boring out a 4.0

[evanbugay]

everyone wants to put a 5.0 in their stuff,but why not just bore out your 4.0. the 4.0 will pump out more hp than the stock 5.0. my rear main seal just left town, and i always wanted an engine upgrade but now is the perfect time. any suggestions.

 

[Texan01]

Well it would making putting all back into the car a lot easier than trying to shoehorn a 302 in there.

How much you can bore out depends on how thick the cylendar walls are. Probably no more than .030" over would be safe, that'd give you an extra 4 cubes to generate power. 60 over is getting a bit thin even in the meaty blocks from the '60s.

That is unless you sleeve the block with bigger bores than what you can machine out. but even the 4.0 is about as big as you can take the original 2.6 liter block without redesigning the block drastically.

This site has got some useful info for ya.
Dead Link Removed

 

[mrboyle]

One reason many people here are swapping to the 5.0L is due to the weak tranny (auto) the have in the first generation X. It is definatley possible to pump some serious ponies out of the 4.0L, but IMHO it would be money thrown down the drain, considering the tranny couldn't take the abuse.

 

[Diff Whack Daddy]

If you were to bore it out 30 over, what kind of gains can you expect.

 

[LukeDog3D]

You could expect basically negligable horsepower gains, with perhaps a very small gain in torque. Simply boring out the 4.0 will not produce power levels anywhere near the stock five liter.

 

[SteveVB]

.040 over is the max bore.

You may get 1 or 2% out of just the bore increase. Cam and head work will be more fruitful. Do a search I remember a long thread about boring and stroking- even an idea about using 302 pistons and offset grinding the crank -$$$$ if you can spend some money.