4.1 Which Casting?

[DOC420]

Buick made three different castings of this block all in 80-84. Casting numbers are as follows: 25506484, 25505553, and 25514291. Found a 4291. any good or is it junk?

 

[boostingbuick]

I've been told 484 casting. I have run two of those with no issues. I do have a crack from headbolt hole to coolant passage. The one in my car is like this now with no issues. But if you can find without I would get that. If not then I would hope to get a good price on it.

 

[DOC420]

The block i found has already been to the machine shop and no issues. Should i go for it. i went and looked at it today. looked solid and clean.

 

[boostingbuick]

I have never used that casting number, however I cant see them beeing that different. Have the machine shop drill and tap you return hose for the turbo. Other than the cost of pistons the rest of the build is just like a 3.8. You will need to keep in mind that a 4.1 will need more fuel and loves big turbo's. I love my 4.1. I have no plans to go back.

 

[DOC420]

Thats the only thing i noticed that it did not have a return line hole in front of the block. SHould I just have them bore it .035 over. I would think it would be easier to find a 4 inch piston (350 ci piston) rather than a 3.965. thanks for your 2cents.

 

[CTX-SLPR]

I wouldn't, you will need custom pistons anyway and thinner walls will just up the heat in the motor and make them weaker. My 484 is at 3.995 to keep things as thick as possible. Diamond made me a wonderful set of pistons for about $750 with pins and locks.

 

[87GNSteve]

The 291 is the better block on its deck design.
The 484 is prone to crack from the water jacet to head bolt holes.
For more info go here:
TurboBuicks.com - Build a Budget 4.1 Motor!
and here:
4.1 casting numbers - TurboBuicks.com

 

[boostingbuick]

My 4.1 bore is 4.020. With a f-body radiator it runs in the 190 to 210 range with the air on in 90 degree weather. If you are going to bore it spend the money and have it sonic checked.

 

[49-blues]

.040" over will give you a .005 piston to wall clearance on a 4.00" easier to find piston.

 

[chris]

If your looking for a 4.1, I have one that is ready to go.