Hi all,

I've got an '89 roller cam engine and I've recently fired it up after rebuilding it with TPI. It didn't run right so I did a compression test and got these figures...

#1 155
#2 150
#3 0
#4 0
#5 45
#6 120
#7 150
#8 110

This is obviously my problem, but I discovered when I backed the lash off the rockers on cylinder three half a turn, the pressure jumped up to 150psi, and went to 180psi if I back off a whole two turns. Initially a friend did all the rockers before I started the engine and the above numbers are from his work. Then I redid the rockers and after another compression test I got the same numbers back.

The lifters I'm using are reused, but I took them all apart and cleaned them, and soaked them in oil before installing into the engine. Does it sound like collapsed lifters? If so, where's the best and cheapest place to get them?

 

0 PSI? Sounds like you are doing the test wrong. Even if both valves stayed open you should get some (minimal) pressure. If you have bad lifters, they will be really loud. I find it more likely that they are just over lashed.

 

Looks to me like you're not adjusting the lifters right. Sounds like you're just tightening them as far as the nut will go, instead of setting them to where they preload the lifter plungers to somewhere in the middle of their travel.

Back of #3 and #4 2 turns each. Then start the motor. Find any obviously noisy rockers and tighten them until they shut up. Then, one at a time, SLOWLY back off each rocker until it just begins to tap, and re-tighten it SLOWLY until it just shuts up again. Do all 16, just like that. Then turn the motor off, and tighten each rocker nut exactly ½ turn more. Wait about 5 minutes, restart the motor. Run it for a minute or so, turn it off, and re-do your compression test if you think you need to (you probably won't...).

 

I've been taught how to do a compression test by someone who knows what they're doing so I'm quite familiar with the procedure. If on #3 and #4 I crank the engine with my thumb over the spark plug hole I can feel a faint puff of air which probably isn't enough to make the compression gauge show a reading. The cylinders that give me better compression feels like a mini hurricane whizzing over my thumb.

The method I used to lash the valves was the same on all of them, yet it seems to give different compression results. The technique was to tighten the rocker nut while rotating the push rod in my fingers and tighten it just until the push rod stops rotating. Then give the nut a half turn. I've been shown this by two people.

I was thinking it's collapsed lifter?

The engine isn't in the car at the moment and doesn't actually have a radiator attached to it, so I can't run it for very long. Neither do I have a full length exhaust. Because of that, I doubt I'll be able to hear the sound of a noisy rocker over the exhaust if adjusting it that way.

 

Are they sneaking out at night and jamming themselves into unsuspecting bores in a Ford block? (That might be more "naughty" than "bad"...)

Are they cheating by claiming "push rod flex" as a net loss on their tax returns?

Are they refusing to lift on May 1st because they were imported?

Are they banding together in gangs, roaming the streets, and holding up parts stores for all the Mobil 1 they can carry off?

If you answered "yes" to any of the above questions, your lifters may be BAD!


I'm also inclined to believe the lash adjustment is wrong, or the valves are not seating due to other damage or mechanical problems. If you back off the rocker adjustments a few turns ad repeat the compression tests, what are the results on 3 & 4?

 

Wow, 0psi, thats brutal!


Did you remember to put the slugs back in when you were putting it together?


Somethings definately wrong here, it has to be something more than just improper lash...


What exactly was done to the motor during rebuild?

Was the block punched out .060 and your still using std rings and slugs or something?



pour a bit of oil down the cylinder and try testing it again, if the compression jumps right up its a ring problem if it stays low then its most likely a valve issue.

 

Your rockers are too tight.

Adjust them properly.

 

I like your winter toy. Heres mine.

Auggie

 

HAHAHAHAHAAHAHAHHAAHHAHAHAHAAHAHAA

 

Did you rotate the crank to it`s proper position between adjustments,or did you just adjust all of them with it in the same position?

 

I'm going to have to go with hanging out in gangs. I've had words with them about it, but to no avail.

If I back off the rocker adjustment half a turn, then compression jumps from 0 to 150 immediately. So yeah, it probably is just bad lash adjustment.
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I rotated the crank to its proper position. This was confirmed by the position of distributor as it was pointing to the cylinder that I was about to set the rockers for.

A head specialist very recently told me that instead of rotating the push rods between my fingers I could try moving the push rod up and down, as if I take my time in adjusting the rocker (which I kinda did), the lifter can move and upset my adjustments.

I guess I'll go and readjust the rockers while the engine is running.

Thanks everyone.

 

OK, I've adjusted my rockers and now get about 150psi on all of them. I noticed that if I back off the rocker nut a bit further I can increase compression a little further to 180psi - should I do that or leave them all at 150?

 

Now that it might actually run, you should start the motor up and adjust the lifters properly, as I described above in my first reply.

 

Will do. Might wait though until it's installed in the car, as I don't have a full exhaust so I doubt I'd hear the rockers rattling over the loud exhaust!

 

 

OK, time for an update...

Got the engine in the car and the engine running, so thought it would be a good time to adjust the rockers correctly. For this I got a mate to do it as he's built engines countless times and honestly knows what he's doing.

After some playing around he couldn't for the life of him get the rockers to adjust right - on all cylinders. The first time this has happened to him. It seemed as if once they were set they'd then collapse and the rockers would go loose. Tighten them too much and the engine gets grumpy.

It's been suggested to me that this is happening because I'm using run in oil and not the "proper stuff", and the run in oil is too thin and causing not enough pressure to build up inside the lifter and that I should use 25W-50 Pennzoil racing oil. Could this be a fair statement? I do have good oil pressure at idle, over 30psi from memory.

 

i like 5w30 for my engines...25w50 would be for racing (as the name suggests), or more commonly, quieting a noisy set of bearings till you can trade it in the next day. i have personally seen sbc's run quietly w/ 10 psi and 2 quarts low. so unless your break-in oil is more like kerosene, it should work

 

I just happened to be passing by and noticed this old thread of mine and thought I would give an update of how I solved this.

The problem was not my lifters even though I did buy new ones. To cut a long story short, the custom camshaft I had made was faulty. There was runout on the base circle for cylinders 3 & 4, as the compression test above indicated.

Before I figured out it was the cam I bought long slot Comp Cams roller tip rockers and installed those. I did this because I thought with the amount of lift I had on the camshaft it was causing the factory rockers to not open and close valves properly. It made the problem worse because the Comp Cam rockers really are 1.5 ratio, unlike the factory stamped steel ones which are usually less than that.

I got the cam reground, put everything back together and now I have a rocket ship 305.