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Yet another thread about Chevy rockers.

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48kenworth
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Yet another thread about Chevy rockers.

Post #1 by 48kenworth » Tue Mar 19, 2019 9:51 pm

Is it normal that Chevy rockers made my 300 clatter like a singer sewing machine that valve lash being to loose sound? I checked to make sure the rockers were not hitting the valve cover already. I have not messed with little gas engines in 20 years and back then I was all about small block chevy's but I don't remember high ratio rockers causing valve train noise. Thanks for humoring a newb here!

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Re: Yet another thread about Chevy rockers.

Post #2 by pmuller9 » Tue Mar 19, 2019 11:02 pm

It should be quite.
Does the engine have a stock cam?
What procedure did you use the adjust the lifter preload?

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Re: Yet another thread about Chevy rockers.

Post #3 by 48kenworth » Wed Mar 20, 2019 10:46 pm

Yes it has a stock cam, I just tightend the rocker nuts up the same as with stock rockers.

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Re: Yet another thread about Chevy rockers.

Post #4 by pmuller9 » Wed Mar 20, 2019 11:15 pm

Here is the procedure.

Take each cylinder one at a time starting with #1
Turn the crank clockwise until the EXHAUST valve just begins to open and stop. Then adjust the INTAKE valve with 1/2 turn past zero lash.

Now turn the crank clockwise again till the INTAKE valve opens and begins to close. Just as the intake valve closes stop and adjust the EXHAUST valve with 1/2 turn past zero lash.

Continue the process on remaining cylinders 2,3,4,5 and 6.

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Re: Yet another thread about Chevy rockers.

Post #5 by sdiesel » Thu Mar 21, 2019 12:40 am

paul,
this procedure is of course with lifters fully pumped, right?
a long love affair with the 300 six.
my lastest and final fling is a fresh 300 in an 88 ford f350 dually 4X flatbed

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Re: Yet another thread about Chevy rockers.

Post #6 by pmuller9 » Thu Mar 21, 2019 1:21 am

sdiesel wrote:this procedure is of course with lifters fully pumped, right?

Doesn't matter.
The plunger in the hydraulic lifter is spring loaded so it will be at the top against the retaining clip whether there is oil in the lifter or not.
The rocker is tightened down till there is no more pushrod free play and now the pushrod is pushing against the spring loaded plunger creating some resistance as you rotate the pushrod between your fingertips.
Then you turn the rocker nut another 1/2 to 3/4 turn and stop.
The adjustment for that rocker is done.

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Re: Yet another thread about Chevy rockers.

Post #7 by xctasy » Thu Mar 21, 2019 4:09 am

48kenworth wrote:Is it normal that Chevy rockers made my 300 clatter like a singer sewing machine that valve lash being to loose sound? I checked to make sure the rockers were not hitting the valve cover already. I have not messed with little gas engines in 20 years and back then I was all about small block chevy's but I don't remember high ratio rockers causing valve train noise. Thanks for humoring a newb here!



Yes. Rocker squeek is endemic, and it has driven two people on this forum to remove them. The problem is NVH, and you have to look at better securing , and getting alloy or steel rocker covers and side plates to quell the noise. Aramid (Carbon fibre) pushrods often help damoen to NVH paths.

Ford truckd were the first US Fords to get knock sensors. In a quest for cold start refinement in Hi Altitude areas, Ford moved from steel to alloy to fiber timming gears and other changes, and employed Kellar from Switzerland to quieten down a bunch of rowdy/noisey engines , speciffically the Lima 2000/2300 engines and Essex 90 degree truck engines that also found there way in to the Thunderbird and Cougars. Ford decided not to do any major NVH or 1.7 to 1.73 to 1.75 rocker ratio work on the 300. The EFi was probably a quiet engine
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Re: Yet another thread about Chevy rockers.

Post #8 by 48kenworth » Thu Mar 21, 2019 6:29 am

pmuller9 wrote:Here is the procedure.

Take each cylinder one at a time starting with #1
Turn the crank clockwise until the EXHAUST valve just begins to open and stop. Then adjust the INTAKE valve with 1/2 turn past zero lash.

Now turn the crank clockwise again till the INTAKE valve opens and begins to close. Just as the intake valve closes stop and adjust the EXHAUST valve with 1/2 turn past zero lash.

Continue the process on remaining cylinders 2,3,4,5 and 6.


That sounds like a modified version of a standard valve adjustment procedure for almost anything that doesn't have positive stop rocker studs. Problem is the stock positive stop studs do not allow for adjustment. Unless I am really missing something.

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Re: Yet another thread about Chevy rockers.

Post #9 by pmuller9 » Thu Mar 21, 2019 10:40 am

48kenworth wrote:That sounds like a modified version of a standard valve adjustment procedure for almost anything that doesn't have positive stop rocker studs. Problem is the stock positive stop studs do not allow for adjustment. Unless I am really missing something.


Evidentially the Chevy six rockers you have are slightly different in geometry than the Ford six rocker.
The proper solution is to get longer pushrods. You can shortcut instead by using washers under the rocker adjustment nut.
Last edited by pmuller9 on Thu Mar 21, 2019 10:44 pm, edited 1 time in total.

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Re: Yet another thread about Chevy rockers.

Post #10 by 48kenworth » Thu Mar 21, 2019 9:45 pm

My original 78 head does. 3/8th studs with 5/16th threads. They only have barely more than a full nut worth of threads on them. I wish I could show you a picture.

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Re: Yet another thread about Chevy rockers.

Post #11 by pmuller9 » Thu Mar 21, 2019 10:04 pm

48kenworth wrote:My original 78 head does. 3/8th studs with 5/16th threads. They only have barely more than a full nut worth of threads on them. I wish I could show you a picture.


I found a picture. Thanks for the info. I learned something.
I'm finding pictures of heads with both positive stop 5/16" nut studs and adjustable 3/8" nut studs.

You may need to remove the side cover to see if the lifter plungers are down from the retaining clip when the lifter is all the way down.
If the plunger is up against the clip and there is pushrod clearance then you can use washers under the rocker nut to shim the lifter preload.

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Re: Yet another thread about Chevy rockers.

Post #12 by 48kenworth » Fri Mar 22, 2019 8:15 am

Your right it may be worth pulling the tappet covers off to have a look at the lifters, but Xctacy may be correct about the noise as it is much less noticeable with the valve cover off. I remember the old two stroke Detroit's were the same way, on the later silver series engines Detroit used fully rubber isolated aluminum valve covers to make the engines nearly 20db quieter.

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Re: Yet another thread about Chevy rockers.

Post #13 by CNC-Dude » Fri Mar 22, 2019 9:55 am

The studs you are describing also do not compensate for wear over the years, so it might be a good time to upgrade to the adjustable rocker studs. Not all the lifters, rockers or cam lobes wear at the same rate, or at the same amount. So it's always best to have full adjustment to allow for these inconsistencies.
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Re: Yet another thread about Chevy rockers.

Post #14 by pmuller9 » Fri Mar 22, 2019 9:58 am

The one case of rocker squeak that Xctacy is referring to was a stock type rocker arm being used with an aftermarket cam at near .500" valve lift along with heavier valve springs. He tried replacing the rockers with heavier duty stamped steel rockers and different pivot balls with the oil slots to no avail.
Finally switch to roller rockers to get rid of the squeek

What you are describing sounds more like loose pushrod clearance clatter.

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Re: Yet another thread about Chevy rockers.

Post #15 by Max_Effort » Fri Mar 22, 2019 5:57 pm

pmuller9 wrote:
48kenworth wrote:My original 78 head does. 3/8th studs with 5/16th threads. They only have barely more than a full nut worth of threads on them. I wish I could show you a picture.


I found a picture. Thanks for the info. I learned something.
I'm finding pictures of heads with both positive stop 5/16" nut studs and adjustable 3/8" nut studs.

You may need to remove the side cover to see if the lifter plungers are down from the retaining clip when the lifter is all the way down.
If the plunger is up against the clip and there is pushrod clearance then you can use washers under the rocker nut to shim the lifter preload.


The washer under the nut was a common used car dealer “trick” on ford V8’s that had that style stud back when.

Use a washer so you get .030” to .050” preload on the plunger and it should be good.

Its good advice on removing the side cover so you can see what’s going on.

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Re: Yet another thread about Chevy rockers.

Post #16 by 48kenworth » Fri Mar 22, 2019 9:18 pm

I'll check the lifters pretty quickly as I don't really want to beat up my valve stems. I'll report back what I find and the solution when I do.

Edit: I just looked and I even have a tappet cover gasket handy. Easy enough.

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Re: Yet another thread about Chevy rockers.

Post #17 by 48kenworth » Sat Mar 23, 2019 1:25 pm

Well it sounded like excessive valve lash because that in fact is the issue, the lifter plungers are all the way up and i still have lash. The stock pushrods are 10.140 I did a little measuring and have ordered a set of 10.198 pushrods. Should be almost perfect.

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Re: Yet another thread about Chevy rockers.

Post #18 by old28racer » Sat Mar 23, 2019 10:59 pm

If I might ask how much rocker to valve stem gap did you have with the stock 10.140" pushrods?
What is your Int / Exh Camshaft lift?
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Re: Yet another thread about Chevy rockers.

Post #19 by 48kenworth » Sun Mar 24, 2019 6:43 am

old28racer wrote:If I might ask how much rocker to valve stem gap did you have with the stock 10.140" pushrods?
What is your Int / Exh Camshaft lift?


As it turned out I had about 0.010 +/- 0.003 of lash depending on the valve. I did not measure actual lift as my dial indicator is at work 45 miles away and I didn't really find it relevant, but I am running a stock cam.

I took some liberty on figuring needed pushrods length as I really do not know how much availible stroke the lifter plungers have or what an optimum plunger preload would be. So I made a few assumptions. The stuff I work on for a living all has solid lifters and valves are set with a feeler gauge.

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Re: Yet another thread about Chevy rockers.

Post #20 by Max_Effort » Sun Mar 24, 2019 7:51 am

48kenworth wrote:
old28racer wrote:If I might ask how much rocker to valve stem gap did you have with the stock 10.140" pushrods?
What is your Int / Exh Camshaft lift?


As it turned out I had about 0.010 +/- 0.003 of lash depending on the valve. I did not measure actual lift as my dial indicator is at work 45 miles away and I didn't really find it relevant, but I am running a stock cam.

I took some liberty on figuring needed pushrods length as I really do not know how much availible stroke the lifter plungers have or what an optimum plunger preload would be. So I made a few assumptions. The stuff I work on for a living all has solid lifters and valves are set with a feeler gauge.


As I wrote a few posts up, .030” to .050” is target preload.
Stock hydraulic lifters have at least .120” plunger travel, some as much as .200”.


Short travel racing lifters will have less, typically .050” - .060” depending on brand.

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Re: Yet another thread about Chevy rockers.

Post #21 by 48kenworth » Sun Mar 24, 2019 8:24 pm

Max_Effort wrote:
48kenworth wrote:
old28racer wrote:If I might ask how much rocker to valve stem gap did you have with the stock 10.140" pushrods?
What is your Int / Exh Camshaft lift?


As it turned out I had about 0.010 +/- 0.003 of lash depending on the valve. I did not measure actual lift as my dial indicator is at work 45 miles away and I didn't really find it relevant, but I am running a stock cam.

I took some liberty on figuring needed pushrods length as I really do not know how much availible stroke the lifter plungers have or what an optimum plunger preload would be. So I made a few assumptions. The stuff I work on for a living all has solid lifters and valves are set with a feeler gauge.


As I wrote a few posts up, .030” to .050” is target preload.
Stock hydraulic lifters have at least .120” plunger travel, some as much as .200”.


Short travel racing lifters will have less, typically .050” - .060” depending on brand.


That should put my choice of pushrods on average right in the middle of optimum after subtracting lash. I'll report my results when I get them installed.

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Re: Yet another thread about Chevy rockers.

Post #22 by 48kenworth » Sat Mar 30, 2019 12:20 pm

Results report.
The pushrods I got were ended up being just a tad to large in diameter to fit through the cylinder head. It didn't occur to me at the time that I needed to verify the diameter in thousands instead of just going off a fractional measurement, luckily they were not special order so I'll just send them back. I ended up taking advise given here and took my calipers to the hardware store and found twelve 3/8's washers that were all exactly 0.052 and installed them under the rocker nuts. Upon starting the engine I had a bad tap from #1 intake but I backed off the rocker nut and slowly snugged it back down again with the engine running which resolved the problem. I guess the push rod just wasn't seated quite right in the lifter. Anyhow it's quiet as a mouse now, all is well with the world and I really appreciate all the help and attention.

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Re: Yet another thread about Chevy rockers.

Post #23 by old28racer » Sat Mar 30, 2019 1:28 pm

Interested in the push rods you got that were to big on the OD.
Who did you get them from?
Were they "5/16" .3125" OD push rods as are OEM?
If they were 5/16 they should fit any 240 / 300 head push rod holes.

Got to say the washer trick is a lot less money than a new set of push rods.
Thanks for the information.
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Re: Yet another thread about Chevy rockers.

Post #24 by pmuller9 » Sat Mar 30, 2019 2:02 pm

48kenworth.
Great job on resolving your problem and helping me learn something new about the 300 six rocker studs.

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Re: Yet another thread about Chevy rockers.

Post #25 by 48kenworth » Sat Mar 30, 2019 7:30 pm

old28racer wrote:Interested in the push rods you got that were to big on the OD.
Who did you get them from?
Were they "5/16" .3125" OD push rods as are OEM?
If they were 5/16 they should fit any 240 / 300 head push rod holes.

Got to say the washer trick is a lot less money than a new set of push rods.
Thanks for the information.


The pushrods were sealed power 5/16ths stock replacements for a big block caddy, purchased from summit racing. They turned out to be .343 diameter pushrods.

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Re: Yet another thread about Chevy rockers.

Post #26 by old28racer » Sat Mar 30, 2019 8:18 pm

Sounds like Sealed Power & Summit use the term 5/16" rather freely. As the 300 head have round push rod holes and need guide plates installed (welded SBC adjustable plates do the job, but not sure a .3430 " push rod would fit a SBC guide plate. Thanks for posting the information.
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