ragtopnova

I've tried searching but really can't find much on these blocks. There are gm 4.8L and 5.3L blocks that are stamped "4.8L" or "5.3L" on front passengers side of the block. Most 4.8/5.3L blocks can be bore to ls1 size bores but that's about it. These blocks were supposedly the same starting/casting blocks as the 6.0L blocks; therefore, they can be bore out past 4" just like the 6.0L blocks. Is there a way to know which year range and vehicle type these were put in? Does anyone know anything about these blocks???

TXsilverado

iTrader: (18)

Unicorn? LOL...we're tripping over 4.8 and 5.3 engines around Houston.

ragtopnova

Yep, here also. I'm specifically interested in ones that have the 4.8L or 5.3L that are stamped on the front passengers side of the block. . . like the post says. Trying to find out more info on those specific castings.

TXsilverado

iTrader: (18)

99-present Silverado, Tahoe, suburban, sierra, and most mustangs around here.


make sure to sonic check your 5.3 if you plan to go to a 4" bore. I've HEARD that the gen 4 5.3 has thinner walls, so I would stick to a gen 3 iron block to be safe. all of the blocks I've seen have the CI stamp on them.

murphinator

iTrader: (2)

the older ones I have seen are stamped with both 4.8/5.3 the way to tell which is flattops on the 4.8

TXsilverado

iTrader: (18)

the aluminum block 5.3 also came with flat tops.

big hammer

Supposedly the "unicorn blocks" are stamped 4.8-5.3-6.0

y2k_ta

iTrader: (80)

That's an "old wives' tale". The 4.8 and 5.3 iron blocks had both displacements stamped on the front of the block. Like mentioned above, the only way to tell the which one you have or are buying is by pulling a head and looking at the pistons. 4.8 got the flat topped pistons.

murphinator

iTrader: (2)

pull a plug and use a borescope to check for flat tops if your on a budget and don't want to buy gaskets and replace tty hardware , plus its always nice if you can make power while disturbing as little as possible.

elkydragger

iTrader: (7)

I have a 2000 4.8/5.3 bare block that has been setting out side. It Says 4.8/5.3 on front and back. It would clean up good. $100 plus freight if anybody wants it.