Re: 4.0 Head on a 258 shortblock

[farna@xxxxxxx]

On May 5, 2005 Brien Tourville wrote:

> YOu can make sleeves to take up the
> slack between the 1/2" holes of the
> 4.0 head and your 7/16" headbolts
> or you can tap your block to use
> 1/2" headbolts (better).

You really only need to drill/tap two head bolts, one on each end of the engine, to properly align the head. The 7/16" bolts can be used in all other holes.

One thing I failed to mention is you must have 81 or later intake and exhaust manifolds when using the 4.0L head. The intake ports are higher on all 4.0L heads, higher still on 91+ models, than 199/232/258 ports. That's the main thing that makes the swap worth-while. The higher port makes for a straighter shot into the cylinder, which increases flow even though the ports are actually smaller (increase in velocity increases flow). You can make an early intake fit by unbolting the exhaust manifold, but will still need to use a 4.0L manifold (best idea!) or 81-89 258 manifold. If you use an 81-89 you will also need to make plates to hold the manifold s on as the washers used stock aren't large enough. 

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