LS3 cam base circle difference from dod cam delete - Pontiac G8 Forum: G8 Forums - G8Board.com
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post #1 of 29 (permalink) Old 12-13-2016, 12:50 PM Thread Starter
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LS3 cam base circle difference from dod cam delete

so, I have the motor disassembled (down to the short block,cam out) and doing some comparison on the LS3 cam vs the removed dod cam ,,I found that the LS3 cam has a .035 smaller base circle than the dod cam,,has anyone checked this on their install ,, I have read several threads guys end up with noisy valve train after doing LS3 on their cam swap ,, is their a part number for LS3 push rods?,, looks like the push rods need to be .035 longer to maintain the quietness of the valve train ,, give me your thoughts ,,gmonde

to add if this is the case then I could mill off .035 on the heads and not have to change out push rods ,,,,hhhmmmmmmm
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post #2 of 29 (permalink) Old 12-13-2016, 01:21 PM
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The LS3 and L76 use the same push rods.

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post #3 of 29 (permalink) Old 12-13-2016, 05:40 PM
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Well, if you measured the base circles with a caliper or mic and found a .035 difference , that is .015 on each side.
SO your preload , all other being equal , would change by .015.

Likely best bet , just measure the actual preload and make a decision from there.

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post #4 of 29 (permalink) Old 12-13-2016, 06:51 PM Thread Starter
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Originally Posted by 95wagon View Post
Well, if you measured the base circles with a caliper or mic and found a .035 difference , that is .015 on each side.
SO your preload , all other being equal , would change by .015.

Likely best bet , just measure the actual preload and make a decision from there.
actually I measured it both ways with a caliper around the base and came out to .070 difference ,then measured from the cam journal to the bottom of the lobe base with a depth gauge micrometer and cam up with .035

I will have to see what the difference is between the oem head gasket and the felpro that is .051 compressed
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post #5 of 29 (permalink) Old 12-13-2016, 08:51 PM
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Originally Posted by gmonde View Post
came out to .070 difference
Well then, yes I believe you are onto something.

With the way the all aluminum L76 gains lash (looses preload) as it heats, losing .035 preload from what ever it started with, yes, maybe that is why some guys cam swaps with no other changes are noisy.

Like any valvetrain mod, you are wise to verify preload,as opposed to following the party line.
The fact you were checking base circle difference illustrates you are on top of things already.
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post #6 of 29 (permalink) Old 12-17-2016, 07:54 PM Thread Starter
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I am wrapping up the dod delete-ls3 cam ,, I did some comparison on the dod springs vs the ls3 springs ,, installed height 1.795/80lbspressure and open pressure 1.245/270 lbs (.550 lift ) are the same and this on motor with 55,000 miles ,, coil bind at 1.205 ,also push rod length is on the fence ,,"I should of checked the actual preload before I took it a part" ,with the stock length pushrod 7.400 I get a turn and a half to torque = .070 (22 lbs) ,,with the 7.425 length I get 2 turns to torque (22 lbs)=.094,, start up will be the tell tail ,, has any 0ne actually checked the preload on the dod cam profile ?? ,, I will update when I start it up ...

question is .094 to much preload for the ls7 lifter and will it hang the valve off the seat,, ??
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post #7 of 29 (permalink) Old 12-17-2016, 08:39 PM
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I may be misunderstanding you (not the first time) but are you measuring actual pushrod travel or calculating preload based on rocker bolt pitch and rotation?

I ask because 1 1/2 turns would be about about .074 travel at the bolt

Because the bolt is midpoint (sorta) the travel at the pushrod end is more.

I read the LS7 lifter will tolerate over .100 , personally I would be shooting for .07ish

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post #8 of 29 (permalink) Old 12-17-2016, 09:12 PM Thread Starter
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Yeah sorry for not being clear, ,I am mesuring at the bolt thread ,so I would have to multiply the bolt travel by the rocker ratio and that should give me the preloaded travel
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post #9 of 29 (permalink) Old 12-17-2016, 09:21 PM Thread Starter
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Just did some math and it works out to be .119,,,but I know it's not 1.7,,,it has to be less because you mesuring on the small end ,,,I will have to put a dial indicator on it to be sure ,,,,
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post #10 of 29 (permalink) Old 12-18-2016, 08:21 AM
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Best way to check for proper pushrods length is using a dial indicator on the pushrods side of the rocker or using an adjustable length pushrod checker. This is the one I have: https://www.summitracing.com/parts/c...MobileSwitchNo

The difference in base circles is normal. Higher lift cams reduce the base circle diameter to get the higher lift.

Regardless of whether you mill the heads or not, you should always measure for proper pushrod length as that is the only way to truly know what length pushrods you need.

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post #11 of 29 (permalink) Old 12-18-2016, 08:48 AM Thread Starter
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I just did a mesurment, .090 on the intake and .105 on the exhaust ,measured @ the rocker tip
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post #12 of 29 (permalink) Old 12-18-2016, 12:21 PM
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Quote:
Originally Posted by gmonde View Post
I just did a mesurment, .090 on the intake and .105 on the exhaust ,measured @ the rocker tip
Measured on the rocker tip side, your numbers translate to about 0.053 and 0.062 of actual preload. Assuming you are using LS7 lifters, you need 0.025 longer pushrods. LS7 factory lifter preload is 0.082 and with 0.025 longer rods you will be at 0.078 and 0.087 preload which is near perfect.

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post #13 of 29 (permalink) Old 12-18-2016, 12:35 PM
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Lots of bad info in here.

The updated "LS7" lifters are quite forgiving. However, keep the preload on the mild cams to a maximum of 0.060". 0.030" - 0.040" is ideal for most streetable setups (especially a setup close to coil bind like this one), but makes a little noise at idle. That's only a 3/4 turn of the bolt.

Stock pushrods are 7.380"

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post #14 of 29 (permalink) Old 12-18-2016, 01:14 PM Thread Starter
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Sorry for the misread,That mesurment was taken on the push rod side (actual plunger travel)
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post #15 of 29 (permalink) Old 12-18-2016, 05:41 PM
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Quote:
Originally Posted by gmonde View Post
Sorry for the misread,That mesurment was taken on the push rod side (actual plunger travel)
Gotcha. You need a .025 inch shorter pushrod then and you are good to go.

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post #16 of 29 (permalink) Old 12-18-2016, 05:54 PM
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Quote:
Originally Posted by Marc 85Z28 View Post
Lots of bad info in here.
Please enlighten us with specifics

Quote:
Originally Posted by Marc 85Z28 View Post

The updated "LS7" lifters are quite forgiving. However, keep the preload on the mild cams to a maximum of 0.060". 0.030" - 0.040" is ideal for most streetable setups (especially a setup close to coil bind like this one), but makes a little noise at idle. That's only a 3/4 turn of the bolt.
And how much lash -preload change are you seeing between room temp (cold) and stinking hot?
You don't see .030 cold going into lash at high temps ?
You have no concerns with the plunger beating up the clip in the lifter?

Why do you see .070 an issue, ?

Thanks for your info.
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post #17 of 29 (permalink) Old 12-18-2016, 07:50 PM Thread Starter
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I did some checking with the non dod lifter I removed (aka ls7 lifter)and the plunger travel from top to bottom is .210 travel ,, doing the math on the base circle difference between the two cams ls3 and the dod, I come up with the plunger down .125-.135 with the dod cam ,this make sense because I have .090-.105 with the ls3 cam,, keep in mind I did not cut the heads and used the same gm part number head gasket ,when racing stock eliminator you where forced to use the hydraulic lifter and you would only want minimal preload (1/4) turn ,so the lifter wouldn't pump up and cause the valve to stay off the seat at high rpm 7000 or so (racing application) to add the valve spring pressure was and is real high ,,,but not the case here ,, so I believe that the preload was designed to have over .100 preload ,, I will stick with the stock push rods for start up ,, but the math tells me that I will need to go back to my initial thought that the 7.425 will be the best operation for a quiet valve train ,, this all goes out the window if gm indeed change the travel in the newer lifter and I didn't think to check the new set ,, but I would think that we would here more complaints of engines running poorly due to the stock push rods being to long hanging the valves off the seat --- more to come on start up gmonde
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post #18 of 29 (permalink) Old 12-24-2016, 08:12 AM Thread Starter
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update!!!!! as I still wait for my mid pipes, I did prime and start the motor ,, smooth idle and a very quiet valve train so far , I will run it up to temperature today ,, I have the valley cover with updated pcv/breather port in front .. how did you guys configure your pcv ??? i have the right side (passenger side) plugged , the left side valve cover(drivers side) is connected to the intake behind the throttle body (stock location) ,,the valley cover port is routed to the cold air intake port in front of the throttle body ,,, let me know your thoughts thanks gmonde
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post #19 of 29 (permalink) Old 12-28-2016, 08:29 AM
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Please enlighten us with specifics
It's all there in the post. READ.

Proper valvetrain setup is usually done wrong on the LS engines because it takes time, effort, and knowledge. Even most of the knowledgeable guys are STILL doing it wrong. But even wrong they are forgiving enough to still run well.

There are two different "LS7" lifters, one being superior to the other, and each likes a different preload. ALWAYS use the 12576400 lifter, and set it to 0.060" max. Again, for most LS setups 0.060" is still too much.

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post #20 of 29 (permalink) Old 12-28-2016, 08:36 PM Thread Starter
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Originally Posted by Marc 85Z28 View Post
It's all there in the post. READ.

Proper valvetrain setup is usually done wrong on the LS engines because it takes time, effort, and knowledge. Even most of the knowledgeable guys are STILL doing it wrong. But even wrong they are forgiving enough to still run well.

There are two different "LS7" lifters, one being superior to the other, and each likes a different preload. ALWAYS use the 12576400 lifter, and set it to 0.060" max. Again, for most LS setups 0.060" is still too much.
well here is the issue with the part numbers that you list for being the different preload and I have come across ,lots of superseded numbers for the lifters ,, it sounds like it could be a place of manufacturing.. the only way to find out what you have is to get each part number lifer and disassemble them to compare the specs ,, so if any one has one of the part number lifers ,take them a part and measure, also measure complete travel and bleed hole location

the part number that I used was 12499225 and crosses to all the numbers below SOOOOOOOOOO, if any has a spec sheet for each of the posted lifter part numbers ,please post them .. I am interested

on a another note on the dod delete with the ls3 cam swap I fabricated some mid pipes (no cats and turned off the second o2 sensors ),, motor is real quiet and performs great with real noticeable seat of the pants performance ,, hits the chip much faster in first gear ,, on my way to the 11.99 time slip

see below for the part numbers in qusetion

Manufacturer:
Made by OEM supplier General Motors Components Holdings (formerly Delphi)
Cross reference:
These are same as the GMPP and LS7 lifters except that they are purchased in bulk so the are not individually boxed
Equivalent to GM part number 17122490 (ACDelco part # HL124).
GMPP part number 12499225 is just 16 of part # 17122490 packaged into a set of 16 pieces
Also compatible with GM part number 12576400 (HL128
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