Jeep Strokers

Hey all,

I've been measuring for needed pushrod length and had been getting some really strange numbers (about .070" total variation overall)... On this last go, I finally started examining other dependencies (namely the rockers and valves) and discovered that on cylinder 1, the exhaust valve stem is nearly .080" taller than the intake valve stem. I called the machine shop who did the head work (new seals and guides when I had it planed) and they said that's totally normal, and quoted some lifter preload specs that I wasn't exactly comfortable with.

Lifters are bone dry aside from cam break-in lube from the cam lobes.

What the hell do I do here? Run multiple pushrod lengths, or find another machine shop? I'm not too keen on the idea of dropping nearly $100 on new gaskets.

Update: went ahead and reinstalled the Melling MPR-301's I'd picked up (supposedly 9.594" long) and measured lifter preload:

1. Exhaust: 0.088"
   Intake: 0.062"
2. Intake: 0.059"
   Exhaust: 0.068"
3. Intake: 0.034"
   Exhaust: 0.063"
4. Exhaust: 0.063"
   Intake:0.054"
5. Exhaust: 0.059"
   Intake: 0.045"
6. Intake: 0.049"
   Exhaust: 0.077"

Most of these are close enough to spec that I'm not worried... But cylinders 1, 2, and 6 have me a bit concerned.

Procedure: rotate engine to TDC on cylinder 1, torque first rocker bolt to spec (leaving its partner extremely loose), place dial indicator on top of the lifter's pushrod pocket (not in the oil hole), and loosen the bolt until the reading reaches a high-water mark. Fully loosen bolt, and repeat on the 2nd valve for said cylinder. Once measured, rotate engine 120 degrees clockwise and repeat following the firing order (1, 5, 3, 6, 2, 4).

Thoughts? I get the feeling these pushrods aren't the most consistent pieces of kit, so I'm going to do some swapping and see what happens.

Swapped the pushrod on 1's exhaust with 3's intake, and got 0.088" of preload again on 1's exhaust. Looking like the pushrods aren't the culprit here...

When doing the valve work on a cylinder head that doesn’t have an adjustable valve train such as our 4.0 Jeep, it’s important that the tip height is set up properly previous to final assembly.

I had the same issue after the first machine shop I went to, among the list of other things I found after measuring everything. I actually had zero piston to wall clearance on all cylinders, and could not turn the cam by hand when I got it back. Go somewhere else. I found a much better shop with great attention to detail that got everything straightened out. I'm just happy I checked everything 'cause...

Russ is correct that the machine shop should have set them when they faced the seats.
But I also believe that guys FREAK OUT! WAY!! to much about this!!, I've seen Chevy 4.3 propane engines with the exhaust valves sunk into the seats .100" or so and they didn't come back because the cylinder heads, they were BURNING oil because there were NO rings left in them from being ground out by CRAP drawn in thru the intake!
I'd be more worried about rocker arm geometry than lifter preload! and pushrods don't have anything to do with that on a non adjustable rocker engine.

Hmmm... So I know that in an ideal world, I should pull the head and take it to another machinist, or order one of Russ's ported heads...

...but this damn thing has been out-of-commission for 15 months now and I'm running out of patience. I've picked up pushrods that will bring 1 and 6 into spec (~.041" shorter), along with a set of Ford rocker shims (.030" and .060") as a last-ditch effort (assuming geometry isn't messed up by it).

Am I looking at a world of pain if I run it as it is? Once the cam, etc, are broken in, I'm sure I'll be game for a head swap/upgrade down the road at which point I can revisit the topic.

Looks like you solved your problem. Shortening up your number 1 and 6 exhaust is your fix.

Get that bad boy back on the road. : )

Thanks for the input, guys. I swapped the exhaust pushrods on 1 and 6 with the shorter ones and they're now in-spec (0.054" and 0.050" respectively). Can't wait to wrap this up.