Help! doing the 4.0 head swap on a 258!

Maybe a dumb question but have you checked the position of the distributor rotor for pointing to #1 cylinder? If not try turning the crank 360 degrees.

JoBo

You do have 2 TDC positions for #1. One is the compression stroke and the other is in between the exhaust and intake so both valves are tight.

Other than that, did the timing chain get moved?

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Harris Family wrote:

No.

You have 2 TDC's. One has the valves closed, one has them both open. Check the distributor's position.

Mike

Harris Family wrote:

Have you made sure the timing chain is on right? If the chain is not installed correectly, there is no telling where the cam is going to be. the chain must be installed with the crank in the right spot. Actually, the crank and cam are keyed, you can be off by half because the crank goes around twice for each rotation of the cam. It sounds like #1 isn't in the front anymore.

And, I think you probably should be using the 4.0 rockers, etc. I am not sure on that though.

Spin the crank one full rotation.

the crank goes around twice for every rotation of the cam, so the crank can be at the top on one rotation, and the valves are in transition between exhaust open and intake open. You would have troubles putting the pushrods in if this were the case.

Having said that, the rockers and pushrods on the 4.0 could easily be different than on the 4.2.

You use the 4.2 ones.

Mike

CRWLR wrote:

See following article:

The way I read it, use all 4.0L parts regarding the head and 4.2L parts from the pushrods down.

Bill

This site implies using the 4.2 rockers and pushrods.

Rockers and rods aren't on the needed parts list.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

William Oliveri wrote:

and make sure that you have the pushrod seated in the lifter bore and not canted slightly off kilter where it is sitting on the raised edge

You didn't seem to want to take our suggestion about opening the distributor cap as a second opinion on TDC just to make sure seriously, so forgive our double check advice.

It really sounds like you are reading the exhaust/intake stroke instead of the compression stroke all across.

Something silly is wrong and putting strange lifters in isn't likely to fix it.

Mike

Harris Family wrote:

How can you do it with the distributor cap in place?

Mike

Harris Family wrote:

With those lifters and rods in, will the valves close at any point in the crankshaft's revolution?

Mike

Harris Family wrote:

Quite simply, Pull the spark plug from #1 and feel the air rush out as you turn the crank to the 0degree mark. The air rush is the compression stroke bringing you to TDC.

compression.