2686 Cylinder head

[fknprtsguy]

Is a 2686 cylinder head compatible for a swap on an 88 4.2? i dont see much talk about this head but i got 1 for a deal (free) and want to make sure it will work before dumping in the money.
Hope someone can help..

Thanks

[John]

87-90 Renix head should be the model that came on your block from the factory. Not a H.O. head, flows a bit less than the heads that followed it. Will it work, yes. Is there better choices, yes.

John

[fknprtsguy]

Thank you that answers my question

[5-90]

John - the 2686 was a head for the 242ci/4.0L engine, not the 258ci/4.2L engine. The 4.2L engine should have a 2685 head on it.

The 2686 is a fuel-injected head, and the manifolds for the 2685 may not fit. However, swapping to FI (for your head, you'd find the rest of the setup in a 1987-1990 XJ/MJ with 242ci engine) could net you some additional performance benefit, apart from the 2686 head being a bit better breathing than the 2685 head, and offering slightly increased compression (due to smaller chambers.)

If you want to upgrade to FI, you can swap /any/ 242ci top end onto your late 258ci block - as I recall, your 258 should be late enough to use 1/2" cylinder head screws, which makes it even easier to swap the entire top end. If not, you can have sleeves made (any good machinist should be able to turn them for you, and they don't need to be full-length. 1/2" long should do it...) to expand a section of your 7/16" head screws to 1/2" and positively locate the cylinder head.

[John]

Brain fart............ I missed the 4.2 was thinking of the 4.0 Chero motor.
John

[fknprtsguy]

My main reason for doing the head swap is i put the mopar FI kit on my 4.2 & it pings bad at higher speeds under any kind of load ( slight up hill grade) I was told the only way to really cure the problem was the 4.0 head swap. I just didn't realize there were so many versions of the 4.0 head & don't want to use the wrong head & find out i did it for no reason.

Thanks

[John]

Ok I gather that the answer might be what you were asking after all. Have you read this thread about swapping a 4.0 head to a 4.2 block? viewtopic.php?f=8&t=692 I think it is what you are considering.
John

[5-90]

Brain fart............ I missed the 4.2 was thinking of the 4.0 Chero motor.
John

No worries - we all have our moments of low brain voltage (some of us more than others - see? My hand's up! )

So, just tryin' to help...

[John]

My hand my be locked in that position. Thanks
John

[fknprtsguy]

That is exactly what i'm doing. Just want to make sure i put on the correct head. Going into it i thought a 4.0 head was a 4.0 head. Luckily i found this forum & learned differently. Sounds like the 7120 is my best bet. Thank you all for all your help!