Tell me if I'm on the money. The 69 442, 400 and 455(w30?) are the same Blocks. If they are, can you Bore out the 400 ('68 - '69 3.870 4.250) to 455
('68 - '72 4.126 4.250 specs) and use the 455 pistons and crank and keep the same heads from the 400? I'm also assuming that everything else will be the same between the 2 engines. Thanks for any input:

 

No,you can NOT. The 68/69 400 blocks have a much smaller bore,& with that,the cylinder walls are not thick enough to go anywhere near a 455 bore size.The crank & rods are the same as the 455 though.keep it safe,& just do a +.030 overbore on the cylinders.

 

Oh Ok. I always thought that the G blocks were all the same dimensions. The only difference was the bore dimensions. Seeming that the heads interchange between both engines (400 and 455) I would assume that the cylinder centre spacing would be the same also. If this is the case there should be more wall thickness on the smaller bore engine. Now this is all just assumption on my part not having personally seen the bare blocks of either engine. I guess that the cooling chambers might be closer and this might hamper the over boring to 455 specs. Not sure.

 

They have the same EXTERNAL dimensions, but they are DIFFERENT castings from different patterns, which is why they have different casting numbers. Now having said that, years ago Chris Witt claimed to have seen a cutaway G-block that DID have very thick cylinder walls. All I can say is to have the cylinders sonic checked for thickness and see how far you can go.

 

Thanks for that Joe. I will definitely do that when I get it out.

 

Talk to Bill Trovato at BTR.I know he has done a few 68/69 400's,& he might have a good choice for a piston for those.

 

Thanks again for the info will google it asap