Rebuilt a 6.0L for my dads van. First time i had it running, it sounded bad and was shaking a lot. Put in 7.350 pushrods, after finding out i was running a lot of lifter preload. That didnt help anything. The motor was still shaking and it sounded like it was the bottom end knocking, so i swapped out the crank.

Now the reason I was quick to swap the crank, is because of how the machine shop balanced the crank. I brought them early pressed pin piston/rod assemblies and he was worried he'd damage the piston when removing it from the rod. He assured me he could balance it with the piston and rod together.

Anyway, i put in a factory balanced crank and checked all clearances with plastigage. Now the motor runs smooth but still has a knock/tap that gets louder under load. It has new "LS7" lifters, 7.350, pushrods, blue LS3/LS6 springs, and LS2 cam. Listen to the video below and tell me what you think. Did I just get unlucky with a bad lifter?

https://www.youtube.com/watch?v=BkIb...ature=youtu.be

 

Hard to tell in the video, BUT, I had issues with new LS7 lifters as well. Had my cam swap done and the first test drive it started making a tapping sound, about 10-15min in, that got progressively louder. The shop checked them out and found one or two that you could push in on the plunger.

 

When I did my cam swap I let the lifters soak in oil for 24hr prior to install. When we first fired it up it taped very loudly for 2-3 min and then stopped. I have put 50K on my ls7 lefters and it will still have a noticeable random tap tap tap from the drivers side during the summer at idle. I constantly tare my oil filters apart during oil changes looking for metal flakes, but never find anything.

My point being, I was assured by several mechanics and members on the form that tap noise was just from the ls7 lifter being noise in general and after 50K miles with no issues I'm starting to believe them.

Side note.... even though the LS7 lifter plunger is 0.05 taller does not mean you need to go 0.05 shorter on the pushrods. Did you originally try the 7.4" before the 7.350"?

 

I had stock pushrods in it first and had around .110" preload. And I think stock pushrods are around 7.3800-7.3900.

 

ls2/ls6 cam should require alonger pushrod, always read it was a 7.425 for a ls6 cam as the base circle required it

ive never ran smaller then 7.4 with ls7 lifters

 

Always use a pushrod length checker to be sure....$$$ spent today, and it is not that much, is $$$ saved down the road.......

 

I used a length checker and 8" measuring calipers. I used stock pushrods in my LS2 with comp cam and new lifters without issue, so i know that it can work. Honestly, checking and changing the pushrods in this motor was a shot in the dark.

I got the lifters out of the passenger side and I CAN'T depress the plungers in any of them. I tried freaking hard too. Im going to take a look at the driver's side, hell, maybe pull that head too.

 

I did a lot of reading on tech about the ls7 lifters and several people said there's had a lot of trash left over from manufacturing in them. They cleaned them thoroughly and then soaked them in oil and had no issues. Ls7 lifters seem to be real hit and miss though.

 

Good deal! That eliminates it being the pushrod. Yea stocks are 7.3800. I guess pull the lifters and clean them with some carb cleaner, check the plungers, soak in oil and put back together.

Or you can bite the bullet and get some better lifters, I know on my next cam build I will not be using LS7 lifters.

 

It pisses me off that it's in a work van that I don't want to be working on in the first place. It shouldn't need better lifters as it will spend most of its life below 3500rpm.

Pulling the driver side head now. Just going to swap them all and see what happens. Using eBay studs this time to avoid wasting bolts.