4.0L Head Conversion for the 258
 

Recently I've been reading about the 4.0L head conversion for the 4.2L
258 Jeep Engines. I have a 1990 Wrangler with the 4.2L 258 engine
that needs to be rebuilt. While having this done I was thinking of
doing the 4.0L head conversion and was wondering if anyone had any
good feed back for the conversion or negative feedback. I understand
it can give me more horsepower and better gas mileage as well.

After looking into it it seems that the casting numbers for the 4.0L
heads that I should look for are either the 7120 or the 0630 because
of flow rates or something. As you can tell I've read some but am not
very good at this stuff so was hoping for feedback again.

Thanks.

Re: 4.0L Head Conversion for the 258
 

If you are going to be rebuilding anyway, I suggest finding a complete
4.0 and putting your 4.2 crank and rods in it for a 4.6 stroker.



NewbieJeepGuy wrote:
> Recently I've been reading about the 4.0L head conversion for the 4.2L
> 258 Jeep Engines. I have a 1990 Wrangler with the 4.2L 258 engine
> that needs to be rebuilt. While having this done I was thinking of
> doing the 4.0L head conversion and was wondering if anyone had any
> good feed back for the conversion or negative feedback. I understand
> it can give me more horsepower and better gas mileage as well.
>
> After looking into it it seems that the casting numbers for the 4.0L
> heads that I should look for are either the 7120 or the 0630 because
> of flow rates or something. As you can tell I've read some but am not
> very good at this stuff so was hoping for feedback again.
>
> Thanks.
>

Re: 4.0L Head Conversion for the 258
 

If you are going to be rebuilding anyway, I suggest finding a complete
4.0 and putting your 4.2 crank and rods in it for a 4.6 stroker.



NewbieJeepGuy wrote:
> Recently I've been reading about the 4.0L head conversion for the 4.2L
> 258 Jeep Engines. I have a 1990 Wrangler with the 4.2L 258 engine
> that needs to be rebuilt. While having this done I was thinking of
> doing the 4.0L head conversion and was wondering if anyone had any
> good feed back for the conversion or negative feedback. I understand
> it can give me more horsepower and better gas mileage as well.
>
> After looking into it it seems that the casting numbers for the 4.0L
> heads that I should look for are either the 7120 or the 0630 because
> of flow rates or something. As you can tell I've read some but am not
> very good at this stuff so was hoping for feedback again.
>
> Thanks.
>

Re: 4.0L Head Conversion for the 258
 

If you are going to be rebuilding anyway, I suggest finding a complete
4.0 and putting your 4.2 crank and rods in it for a 4.6 stroker.



NewbieJeepGuy wrote:
> Recently I've been reading about the 4.0L head conversion for the 4.2L
> 258 Jeep Engines. I have a 1990 Wrangler with the 4.2L 258 engine
> that needs to be rebuilt. While having this done I was thinking of
> doing the 4.0L head conversion and was wondering if anyone had any
> good feed back for the conversion or negative feedback. I understand
> it can give me more horsepower and better gas mileage as well.
>
> After looking into it it seems that the casting numbers for the 4.0L
> heads that I should look for are either the 7120 or the 0630 because
> of flow rates or something. As you can tell I've read some but am not
> very good at this stuff so was hoping for feedback again.
>
> Thanks.
>

Re: 4.0L Head Conversion for the 258
 

I've checked into that a bit, but not sure I want to go all the far as
of yet. Does anyone else have any thoughts on my conversion and
whether the casting numbers on the 4.0L head of 7120 or 0630 are the
best to go with?

If I change engines completely I've thought of going to the '97 5.2L
tsi engine because I was told that would bolt right in as well.

Thanks.

Re: 4.0L Head Conversion for the 258
 

I've checked into that a bit, but not sure I want to go all the far as
of yet. Does anyone else have any thoughts on my conversion and
whether the casting numbers on the 4.0L head of 7120 or 0630 are the
best to go with?

If I change engines completely I've thought of going to the '97 5.2L
tsi engine because I was told that would bolt right in as well.

Thanks.

Re: 4.0L Head Conversion for the 258
 

I've checked into that a bit, but not sure I want to go all the far as
of yet. Does anyone else have any thoughts on my conversion and
whether the casting numbers on the 4.0L head of 7120 or 0630 are the
best to go with?

If I change engines completely I've thought of going to the '97 5.2L
tsi engine because I was told that would bolt right in as well.

Thanks.

Re: Re: 4.0L Head Conversion for the 258
 

On Fri, 09 Nov 2007 06:09:08 -0800, NewbieJeepGuy <ndittoo@yahoo.com>
wrote:

>I've checked into that a bit, but not sure I want to go all the far as
>of yet. Does anyone else have any thoughts on my conversion and
>whether the casting numbers on the 4.0L head of 7120 or 0630 are the
>best to go with?
>
>If I change engines completely I've thought of going to the '97 5.2L
>tsi engine because I was told that would bolt right in as well.
>
>Thanks.


I have read in the past about using 4.0 head on a 258 and it is not a
bad idea. A quick search to refresh my memory revealed a article over
in Geocities of such a conversion complete with pic's! It will give
you more HP than stock head and more torque than a 4.0 because of
increase displacement even if you do not stock it more. Again I would
say I think is is a very worthwhile mod.

http://www.geocities.com/035jeep/40L.html
-----------------
TheSnoMan.com

Re: Re: 4.0L Head Conversion for the 258
 

On Fri, 09 Nov 2007 06:09:08 -0800, NewbieJeepGuy <ndittoo@yahoo.com>
wrote:

>I've checked into that a bit, but not sure I want to go all the far as
>of yet. Does anyone else have any thoughts on my conversion and
>whether the casting numbers on the 4.0L head of 7120 or 0630 are the
>best to go with?
>
>If I change engines completely I've thought of going to the '97 5.2L
>tsi engine because I was told that would bolt right in as well.
>
>Thanks.


I have read in the past about using 4.0 head on a 258 and it is not a
bad idea. A quick search to refresh my memory revealed a article over
in Geocities of such a conversion complete with pic's! It will give
you more HP than stock head and more torque than a 4.0 because of
increase displacement even if you do not stock it more. Again I would
say I think is is a very worthwhile mod.

http://www.geocities.com/035jeep/40L.html
-----------------
TheSnoMan.com

Re: Re: 4.0L Head Conversion for the 258
 

On Fri, 09 Nov 2007 06:09:08 -0800, NewbieJeepGuy <ndittoo@yahoo.com>
wrote:

>I've checked into that a bit, but not sure I want to go all the far as
>of yet. Does anyone else have any thoughts on my conversion and
>whether the casting numbers on the 4.0L head of 7120 or 0630 are the
>best to go with?
>
>If I change engines completely I've thought of going to the '97 5.2L
>tsi engine because I was told that would bolt right in as well.
>
>Thanks.


I have read in the past about using 4.0 head on a 258 and it is not a
bad idea. A quick search to refresh my memory revealed a article over
in Geocities of such a conversion complete with pic's! It will give
you more HP than stock head and more torque than a 4.0 because of
increase displacement even if you do not stock it more. Again I would
say I think is is a very worthwhile mod.

http://www.geocities.com/035jeep/40L.html
-----------------
TheSnoMan.com