**My engine info can be found here: https://ls1tech.com/forums/dynamomet...241-heads.html




So I took the RX-7 out for a spin today and as usual I noticed the sewing machine effect from my valve train. I have always noticed it since I built the car, the noise is noticeable but subtle. Around 2000 rpm it is the most profound but still not like the noise of a collapsed lifter or bent pushrod....just slightly louder at that particular rpm and simmers down above 2K.

Anyway, tonight I got a hair up my *** and decided to inspect my valve train since I haven't been in there in about 2 years since the head swap. Took my rocker covers off and everything looked fine.

I then decided to grab my comp cam adjustable push-rod(6.800) and found the cylinder that had the exhaust valve open and the intake valve closed. took that rocker off, pulled out the 7.400 Texas speed push rod and inserted my adjustable push rod set at 7.200. I torqued the rocker down to 22ft/lb and adjusted my push rod until zero lash.

What I found was very interesting, my adjustable push rod was 9(.450) & 1/4(.0125) turns. That equates to 7.2625''. Now alldata says that the LS1 preload on the lifter is ideal @ .060, so that added to 7.2626 = 7.3225 :o

So I tried it again on 3 more cylinders. All together I tested #2,6,5 & 7 cylinders. All were same 9 & 1/4 turns on the push rod checker.

Again I have been running 7.400 since my swap. So realistically that means with lifter preload(if mine is in fact around .060) the Texas Speed pushrods were at about 7.340 right?

So as of right now I want to order some new pushrods thinking this might hush my valve train up. Will the .0175 make that big of a difference?

I came across some pretty common threads on guys running shorter pushrods over the "recommended standard" 7.400 and having good results.

Let me know what you all think. Thanks!

 

General rule of thumb, you should have a small amount of side to side play on the rocker, but no up and down play when the valve is fully closed.

 

^
Appreciate the response. I did have no up and down play. Rocker did wiggle side to side (my fat fingers kept wiggling the rocker while adjusting the push rod checker).

 

the procedure in the video should help you out, i believe the ole marker on the top of the valve stem trick works as well.

 

Did you measure the last time or just blindly throw the pushrods in? Also, did you verify that the lifter was on the camshaft's base circle when you measured?

For reference, when I swapped cams in my engine, I had to go from 7.325" to 7.350" pushrods. I ran the 7.325" rods while I waited for the new ones to come in, and that .025" made a huge difference in valvetrain noise. I also have a 5.3 on an engine cradle with 862 heads, an LS2 cam, and LS7 lifters, and it measured out to needing 7.325" pushrods. So, it is possible that your engine requires that length pushrod and you have been running .075" more preload than you needed to, given that you were on the cam base circle when you measured.

Your pushrods were 7.400" long. You don't subtract lifter preload from the pushrod length.

 

I already measured man. Did it both ways, 1st attempt with push rod checker installed then rocker torqued and then adjusted pushrod checker(hard way lol). 2nd attempt was exactly like the video above.

Both attempts at zero lash I am at 7.2625.
If I shoot for .060 preload that would make my new push rod length 7.3225

Car previously has 7.400 installed.

Will a shorter push rod quite things down in my valve train?

 

I was just making sure you measured correctly. From the first post, it kind of seemed like you had assumed the lifter was on the base circle base on the rocker positions.

You are essentially running .135" of preload right now, so yes, the appropriate length pushrod should quite down your valvetrain some. Granted, with the XER lobes, you still will hear the valvetrain, but it shouldn't be as pronounced.

 

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Thanks man and my reply was for the post above yours .

I just discovered that my 2004 LS1 has lifter p/n 17122490 with a preload of .082''

That means I need a pushrod length of 7.3445. I was running .055" more then I needed to with the 7.400 TS rods.

I will give it a shot. Will keep you all posted

 

Would consider a lifter upgrade to a minimum of Morel 5315. Upgrade pushrods to 11/32", as well. X-ER lobes can wreak havoc on lifters & pushrods. Do you hear a smack/knock on startup 'till the lifters pump up? If so, one or more lifters are bleeding down while the engine is off due to heavy dual spring force applied to the GM lifters.

 

Your lifter plunger is near the bottom of its travel, although Crane was recommending 0.120" preload with their rockers several years ago. If you have a dial indicator, you can use that to definitively determine your current preload and work from that.

 

thanks for the advice, maybe in the future i will go all out. Like I stated earlier I have ran the engine like this since 2011 with no issues. I have never had a start up with any of the lifters bleed down beside the head swap start up 2 years ago from sitting static so long. Never had that extreme of a noise driving either......just the subtle noise I described in post #1.

 

Someone said it above, but even with perfect rod length XER lobes are not stealthy. There will be some amount of noise regardless. FWIW, sounds like you have the length issue sorted.

If you really want to quiet it down, consider calling cam motion or EPS. Smoother lobes, and make more power.

 

Two things I started doing that made me more comfortable with my measurements. One was to use my .001" feeler gauge between the rocker and valve to determine when I stated to get drag approaching zero lash and the other was to ditch the "counting turns" thing to measuring the adjustable rod out of the car with a caliper micrometer. That took all the guess work out.

 

Another thing of note is to always make sure you measure intake and exhaust lobes at least once. I have a slight variation on my custom grind. My intake side likes 7.395 and my exhaust side likes 7.375. I run the 7.395's on all 16 but if i wanted to dial it in more accurately id run two different sets.

 

My last set of heads had different intake and exhaust rods after I had them worked on. This set of heads were the same on the four valves I checked.

 

Different cam perhaps? Never heard of a head making a different on intake/exhaust because the head should be cut uniformly.

 

The heads were the difference. The intake seat was cut for 2.02 valves and the exhaust left the same. The valves ended up being two different heights.

 

ah gotcha, makes sense