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Engine does not run right after valve job


rraulston

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Oct 12, 2018
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In a previous thread, I posted about a P0301 misfire. #1 compression was 125. The rest were 160... So I pulled the head and discovered the exhaust valve was not seating correctly. I sourced another 0331 head and had the machine shop magna flux/shot peen/valve job/deck it. Basically the head looked new when I picked it up. I figured while I was in it this deep I would put new lifters, water pump all hoses etc. This job is a lot of work but fairly straight forward. I installed the intake and exhaust manifolds while the head was on the bench. I felt like I could be more accurate on seating the gasket and meet proper torque specs. Once assembled, I added all fluids and started the motor. WOW it was super quiet and idled flawless. I heat cycled it and continued to add antifreeze. Time for a road test. This is where it went down hill... It has no power. Then misfires everywhere. There is a mechanical sound when the misses occur but it idles perfect. Pulled it back into the shop and checked compression. 150 on all 6. Spark plugs were very clean. This acts just like a time when I had the wrong length push rods in a motor I built years ago. I checked all electrical plugs, cleaned the grounds. I then removed the valve cover and re torqued the rockers. All fine. I think it has something to do with the lifters but would like to know for sure before pulling the head again. I used speed pro lifters from Rock auto... What I didn't do it check the valve lift... I should have. Any words of wisdom??
 

twistedlv

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I always heard it was a bad practice to use new lifters on an old cam, but I doubt that is your problem. What procedure did you use to adjust tappet clearance? Hydraulic lifters still usually need some preload.
Did you bleed the lifters prior to install?
 
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rraulston

rraulston

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I always heard it was a bad practice to use new lifters on an old cam, but I doubt that is your problem. What procedure did you use to adjust tappet clearance? Hydraulic lifters still usually need some preload.
Did you bleed the lifters prior to install?
I installed them out of the box. I haven't read anything on bleeding them prior to install...
 

TjSteve0305

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Have you ever heard engine detonation? Does it sound like that?

Does it still idle good?

If the head was machined you might want to just verify lifter preload. You will need a dial indicator.
 
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rraulston

rraulston

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Interesting. There is no continuous tappint, only an o
Have you ever heard engine detonation? Does it sound like that?

Does it still idle good?

If the head was machined you might want to just verify lifter preload. You will need a dial indicator.
Idles perfect with half of the noise prior to the rebuild. When I rev it up, the noise and miss fire occasionally occurs as the engine comes back to idle. Its sporadic. Driving under load, foot to the floor, it has no power. Zero detonation. Not running rich as the plugs were almost too clean. Maybe not enough air?? Nothing changed in the fuel system. Only a valve job. What is interesting is I had a few cylinders on the previous head read 165. Now they all read 150.... I just question if the valves are opening up enough... Ill research and check valve lift. I have a dial indicator.... The machine shop stated they removed .005 from the head.
 
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rraulston

rraulston

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1595804845600.png


or


SEALED POWER RP3275 {#33002986, BRP3275} Info
9.6410" O.A.L. (Size: Standard)
on Rockauto, there appears to be two different length pushrods for an 05 TJ. The valve not opening up enough makes total sense. Sucks you cant change lifters with the head on....
 

twistedlv

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Yeah, you would think that if they decked the head, that compression would be higher across the board.
 

TjSteve0305

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View attachment 179622

or


SEALED POWER RP3275 {#33002986, BRP3275} Info
9.6410" O.A.L. (Size: Standard)
on Rockauto, there appears to be two different length pushrods for an 05 TJ. The valve not opening up enough makes total sense. Sucks you cant change lifters with the head on....
I would check preload first, that will tell you a lot.

Set a cyl to TDC, loosen a rocker arm until a pushrod is loose. Slowly tighten down the rocker just until all slack is taken up and there is resistance to spinning it. Set your dial indicator at that point and tighten the rocker. Record that measurement.
 
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rraulston

rraulston

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I would check preload first, that will tell you a lot.

Set a cyl to TDC, loosen a rocker arm until a pushrod is loose. Slowly tighten down the rocker just until all slack is taken up and there is resistance to spinning it. Set your dial indicator at that point and tighten the rocker. Record that measurement.
ok. I will do that this Friday and report back....Other than the head rebuild, the lifters were the only engine part I changed....Rockers and pushrods were reused as the engine only had 90k with minimal wear...
 
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rraulston

rraulston

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should I order rockers and new pushrods?? mine didn't look bad and it ran just file with the old head. The other question is are all 0331 cast heads the same?? I could rebuild my original head. Honestly, its cheaper getting a rebuilt one from Rock Auto than it is having my local machine shop do mine....
 

TjSteve0305

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should I order rockers and new pushrods?? mine didn't look bad and it ran just file with the old head. The other question is are all 0331 cast heads the same?? I could rebuild my original head. Honestly, its cheaper getting a rebuilt one from Rock Auto than it is having my local machine shop do mine....
You might be ordering different length pushrods if that’s where your issue is. I would hold off for now.

IIRC the only difference in 0331’s is the earlier ones had a thinner deck prone to cracking. Other than that they should be the same.

Edit: grammar
 

Goatman

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Crank to cam timing off can let it idle smoothly, but the higher the rpm the greater the chance of misfiring. Or using the new lifters has wiped out a cam lobe or two. Or cam, crank position sensor problem. Or lifter not pumping up right. Lots of possible issues. Go slow and start with the easy stuff first, eliminate that then go to the next. Having a good OBDII reader can help. Vaccuum also possible. Or fuel delivery (unlikely). Check all connections for good clean contact with no bent pins.
 
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rraulston

rraulston

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I would check preload first, that will tell you a lot.

Set a cyl to TDC, loosen a rocker arm until a pushrod is loose. Slowly tighten down the rocker just until all slack is taken up and there is resistance to spinning it. Set your dial indicator at that point and tighten the rocker. Record that measurement.
Well, i can spin all the push rods with the exception of the cylinders with visually open/actuated valves......So I cant get a good measurement. Also think the valves are actuating about .370. I put the gauge on the rocker/valve end and rotated the engine. Its difficult at best as I couldn't find a solid piece of steel for the magnetic base, but am close. I am 1 inch away from re-installing the old lifters. Problem is Since I replaced them, I just threw them in a box and didn't mark them... I know the "rule", but at driving 3k a year, it should get me by until I rebuild it. The foot of the lifters are perfect looking.....
 

Dlo250

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Jun 25, 2020
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If you changed lifters, but not the cam, I’d be worried about wiping a cam lobe. I just rebuilt my 4.0 and the new camshaft came with a piece of paper that recommended break in with delvac, rotella t, or delo 400 due to their higher zinc and phosphorus concentration.

This article explains a bit more: http://www.superchevy.com/how-to/corp-0808-worn-down-engines

Here’s what I think I’ve learned during my rebuild: flat tappet engines are high contact, high wear setups. The design of the 4.0 goes back to AMC, and is rather old. “Older” motor oil also had higher amounts of zinc and phosphorus as those elements are very effective additives in motor oil. However, Z and P will clog catalytic converters, so we moved away from them as emissions standards improved. Today’s motor oil has very little Z and P, which our 4.0 really need.
While you didn’t change the cam, the tappets ride it. I would pull my distributor and attempt to check the condition of the camshaft. If the cam is good, I would check the bottom of the lifters.
And I would use a zddp additive going forward!
 

freedom_in_4low

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I don't think it's nearly as risky to use new lifters on an old cam as it is old lifters on a new cam. From what I've been reading, the lifters already start with a very hard and smooth machined surface, while the cam starts with a rougher, softer surface that hardens during breakin. The lifter isn't just sliding straight on the lobe either, there is an offset shape involved that causes the lifter to rotate as it rises up and over the lobe. Once the cam is broken in, as long as the lifter that came out wasn't significantly worn as to inhibit that rotation, putting a new one in isn't going to immediately destroy lobes.

A dial indicator on your pushrods should tell you how much cam lift is there but I'm suspecting pushrod length since you're not getting any preload there.

I always heard to bleed the lifters as well but I don't know if it's necessary or if it'll just take care of itself after a while... Like people that prefill their oil filters.
 
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