I recently installed a new Lunati Cam and Lifters in my 73 302. The break in went smooth but after about driving it a 100 miles my number one intake developed what sounds like a lifter knock. I have tried varying lengths of push rods, and have replaced that lifter, I have compression of 125lbs., the headers are nice and tight, and the plug wires are not crossed. If I remove the rocker and push rod, the noise goes away. Also, the noise seems to vanish at about 1800 RPM's and returns as I idle down.........
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Lifter Knock
- Thread starter jmbour66
- Start date
Could it be that you just can't hear the noise at higher RPM due to normal engine noise? I'm sure you have/are considering the possibility you may have a lobe that has been damaged. I've seen a number of posts in the past few years of brand new cams failing with similar symptoms. If you are sure the noise is coming from a particular lifter I would pull the intake and lifter and drop in a solid and measure the lift to see if it is within spec. This would very clearly show if you had a cam issue. You'd have to disassemble this far to swap in a new lifter anyway...and it may very well just be a bad lifter after all.
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Anonymous
Guest
If you have hydraulic lifters they compress, solids don't. I think most of the cam problems occur to the solid variety!
Like Mark said, a hydraulic lifter will compress and give you a false reading. In the simplest of descriptions, a solid lifter is just a "spacer". Replace the suspect lifter with a solid and set-up a dial indicator to measure the lift at various points or cam rotation. Make sure that peak lift is one measurement. Then do the same on another matching lobe and compare the results."jmbour66" said:
With today's oils, it is becoming increasingly more common to suffer premature cam failures if not using a good oil additive.
Here's a pic giving you the general idea of how to set up to make the measurements.
Did you install new matching springs with the cam? I honestly wouldn't put a spring issue high on my suspect list, provided you installed a new set with the cam. What kind of rocker are you using? I'd look there before the spring."jmbour66" said:
Thanks again Horseplay,
I'll get my hands on a dial indicator. I am using a Zinc additive by Lucas oil specifically for break in.
The rocker arms are the Stock Rail type, and I did switch springs at time of cam and lifter install.
I wish I would have spent the money to go Roller through out!
I'll get my hands on a dial indicator. I am using a Zinc additive by Lucas oil specifically for break in.
The rocker arms are the Stock Rail type, and I did switch springs at time of cam and lifter install.
I wish I would have spent the money to go Roller through out!
What kind of lift are you getting out of your cam? Take a real good look at your rocker and, I presume, threaded rocker stud. Make sure you aren't seeing any signs of interference/wear caused by the rocker slot bottoming out against the stud or such. Are you using pushrod guide plates? It is not unheard of to find a variation in a set of stamped rockers. You may just have a "flaw" in that particular rocker."jmbour66" said:
Check with your cam manufacturer about the need for guide plates. I always ran them in my engines but my cams had higher lifts. I can't recall at what point you need to go to plates but I'm thinking your lift numbers are pretty close to that point. Do you have threaded rocker studs? Another possibility is you have a rocker stud pulling up out of the head."jmbour66" said:
Yeah, you can certainly switch rockers to see if it makes a change but you should be able to visually see if one is different, I would think. Look for a different wear pattern or placement.
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Anonymous
Guest
Any chance the stud has pulled out which would affect the geometry and move the rocker off the valve center, hitting the retainer or spring? It sure looks off in the video!
Take a sharpie and cover the valve tip and retainer, re-install and turn the engine over without it firing off. Remove rocker and take a pic of the valve tip and retainer, post the pic.
Take a sharpie and cover the valve tip and retainer, re-install and turn the engine over without it firing off. Remove rocker and take a pic of the valve tip and retainer, post the pic.
Sluggo
Active Member
Is there still a slight dome on the bottom of the lifter?
If it is dead flat or starting to dish you're having cam problems?
How did you set the lifters for break in. The last time I did mine I used the opposing cylinder method and purposely left them loose until after break in. I tightened them to zero lash and then gave them a 1/4 turn.
Once broke in I tightened them to Lunati's instructions.
If it is dead flat or starting to dish you're having cam problems?
How did you set the lifters for break in. The last time I did mine I used the opposing cylinder method and purposely left them loose until after break in. I tightened them to zero lash and then gave them a 1/4 turn.
Once broke in I tightened them to Lunati's instructions.
"silverblueBP" said:
I've taken a straight edge along the tops of all the rocker studs and it lays flat, so I don't think a stud is pulling out.
Attached are pictures of the rocker and valve tip, as suggested I covered each with a black sharpie and let it dry before placing back on the head. The pictures show the wear pattern.
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Anonymous
Guest
That valve tip looks beat to hell and the wear pattern looks horrible. The rocker pic looks like the tip is beat up as well.
Here's a pic I took while I was getting the geometry correct on my rebuild last winter. I actually fine tuned it so it was centered on the valve tip and not as wide, but didn't take pics!
Here's a pic I took while I was getting the geometry correct on my rebuild last winter. I actually fine tuned it so it was centered on the valve tip and not as wide, but didn't take pics!
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Jon,
The pattern on the valve tip is rather broad which tells me that your rocker is moving across it far too much. Something is amiss in the geometry. Since this is a later head set-up that leads me to think you have an incorrect push rod length or your rocker isn't fully seated (tightened down). Based on our discussions yesterday and what these pics show I suggest you measure that pushrod and make sure it is the same as the others and swap over a different rocker and see what you get. Make sure to re-mark the valve tip so you can see the new pattern on it.
If that doesn't reveal something, you're back to checking the cam again.
The pattern on the valve tip is rather broad which tells me that your rocker is moving across it far too much. Something is amiss in the geometry. Since this is a later head set-up that leads me to think you have an incorrect push rod length or your rocker isn't fully seated (tightened down). Based on our discussions yesterday and what these pics show I suggest you measure that pushrod and make sure it is the same as the others and swap over a different rocker and see what you get. Make sure to re-mark the valve tip so you can see the new pattern on it.
If that doesn't reveal something, you're back to checking the cam again.
"jmbour66" said:
It takes the force of the rocker to push the valve open and hold it open against the tension of the valve spring. In order for the valve to "slap" against the valve seat (head) you would have to in some way have the rocker release from the valve tip allowing it to move freely. The only way I see this happening is if you had a serious flat spot in the profile of the cam lobe that let the rocker come loose.