Is there any net benefit to replacing stamped steel rockers with roller rockers? Engine is a 389 and the cam has a little more lift than stock. I have one valve assembly that makes a little too much noise when at operating temperature and I cannot seem to quieten it out. It has been like this for many years.
My main question is if roller rockers are any quieter than stamped steel. I should have made that more clear.
No, roller rockers are not quieter than stamped steel. They do reduce friction so they free up a little HP. If you have a noisy valve, it may very well be that a lifter has gone flat and needs replacing. You’ll never adjust that noise out if that’s the problem. That will be cheaper than a set of roller rockers.
Pull the intake and lifter cover and remove the lifter from the noisy cylinder. Make sure the underside that rides on the cam isn’t torn up. It may be worthwhile to check 'em all while the top is open. It may be worthwhile to replace them all while the top is open.
Mustangman: I have no experience with Pontiac engine internals. I’m assuming the 389 cu in GTO has hydraulic lifters. Could a rocker arm adjusting nut have slipped? I would check that first. I agree that if the OP has to replace one lifter they should replace all lifters. Also replace pushrods and visually inspect cam lobes. I’m ecstatic that I can comment on something mechanical involving no sensors, computers, or OBD2 codes which are beyond my formal training and experience which was pretty much arrested in 1976.
What year is this puppy anyway? How many miles does it have?
Roller rockers won’t make a discernable noise difference in a daily driver, but as engines wear there are things that will. Valve springs weaken, lifters wear, cam lobes wear, hydraulic lifters can lose their hydraulic abilities, there are other things that should be checked if the noise bothers you. My bet is that you don’t have a rocker issue, you have a simple wear issue.
It is a 66 with about 55,000 miles I had the motor rebuilt about 20-25 years ago. I am sure at that time there was no noise coming from the valve train. I have tried both stock jam nuts and double nutting the noisy rocker. Can this be a geometry issue? Is there some way to get a fix on exactly which point(pushrod to rocker, pivot, rocker to valve, valve spring etc) the clearance is increasing to create the ticking? Can a broken or cracked valve spring do this? I would run this thing up to at least 6000 rpm regularly. Springs are probably 35yrs old or more.
When you replaced the cam did you also replace the lifters? That’s a must on flat tappet camshafts.
@sgtrock21 Pontiacs have ball-and-rocker arms much like Chevy’s Plus a flat tappet hydraulic cam, unless someone switched the cam to a solid lifter model. Either way, the noise, if you can’t see a broken valvespring and can’t adjust the noise away, the problem is at the lifer and cam lobe. And its got to be opened up to determine the problem.
BTW, if the OP has been using regular oil with no additives, for many years, the cam may be trashed because of the absence of zinc ans sulfur additives in the oil.
The rockers on the Pontiac engine are not adjustable. You lock them down and that is it. I have had this type of rocker get off center on a Ford engine and it wore into the side of the post, so every time the rocker moved, it made a ticking sound. When these get noisy, that generally means a bad lifter, except in that Ford I had.
For a stock cam, roller rockers may help a little, but if you go for a high performance roller cam set up, you will definitely need those roller rockers.
Use Diesel lube in these old Guys and your lawn mower engines ,you will be glad you did,
You dont tach Her to 6 Grand often now do you ? Believe it or not thats fairly tight,IMO anyway (the guys here used to get on me when I claimed I was spinnig the little powertech V6 tight-5.5K seems pretty tight on that little engine)
The rockers on the Pontiac engine are not adjustable. You lock them down and that is it.
No, that’s just plain wrong.
Pontiac motors of that era use stamped steel rockers and acorn nuts with oval shaped holes. They’re pretty much a one time use nut, and if they’re ever adjusted they may not stay put. Get new nuts, or better yet, get aftermarket nuts and install them CORRECTLY. That usually involves milling the studs flat for the nut locks to have something positive to lock to.
When properly adjusted the pushrod should spin when the engine is running. If the push rod does not spin the lifter is likely wiped out and the camshaft lobe under it as well but such a failure is usually very quiet.
The face of flat tappet valve lifters should also be convex. Once the convex wears off they will stop rotating on the cam lobes.
That’s one reason why I was wondering if the new cam was used with what are now used concave valve lifters.
Tapperts rorate because they are off center to the cam lobe.
I have to respectfully disagree to some extent. Flat tappet lifters (or at least new or good ones) have convex faces and the cam lobes on flat tappet cams are a shade taller on one side of the lobe compared to the other side. The offset lobe working on the convex causes rotation.
That’s how flat tappet lifters are checked; with a single edge razor blade. If the blade rocks on the lifter face with daylight on the edges the lifter is good; assuming no pitting or galling.
No rocking and daylight in the middle means a worn lifter which needs to be replaced.
@JayWB The acorn nuts were tightened down to the shoulder on the stud. It was not adjustable.
Maybe the years of tapping has mushroomed a valve stem.
@keith , I owned one for years. A 65 GTO with a 389 bought with bad bearings, replaced by a 326 replaced by a modified 400. It was certainly possible to tighten the rockers all the way down, collapsing the lifters, and it would even run that way. But that’s not how they were supposed to be adjusted. They were supposed to be tightened until they stop clacking, loosened until they started clacking, then tightened until they stopped again. And then tightened another quarter or half a turn, can’t remember which (it was 40 years ago).
Any “Roller” type of part is to reduce frictonal losses… In your 389 Poncho motor…they really werent looking for much “free Hp” It was all done by brute force…cool on one hand…not so much on the other.
If you installed a higher lift cam…you also introduced more frictional effort…and Loss to the engine. You probably will never know or feel these losses as you aren’t the one tasked with actually turning those rotating assemblies by hand…but if you were…you would notice.
Since motor oils have changed a good bit over the years since your engines design… You need to be wary of the Zinc content of your motor oil… Conventional oils used to have this covered as most engines used non roller valve trains…so they added an element to help assist these plain surfaces.
If you are mechanically inclined enough…I would look toward installing some roller lifters AND rockers…to help reduce frictional losses. Of course this would take research into if those parts even exist…they probably do… Cant hurt… But if you are using the correct motor oil…with the correct additives your valve train will be fine. The purpose behind any “Roller” anything…is to reduce the mechanical effort to drive that piece…and less is more in that category.
Here is a quick little blurb about Zinc…or ZDDP in motor oil…what it does, why its there…and…maybe even mentions that modern oils…no longer contain the stuff… Info you need with an older engine such as that 389.