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4.0 head to 4.2 block conversion

Anyone out there dome a 4.0 head conversion on a 258 engine? I know about the water jacket passages that need blocking and exhaust manifold and valve covers need replacing but what else? It just seems too easy....or is it that easy? I've read a number of articles on the net but none seem to mention about any valvetrain mods needed to do the job. I can't imagine that the rods just go right in without change... and how did you check to make sure the valves opened correctly? Any feedback would be helpful. Thanks, Rich

86 CJ7 1"body lift, 2-1/2"YJ spring Rubicon express lift, Detroits front and rear, 4:10 gears, 1pc axles, Mopar MPFI and other miscellaneous offroad related crap.
Reply to
Richard Harris
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richard-check out this site:

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as far as i know, you should be able to use the stock lifters and pushrods. unless you have the head milled a lot. i'm going to be doing this swap (along with rebuilt block and 258) in a few months. i'll post the results. william oliveri in this group has done the swap.

Reply to
serg

Well, I had the machinist do mine and he told me he used the 4.2L push rods. I used the recommended 4.0L block cast # 7120. Had a 3 angle valve job done on it and the water jackets were sealed by the previous owner as he was going to do this swap but changed his mind.

Other than that, every thing else was stock 4.2L parts on the short block and stock parts on the 4.0L head. No changes to the valve train.

It depends on where you get your exhaust manifold. I got mine from

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and had to add the O2 sensor bug. I also had to modify my tail pipe to fit to the new exhaust manifold. I had to get a new 'donut' fitting to marry to the exhaust pipe.

Just a bunch of little things which did add up.

Bill

Reply to
William Oliveri

Reply to
Richard Harris

I can't give you a clear picture yet as I'm still breaking it in and I need to get a CV Shaft to tone down the drive shaft vibration after I added my 4" lift kit. I get this vibration at around 40 mph so I'm being delicate with it now.

I can let you know further on down the road.

Bill

Reply to
William Oliveri

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