Calling all big giant mopar brains. I am putting together a 340 la stroker with 190 trick flow heads and Harland Sharp rocker set #s7002k with lunati lifters #97413 from edelbrock. Hoping someone might know the correct length. Assembly works with shaft oiling &5/16 cup end push rods. Any help would be greatly appreciated
Push rod length
- Thread starter 4 Banger
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Your best bet would be to get a pushrod length checker. That way there is no guess work as to the correct length pushrod you will need.
Dave999
Well-Known Member
How i did it.. there will be other ways i just made this up as i went along
the correct length is when you have the rocker at the mid point of its rock. when the cam has lifted the lifter by half of the total lift, and hopefully the roller tip is in the middle of the valve stem.
Vary the angle of the rocker to achieve this middle coverage of valve tip, slightly, if you need to, but check it doesn't go into bind or hit the retainer at the extremes.
just paint the valve tip with sharpie ink and roll the cam through a rotation or two to get a valve tip coverage pattern.
for solid flat tappet
i took a scrap pushrod which i already knew was too short because using it i could not achieve rocker level at mid lift and rocker roller was off on the valve tip, rocker was leaning too ar back for my liking onto the pushrod side at all lifts
installed my old pushrod so i could see where it was visible in the partly assembled engine and i could access an adjuster
removed it
cut it at that point
stuffed a piece of threaded rod down 1 end and left it so that it stuck out far enough to mount the other end onto it
i then used hardened steel washers to shim the length at my cut-point until it was right
ordered pushrods that were standard length + the thickness of my shim washers
done this way because there are no "checking" pushrods to be purchased for my engine. if you can get one it comes with an adjuster already and you just measure it or send it to the custom pushrod shop.
if you have rockers with a screw in adjuster cup,
you do this with the adjuster wound out by 2 threads only you don't want a 1/4 inch of thread showing, the adjuster will just snap in use, and you do need a little adjustment in both directions hence 1-2 threads out is your base setting
clay smith sorted me out with a great set of pushrods
used them because i know a man who brings stuff from clay smith to the UK
hydraulic and roller method may differ, saying that because i haven't done it
i had bit of a learning curve mind. ford 1.72:1 rockers, on a mopar engine, using chevy ball stud, studs and posi locks, to hold down individual trunnion mount double roller rockers on an engine where the valves have 18 degrees between them. i.e wrong geometry in any way caused the rocker trunnion of the inlet on one cylinder to hit and push out of alignment the exhaust rocker trunnion on the next. perfect example of a complete pain in the ***, but very obvious when you got it right.
Dave
the correct length is when you have the rocker at the mid point of its rock. when the cam has lifted the lifter by half of the total lift, and hopefully the roller tip is in the middle of the valve stem.
Vary the angle of the rocker to achieve this middle coverage of valve tip, slightly, if you need to, but check it doesn't go into bind or hit the retainer at the extremes.
just paint the valve tip with sharpie ink and roll the cam through a rotation or two to get a valve tip coverage pattern.
for solid flat tappet
i took a scrap pushrod which i already knew was too short because using it i could not achieve rocker level at mid lift and rocker roller was off on the valve tip, rocker was leaning too ar back for my liking onto the pushrod side at all lifts
installed my old pushrod so i could see where it was visible in the partly assembled engine and i could access an adjuster
removed it
cut it at that point
stuffed a piece of threaded rod down 1 end and left it so that it stuck out far enough to mount the other end onto it
i then used hardened steel washers to shim the length at my cut-point until it was right
ordered pushrods that were standard length + the thickness of my shim washers
done this way because there are no "checking" pushrods to be purchased for my engine. if you can get one it comes with an adjuster already and you just measure it or send it to the custom pushrod shop.
if you have rockers with a screw in adjuster cup,
you do this with the adjuster wound out by 2 threads only you don't want a 1/4 inch of thread showing, the adjuster will just snap in use, and you do need a little adjustment in both directions hence 1-2 threads out is your base setting
clay smith sorted me out with a great set of pushrods
used them because i know a man who brings stuff from clay smith to the UK
hydraulic and roller method may differ, saying that because i haven't done it
i had bit of a learning curve mind. ford 1.72:1 rockers, on a mopar engine, using chevy ball stud, studs and posi locks, to hold down individual trunnion mount double roller rockers on an engine where the valves have 18 degrees between them. i.e wrong geometry in any way caused the rocker trunnion of the inlet on one cylinder to hit and push out of alignment the exhaust rocker trunnion on the next. perfect example of a complete pain in the ***, but very obvious when you got it right.
Dave
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While pushrod length will change the rocker ratio, it has zero affect on geometry other than the small ratio change.
On shaft rockers the position of the shaft is what changes the geometry.
Dave999
Well-Known Member
ok well i found using a pushrod that got the rocker sitting level at mid lift would place its roller in the middle of the valve stem at mid lift
if i had the rocker on the too short pushrod the roller was biased to the pushrod side of the valve tip and while still potentially acceptable i wanted the vast majority of the rolling to be in the central third i.e the middle of the valve tip
this is potentially due to the fact that the height above the head for each of my rockers is set by the adjuster on their own individual stud. longer pushrods meant I sat them up higher which brought the roller tip down, making them level at mid lift and parallel with the deck of the block, which gave my rocker a tiny bit further reach across the valve tip.
go too high and everything bangs into each other because on mine the rockers for each cylinder lean away from the cylinder centerline along the length of the engine (hence i can fit 2.02 inch big block valve in a 3.91 inch bore) anyway too high and no.1 inlet hits no.2 exhaust.
on a v8 i guess this is similar to shimming up shaft mount rocker pedestals. move the rocker pivot point further away from the head, the back of the rocker rises against the height of a static valve, and the tips position in respect to the centre of the pivot point is changed when in contact with the valve tip. if its a scraper rather than a roller you will be using a different part of the tip as well.
raise the shaft and lengthen the pushrod and you can alter the attitude of the rocker in respect to the valve, if it works it works
as i say i just had to work it through to get satisfaction
if i had the rocker on the too short pushrod the roller was biased to the pushrod side of the valve tip and while still potentially acceptable i wanted the vast majority of the rolling to be in the central third i.e the middle of the valve tip
this is potentially due to the fact that the height above the head for each of my rockers is set by the adjuster on their own individual stud. longer pushrods meant I sat them up higher which brought the roller tip down, making them level at mid lift and parallel with the deck of the block, which gave my rocker a tiny bit further reach across the valve tip.
go too high and everything bangs into each other because on mine the rockers for each cylinder lean away from the cylinder centerline along the length of the engine (hence i can fit 2.02 inch big block valve in a 3.91 inch bore) anyway too high and no.1 inlet hits no.2 exhaust.
on a v8 i guess this is similar to shimming up shaft mount rocker pedestals. move the rocker pivot point further away from the head, the back of the rocker rises against the height of a static valve, and the tips position in respect to the centre of the pivot point is changed when in contact with the valve tip. if its a scraper rather than a roller you will be using a different part of the tip as well.
raise the shaft and lengthen the pushrod and you can alter the attitude of the rocker in respect to the valve, if it works it works
as i say i just had to work it through to get satisfaction
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dano
Evil Handy Man
You can make a length checker with an old push rod. Cut it in half, shorten it if you need too, tap the inside for a threaded rod that works, install some jam nut and done. Use a 5/16 or appropriate size ball bearing if one end is a cup and the rocker is a cup.
9secRR
Well-Known Member
only way to find the correct length is to measure. can't assume anything. this is the main reason the vendors get a bad reputation.
Thanks you've given me alot to think aboutok well i found using a pushrod that got the rocker sitting level at mid lift would place its roller in the middle of the valve stem at mid lift
if i had the rocker on the too short pushrod the roller was biased to the pushrod side of the valve tip and while still potentially acceptable i wanted the vast majority of the rolling to be in the central third i.e the middle of the valve tip
this is potentially due to the fact that the height above the head for each of my rockers is set by the adjuster on their own individual stud. longer pushrods meant I sat them up higher which brought the roller tip down, making them level at mid lift and parallel with the deck of the block, which gave my rocker a tiny bit further reach across the valve tip.
go too high and everything bangs into each other because on mine the rockers for each cylinder lean away from the cylinder centerline along the length of the engine (hence i can fit 2.02 inch big block valve in a 3.91 inch bore) anyway too high and no.1 inlet hits no.2 exhaust.
on a v8 i guess this is similar to shimming up shaft mount rocker pedestals. move the rocker pivot point further away from the head, the back of the rocker rises against the height of a static valve, and the tips position in respect to the centre of the pivot point is changed when in contact with the valve tip. if its a scraper rather than a roller you will be using a different part of the tip as well.
raise the shaft and lengthen the pushrod and you can alter the attitude of the rocker in respect to the valve, if it works it works
as i say i just had to work it through to get satisfaction
dano
Evil Handy Man
Dave999
Well-Known Member
just checked my pile of history Smiths Bros not clay smith for my pushrods great service
got my "smiths" mixed up...
got my "smiths" mixed up...
4eighteener
Well-Known Member
Late to the party,
Not sure where you are in Florida, but if you are in the southeast part of the state, I have a pushrod measuring tool and a wide mouth caliper you can borrow.
My 340 stroker has trickflow heads, prw 1.6 rocker arms, and tallish Morel hydraulic rollers, I also have the b3 geometry correction shims under the shafts which add height, and ordered 5/16 x 080 7.1" ball to ball pushrods. The decks on my motor had also been severely cut by the previous owner, so I am pretty sure my pushrod measurement won't be what you need on yours. You'll have to measure.
Typically, I order from Smith brothers but they had like a month lead time when I needed them so I tried Manton in California and I had them in Florida 2 days later and what appears to be the same good quality of Smith. I believe their price was similar.
Not sure where you are in Florida, but if you are in the southeast part of the state, I have a pushrod measuring tool and a wide mouth caliper you can borrow.
My 340 stroker has trickflow heads, prw 1.6 rocker arms, and tallish Morel hydraulic rollers, I also have the b3 geometry correction shims under the shafts which add height, and ordered 5/16 x 080 7.1" ball to ball pushrods. The decks on my motor had also been severely cut by the previous owner, so I am pretty sure my pushrod measurement won't be what you need on yours. You'll have to measure.
Typically, I order from Smith brothers but they had like a month lead time when I needed them so I tried Manton in California and I had them in Florida 2 days later and what appears to be the same good quality of Smith. I believe their price was similar.
MOPAROFFICIAL
If it has tits, it's a liabilititty.
Like mentioned already, you need to get the cam , lifters , heads and rockers on that block and then measure. I like to take a stock push rod of the correct end style, be it ball/cup or ball/ball , cut it in half, lop off another 1/2 inch from one side and use smaller diameter "all thread" with nuts and fit the all thread inside each piece of the halved pushrod..using the nuts to adjust or separate them to the desired length that gives the correct amount of preload or lash.
I like .030 preload for hyd roller/hyd flat tappet.
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cookietruck
Well-Known Member
Gotta check each build. Deck height and cam base circle will make every build different even if using all the same heads, gasket, rockers etc.
I think you want to shoot for zero to one thread showing on the adjuster.
I think you want to shoot for zero to one thread showing on the adjuster.
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