3.995" Bore, how big of gasket bore

[CTX-SLPR]

Howdy,

I have my production 4.1L block bored out to 3.995". Is a 4.060" bore gasket big enough to keep the firering out of the block chamfer?

Thanks,

 

[gnxtc2]

Hopefully the engine is not assembled yet.

Put some Dykum around the chambers on the heads. Attached the heads to the block and flip the block over so the crankshaft area is up. Stick your hand through the bore and scribe each bore onto head.

Now check if the chamber extends past the bore. This will determine your gasket size. The fire ring must not land in the chamber. Hopefully bore and chamber are close in size.

Billy T.
gnxtc2@aol.com

 

[CTX-SLPR]

Engine is still in pieces. I have FelPro-1000's for it now with 4.1" bore. The heads are Champion CNC irons so if the chambers fit a 3.8" bore 3.8L block, they will be way inside the 0.195" larger 4.1L bore.

 

[dlafont]

I have a 4.1 turbo. It has the following specs and uses the felpro 1000 without trouble. Not sure of the final bore size is though (I'm not sure how much +.040 takes me to far as final bore size... Maybe somebody can tell me?).

- 291 block, +.040
- Stock turbo crank, 10/10
- Stock rods, resized
- +.040 SpeedPro hypers with coated skirts
- ARP rod bolts and head studs
- Oiling mods

Don

 

[ijames]

I'm pretty sure the stock GM 3.8 and 4.1 gaskets both had fire ring id's that were 0.090" bigger than the stock bore. I always assumed that meant they thought that at 0.060" over, an extra 0.030" clearance was enough.

 

[CTX-SLPR]

I have a 4.1 turbo. It has the following specs and uses the felpro 1000 without trouble. Not sure of the final bore size is though (I'm not sure how much +.040 takes me to far as final bore size... Maybe somebody can tell me?).

- 291 block, +.040
- Stock turbo crank, 10/10
- Stock rods, resized
- +.040 SpeedPro hypers with coated skirts
- ARP rod bolts and head studs
- Oiling mods

Don

4.1L 0.040" over is 4.005"

 

[Lee Thompson]

1000

won't work with a 4.000 bore --you need 1026