I know this has been disecussed but I couldn't find it using search. Is there any way to tell a 4.8 from a 5.3? I am picking up the motor for 71 Blazer tuesday and want to make sure i get the motor I paid for.

 

Far as I know, the only 2 ways to be SURE would be if you had the correct VIN from the donor truck, or maybe take a spark plug out and try to turn the crank until a piston top is at TDC...maybe you can tell if it's a flat-top (4.8) or domed (5.3) piston.

 

What TarheelZ said makes a lot of sense. The only other way to know would to have the heads pulled off to verify what shape of pistons it has.

 

Yep, what they said.
Another way is to pull the pan and check the part number of the crank, I think the 5.3L ( and all other GenIII motors ) ends in 215. The pistons are the best bet IMHO.

 

No external differences, Good luck with the piston thing. Bring a flashlight with you, I dont know how good you can see into the spark plug hole, but I doubt you will be able to see all the way to th ecly wall to see ig its flat top, or dished. Let me know, cause I may be looking for another 6l, and thats the diff between the LQ4, and LQ9

 

thanks I guess I will have to take their word for it.

 

Use a small wire and stick in the spark plug hole and see ifyou can feel the rim on the piston. It should have a small "wall". Just dont get too rough with it.

Derek