Rocker arms with Lunati camshaft

[MiGorda]

Hello

My engine was rebuild around 9,000 miles ago. Recently hear the thicking on the push rods so I'm trying to recalibrate them.

I did the procedure of loosing the nut until make the noise, then tighten until the thick is gone and turned it 3/4, everything looks and sound correctly but when I drive my truck and push the throttel a little deeper, there are bangs coming from the TBI, so I guess the intake valves are not closing enough when the compression is working and that is caused because the rocker arms nuts are loose.

So what you think, I've done some research and some guys recomend only 1/8 of preload and others even a 1 complet turn.

The engine is a 350 TBI with flat pistons and a Lunati 10120101.

Should I loose or thight the rocker arms nuts?

Thanks

 

[PlayingWithTBI]

Should I loose or thight the rocker arms nuts?

Try loosening them. You have to be careful taking the slack out of the push rod to the rocker/lifter, so you have zero lash, not a compressed lifter spring, before turning 1/2 turn.

 

[Hipster]

I do 1/2 turn seems to be a happy place with most aftermarket lifters.

 

[MiGorda]

Thanks for your reply but I've removed the valve cover and there is a bigger problem, one exhaust rocker arm is not wagging, maybe I overtighted and damaged something

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The number 4 coming from the firewall.

What could be the problem? the valve damaged or just the pushing rod?

 

[MiGorda]

I just removed the push rod and seems to be slightly bent.

Even with a minimal damage in the rod could cause a bad function in the valves?

Took a look through the hold of the head and the lifter looks fine. The spring of the valve also looks fine, it is firm.

The engine was working correctly, just a little thick from the rocker arms, tried to calibrate them but I guess I screwed it.

 

[PlayingWithTBI]

What could be the problem? the valve damaged or just the pushing rod?

Maybe the cam and/or lifter wore/ground down? Do you see any metal filings in the pan?

 

[MiGorda]

Maybe the cam and/or lifter wore/ground down? Do you see any metal filings in the pan?

You mean the oil pan? or in the intake surface?

Through the hole in the head I can see the lifter and its retainer, both looks fine, in its correct position and not debris.

After I opened this post, try to recalibrate them and the first rocker arms were working fine but when arrived to the damaged, I started loosing the bolt to hear the thicking and the noise was very loud, so I tightened it but the noise remain, lower but the more engine revs up the more noise increases.

I guess the next step would be to remove the intake, correct?

 

[MiGorda]

Inserted a magnetic "pen" trough the head hole and it didn´t catch any debris.

Te Lunati camshaft is almost new, around 9,000 miles and maybe overtighed the rocker arms nuts but not too much, like I mentioned, only 3/4.

 

[Hipster]

Really need to examine bottom of lifter where it rides against the cam, looking down the top doesn't tell much and if you have a bent pushrod you may have bigger issues. What your describing doesn't sound good.... If you can fish one of the lifters out via a hole in the head, but if not removing the intake is going to be necessary.

 

[PlayingWithTBI]

I guess the next step would be to remove the intake, correct?

Te Lunati camshaft is almost new, around 9,000 miles

Yes, pull the intake manifold and pull the lifter(s) out to inspect/clean them. Keep them in the same position they came from!

I didn't even get to 9,000 miles before my lifters started wearing out and grinding the cam down (a Lunati too BTW). I found a collapsed lifter and one ground down.

Here's a couple - 1 worn down, notice the dish in the bottom. The other is collapsed.

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BTW I had the same lobe wear down - arrow on the right.

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