Top-end rebuild; truck runs like ****

[mayvillain]

Just finished a top-end rebuild on my '92 K1500 and it runs AWFUL. Ran perfect before blowing a head gasket. Here are the symptoms I'm seeing:

1. Rough idle on start with loud 'hissing' noise coming from throttle body (without air cleaner installed).
2. Muffler (mid-truck) sounds like a washing machine; an almost 'banging' or rumbling sound (like shaking a coffee can with a baseball inside).
3. After a few minutes of warming up, the idle smooths out, hissing from throttle body/intake manifold stops, and it actually seems to idle kinda normal.
4. When in neutral, truck revs pretty normal. In any gear, including Park, runs rough with low idle and almost stalls at times.
5. When driving, NO power. After about 15-20MPH, I can floor it with no throttle response. Can barely get up a steep hill at 5PMH.
6. If driving on flat road, there seems to be a delayed throttle response; like it will pick up speed after a few seconds if I keep my foot down.

Some other observations:
- Truck PASSES the coolant combustion test; there is no exhaust gas in the cooling system
- Upon spraying carb cleaner around intake manifold seals while running, NO CHANGE in revs

Here is a list of all the work I did:
- Cylinder heads machined (no cracks) and valves re-seated by reputable machine shop
- Replaced head gaskets (Fel-Pro)
- Replaced intake gaskets (Fel-Pro)
- New water pump + gaskets (Fel-Pro)
- New radiator (OEM-style replacement from O'Reilly)
- New thermostat
- New PCV valve
- New oil pressure sensor (my gauge was always just bouncing around since I've owned the truck ~2 years)
- New TBI gaskets (Fel-Pro)
- New timing chain
- New distributor (rotor + cap)
- New spark plugs (Iridium, no gap) and spark plug wires
- New TV cable (I broke the original during tear down. This new one has been adjusted by a shop, but I think it might need a slight tightening; still getting a long shift on 1 -> 2)
- Transmission fluid fill
- Properly set lifter pre-load to the best of my ability (spent lots of time on this, used the "Engine RUNNING Hydraulic Lifter Adjustment" protocol
- Oil change

Any idea what might be causing the symptoms #1-6 listed above?

 

[95burban]

Are the valves adjusted correctly? Did you unplug the timing connector when you set the timing?

 

[smdk2500]

Did you get the timing set correctly?

 

[mayvillain]

Are the valves adjusted correctly? Did you unplug the timing connector when you set the timing?

OK this just got me thinking:

I set the 'rough' timing, and asked the autoshop to fine tune it—which they claimed they did. However AFTER that, I adjusted the lifter pre-load (because I had messed this up, way too tight, before I started it up).

Do I need to adjust timing again if I've messed with the lifter preload (valve adjustment) after the timing was set?

 

[rebelyell]

If this motor has Hydraulic Flat Tappet style lifters (Not Roller):
did you initially Over-Tighten the valves (rocker arm Nuts) ? --- potentially causing valve spring coil bind ? --- possibly preventing lifters from spinning in their bores; thereby wiping-flattening cam lobes ?

 

[mayvillain]

If this motor has Hydraulic Flat Tappet style lifters (Not Roller):
did you initially Over-Tighten the valves (rocker arm Nuts) ? --- potentially causing valve spring coil bind ? --- possibly preventing lifters from spinning in their bores; thereby wiping-flattening cam lobes ?

It's a stock TBI 350, so it should have Flat Tappet style lifters. Yes, I believe I over-tightened the rocker arm nuts during reassembly; most likely 1/2 to a full turn. I was following direction from this video, which was overall very solid, but I think they're wrong about how to adjust valves.

I can't tell if I'm experiencing the problem you described. I'd rather not take the intake manifold off again, but it may lead to that.

 

[Schurkey]

'92 K1500

and it runs AWFUL. Ran perfect before blowing a head gasket. Here are the symptoms I'm seeing:

1. Rough idle on start with loud 'hissing' noise coming from throttle body (without air cleaner installed).

Probably the IAC wide-open trying to get the engine to idle at an appropriate speed. Fix the real problem, this likely goes away on it's own.

2. Muffler (mid-truck) sounds like a washing machine; an almost 'banging' or rumbling sound (like shaking a coffee can with a baseball inside).

MID-truck? More like the catalytic converter than a muffler; and it's dead, Jim.

4. When in neutral, truck revs pretty normal. In any gear, including Park, runs rough with low idle and almost stalls at times.
5. When driving, NO power. After about 15-20MPH, I can floor it with no throttle response. Can barely get up a steep hill at 5PMH.
6. If driving on flat road, there seems to be a delayed throttle response; like it will pick up speed after a few seconds if I keep my foot down.

What is the fuel pressure at prime, and at idle.

- New timing chain

Was the cam degreed, or the gears just lazily crammed-in "dot-to-dot"?

WHAT IS THE CRANKING COMPRESSION?

- New spark plugs (Iridium, no gap) and spark plug wires

Of course there's a gap. Do you mean you didn't adjust the gap?

Are the plug wires going to the correct cylinders?

- Properly set lifter pre-load to the best of my ability (spent lots of time on this, used the "Engine RUNNING Hydraulic Lifter Adjustment" protocol

That "should" be adequate. Have you ever adjusted lifter preload before?
https://centuryperformance.com/tech-zone/valve-adjustment-procedure/

Are the valves adjusted correctly? Did you unplug the timing connector when you set the timing?

Did you get the timing set correctly?

Agreed.

I set the 'rough' timing, and asked the autoshop to fine tune it—which they claimed they did. However AFTER that, I adjusted the lifter pre-load (because I had messed this up, way too tight, before I started it up).

Do I need to adjust timing again if I've messed with the lifter preload (valve adjustment) after the timing was set?

Neither the ignition timing nor the camshaft timing are affected by adjusting lifter preload.

 

[rebelyell]

It's a stock TBI 350, so it should have Flat Tappet style lifters. Yes, I believe I over-tightened the rocker arm nuts during reassembly; most likely 1/2 to a full turn. I was following direction from this video, which was overall very solid, but I think they're wrong about how to adjust valves.

I can't tell if I'm experiencing the problem you described. I'd rather not take the intake manifold off again, but it may lead to that.

I can speculate all day about what lifters it should have in it. You saw em; not me.
You had the intake off and You looked at tops of lifters; we didn't do either. You saw em; not me.
It seems You Know ya got the valve adjustment wrong; I'm not gonna watch some video that led you down the road you're on now.

Wanna see a really easy peasy, all-but fool-proof valve adjustment video? 22 minutes at Eliison's garage. NOTE, he does NOT soak or fill lifters. That means if You try it, You MUST clean out all the oil from Your lifters; not maybe but You Must. Using this method, You Must empty lifters out Before You start over.

xc_hide_links_from_guests_guests_error_hide_media

Which means you'll pull lifters out And You can also give Each Lobe AND Lifter Face a close inspection for any potential damage. Maybe it's all AOK; Maybe Not. We sure can't & don't know.

* disaasembling & reassembling Lifters is Not rocket science. Maintain the lifters in same order as they were removed so that each lifter retains its position on the same lobe it Was on. Do each Lifter separately; that way you cannot make the mistake of mixing a part from Lifter 1 with Lifter 13 etc.

 

[CumminsFever]

Possibly plugged exhaust? You mentioned rattling in the muffler...

 

[mayvillain]

UPDATE:

I've decided to try a new fuel pump + fuel filter.

The timing may still be off, but that would not explain why I could be cruising down the road in 2nd gear going 20MPH, floor it, and get zero response.