Had a cam swap. I also had my stock push rods replaced with 7.4" hardened push rods and stock springs replaced with some 918's).

To rid the noise, should longer push rods be installed? I have heard that with a cam swap, louder valve train noise is normal. I have heard it from someone at Thunder Racing, Nelson Tune and Cam Motion.

Truck runs great (except for a couple of times I had smoking issues that have not returned, yet.).

 

Sewing Machine Sound Comes From The 918's, Very Common

 

The valvetrain noise that comes with a cam swap is definitely common, but I still have trouble swallowing that it's "normal". Seems that almost everyone who has swapped to a larger cam experiences the sewing machine noise, no matter what springs they're using. I know guys with Crane duals and the noise, mine did it with the 915's, and still does it with the LS6's I have in there now.

I've asked the same question, and a few times it has been recommended to me that I swap in a 7.425 pushrod, as the noise is actually from the lifter jumping off the cam lobe, not the valve spring.

 

It's my understanding that the 918's are supposed to prevent the lifter/pushrod/rocker from seperating or "jumping" off because the 918's are a stiffer spring.

Am I incorrect?

 

Colby i think you are right, but the springs are noisy because of the speed and force with which they move the valve. So I'm not sure the noise is coming from the block components. So I have read.

 

I was just responding to the reply about the noise being the possibility of the lifter or rocker arm "jumping" off of the cam or push rod due to the steep ramp of the lobe.

I can't wait to hear my sewing maching fire up!!!

 

Probably both, especially on those really aggressive Xer lobes that comp has.

 

I had more noise with my TR220, 918s, & TR7.4 pushrods than I do with my TR230, Patriot Dual springs, & TR7.4.
Actually the new setup is almost stock quite sounding.

I've heard people talking about the lifter jumping off the lobes but there were a lot of people saying that just isn't possible. Plus I would think you would see a lot of wear on the cam lobes from the lifter smacking the lobe that many times. I pulled my TR220 out and it looks just like when I put it in, even though I thought I had excessive noise.

 

Thankfully, I haven't experienced this issue with my new cam. I don't know whether it's because I chose a mild Lunati cam or because I used the Lunati Pro Mod springs, but the sound of the engine at idle is very little different from stock. It idles at 400-500 RPM with no valvetrain noise.

 

Yea the sewing machine sound is characteristic of the Comp 918 springs. No worries.