Kevin Doe

iTrader: (1)

My engine is a 2004 GTO LS1. I put in an MS4 cam, PRC 7.400" pushrods, and their dual spring kit. I've had the cam in for 3000 miles. The last 500-1000 miles my valve train noise it getting louder and louder. It sound like the stereotypical sewing maching noise when I'm driving next to something that reflects the sound.

I called TSP and asked them what they thought. They suggested I pull the valve covers and check and make sure the rockers are still bolted tight, because sometimes they come loose and cause some play. I did this and checked. All the bolts are tight. I then wiggled some of the rockers around. Wiht the valves closed, I could move the rocker side to side a little bit. It doesn't seem like there is much preload on the lifters, but I'm no pro, so I'm asking for advice. Does this seem normal. It is very easy to move them side to side with teh valve open.

I'm installing a set of 2.5 5.3l heads and LS7 lifters so its probalby a moot point, but I want to know the cause of the noise so I can prevent it from following me on my new head setup. With the new heads I'll be checking for proper lifter preload, so again it might not be an issue. Let me know what you think.

Thanks!

jermzz

iTrader: (18)

Do they all do that? They shouldn't move, atleast mine never did. Are they at 22lb/ft?

Did you check that they sent you the correct length pushrods?

Haans249

iTrader: (24)

Yea, that is definitely too much movement there. I'd bet your preload is not high enough, which means your pushrods are not long enough. I would also suggest doing the harland sharp rocker arm mod. That is definitely causing the noise. Mine move side to side maybe a mm.

Kevin Doe

iTrader: (1)

Yes, all the rockers do that. I checked to make sure there wasn't any actual space between the valve tip and rocker. I used the smallest feeler gauge I had, 0.006", and it wouldn't fit. I didn't get any noise at first, but do now. Does that suggest that the stock lifters are not doing their job anymore? The pushrods are actually 7.400, as they are laser etched or somthing like that.

All the rocker bolts are tight to 22 ft-lbs.

jermzz

iTrader: (18)

so whats the rocker do when the valve is closed if there's that much play when its open???

in the movie it looks like the valve is closed (uncompressed spring) are you even at zero lash???

MeentSS02

iTrader: (11)

That ain't right...not sure what would cause that though.

Kevin Doe

iTrader: (1)

That video was with the valve closed. There is no lash, there is some preload, although not sure how much. I tried to slip an 0.006" feeler gauge in adn ti wouldn't fit. With the valves open, I cannot move the rockers liek that.

jermzz

iTrader: (18)

I dunno man. I'd say if you have stock heads and just the cam kit that something is screwy with your pr length or preload.

you need to get an adjustable pr length checker and figure out what length pushrod you need.

dz999

iTrader: (3)

Even with the valve close mine move like that too after the lifters bleed down. At first I though something was wrong and use a pushrod checker on all cylinders and valves; the preload was around 0.080 so it seems ok.

Gauge

iTrader: (3)

Mine definitely don't do that when torqued down. Get a PR length checking tool to test it out. I seriously doubt it's a lifter issue because the chances of it happening to all the lifters is very slight.

It's possible that the lifters might have become just a tad lazy, but if all of your rockers are that loose, then the PRs were too short to begin with and that slight wear on the lifters might have made it finally become noticable.

That's just my opinion.

mvvette97

iTrader: (18)

I would say you need a set of 7.425 pushrods. Since the base circle on your cam is smaller you just lost preload using the 7.4 pushrods. I also run the 7.425. I really needed a 7.440 but they didn't make that length, just a 425 or 450 so I figured it would be better to be a little under preload than over.

Gauge

iTrader: (3)

I initially went with 7.4s, as I recall, and I had to buy another set that was longer. I believe I had to make the choice between 7.425" and 7.450", but I can't remember which I went with. I was in the same boat as mvvette97; my measurements said I needed somewhere in between.