Squeaky/tapping noise on #8 cylinder

[Mrturner1]

Hey guys, I'll give you a quick run down of what it is, and what's goin on. I'm gonna pull the valve cover after I post this and take a look.

It's a 1970 c10. Just did a top end on it, it's been an on going tuning lesson for me, and I think whatever is happening is part of the problem. New heads, cam and lifters, intake manifold. I went with a Comp 280H magnum cam. I used 1.5 roller tip rocker arms. I've been trying different timing settings to see what it likes, right now I'm at 34*. It's got 12* initial, and it has a GM performance HEI (not sure if the vacuum advance is adjustable on those)

Drove it to town and it was running good, not great. Noticed a little knocking type noise at #8 this more but nothing loud. After I left the store, it was hard to start, had to hold the gas pedal to the floor. Idled funky and real low rpm so I brapped the throttle a few times to get it to idle. It went back to normal idle. Found a strait away coming home and accelerated hard but never letting it kick down, held 3rd gear, and it started studdering at about 3300rpm so I let off. Drove home ok, but it didn't like that hard acceleration at all. Stopped at the mail box and heard that same cylinder but now it was making a squeaking kindof noise with a tap. Definetly not an exhaust leak, and definetly the same cylinder I heard earlier when it was just a slight tap.

What do you guys think? Keep in mind it was my very first top end, and I did it myself including the valve adjusting and setting preload. I'm gonna go pull the valve cover, thanks for any input guys

[hugger6933]

Matt, my first thought was bent pushrod as I opened the post and started reading then my mind has gone to bearing on the crank[ spun rod] the hard to rev and not wanting to rev up is scary to me. Jim

[Mrturner1]

Originally Posted by hugger6933

Matt, my first thought was bent pushrod as I opened the post and started reading then my mind has gone to bearing on the crank[ spun rod] the hard to rev and not wanting to rev up is scary to me. Jim

I hadn't considered a bearing but that would make sense given the squeaking sound. Here's more of what I know as of now. It makes the noise in rhythm with the firing sequence, almost like it's making the noise when #8 fires, so I'm hoping that means the bearings are ok and that this is a pushrod or valve adjustment issue. I'm pulling the rocker arms off of #8 right now so I'll know more about the pushrods soon. Thanks for the quick reply Jim!

[davepl]

I'd get both pushrods on the base circle (TDC for that cylinder) and double-check the lash, make sure one isn't too loose to too tight.

Too loose could cause the tapping; too tight could cause the idle. Not sure what could cause both, but check then for straight like Hugger said as well (roll them on a flat surface).

[Mrturner1]

Originally Posted by davepl

I'd get both pushrods on the base circle (TDC for that cylinder) and double-check the lash, make sure one isn't too loose to too tight.

Too loose could cause the tapping; too tight could cause the idle. Not sure what could cause both, but check then for straight like Hugger said as well (roll them on a flat surface).

Thanks Dave! I'm hoping you're right.

[Mrturner1]

Ok pushrods from #8 are showing me some terrible stuff going on. The looks like the end of one has been ground off, it's significantly shorter than the other. The one that has a ground off end is the intake side.

[Mrturner1]

Top view

[Mrturner1]

Closer pic

[Mrturner1]

Somebody break the news, how bad is this? Neither one is perfectly straight when rolled on the table. Very very slight bend it seems, because when rolling slow they pick up speed on there own then slow down, then go faster again, then slow down (all in about 12" of rolling and very slow obviously)

What could cause the end to grind off? Is this just a pushrod replacement of are the lifters coming out? Bad lash adjustment maybe?

[jocko]

well, it aint "good" - which end of the push rod is that - lifter or rocker? Either way, you've technically got some metal in the motor floatin around. Question is whether or not it's fine enough (or if you're comfortable enough) to just drain it and refill... But for the base problem - sure looks like lash was perhaps set too tight - even if set on the base circle. What does the lifter (or rocker) interface look like? New valve springs?

[Mrturner1]

Originally Posted by jocko

well, it aint "good" - which end of the push rod is that - lifter or rocker? Either way, you've technically got some metal in the motor floatin around. Question is whether or not it's fine enough (or if you're comfortable enough) to just drain it and refill... But for the base problem - sure looks like lash was perhaps set too tight - even if set on the base circle. What does the lifter (or rocker) interface look like? New valve springs?

It's the rocker side, and it's a little wollered out now that I'm lookin at it. And it got new valve springs and seals upon the rebuild. They are Comp springs

[Mrturner1]

Rocker

[Mrturner1]

Here's the underside of the valve cover, lots of fine metal dust over the #8 side

[Mrturner1]

I would guess that the amount of time and money going into fixing this is relative to what caused it. I did re-use the pushrods it had in it, so maybe this is just confined to that one cylinder. If it's valve lash, this could potentially be happening to the other cylinders right?

Either way, they don't sell rockers by the pair so I'm buying a set of those. If this is lash, replace those two pushrods and leave the rest? Or buy a whole new set and do them all.

Sheesh, I was all ready to move on to suspension!

[hugger6933]

If those are comp call them up and they will sell you one or a pair. Those guys are really pretty helpful. How big are the valve springs did you buy them with the cam[not just at the same time] but what I'm saying are they matched to the cam or are they real heavy or stiff for a BIG cam. That will eat up the rockers bend the rods and screw over the lifters and if the springs are too to heavy for the cam it will wipe the lobes off of it. Now where you are now I'd run the valves again and make sure you have the valves adjusted right to a little loose. The spec @ zero lash has been 3/4 to 1 and 1/2 turns on the rocker nut after zero lash, I caution on the loose side and go between 1/2 to 3/4 of a turn. Matt what was your oil pressure gauge saying while all of this was going on? Did it ever drop low or has it lowered lately?

[Mrturner1]

Originally Posted by hugger6933

If those are comp call them up and they will sell you one or a pair. Those guys are really pretty helpful. How big are the valve springs did you buy them with the cam[not just at the same time] but what I'm saying are they matched to the cam or are they real heavy or stiff for a BIG cam. That will eat up the rockers bend the rods and screw over the lifters and if the springs are too to heavy for the cam it will wipe the lobes off of it. Now where you are now I'd run the valves again and make sure you have the valves adjusted right to a little loose. The spec @ zero lash has been 3/4 to 1 and 1/2 turns on the rocker nut after zero lash, I caution on the loose side and go between 1/2 to 3/4 of a turn. Matt what was your oil pressure gauge saying while all of this was going on? Did it ever drop low or has it lowered lately?

Actually now that you mention it I do remember looking at the oil pressure gauge right before I shut it down and it was a little on the low side. Gauge read about 15-20 psi at idle, and I never checked while I was driving just before I shut it down. However, it never made any noise like low oil pressure does. If I remember right, I was trying to be consistent on 3/4-1 turn after zero lash. Definetly didn't set any at 1/2 turn past zero though, might be the magic number for the rest of them. I'm gonna take that advice and go through all of them, I just need to read up about getting the base circle at TDC when the engine is all put together so I can re-adjust.

As for the valve springs, they are pretty heavy, but when I bought the cam I also got the matching part number for springs so they should be spot on.

The rockers are made by Comp but sold under a different name. I'll check with PWR or PWM or whatever the companies name is about replacing a couple

[Mrturner1]

PRW! That's the company, I couldn't remember but I was close lol

[Mrturner1]

Might be time for a new set of hardened pushrods too. The old pushrods have worked well and I saved a bit of money, but I have a feeling that this could have been a lot worse than it is.

Motor revved fine, but it was studdering when I accelerated pretty hard at about 3300 rpm

[Mrturner1]

Is this definetly a valve lash adjustment issue? Or is there something else that could have ground off the pushrod like that?

[GRX]

Likely a lash issue. That rocker got a bit loose allowing the rod to wiggle around inside the cup.

Have not seen where rocker nuts were mentioned. Did you buy new ones? Stock ones should not be re-used. Unless you swedge them again. Otherwise they will tend to back off.

[Mrturner1]

Originally Posted by GRX

Likely a lash issue. That rocker got a bit loose allowing the rod to wiggle around inside the cup.

Have not seen where rocker nuts were mentioned. Did you buy new ones? Stock ones should not be re-used. Unless you swedge them again. Otherwise they will tend to back off.

So this is an issue of being TO LOOSE then and not to tight? The rockers I bought from PRW came with new nuts

[trac209]

I've seen cases where a cam lobe started to wear due to improper break in of the cam, once the cam wears a bit the excessive clearance can wear the pushrod and rocker like that. Or using too heavy a valve spring during break in of cam as well can cause issues.

[Mrturner1]

Originally Posted by trac209

I've seen cases where a cam lobe started to wear due to improper break in of the cam, once the cam wears a bit the excessive clearance can wear the pushrod and rocker like that. Or using too heavy a valve spring during break in of cam as well can cause issues.

I didn't change the springs at all during break in, I just assembled the heads and broke it in that way.

During the cam break-in, I got about 10 minutes in at 3200 rpm and a belt broke. So the next day I got a new belt and gave it 20 more minutes. I thought no big deal, but it's my first so I could be wrong.

[trac209]

Originally Posted by Mrturner1

I didn't change the springs at all during break in, I just assembled the heads and broke it in that way.

During the cam break-in, I got about 10 minutes in at 3200 rpm and a belt broke. So the next day I got a new belt and gave it 20 more minutes. I thought no big deal, but it's my first so I could be wrong.

Ok so you broke in the cam with a heavy spring I assume since you didn't have to change them after. It could be a cam issue but without have a dial gauge to check lift its hard to tell from here obviously. I would take out a couple of pushrods from another cylinder if you don't have spares and install them in number 8. Adjust the valves on that cylinder using eoic method and check lift with a dial gauge. If it's not the same as others you have a cam going flat. I'd also redo the lash on the other valves to be safe.
As for the metal bits you'll have running through the engine well that's a problem I'd look at after adressing this issue and considering what you can live with. You could change oil and filter a couple times and hope for the best or start over. But if the cam is going flat you're starting over for sure anyhow

[geezer#99]

Originally Posted by Mrturner1

I didn't change the springs at all during break in, I just assembled the heads and broke it in that way.

During the cam break-in, I got about 10 minutes in at 3200 rpm and a belt broke. So the next day I got a new belt and gave it 20 more minutes. I thought no big deal, but it's my first so I could be wrong.

10 minutes was good but 3200 rpm with stiff springs on a fresh cam is a killer!!