I recently acquired a 68 Cutlass convertible that is a 442 clone. It has all of the 442 components on/in/under it other than the VIN # including a 68 400 G block. The engine was running rough when I bought it (seller told me it was the carb). I ultimately did a compression check to find that one cylinder had 55 lbs while the others were 140-145. We did a test with air for that cylinder and the air came out the oil fill tude so we knew that it was a piston/ring issue. We pulled the engine and upon pulling the pistons, found 5 of the cylinders had cracked rings, some of the cylinders had taper in them and 3 of the pistons had material worn away/missing from the rings flexing/movement within the cylinder. The crank, rods, heads, etc are all fine. The bore was the factory 3.870. The thought was to do a bore job to clean up the cylinders and new pistons/rings but new pistons appear to be fairly hard to find and expensive. On the other hand 455s are cheap and plentiful. The car is not a race car but a nice cruiser. I'd like to keep the 400 G block from an originality perspective (yeah I know, that is an oxymoron....wanting originality in a clone). What suggestions/routes should I go for a set of new pistons to use the 400? Or should I just forget about that block and find a 455?

 

The G-block is one of Oldsmobiles worst engine designs. Some folks have gone up to a 4.000 bore on these blocks, giving you a 427 Olds. I think more real 68-69 442s have 455s instead of G-block motors anyway. I'd probably go that way. If the casting number is really important to you, talk to Chris Witt.

 

Correct, you can make it a 427 fairly easily by using a Mopar piston and a 7" rod. If you do that you can make an honest 375hp pretty easily with the right combo.

 

Use a 425, change the casting number to appear to be the "correct" G...
All problems solved.

 

Welcome Jim.
We need some pics....

 

OK, I found a ready to go 455 locally that a guy has in a 69 Cutlass and wants to go to a LS engine. Unfortunately the machine shop has already done some work to the old 400 and so I'm going to have some sunk costs which I need to try to recover if I go the 455 route. What are a set of freshly redone C heads (new valves, guides, hardened seats) and a fresh polished crank worth?

 

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That is nice Jim!
Looks pretty good for a clone.
I couldn't guess on the worth of
the parts though.

 

You can probably recoup some of the costs for the heads and crank when you sell them. What are the specs of the 455?