ls1 pushrod length

[brad hsv]

hi all im set up a ls1 engine i have a pushrod that measures 7.393 .fitted them to my motor and checked the preload and got .111 .so way to much preload i need .40 so my maths is it needs to be .71 shorter makeing pushrod length that i need to be 7.322 witch will give me .40 preload and with 0 lash sound ok ?

[gaz05]

The standard pushrod is 7.385, we just call them 7.4 if you have a hydraulic street style cam fitted you generally use 7.450 which is .050 longer because of the smaller base circle on the cam. If your measurements are right I would guess there has been material cut off the heads. Have you fitted a cam? has the heads been milled?

[peter b]

Get a pushrod length checker FYI I have never fitted a longer pushrod when fitting a camshaft

[brad hsv]

yes is a new cam.gross valve lift .559 intake and exhaust .566 duration @ .05 intake 214 and exhaust 222 lobe lift .3290 intake and exhaust .3330 lobe separation 117.0 and yes .10 off heads and .10 off block . and the pushrods are the old ones from engine just used them to see what i needed for lenght and if my maths is right then 7322 is the pushrod i need that has the .40 add in to it .

[peter b]

I take 40 thou off heads with larger cam etc and don't need to go that short a pushrod. Make sure you are measuring it correctly.
Best option as I said before is get a pushrod length checker it is a two piece pushrod has thread and winds into itself so to speak then you can set length and check preload.
Always check preload when on the base circle of the cam.

[white lie]

Definitely agree, for the cost of the pushrod length checker, it sure beats guessing

[macca_779]

I've been taught an alternate way to check geometry. Mark the valve stem with permanent marker. Install a rocker on it. Motor it over a few times. Remove rocker and check swipe area. It should be central with the right rod length. If its to low the rod is to long. To high and its to short.

This illustrates when it's good. In my case. Stock rod. But .040" off the head. .600" lift cam

http://i68.photobucket.com/albums/i39/macca_779/DC84C530-87E8-433D-B0D3-3DEBE2A2A616-15476-00000B23D09CBD21_zpscb65d568.jpg

[peter b]

How much preload did you end up with?

[brad hsv]

when i checked .111 thou with a 7393 thou pushrod and this is with the rocker touqed down so i deduct 71 thou .leves me with 40 thou preload set and checked to comp specs .first i marked the pushrod after both the exhaust and intake valves have opened and closed completely then let the lifter bleed down then made a mark on the pushrod then unbolted rock and made a mark from the same point and thats where i got the .111 thou from

[peter b]

Wind rocker down to zero lash where the rocker doesn't rock anymore then measure how far down the bolt/rocker goes until it locks up. 3/4 turn = 40 thou
Seems like you are over complicating it mate as I said with 40 thou off normally only going down as far as 7.350 with a 40 thou head gasket. But does depend on lifters used as some are taller.
But makes your job easier with the adjustable pushrod takes your guess work out of it

[peter b]

I've been taught an alternate way to check geometry. Mark the valve stem with permanent marker. Install a rocker on it. Motor it over a few times. Remove rocker and check swipe area. It should be central with the right rod length. If its to low the rod is to long. To high and its to short.

This illustrates when it's good. In my case. Stock rod. But .040" off the head. .600" lift cam

http://i68.photobucket.com/albums/i39/macca_779/DC84C530-87E8-433D-B0D3-3DEBE2A2A616-15476-00000B23D09CBD21_zpscb65d568.jpg

This checks swipe not preload. Real good method if have adjustable rockers as can set the preload with the adjuster. It basically says rocker is central however 25 thou either way won't show a massive change either only really shows up when 50 thou plus off and due to the large surface on the factory rockers this can prove difficult to prove I will take a stab that you have around 80 thou preload if not more?

[macca_779]

This checks swipe not preload. Real good method if have adjustable rockers as can set the preload with the adjuster. It basically says rocker is central however 25 thou either way won't show a massive change either only really shows up when 50 thou plus off and due to the large surface on the factory rockers this can prove difficult to prove I will take a stab that you have around 80 thou preload if not more?

Actually pete when I first trailed a set of 7.425" rods it's was clear as daylight they were to long off the swipe. I was sure that's what I would of needed but nope, Cuz was right 7.4 is what it needed. Swipe I believe is quite important over preload. As if swipe is out your going to significantly shorten the life of the guide. Especially if its bronze.

[peter b]

If it is a bronze guide then will be running roller rockers the factory ones will eat the bronze ones regardless of swipe. I am not saying it isnt important by any means however pending type of lifter determines the preload i set. For LS7 style lifter or street series tie bar 40 thou is ideal for a race series lifter I am for 25 thou however given the combo when I use the race type lifter generally has a quite aggressive cam I opt for adjustable roller rockers anyway.
Have seen in several cases when people have opted for a longer pushrod and more preload the engines dont seem to carry well in the top end is like they hit a wall and become unhappy if that makes sense. But go too little preload and lifters become noisey. Hydraulic gives you a fair bit of leeway just never had an issue with setting them up the way I do it in both terms of preload and where the rocker is running on the valve.
Im not picking on you just asking how much preload you ended up with going stock rods on heads that have had 40 taken off em.
Only way that it would be happy with stock length is if your lifters are shorter than factory or you valve heights have been altered?
When you got them decked did you by chance ask for them to be serviced as well?
Have had people get heads serviced and decked only to find that installed heights are now all over the place compared to factory even though they didnt ask for valve seats to be cut machinist took it upon them and did it also chops out spring seat and open pressure

[macca_779]

New seats were fitted Pete. Jimmy young looked after the heads, so I trust he set them up well. As for bronze guides needing rollers. My understanding is that as long as you don't got to carried away with lift they're fine. I'm running .600 .598 and don't foresee a problem.

[peter b]

New seats were fitted Pete. Jimmy young looked after the heads, so I trust he set them up well. As for bronze guides needing rollers. My understanding is that as long as you don't got to carried away with lift they're fine. I'm running .600 .598 and don't foresee a problem.

What can happen is the factory rocker CAN put unwanted sideways pressure on the guides and wear them out prematurely is regardless of lift really is just something that will happen over time. However I can't give you a timeframe it could last a year it could last 10 is just one of those things.
Factory guides are cast.
Well that gives a little more background info as when changing seats it generally raises your installed heights which means springs would have had to be shimmed back up which isn't generally a problem however may explain the length of pushrod. If your still running factory pushrods I would still advise to replace them with aftermarket pushrods despite what people think they don't really mix with dual springs and high rpm have seen them bend and when they do they are a pain to remove generally take the shape of a Z.

[macca_779]

Stock length. Not stock rods sorry

[brad hsv]

Wind rocker down to zero lash where the rocker doesn't rock anymore then measure how far down the bolt/rocker goes until it locks up. 3/4 turn = 40 thou
Seems like you are over complicating it mate as I said with 40 thou off normally only going down as far as 7.350 with a 40 thou head gasket. But does depend on lifters used as some are taller.
But makes your job easier with the adjustable pushrod takes your guess work out of it

well i did what u said and have come up with 1 1/2 or just over turns is this ok

[peter b]

With what length pushrod?
Or is that using stock length?
It's not terrible but would like to see where you would end up with 7.375 pushrod

[brad hsv]

With what length pushrod?
Or is that using stock length?
It's not terrible but would like to see where you would end up with 7.375 pushrod

Thats with a 7.393 pushrod

[peter b]

Ok and this is why I mentioned the adjustable pushrod as can change the length and can then measure preload etc and get the right length pushrods. Ultimately your aiming for 3/4 of a turn after zero lash

[JezzaB]

I've been taught an alternate way to check geometry. Mark the valve stem with permanent marker. Install a rocker on it. Motor it over a few times. Remove rocker and check swipe area. It should be central with the right rod length. If its to low the rod is to long. To high and its to short.

This illustrates when it's good. In my case. Stock rod. But .040" off the head. .600" lift cam

http://i68.photobucket.com/albums/i39/macca_779/DC84C530-87E8-433D-B0D3-3DEBE2A2A616-15476-00000B23D09CBD21_zpscb65d568.jpg

Thats ok with stock rockers but use something like T&D etc and you must set the geometry up first (shim or machine the stand to adjust for the pivot height in relation to the valve tip) then setup the preload and swipe. Mr Young will confirm this ;)

[macca_779]

Thats ok with stock rockers but use something like T&D etc and you must set the geometry up first (shim or machine the stand to adjust for the pivot height in relation to the valve tip) then setup the preload and swipe. Mr Young will confirm this ;)

Yep. That's a no brainier Jez. But I probably should of mentioned it for those reading.

[peter b]

Something interesting for those interested back to back checking stock rocker versus T&D both 1.7 ratio or advertised as that anyway the factory were spot on T&D were 1.74. Not a big problem by any means but have found another issue I have with the T&D rockers is the pivot angle it ramps it up so to speak. Compared with jesel sportsmans rockers our piston to valve clearance changed dramatically as with a few other things like the need to shim up the t&d's where as the jesel didn't need shims and the jesel rockers kept the pushrods central where T&D dragged them into the head.
With adjustable rockers all you really care about in regards to setting length is swipe as you set either your lash or preload through the adjuster.