push rod length?

[3rdelke]

bob here, once again need a drink from the well of knowledge. getting ready to switch my sons upper valve train to roller rockers. hydraulic lifter, big block stroker. do I really need to pull intake and use a solid lifter to determine pushrod length as described @ 4 seconds flat? HELP, bob

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might add we have had this new build running for about an hour so lifters are pumped up. just put his new dual quad setup on hate to pull the intake if we don't have to

 

[lewtot184]

you don't want to check push rod length with a solid tappet if using a hydraulic tappet. just be careful to have a gentle touch when extending the checking rod. the type of head/rocker and cam come into play here. some adjustable rockers will have an increase in ratio even if you specify a stock ratio. this can lead to coil bind or retainer to guide problems that can lead to a dropped valve. ask yourself this, why am i changing the rockers? does it make sense?

 

[3rdelke]

that's what I thought at first. set rocker with a thread showing at the bottom, lengthen adjustable push rod till it snugs or slightly engages rocker to lifter. and that should be the push rod length? comp cams said they only recommend .004 preload, so maybe have push rods cut .004 longer? I think smiths bros, also wants to know the valve spring pressure, which I don't know, before they cut new rods...double comp springs, comp hyd lifters, comp cam. thx bob

 

[Rick62]

You may find this helpful: http://www.compcams.com/Products/CC-'Pushrods'-0.aspx

 

[lewtot184]

that's what I thought at first. set rocker with a thread showing at the bottom, lengthen adjustable push rod till it snugs or slightly engages rocker to lifter. and that should be the push rod length? comp cams said they only recommend .004 preload, so maybe have push rods cut .004 longer? I think smiths bros, also wants to know the valve spring pressure, which I don't know, before they cut new rods...double comp springs, comp hyd lifters, comp cam. thx bob

you might consider checking with zero threads showing and then set the pre-load. this will depend on what rocker/adjuster your using. if you know the spring number then you can look up the pressure. smith bros wants to know the pressure to determine the thickness of tubing to be used.

 

[3rdelke]

lewt, thx, curious why they don't just sell the stiffest, best size that doesn't have clearance issues

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think ill take your advice on no threads, then put in pre load

 

[747mopar]

What brand of rockers??? Before I ordered anything I'd suggest checking the roller to valve stem contact! There are some really crappy rockers out there that aren't even close to where they should be. What I do is paint the head of the valve with a marking compound like used when setting up gears and cycle the rocker threw it's motion and check the pattern. Your looking for the roller to start just barely off center on the valve, be on center at half lift and then travel to the opposite side the same amount. I had one that started on the edge and never even made it to the center which would cause a side load on the valve and eat up the guides. Harland Sharp and Comp Cams Magnum rockers are 2 I'd recommend, cheaper companies use Chevy rockers adapted to a shaft mount and are far from perfect.

 

[3rdelke]

we bought ours from 440 source, after a recommendation from a dude with a blown bb. don't tell me their no good as we already bought them, hell I have even heard some people don't even like Harland sharpe! I think I may get pushrods from them as well, or smiths...thx bob

 

[1wild&crazyguy]

since you have it together already, i would recommend making a an adjustable push rod 1st out of an old one with some all thread and a couple nuts to so you can extend it.
Set the adjustment screw with a couple/few threads showing bottom and top of rocker and adjustment nut...then with adjustable push rod shortened to fit between lifter and adjuster....extend the push rods to compress the lifter about .030. to make this easy....pull a lifter and bleed it off 1st.

Hope im not confusing you.

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I will add that i recommend you measure cyl 1,8,2,7 or all 4 corners incase the decks are off a bit then average the lengths.

 

[Cranky]

What rockers do you have on it now and how big is the cam? Like Lew said, do you really need them? Do you really need rollers? Dyno tests show that with most mild performance cams, they do not free up any horsepower or enough to write home about. Heck, I ran a 440 with a .660 lift Isky and turned that junk to over 7000 rpm for over 300 passes using non roller ductile iron Isky rockers and when I tore the engine down, the guides showed normal wear and wasn't excessive at all. With bigger cams, yeah, roller rockers help reduce guide wear and actually free up some horsepower. Another plus to non rollers is you don't have to worry about one coming apart and putting needle bearing rollers all over the motor.

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since you have it together already, i would recommend making a an adjustable push rod 1st out of an old one with some all thread and a couple nuts to so you can extend it.
Set the adjustment screw with a couple/few threads showing bottom and top of rocker and adjustment nut...then with adjustable push rod shortened to fit between lifter and adjuster....extend the push rods to compress the lifter about .030. to make this easy....pull a lifter and bleed it off 1st.

Hope im not confusing you.

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I will add that i recommend you measure cyl 1,8,2,7 or all 4 corners incase the decks are off a bit then average the lengths.

Had a block that was .005 out of square.....but wouldn't think that would make much of a difference. Anything more than that should be corrected mostly for piston height but you can also put your longest rod/piston combo in those holes. You wouldn't want to put your shortest ones in those fer shore

 

[lewtot184]

we bought ours from 440 source, after a recommendation from a dude with a blown bb. don't tell me their no good as we already bought them, hell I have even heard some people don't even like Harland sharpe! I think I may get pushrods from them as well, or smiths...thx bob

440 source rockers aren't top tier. chinese copies of harland sharp. there have been some tip alignment and bearings falling out issues with some.

 

[1wild&crazyguy]

What rockers do you have on it now and how big is the cam? Like Lew said, do you really need them? Do you really need rollers? Dyno tests show that with most mild performance cams, they do not free up any horsepower or enough to write home about. Heck, I ran a 440 with a .660 lift Isky and turned that junk to over 7000 rpm for over 300 passes using non roller ductile iron Isky rockers and when I tore the engine down, the guides showed normal wear and wasn't excessive at all. With bigger cams, yeah, roller rockers help reduce guide wear and actually free up some horsepower. Another plus to non rollers is you don't have to worry about one coming apart and putting needle bearing rollers all over the motor.

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Had a block that was .005 out of square.....but wouldn't think that would make much of a difference. Anything more than that should be corrected mostly for piston height but you can also put your longest rod/piston combo in those holes. You wouldn't want to put your shortest ones in those fer shore

I here ya on piston deck heights. I had similar happen with push rods and with these harland sharp adjusters on some comps that only gave about 1-2 threads up top and maybe 2 below, wasn't much room but they ended up within .005 @ around 6.4 long
Its all stacking with the decks, valve stem heights cam lobe...but they always grind them exactly perffff , right?:icon_wink:

 

[747mopar]

we bought ours from 440 source, after a recommendation from a dude with a blown bb. don't tell me their no good as we already bought them, hell I have even heard some people don't even like Harland sharpe! I think I may get pushrods from them as well, or smiths...thx bob

I honestly can't tell you if they are any good or not but to just check them. All I can testify to is the Comp Cam Magnum rockers were spot on, no issues.

 

[cryplydog]

I've always fretted over valve geometry and sometimes you can get things to close or tight. If you get the pushrods to long you can get into the underside radius of the rocker with the p-rod cup. It all depends on parts dims. what ever you come up with make sure you run it thru and check these clearances. Its also a hell of a lot easier for p-rod installation if you back off from the absolute dim. some. Plus its nice to have some additional adjustment capabilities for maybe head gasket- cam- lifter-head changes without having to make new pushrods everytime! I really like the Crane iron rockers as well as the iskys after they are worked but now I am running the Hughs rockers [1 season] and I think I really like them so far. Watch out for the cheapies! good luck

 

[3rdelke]

thanks to all. I think I got it going my way, here is the 'witness' mark on valve stem, you can just see it

 

[747mopar]

That's what you want to see! Now we all know 440 Source rocker at least have the proper contact.

 

[lewtot184]

geometry at the valve looks good. i just started doing something different on the valve tip geometry check. i've been bench testing some heads using typewriter carbon paper. it works.

 

[3rdelke]

lew, good idea

 

[1wild&crazyguy]

It's centered, thats a good start...however it may still not transfer the cam lobe perfectly, but don't fret...most of our stuff is never EXACT anyhow.
Check out the B3racingengines website and read their geometry write up and rocker shaft kit that fixes it all.
Remember the pattern on the valve stem is wide cause the roller is moving across it.

 

[3rdelke]

wanted to say a special thanks to all you guys, roller rockers and new smith bros. push rods are in and it sounds wicked! haven't driven it yet, waiting for throttle linkage clamp. dual quads seem sweet as well! I did pull one spark plug after running it for a couple of minutes, looked pretty fuel soaked, hope the pressure regulator will cure that....again thanks for all the help...bob and kev