A couple of years ago I did a H/C swap. I went with a comp cams 228/232 .571/.573 112 with comp cams 850-16 oem lifters. Other mods include Dart PRO1 heads, headers, and a FAST intake. I bought a comp cams pushrod length checker and determined that the correct size pushrod to use was 7.4". I went with the comp cams hi-tech pushrods. Please note that while OEM push rods are supposed to be 7.4" they are in reality 7.385", which is apparent if you place them side by side with a real 7.4" push rod.

I remember determining that with the 7.4" pushrod my preload was somewhere between .080"-.100 preload. I spent a lot of time checking for the pushrod length and I checked on several cylinders. It still seems like somewhat of a subjective procedure and I didn't feel it was too accurate.

The engine is quite noisy (and shakes the car quite a bit at the 900rpm idle). I can't really tell if I hear ticking of something else. It seems to get louder after a 20 min drive and the engine is nice and hot.

I've heard people refer to the "sewing machine" sound. While I can hear the sewing machine sound it certainly has more of a "clatter" sound. It is a bit annoying. I've thought of installing some SLP loudmouths to drown out the sound.

Would it be a good idea to try the 7.425" pushrods? If my calculations are correct that would put my preload at .095-.125".

Is that too much preload? Any thoughts?

I've put on at least 5k miles since the install and I have visited the rev limiter many-o-time (6200).

 

I'm not so sure you can do anything about valve train clatter. I think it is what it is. I have a similar cam 228/228 and 588/588. I checked my wipe pattern and centered it up before measuring. I have 7.425 pushrods and get approximately one turn past zero lash, which if memory serves me correct equates to about .1 preload. It's noiser than I would like, but I just assumed that was normal with such big lift (as compared to the lift of the first gen small block)

 

http://forums.corvetteforum.com/c5-t...ic-lifter.html

 

Did the car have these characteristics when you first installed the heads and the cam? Are you running stock rockers? Is the shaking just the cam overlap or is there a miss?

 

I have a 228/232 .600/.600 cam with about the same setup in my Z and it pretty much sounds the same way you described yours. I have read post after post about this and the consensus is usually the same. It's the nature of the LS6 beast to sound like a sewing machine. I also read somewhere that you will hear more ticking if you have headers because the walls of headers are thinner than the walls of stock manifolds so it lets more engine noise out. Someone please correct my thinking if that was bad info.

-Scott

 

Yes, the car had these characteristics when I first installed the heads and cam.

Yes, I am running stock rockers.

I think that the shaking is largely due to the overlap. However, there may be a miss. If I hold the RPM around 2K it still seems to stumble a little which may indicate a miss. I also have new plugs and wires.

 

Would you describe yours as:
1)sewing machine
2)sewing machine with clatter

 

Sewing machine with a little clatter. I don't have a miss though. The car runs like a top. It really bothered me at first and that's why I sought out the forums. It gets really noticeable when the car is warmed up. After I heard a couple of my buddie's cars doing the same thing I realized it was just one of those things.

 

If there was a miss it should show up as a code unless the tuner shut off the low RPM mis-fire detection for the cam. Mine shakes the car a little and mine is on a 114 LSA so it isn't quite as lumpy. At 2,000 it is smooth though. I have the sewing machine noise and the headers do make it more noticable as does the FAST intake, which is thinner then the LS6 intake.

 

When I did my H/C install a few years ago I thought the valvetrain noise wasn't any louder than stock, but kind of hard to tell, with SS headers, and roller rockers added to the mix. I just changed to a smaller lift,and 116 LSA blower cam, and it seems louder to me. Like the "sewing machine" with a little clatter. It doesn't miss, and it runs great, though I haven't been able to take it over 4k RPMs, until I get it tuned with my new setup.

 

I swapped out a 226° XER lobe for a 224/230° XFI lobe hoping to have a little less aggresive ramp on and off the valve seats. I still have valvetrain noise. Mine is noticeably louder from 1,700 to 2,000 rpm. That is the one part of my modified C5 that just bugs and annoys me. Lately I have been reading about light valvetrain components and stiffer pushrods, but I don't know if that will quiet the valvetrain any. I did recently replace my Patriot Gold springs after running the first set around 50k miles. I noticed a drop in MPH at the dragstrip earlier in the summer, and after the new springs it was back to 94 mph in the 1/8 mile. I didn't see any wear to the valve tips, pushrods, YT rocker arms or even the 50k springs (although I haven't tested the spring load on the used springs yet). I guess the answer to the valvetrain "sewing machine" is to turn up the radio or add some exhaust cut outs.

 

Will full roller rockers help with the noise? I'd like to install roller rockers, what brand do you recommend? I think I'd prefer to go with 1.7 ratio vs 1.8 as I'm concerned about PVC with the DART heads.

About the shake. Before the tune when the motor was set to idle at 550 rpm the car really did shake quite hard. However, the tuner modified the idle to 850-900 rpm. It still shakes quite a bit. In fact everyone who has ever sat in the car comments on it.

Should the shake be as noticible as it is with a 228/232 .571/.573 112 LSA cam, especially at 900 rpm? Perhaps the shake is really a mis. Although I would have thought the tuner would have commented on it. (The tuner has a very good rep - Doug Rippie).

 

.....and have you discussed your concerns with DRM? This would seem like the first stop for info.

 

I think mine is also noticeably louder from 1700-2000 as well. Also, it is very annoying. With the road noise and all the other sqeeks andrattles that result on 50k miles and a stiff suspension the car really sounds like a POS on the inside...nice and shiny on the outside however.
I have thought about running loud exhaust to drown out the noise.

I'm thinking about running a supercharger however I've heard that they sound like a coffee grinder at low RPM. Road noise, sqeeks and rattles, valve train clatter, and a coffee grinder sound might actually drive me insane. I may just have to go with the electric cutouts just so I can put an end to the madness at the flip of a switch.

 

That's the same size as my former cam, except mine had .600 lift and was 112 +5*. I use HS roller rockers, and have had no complaints. Mine idled at 825, with a fairly mild shake, that I thought was pretty cool. My new cam is on 116 LSA, and less lift, and idles smoother, with a tiny shake @850 RPMs. It's yet to be tuned, and I'm hoping to lower the idle to around 800. If you're getting alot of shake, I think your cam is off degree.

 

I actually have not. I'm about an hour from DRM, I might have to drop by to see what they think. They didn't say anything when it was in their shop for the tune, but they all might be def from working on all those high horsepower machines.

If any of you ever get the chance to stop by Doug's shop I highly recommend it. Lots of high dollar eye candy!

 

Yikes.....this sounds less like a vehicle problem.....and more like PMS....

 

Its not a tremendous amount of shake at 850-900 but it was at 500.

 

Sorry to hear about the louder then wanted valve train. These LS engines do get a bit noisy. If the problem isn't getting worse then I'm sure it's the way it is. Doug is pretty good with his hearing still, and being from German blood. He is not afraid to tell you if something isn't right.

You can try the different pushrod, but I'm pretty sure that isn't going to help out too much.

Triple check for exhaust leaks, on a cold morning there will be visible smoke coming out of the engine bay. Many exhaust leaks are mistaken for valve train issues.

If it's a new problem or getting worse then pull valve covers to look around.

Let us know if you want us to listen to her We have some hot cars to look at still this late in the year
Randy

 

Does anybody know how much travel an oem lifter actually has? I remember reading somewhere in the neighborhood of .140.