454 Worn Cam Diagnosis, what did I miss?

[andymarkv]

Question about diagnosing a worn cam....

A buddy of mine inherited a square body C10 with 454 & th400, 4.10 gears. (swapped in 14 bolt full floating rear, truck was used to tow) His uncle had rebuilt the engine 30 years ago, but we do not know any specs except the visible; holley vacuum secondary carb, no name single plane intake, stock HEI dist, generic long tube headers, aftermarket chrome engine tin, stock rocker arms, maybe aftermarket valve springs & cam (there are manley push rod guides, so there may be other aftermarket parts in it)

It runs and idles OK, but has no power at all.

60psi oil pressure on a mechanical gauge, no overheating issues, oil looks good, new plugs wires cap & rotor
WOT is achieved when the gas pedal is pushed to the floor, the secondarys are not stuck shut
Compression check, all cylinders about 150psi
Vacuum at idle, 15

I used a piston stop to determine “true zero” on #1. True zero was at 3-4 degrees advanced on the aftermarket chrome timing tab
We set the timing to a true 16 degrees advanced, 35 degrees total, all in at 3000rpm

We heard some lifter clatter so we pulled the valve covers to look for a worn lobe
All valves moved about the same amount, no visible difference detected, BUT all rockers were loose when on the base circle.

We put #2 on the base circle (intake open, intake closed and a little further) and adjusted to zero lash, spinning the pushrod while tightening until initial bind, then another 1/2 turn on intake and exhaust valve.
Performed the same procedure on #4.
Did a compression test again on 2 & 4, zero compression. Checked the rest of the nonadjusted loose cylinders, still 150psi. Loosened the rockers, compression came back but the rockers were loose

At this point we figured we it was possible that the cam was worn, even on the base circle. Most likely this engine has aftermarket valve springs and has not had ZDDP/zinc additive it its oil since it was removed from all “off the shelf” oils.

We removed the cam and lifters….and they look PERFECT! No detectable wear whatsoever. The cam bearings look beautiful as well.(engine is clean inside as well)
What did I miss? It seems slightly hard to believe this cam is worn 100% even on all surfaces?
I don’t want to stab a new cam in this thing if I have totally missed the diagnosis and there is some other problem.

[OBS454]

More description please on what no power means. Did it fall on its face when trying to accelerate quickly, would it not get out of its own way, etc. Did the vehicle sit for an extended period of time ... possible fuel contamination. Pump a fuel sample into a clear jar - look and smell for separation/contaminates. Is the exhaust path open/clear ... clogged/crushed pipe, cat converter, muffler, etc. It's also possible that air/fuel circuits within the carburetor are clogged. Low fuel pump pressure/fuel line restriction/clogged filter/rubber supply line cracked and sucking air/clogged pickup screen on fuel tank pickup inside the tank. In the past certain types of lifters were marketed that would make noise and pump down (clatter) at idle/lower RPMs and then build up under RPM increase. Have no experience with these just remember others talking about using them. Think Rhoads was one of the brand names.

[geezer#99]

When you set the valves you should do the wiggle all the slack out and not the twist the rod method. Much more accurate.
I wonder if there’s a wild possibility that you have a solid lifter cam with hydraulic lifters. Ramps are a little sharper and might cause the rattling.
Any idea on the lifters make. There were some with fast bleed downs that would rattle.

[sweetk30]

and a single plane intake is for mid to top end . you should be running a duel plane intake for low to mid power .

end of the cam on the dist gear end is there any markings ? might help i.d. the cam .

and if the cam is to big it might be another low power point . need a good bottom to mid rpm cam for big heavy stuff .

[andymarkv]

You're right! I missed a bunch.
The truck DID sit for an extended period of time.
Fuel was drained, filter changed and carb rebuilt
The power valve is new and the accelerator pump squirts a good stream.
I have not done a fuel pressure test.(but I should)
The plugs have a fair amount of carbon on them with minimal run time.

In a no load situation/free rev, the engine will rev fairly well.
Under load it will barely spin the tires in the dirt.
It will drive around, but there is minimal acceleration if you transition from 1/16th throttle to full throttle.
It doesn't fall on its face or breakup, its just slow.
Exhaust seems open? I put my hand over the exhaust pipes and there is flow, nothing seems crushed? (But there could be internal muffler damage?)

The lifters may be part of the issue. I tried to depress the plunger in a lifter and it feels seized with no movement. I didn't realize that could happen.
If they were seized it could explain my loose rockers.
But I'm not sure how that would impact performance?

[andymarkv]

Not sure on the cam, it is stamped;
986
13 46 88
CR

The lifters have no markings on them.

This truck was an older guys, built to haul heavy and tow his cabin cruiser boat.
I agree the single plane is the wrong intake for this application.

[Hollow65]

The 454 in my 92 is a turd too but it will drag my house off the foundation. What’s the engine code and heads?

[Alex V.]

Since you already have it apart it seems it'd make sense to stick a new cam/lifters in it so you know what you have.

[Tiger Joe]

stupid question- are you sure it didn't have solid lifters in it?

also just some food for thought- I ended up buying a 454 out of a 70s C10 that "had no power" When I got it apart found out the guy had a put a pretty large cam in with stock pistons- well this motor was luck to have 8:1 stock, so it ran like crap. Maybe thats what you had, someone put too much cam in the motor and it was a dog?

[tdangle]

You may have this cam:


3883986 1965-72 Hyd Lift .460I/.488E duration at .050 .213I/.217E See Note 2

Note 2: 396 325/350hp L-34/L-35, 427 385/390/400hp L-36/L-68, 454 345/360/390hp LS-4/LS-5, good torque/HP

[DieselSJ]

Originally Posted by Tiger Joe

stupid question- are you sure it didn't have solid lifters in it?

That was my first thought also. Especially since ALL of them appeared "loose".

[mattfranklin]

If you're that far into it, can you see the port side of the intake valves? Is there a lot of carbon build-up on the intakes? If those deposits are really heavy it can cut the flow and cut power.

The more economical brands of gasoline use very little detergent and that leads to intake valve deposits. If the engine still runs, you can use a good (polyether amine) aftermarket detergent like Techron Concentrate to clean up the valves and restore the power.

I've used this stuff on carefully controlled dyno tests. Light deposits can cut power 5-6%, heavier deposits, more. And the Techron cleans it up to restore power. Use as directed and just drive it around normally. Slow, around town, driving gives the detergent a better chance to soak in and soften and gently erode the deposits.

[andymarkv]

Originally Posted by tdangle

You may have this cam:


3883986 1965-72 Hyd Lift .460I/.488E duration at .050 .213I/.217E See Note 2

Note 2: 396 325/350hp L-34/L-35, 427 385/390/400hp L-36/L-68, 454 345/360/390hp LS-4/LS-5, good torque/HP

DANG!!! How did you find that info...? I called Crane and they suspected it was one of theirs, but with no numbers on the front of the cam, they couldn't find it!

I really HOPE that IS the cam!

[andymarkv]

I need to pull a lifter apart and check to be sure they are hydraulic, but when I say the rockers are "loose", I don't mean loose enough to clack, I mean loose enough to wobble around in your hand when the lifter is on the base circle!! REALLY loose! So loose I don't think any oil was getting pumped up the push rods to the rockers...

Thanks for the reminder about looking at the intake valves! The rest of the engine looks clean, but it definitely could be junk on the intake valves.(heck as anyone with an oil separator will tell you ALL, engines with PCV ingest some oil)

I guess what threw me off was that all the rockers were completely loose and the engine LOOKED untouched? I know things can loosen up over time....but every single one exactly the same...I've never had a rocker back off THAT much from what looks like a basically stock rebuild?

The only thing we can come up with is the previous owner backed off all the rockers for storage and he knew how many turns it would take to put it back, but he unfortunately passed away and never had the chance.

Everything else looks perfect! I think I ended up just chasing my tail...looking for answers to the wrong questions.

We are going to throw it all back together(we marked the lifters with lobe position) with just a new timing chain(the old one had slack) and Performer RPM intake(nonairgap)
I'll let you guys know the outcome.