Would this be a bad idea?

[FlDart360]

Here is the Background on the car first. 1971 Swinger 360LA , has a very mild cam ,but I don’t know the specs. RPM intake ,Holley carb, headers, cast iron heads with factory shaft mounted rockers. I have owned the car since 2016 and put about 5000 miles on it. Previous owner said the motor came from eBay and was rebuilt. For the most part it has been mostly trouble free given the unknows with a 50-year-old car. My one gripe with the motor has always been some valvetrain noise that makes it sound like a sewing machine under acceleration. At idle the noise is not as noticeable. The motor runs and performs good ,I just feel things could be better, so today I did some reading up on valve lash. I followed this http://www.hughesengines.com/Upload/productInstructions/ValveAdjust.pdf. What I found was two rocker arms on separate cylinders that have what I would describe as the absences of any preload. I performed the procedure with the motor cold. Now to the question. Could I try a slightly longer pushrod to add some preload? What is the likelihood I have two wiped cam lobes? wouldn’t the motor run like crap? Thanks for the help, this site is a Gods send.

 

[67Dart273]

??? you cannot adjust valves unless you have adjustable rockers and most Mopars don't--have them. So do you ? "have adjustable rockers?"

The next thing is, if you were able to adjust them without getting the valve gear all "out of shape" EG the adjuster clear to one extreme or t' toher, then you are done, unless there is some damage, bent pushrod, abnormal wear on pushrod, rocker, came, etc

If you do not have adjustable rockers, then the only way to make up slack is longer pushrods, but you really need to find out WHY. Is the cam wearing? you have a burned valve? etc?

 

[FlDart360]

??? you cannot adjust valves unless you have adjustable rockers and most Mopars don't--have them. So do you ? "have adjustable rockers?"

The next thing is, if you were able to adjust them without getting the valve gear all "out of shape" EG the adjuster clear to one extreme or t' toher, then you are done, unless there is some damage, bent pushrod, abnormal wear on pushrod, rocker, came, etc

If you do not have adjustable rockers, then the only way to make up slack is longer pushrods, but you really need to find out WHY. Is the cam wearing? you have a burned valve? etc?

Thanks 67Dart273 for the reply,
No i don't have adjustable rockers that is why i was asking about maybe going to a longer pushrod. If I had a burnt valve what symptom would I have? Would there be any harm in trying one of these pushrods on one of the two problem rockers? https://www.hughesengines.com/Index...aHJvZHM=&level2=T2lsIFRocm91Z2g=&partid=23189
Thanks.

 

[ir3333]

at rest they may have leaked down but will pump up when re started.You could disassemble and clean or replace them.

 

[Rat Bastid]

Thanks 67Dart273 for the reply,
No i don't have adjustable rockers that is why i was asking about maybe going to a longer pushrod. If I had a burnt valve what symptom would I have? Would there be any harm in trying one of these pushrods on one of the two problem rockers? https://www.hughesengines.com/Index...aHJvZHM=&level2=T2lsIFRocm91Z2g=&partid=23189
Thanks.

Take the rocker arm shafts off and lay a straight edge across the tips of the valves. If any of them are obviously lower than the rest you can probably use a longer pushrod IF that is the issue.

 

[FlDart360]

Take the rocker arm shafts off and lay a straight edge across the tips of the valves. If any of them are obviously lower than the rest you can probably use a longer pushrod IF that is the issue.

Thanks Rat Bastid,
I will try that, also I failed to mention on the opening post that i have good compression on the cylinders that are showing lack of preload.

 

[Dana67Dart]

Could be bad lifters.

Maybe the oil supply to the lifters is being reduced under acceleration, why, that's the question!

 

[3406pk]

The suggestion to put straight edge on valve tips is good from Rat B. Sometimes a bad valve job can cause sunken valves and uneven tips. There are valve lash caps that could take up some slack, but I have never tried them. If you find some 273 style adjustable rockers, you could then adjust preload.

 

[FlDart360]

The suggestion to put straight edge on valve tips is good from Rat B. Sometimes a bad valve job can cause sunken valves and uneven tips. There are valve lash caps that could take up some slack, but I have never tried them. If you find some 273 style adjustable rockers, you could then adjust preload.

Thanks 3406pk,
I like the 273 adjustable rockers idea might need to check into that.

 

[rumblefish360]

Sounds like a set of crappy Comp lifters on there XE lobe cam. That sound is always heard.

 

[jos51700]

It's supremely easy to measure the lift on the questionable cylinders. They could be Rhoads lifters or who knows what.

If the lift seems OK and the valve tips are relatively even, pull the intake and clean or replace the lifters before you go messing with new pushrods. Make sure you have all the zddp in the oil and follow the new startup procedures to the letter if you replace lifters.

My 360 munched two lobes and ground those lifters through to the lifter guts, and other than burning oil and being down in power, you couldn't hear it.

 

[Wvbuzzmaster]

Hydraulic lifters with lack of preload can result in the retaining clips that hold the plunger in the lifter to fatigue and break out. My 340 came to me with a fresh rebuilt engine and pushrods .030” shorter that stock of 7.500”, and provided exactly zero preload. Consequently there were 7 lifters missing their clips. I ended up buying new set of hydraulic lifters, new custom length pushrods, and Harland Sharp adjustable rockers. This allowed me to perfect my preload setting to around .030 preload per lifter. The rocker arm adjustments for preload were done with the intake off and by rolling the engine over to place lifters on the base circle of the cam lobe to set each lifter exactly where I wanted it for preload. The proof was in the results, no more noisy valvetrain now.

if your lifters are not coming apart on you yet you can skip the new lifter step and just go to adjustable rockers and custom length pushrods to make sure you get the adjusters in the correct range for proper lubrication.

 

[FlDart360]

Hydraulic lifters with lack of preload can result in the retaining clips that hold the plunger in the lifter to fatigue and break out. My 340 came to me with a fresh rebuilt engine and pushrods .030” shorter that stock of 7.500”, and provided exactly zero preload. Consequently there were 7 lifters missing their clips. I ended up buying new set of hydraulic lifters, new custom length pushrods, and Harland Sharp adjustable rockers. This allowed me to perfect my preload setting to around .030 preload per lifter. The rocker arm adjustments for preload were done with the intake off and by rolling the engine over to place lifters on the base circle of the cam lobe to set each lifter exactly where I wanted it for preload. The proof was in the results, no more noisy valvetrain no,
w.

if your lifters are not coming apart on you yet you can skip the new lifter step and just go to adjustable rockers and custom length pushrods to make sure you get the adjusters in the correct range for proper lubrication.

Thanks Wvbuzzmaster,
I know it's all speculation at this point. Right now with the car running good I just didn't want to overthink the problem. There is no one simple answer, and not knowing the rebuild history of the engine certainly does not help.

 

[Wvbuzzmaster]

Thanks Wvbuzzmaster,
I know it's all speculation at this point. Right now with the car running good I just didn't want to overthink the problem. There is no one simple answer, and not knowing the rebuild history of the engine certainly does not help.

That was my theory, but I pulled the valve covers and looked in and saw the lifters were missing clips, at that point, I had to fix the issue. You can see the tops of the lifters without pulling the intake or heads and it costs nothing to take a look. If you see something amiss then you know you need to open it up.