4.0 questions

Hey guys,

Got a few ???? about an HO 4.0 I found.

I have read about these engines going 200 all the way up to 400k miles so I know they are durable. I'm looking at one with 142k to pull the head and all EFI stuff off of it and sticking at least the head and of course the exhaust manifold on my Jeep. With 142k, what should I check to see if it needs work??? Or should I just take it to a machine shop to be checked??? Or, should I just fill the water jackets with JB and stick it on????

Owner states that it ran strong when pulled, don't they all???? I e mailed him with questions about why it was pulled and if it burnt oil and yada, yada.

Also, at some point maybe stick the multi port stuff on or sell it since I have TBI on there now and maybe use that cash to replace cam, timing set, and water pump while I"m in there.

So back to the original question. Would you be concerned using a head off an engine with 140k miles on it with having it checked?????

Thanks

High5

 

Certainly I would inspect the head closely. The usual problems with cylinder heads are 1) cracks, 2) burnt valves, and 3) loose guides (oil burning).

I think this all depends on your tolerance for risk, and how deep your pockets are. If you take the head to the shop, they will advise a rebuild - it just works that way. Unless you are willing to disassemble the heads yourself and inspect the valves and springs, you kinda have to tke your chances and install it, or expect to pay a few hundred dollars to the shop.

The shop will dissasemble and tank the head. They will magnaflux for cracks (good). They will inspect the valves - a burn valve will be obvious, but the edges of the valves have to be more than about 1/16" thick after machining to be usable, esp. the exhausts. They will measure the guides (maybe - I think that most shops routinely advise guide renewal). They will check the head surface for flatness (maybe - IME shops routinely advise surfacing).

You pretty much can't get out of the shop for less than the cost of tank, magnaflux, grind, knurl and surface. If you insist on less, they either won't take the job or won't guarantee it. This work will cost at least a couple hundred bucks, depending on the rates in your area.

Note that you can buy a new 4.0L cylinder head for about $500: http://www.alabamacylinderhead.com/productdetail.php?id=109

 

There's a company on Ebay that sells one all ready to go as well. The reason this is appealing is because of the EFI, valve cover, exhaust manifold, and all the wiring. I know it's not new, but the EFI is usually 1500 or so new. Valve cover off ebay is another 100. Exhaust manifold another 100, and the head 400. I may be willing to risk it now since the Jeep isn't a DD. It can sit if need be. This just sounds like a pretty good deal to me and I wanted some input.

Thanks Tim,

High5

 

Glad I could help.

Get a good, long straightedge and measure the head surface for flatness with a feeler gauge, before you install. There's a spec, like 0.002" over the length of the head or such. This is covered in the FSM.

<edit> Also, there is one head casting number that is prone to cracking. Here's the JeepStrokers FAQ about cylinder heads that covers it: http://www.jeepstrokers.com/forum/viewtopic.php?f=27&t=241