4.0 CYLENDER HEAD REPAIR
- Thread starter OLAF
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5-90
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Olaf -
Valve guides are integral on both cylinder heads, and would require machine work to install separate (usually bronze) guides in the first place.
It is rather common to swap a 242ci/4.0L head onto a 258ci/4.2L engine for a performance boost - as the later head breathes better and offers a slight compression increase.
If you let on with the trouble you're having, perhaps we could give you better advice - my first thought was that you were asking how to weld up a cracked cylinder head (doable, but not recommended unless you're a very good welder...)
Valve guides are integral on both cylinder heads, and would require machine work to install separate (usually bronze) guides in the first place.
It is rather common to swap a 242ci/4.0L head onto a 258ci/4.2L engine for a performance boost - as the later head breathes better and offers a slight compression increase.
If you let on with the trouble you're having, perhaps we could give you better advice - my first thought was that you were asking how to weld up a cracked cylinder head (doable, but not recommended unless you're a very good welder...)
Actually the cylinder head is in good condition, at least two valves are cracked. my jeep is an imported from the U.S.A. and seems that he original valves are difucult t obtain. so I was thinking that I could use the valves
from the 258. now you aroused another question I did ot think of before, can I use the 258 head on my 4.0? will all the fuel injection parts fit on that head? or are there modifications to be made on the 258cylinder head? thank you for your valuable advice. Olaf
from the 258. now you aroused another question I did ot think of before, can I use the 258 head on my 4.0? will all the fuel injection parts fit on that head? or are there modifications to be made on the 258cylinder head? thank you for your valuable advice. Olaf
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That gets a little dicey.
As I recall, the "wide deck" 258ci came around circa 1975, and that would be when they switched to 1/2" head screws (from 7/16" used on earlier AMC sixes. The heads will still swap, but you either have to bush the holes in the block to take 7/16"-14 screws, or bore out the holes to pass 1/2" screws - or go the other way, and sleeve the 7/16" screws out to 1/2", or drill/tap the block holes out to 1/2"-13, or...)
I don't have the heads out where I can look at them - but I'm wanting to think that the intake and exhaust ports may be located differently between the #2685 (late 258ci) and #2686 (1987-1990 242ci) heads - and they damn sure are different between the 258ci and 1991-up 242ci heads!
Are the valves themselves cracked, or are the valve seats cracked? It's just as possible to bore out the integral valve seat and install a replacement as it is to bore out the integral valve guide and replace it with bronze - you just have to have a good machine shop to do it. If it's the valves themselves that are cracked - then, as you've already found, it's just a matter of tracking down a replacement.
I note that you're in Mexico - are you near the border with the States? If you can get someone up here to accept shipment for you and you drive over to pick it up, that could save you quite a bit of trouble...
As I recall, the "wide deck" 258ci came around circa 1975, and that would be when they switched to 1/2" head screws (from 7/16" used on earlier AMC sixes. The heads will still swap, but you either have to bush the holes in the block to take 7/16"-14 screws, or bore out the holes to pass 1/2" screws - or go the other way, and sleeve the 7/16" screws out to 1/2", or drill/tap the block holes out to 1/2"-13, or...)
I don't have the heads out where I can look at them - but I'm wanting to think that the intake and exhaust ports may be located differently between the #2685 (late 258ci) and #2686 (1987-1990 242ci) heads - and they damn sure are different between the 258ci and 1991-up 242ci heads!
Are the valves themselves cracked, or are the valve seats cracked? It's just as possible to bore out the integral valve seat and install a replacement as it is to bore out the integral valve guide and replace it with bronze - you just have to have a good machine shop to do it. If it's the valves themselves that are cracked - then, as you've already found, it's just a matter of tracking down a replacement.
I note that you're in Mexico - are you near the border with the States? If you can get someone up here to accept shipment for you and you drive over to pick it up, that could save you quite a bit of trouble...
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OLAF said:
Well, I was hoping.
If you have trouble finding anything locally (which is fairly likely - the main "performance aftermarket" seems to be up here...) you can try calling a few vendors to see if they'll ship down there. Put a bug in their ear about using USPS - as a for-instance, the "flat rate" boxes I use for cablesets (which should fit a full set of valves without too much trouble and a little creativity) will get down there, usually inside of two weeks, for about $25. I know that's a bit spendy, but it's better than some I've seen (and Parcel Post to CAN or MEX can take up to two months!)
If you get too stuck, someone up here can probably help you out - just don't use me if you're in a hurry, as I'll be gone on holiday for about a week, leaving to-morrow...
