What did they come in. What serial numbers should I look for an where. What will tell me if the motor is an L99?

[BLK95-Z]

I know they came in the D and B bodys from 94-96 and had about 40 less hp than the aluminium headed LT1.

[popo8]

I think 327 means 5.7 LT1..... I know its not a direct answer, but its a start.

[94Blackbird]

Yes, the 327 on the block means it's an LT1. As far as I know, every LT1 block was stamped with the 327 marking, even the 4 bolt main blocks.
There are two different casting numbers for heads, 290 and 320. So far the only differences I have been able to find are the two different numbers.
The Iron headed motors also have larger 64cc combustion chambers and stock for stock flow better than the earlier aluminum heads. That's why a stock Impala SS head gasket is significantly thinner than the stock f body or corvette (.029 for the Impy and .049-.050 for the corvette and f body depending on the source)
The Iron LT1 heads are the basis for the 96+ Vortech 350 heads found in trucks and other large vehicles of that era.
As stated, the Iron LT1's are down a hair on power compared to the aluminum headed motors, but that is because the cam that comes in those motors is designed for the kind of torque that is needed to get a 4000+ pound boat off the line faster than snail speed. The peak torque comes on much sooner and I believe the curve is a little broader, but don't quote me on that. But because of that, stock Iron head motors tend to run out of breath up top.
Also, all Iron headed motors came with the upgraded opti. B and D bodies got it in 94 when they debued the LT1 Iron head motors, while everyone else got it in 95.
That's about all I can think of off the top of my head right now.

[Schweet97Z]

So what did the l99 have stamped on the block? What were the casting numbers for the l99 heads?

[94Blackbird]

L99 block casting number last 3: 588
L99 Head casting number last 3: 890

[Schweet97Z]

Thanks alot! :finger:

[95ImpySS]

If you have the vin from the vehicle you can tell what came in it from the factory by the 8th digit. P means 5.7 LT1. W means 4.3 L99. Also L99s had 19lb injectors. I'll see if I can find part numbers from all the Injectors used. IIRC the L99 had just numbers on the back of the block. Not "5.7l". I pulled L99 out of a 95 Formula at the junk yard once. Man was I pissed.

[94Blackbird]

Also, Iron heads have press in studs where as Aluminium heads have screw in.

[killerz28]

I have access to what i believe are 3 of the iron headed lt1s at a junkyard near me. They could be l99s i'm not sure but is there any value in them if they are the iron headed lt1s. They might be out of police cars, if so is there any difference to the heads?

[79LT1Monte]

I have a set of cast iron heads from my first build that are in great shape, I swapped them for a set of aluminums for the weight savings. If you are interested in them let me know.

[94Blackbird]

If they are out of police cars, then they are probably LT1's. The best way to check is to either pop the valve cover and look at the head casting numbers or look at the block casting numbers. And there are no differences between Iron LT1 heads, they are all essentially the same.

I've got a set of either casting number Iron heads, and so far I can't find any differences. I haven't had them flowed to see if there are any differences between the two different castings there, but from everything I've found so far, the only difference between the two LT1 Iron castings is the numbers