I have seen many references to this situation but no definitive info. on cause or remedies. I have done two cam installs this year on LS1's and both have resulted in the dreaded "sewing machine" noisy valve train. Both installs where flawless, IMO, with no knocking issues and good power gains. Why is it some cam installs result in noisy valve train while others don't? What is the cause and/or remedy? I've heard push rod lengths, push rod contact with tunnel, etc. My first LS1 cam install lasted about a month before I finally pulled the cam for fear there was a problem. Further research revealed the term "sewing machine". My second install went like the first - good install with no issues except.... The sewing machine is back!

Both installs where done but the book. New lifters, well lubed cam, push rod length checker, preloaded (1.5 turn after zero lash on pedestal mounts), etc. I have installed many cams in iron block and have never ran into this.

I now turn to the masses for suggestions.

First cam was a TR224/224 on 112LSA
Second cam is a 230/230 on 113LSA

 

What parts have u changed in both installs besides the cam's....

 

First install - replaced cam, push rods, timing set, lifter trays, oil pump, gaskets and tune.

Second install - replaced EVERYTHING, new block, cam, LS7 lifters, push rods, pump, timing set, crank, all bearings, etc., etc. Nothing was reused

 

I have read that not enough lifter preload will cause that.
Your pushrods aren't bent, correct?????

 

I personally think some of it has to do with the fast ramp rates of these cams.

 

I used new push rods both times. Comp 7.4 first time with stock LS1 lifters. Used Comp 7.425 on second install due to LS7 lifters. I have thought about putting the 7.4's back in to see if it makes a difference on the chatter. I have read about people going down one size (-0.05 - less preload) and it made things quieter. Can anyone confirm this?

 

I have the 'sewing machine' sound to in my valve train.. PRs are to long. TSP recommended me to get 7.425s with my 228/232 cam.. Later found I need 7.4s

 

My old setup in my sig had the sewing machine sound, XER lobes, .080 preload.

The new setup has a cam from Geoff Skinner at EPS (sponsor) and I set the preload to .060 this time and it is very quiet.

I think the ramp rate is the primary noise maker, the lift smacks the lobe I think and then the lighter preload helps also.

 

Same here - My new setup has a cam spec'd by Patrick G. and built by Geoff Skinner at EPS. The question is, in simple terms, what does it take to get to .060 preload. I recall reading a tread that gave a rought estimate of turns to preload math. I can't find it! I am sitting at 1.5 turns to reach 22lbs of torque after zero lash. Is that .080 preload, or more?

 

Its the number of turns times .047

Shane at Thunder Racing gets the credit.

"The TDC method is NOT always accurate. Try the EO/IC method to check pushrod length. I have posted directions on this forum numerous times... Here it is again:

FWIW, EVERY cam install I have done using the LS7 lifter with a cam with greater than .600" lift (read smaller base circle) AND stock heads w/GM MLS gaskets has taken 7.425" pushrods for ~.050"-.060" preload. We measure lifter preload on each and every cam install we do. I have never had a lifter failure nor do we end up with the dreaded "sewing machine" noise.

Its very simple, If you change ANY of the following:
valve sizes, valve job, head milling, thinner/thicker head gaskets, decked block, cam with an altered base circle, etc... YOU MUST CHECK FOR PROPER PUSHROD LENGTH.

I have helped countless numbers of individuals with this process over the phone, via email, and PM's. I've posted the process on at least 3 occasions.

Here it is again in a nutshell:

1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.

For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...

I might not know everything but I will tell you that this method has worked for me year after year cam swap after cam swap. We average 3 cam swaps a week here so you can do the math.

If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:
For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.
For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.

THIS METHOD ALWAYS WORKS!!!

Check it using the above method and see where you are."

Thanks,
Shane

 

Well I can confirm that yes it does work but every car is different. My tuner installed 7.4 in mine and he said if it doesn't quiet down within the first 500 miles then he told me to bring it back and then he installed 7.350. It did quiet it down. With the 7.4 you could hear it standing out side the car and it was noticeable but with the 7.350 the the only time you can hear it is if I'm beside another car and/or riding next to a wall or rail but I guess that's the good benefit of having a loud exhaust. lol

 

Pushrod length is usually the culprit. I redo quite a few peoples/shops cam installs a year due to incorrect pushrod length and valvetrain noise complaints. Most times, it's something as simple as just measuring.

Most of these internet how-to sites will have you believe you just slap it together, throw a 7.4 in there, and smash all the bolts down to 22ft lbs. This is incorrect.

 

69LT1Bird, I just did a cam swap and have what I thought is "sewing machine" noise. I didn't measure for the pushrod length. I did exactly what you said, and measured both the intake and exhaust after the fact with the 7.4's. I came out with 1 3/4 turns, which I think you said is acceptable. To an extent, with the ramp rate of the bigger lift and higher duration cams and the stiffer valve springs, isn't there just going to be more valve train noise?

Thanks for any help!

 

The 1 3/4 puts you at .082", that is pretty much stock I think, I have heard that .080-.100 is the stock range. Over on Hardcore and others on here in the know recommend .050- .060"

Yes, there is always going to some noise. Also, some people mistake the sound of the headers for the extra noise also. The thin material of the headers makes them louder than a stock type manifold.

I checked mine with a length checker and Shane's method and they came out the same. I have heard from several of the cam pro's on here and other sites say the same thing about the aggressive ramp rates, the rapid angle change I think is what they are talking about which causes the lifter and cam lobe to separate which in turn creates the additional noise.

 

.080" is too much IMO, go a little shorter and it will almost always quieten it down. I don't go past 1 1/4 turns

 

Yep, that's where I ended up, 1.25 turns, .059 (.0587) preload.

The old XER lobes and 7.400 pushrods sounded like the old lady's sewing machine. Now it is way quieter, never thought it would be this quiet.

 

So Hville, do you go to Sam Houston State? I graduated from there back in 07 and had a NBM 99 TA

 

I am an old solid lifter guy and the proper way to get valves on the base circle for either measurements or adjustments is as follows. Exhaust open intake intake closed exhaust. Then you can adjust your rod length. The lifters plunger must be near the middle of the travel. This is approximately .060 that is what i shoot for. With that being said will the lifter fail to hold up O lash if its less or more?? Gm says anywhere from .035-.085. The lifter is basically a self adjusting mechanisn (hydrulic). If its within the specks of the plunger travel. I came across this with fords some time back and i agree with 69. Most of the noize is from headers and wild cam specks. The lifters should not seperate or lift from the cam if they are hydrulic. Hydrulic cams do not have clearance ramps. If a hydrulic cam is noizy its not setup correctly. TOM

 

Did you change the oil over after the cam install? Are you using a thinner synthetic oil perhaps? That can result in that kind of noise... Thin oil.. Maybe try something thicker if this is the case?

 

Here is a link to a thread that I have for the push rod hitting the pass through hole. There are some pics and some good info in there. When folks switch to a shorter push rod then at full lift the push rod should be farther away from hitting the bottom of the pass through hole since the angle would be smaller. To me it does not seem like the pre-load adjustment is what is making the noise go away. Either way just look for rub marks on the push rods to eliminate this. Good luck.