I know I know, another pushrod length question, and DO A SEARCH! well, I did... Here is what I came up with.

LS1 with BTR stage 2 turbo cam, 317 heads, LS7 lifters, LS9 head gaskets. Everything else is stock. I'm getting the "sewing machine" noise.

Today I purchase a pushrod length checker. What I came up with is, 7.325 @ zero lash. Add the .082" preload for the LS7 lifter and you come up with 7.407" I currently have 7.4" stock length rods in it now but have the dreadful noise still. Any suggestions?

 

Cam cut by comp? Just curious....what lobes does it use?

 

Yeah the cam was cut but comp. I talked to BTR and they said indeed it is a smaller base circle, but not enough to change PR length.

 

I selected pushrod length based on 1/4 to 3/4 turn to 22 ft/lb of torque after zero lash with LS7 lifters and I have ZERO noise. Im also running PRC 650 dual springs if that tells you anything about the pressure they are under @ .630 lift from the cam Im using.

 

I tried the method you are talking about PER XtraCajunSS and did not understand this method. I still tried it and from zero lash till 22 ft/lb it was 1 and 1/8 turns. The reason why I don't understand this method is because from the point of zero lash till the rocker is seated in the pedestal seems to me the actual measurement, beyond that aren't you just stretching the bolt to 22 ft/lbs?

 

In a way, yes, you are correct. From zero lash until the rocker is seated is basically the measurement you are looking for. I dont think there will be very many degrees extra in the turn to get 22 ft/lbs , hence the 1/4 to 3/4 turn margin. Im fairly confident that your pushrods are too long making your preload too much and causing noise IMO. I originally had this issue on either my exh or int side and had to get 8 shorter pushrods so that all 16 rockers were within spec. The way I checked preload is by making sure the lifter is on the cam base circle. I then used an oily allen socket and turned it by hand until it slipped in my fingers. This indicates there is basically zero lash without any preload on the lifters. Simply torque it down from there and if the reading is 1/4 to 3/4 turns until the torque wrench clicks the preload is good. If its more than 3/4 turn the pushrod is too long. Kyle @ Thompson Motorsports was who told me how to check the preload and recommended a pushrod length based on that. He builds LS engines all day long and his advice worked great for my build.

 

Thanks JRENIGAR, I may resort back to this as the last thing I do and I may contact Thompson Motorsports. I've already contacted a few vendors and I'm trying what they tell me first to see if I can figure anything out.

John

 

Shanes method is wrong. Plain and simple. Dont feel bad I used it on my own engine. When I actually measured for myself I found his method produced near 80 per rotation not the 47 he claims. THAT'S almost double. Mine are like 1 1/2 turns so I'm prolly pushing 120 or the limit of the ls7 lifter. This kinda pisses me off. I hate that ive been a part of sharing such incorrect information over the years.

 

That's what I don't understand. There is so much different information out there. On here most people say 1 turn equals .047 and on yellow bullet they say 1 turn equals .078.
.078 sounds more like it to me but I could be doing something wrong.

At 0 lash with adjustable pushrod at 7.350. A 7.400 pushrod would give me .050 preload. When I put my 7.400 pushrod in and set it to 0 lash, I only get a little more that 3/4 of a turn with the rocker bolt to 22 ft pounds.

That's just like a lot of guys on here say to run around .080 preload on ls7 lifter. A lot of guys over there say to run around .040. I plan to run .050 and see what happens.

 

I used a direct measure method to set preload, and I set it at .038". This was almost an exact half turn, double it and you're at .076" per turn.

Numbers like .047" per turn are at the rocker bolt, not the lifter preload. With the exact measurements for thread pitch and distance from bolt center to cup center and roller tip, and the various angles, could use basic geometry to get the exact numbers.

 

Thread is 8x1.25 mm. 1.25mm = .049" per rotation of the bolt. Off by .002 in previous post

 

47 per turn is the bolt, it is absolutely not at the pushrod. When I directly measured at the pushrod, I got about 80. Shanes method of saying the 47 is lifter preload is flat wrong, and he should be ashamed he spread that info.

 

I'm not saying that any of these methods are wrong, I just don't understand them. I understand turning the rocker arm bolt will directly effect preload, and i'm sure there is some mathematical equation out there that will tell you the amount of turns equals a certain preload but once the rocker is seated in the pedestal there should be no change in preload after that.

http://www.ls1.com/forums/f7/how-mea...length-172530/

This method is what makes sense to me, and it is what I followed. I still have the "sewing machine" noise and am considering changing the lifters to a name brand manufacture who actually knows the preload setting.

John-

 

I agree with this.

Just fought through the pushrod measuring thing. When my Manton 11/32's showed up and torqued to 22 ftlbs in 1/2 turn I almost pee'd myself thinking I measured wrong cause of the Cajun threads.(shooting for .040 preload on a Johnson 2110)

Fired the car up today for the first time... dead silent with a .625 lift cam and BTR springs shimmed .060.

 

Sounds to me like you measured right. Mine is quiet on cold start but as oil heats up the sewing noise comes in

 

Yeah, pretty confident its dialed. I definitely have some sewing machine when at operating temp..but I did with LS7 lifters too. Don't hear it out of the car...easiest to hear when driving with the windows up, radio off and around 2200rpm. Part of the cammed lsx deal I guess.

 

Another piece to my puzzle is that I bought "hand selected" LS7 lifters from Kyle. He claims they buy a huge loose batch of them and test their bleed down rates amoung other things. The ones that dont meet whatever their "specs" are, they trash them. I want to say they cost about $10-$15 more than stock in the box GM LS7 lifters. At the time I bought them they werent listed on their site he just mentioned them. Im also using a Melling 10295 high pressure pump with whatever spring came in it from Melling. With 5w-30 oil it maintains 65-70psi when hot idling. IDK if that has anything to do with mine not making any noise vs others or not but I though Id throw that out there.

 

I think a lot of people use the turn method but mine were something like 1 or 1-1/2 turns on the rocker bolt from zero lash. It's pretty quiet and still has the stock lifters.

 

The stock lifters have something like .170" travel IIRC. 1.5 turns is .115-.120 and probably runs nicely. Upgraded lifters with shorter travel will be horrible with that much preload