Which Is It 6.250 Or 6.272???

[kendawg73]

I mesured one of my stock push rods that came out of my '90 HO motor, and I'm getting 6.253 but yet I keep seeing that the stock length is 6.272, even the FordRacing push rods list for sale say 6.272.

I orderd a TrickFlow push rod checker tool yesterday, so I'm waing for that to come to recheck my length before I order the new push rods. with the old stock ones I got just a hair past a 1/4 turn on the intake but I think the exhust I was right at 1/4 or just a hair before... I didn't get to redo it... since it's so close I'm thinking just a little longer one would be good, I would like to get almost 1/2 turn... so if what I have really is 6.250, then the ford racing ones would be a little longer then... the next ones up are 6.300 from Trickflow but there way more expensive @ 99.xx... Plus I still have to retest the witness mark on the valve tip, which I"m still confused about, can you even adjust this with pedistal rockers??? or is this more of a stud thing? BTW this is for gt40p heads with pedistal Scopion 1.6 RR.

 

[Chuckman]

Stock push rods may very well be 6.272 over a theoretical full radiused end, which is how some manufacturers gauge them. Others go by actual length with the oil hole drilled and chamfered. Even others go by the centerline of the ball end (rare). Most of the aftermarket stuff is listed by option 2.

With the check tool, go by actual measured length plus .030" for lifter pre-load. Push rods normally come in .050" increments so get the closest you can to what you measured. A little long won't hurt as you can also get a shim kit for those rockers to fine tune.

When you're checking for length, check in that .050 increment range and check for the smallest wear pattern (you can just sharpie the valve tip and you'll see where the roller is riding). Don't be as concerned about centering the pattern, just as narrow as it can go. Use the shims to set pre-load, the books say you 1/4-3/4 turns past lash, my old stockers wanted closer to that 3/4 turn side when cold to not tick so much.

If you can, go with the hardened rods, comp/tfs/whoever doesn't really matter, the cheaper ones probably all come out of the same place and are close to the same price (~$100). Really no downside to not using the hardened ones, even in a stock motor.

 

[kendawg73]

Stock push rods may very well be 6.272 over a theoretical full radiused end, which is how some manufacturers gauge them. Others go by actual length with the oil hole drilled and chamfered. Even others go by the centerline of the ball end (rare). Most of the aftermarket stuff is listed by option 2.

With the check tool, go by actual measured length plus .030" for lifter pre-load. Push rods normally come in .050" increments so get the closest you can to what you measured. A little long won't hurt as you can also get a shim kit for those rockers to fine tune.

When you're checking for length, check in that .050 increment range and check for the smallest wear pattern (you can just sharpie the valve tip and you'll see where the roller is riding). Don't be as concerned about centering the pattern, just as narrow as it can go. Use the shims to set pre-load, the books say you 1/4-3/4 turns past lash, my old stockers wanted closer to that 3/4 turn side when cold to not tick so much.

If you can, go with the hardened rods, comp/tfs/whoever doesn't really matter, the cheaper ones probably all come out of the same place and are close to the same price (~$100). Really no downside to not using the hardened ones, even in a stock motor.

were you able to see the picture I posted.. . did it end to end in the center and got that.. so how would they concider that 6.272? If that's not how you measure then how do I measure the adjustable one? becuase now I will secound guess how I"m doing it... lol... I think I'm supper OCD about this stuff...

I do have the ford racing shim kit, I bought that just in case I needed it... I took 2 of my old lifters and weld around the top edge to make it solid... And hears where I'm confused... I watched a bunch of videos ect..and most are dealing with studs, but I'm using pedistal so not sure how much that changes things...

So when I do the witness mark check for the sweep, I want to used the soild lifters I made... and just adjust to zero lash and then turn motor over... I want the thinest where mark, doesn't have to be dead center but somewhere in that area... is that right? And the only way I can change that is to use a shim under the pedistal right? which means then I wound need to lengthen the push rod as well? is this right?

Then once I get that looking good, I then need to make sure the push rods fall into the correct pre-load range... so then I would take the solid lifters out and put the new ones in... set for zero lash, then set torque wrech to 20ftlb and shoot for 1/4 - 3/4 turn to hit that.... right? then measure it like I did in the picture I attached and get the next size up? I'm using gt40p heads with pedistal so I don't have guild plates... but looks like all the rods I seen on trick flows city are the hardend which is fine.. and on sumit 99.xx.

I tried to do the witness mark over the week end, but it was hard to see, it didn't put much of a mark in with the marker.. so I got a dry erasr marker I'm going to try once the adjustable rod gets here... but I think I was close with the stock one... so maybe the next size up that trick flow has is 6.300 then 6.350 ect... so maybe the 6.300 will be what I end up with...

I just hope i'm going this right... I'm loosing sleep think about this... lol

 

[Chuckman]

were you able to see the picture I posted.. . did it end to end in the center and got that.. so how would they concider that 6.272? If that's not how you measure then how do I measure the adjustable one? becuase now I will secound guess how I"m doing it... lol... I think I'm supper OCD about this stuff...

remember that theres a hole and a chamfer at each end that take away some of the material of what, if it was solid, would be 6.272. thats how oem ford (and some other builders) spec them out, as if they weren't drilled/chamfered. the aftermarket comp/tfs specs actual FINISH dimension after the hole and chamfer are put in. so if you were to order aftermarket stock replacements from comp you would order 6.25". See http://www.compcams.com/Pages/417/valve-train-geometry.aspx, section 3.

the same principals apply to both stud and pedestal rockers, just their retention methods and adjustability ranges are different. a stud rocker is "infinitly" adjustable within its range, a pedestal is "incrementaly" adjustable with shims. sometimes a pedestal will be too tall, and you'll have to go to the next longer pushrod and shim some of that extra length back out. its a bit more finicky than a stud, but same idea. cranes old instructions are pretty good, you really want preload to be more on the 3/4 turn side imo to keep them quiet http://www.cranecams.com/uploads/instructions/453e_.pdf

 

[kendawg73]

remember that theres a hole and a chamfer at each end that take away some of the material of what, if it was solid, would be 6.272. thats how oem ford (and some other builders) spec them out, as if they weren't drilled/chamfered. the aftermarket comp/tfs specs actual FINISH dimension after the hole and chamfer are put in. so if you were to order aftermarket stock replacements from comp you would order 6.25". See http://www.compcams.com/Pages/417/valve-train-geometry.aspx, section 3.

the same principals apply to both stud and pedestal rockers, just their retention methods and adjustability ranges are different. a stud rocker is "infinitly" adjustable within its range, a pedestal is "incrementaly" adjustable with shims. sometimes a pedestal will be too tall, and you'll have to go to the next longer pushrod and shim some of that extra length back out. its a bit more finicky than a stud, but same idea. cranes old instructions are pretty good, you really want preload to be more on the 3/4 turn side imo to keep them quiet http://www.cranecams.com/uploads/instructions/453e_.pdf

ok great, thanks for the info... so is what I said the correct way? I guess when I get the adjustable rod, I want to make it bigger then stock, and the adjust to zero lash and try to get at least 1/2 a turn @ 20ftlb, (with the new lifters) then put in the solid lifters and do the witness mark test?

 

[Chuckman]

Start stock length and work you're way up. My bet is you'll only need to go up to a 6.3 if you have one of the "common" aftermarket cams, if it's still a sticker than it might just need stock length assuming nothing crazy is going on (milled block/heads, thick/thin gaskets, etc).

 

[kendawg73]

Start stock length and work you're way up. My bet is you'll only need to go up to a 6.3 if you have one of the "common" aftermarket cams, if it's still a sticker than it might just need stock length assuming nothing crazy is going on (milled block/heads, thick/thin gaskets, etc).

Yes I installed a E303 Cam, block deck wasn't touched so that's stock, the Reman gt40p heads I got from LMR the surface looks freshly cut I'm thinking they just barely surfaced it....., I'm using the Ford racing head gasket, -A302 says compressed is .042 but what I don't get it has 1101-2 on the corner, but felpro lists the 1011-2 as .039 compressed, so I don't know what's going on there.... And I'm using scorpion 1.6 rollers... When I tied the old stock rods I just barley got 1/4 turn before hitting 20 ft-lb, so I'm thinking 6.300 also, so I'm going to start with that.... The rod comes Thursday....

 

[kendawg73]

Start stock length and work you're way up. My bet is you'll only need to go up to a 6.3 if you have one of the "common" aftermarket cams, if it's still a sticker than it might just need stock length assuming nothing crazy is going on (milled block/heads, thick/thin gaskets, etc).

ok, the trick flow adjustable rod came yesterday... so I set it for 6.300.... I put it in with a new lifter, and set zero lash... and then torqued to 20ftlb... I got almost (just shy) of a full turn.... hmmm..
So I put the stock one back in... I got almost 1/2 turn (not sure why I was getting 1/4 before.. I was tired that day so maybe I did something wrong) anyway... in both case's with the 6.300 and stock rod... I loosedned it back up and did it again and got the same... I got the same results on the exhust valve also...

so... with the stock one I'm getting almost 1/2 turn but with the adjustble one set to 6.300 I get just about a full turn... so that little bet of length added 1/2 turn to it...

So then I put the old lift that I made soild in.. colored the tip of the valve in with a sharpie, and set the rocker to zero lash... and turn the motor over until that rover went up and down (3) times. you can see from the pictures below.. I'm not center... it's more towrads the exhust end... and if i'm doign it right.. the witness marks is about in the .08x range... got the same result on both valves...

I tried the adjustble one at 6.300 but was hard to tell the reading... and wife was calling me for dinner... so I'm going to have to try that test again... but... correct me if i'm wrong... with the adjustable push rod longer... the witness mark would move more towards the exhuast side right? so in that case that would be more then what I'm getting with the stock one... so that's not good...

I have the ford racing shim pack, haven't opened it yet... so I'm thinking, if I try a shim with the longer 6.300 (which I would have to anyway since I'm getting about a full turn) so that would recude down the preload... from the full turn which is what I would want, but which way would that move the witness mark? whould that bring it back more towards the intkae??


anyway, the below pictures are what I got with the stock rod... the faint one is the exhuast... you can see the mark a little...

 

[Chuckman]

the witness shouldn't move much if at all with a .050 longer/shorter pushrod, that geometry is set by where the trunnion of the rocker is, all you're doing is checking where it is where in its arc of travel it pushing down the valve. ideally, you want the centerline between the rocker trunnion and the tip roller to be 90 degrees from the valve at half lift, kind of hard to actually check for, but since that setup gives the least lateral movement, you just look for the shortest witness. should only be in the .030-.040" wide range.

do all your length checks with the solid lifter and no shims. make sure you have the little tie bars though. just look for zero lash (slight resistance turning the pushrod by hand). don't torque it down, just concentrate on the witness mark first. once you get that where you want it, measure your checker and add .030 for preload.

after you get your pushrods is when you start seeing if you need to use shims.

 

[kendawg73]

the witness shouldn't move much if at all with a .050 longer/shorter pushrod, that geometry is set by where the trunnion of the rocker is, all you're doing is checking where it is where in its arc of travel it pushing down the valve. ideally, you want the centerline between the rocker trunnion and the tip roller to be 90 degrees from the valve at half lift, kind of hard to actually check for, but since that setup gives the least lateral movement, you just look for the shortest witness. should only be in the .030-.040" wide range.

do all your length checks with the solid lifter and no shims. make sure you have the little tie bars though. just look for zero lash (slight resistance turning the pushrod by hand). don't torque it down, just concentrate on the witness mark first. once you get that where you want it, measure your checker and add .030 for preload.

after you get your pushrods is when you start seeing if you need to use shims.

hmmm well if I'm measuring right, i'm @ .8x with the stock.. and the attempt I did with the checker rod @ 6.300 I think it was even wider (didn't leave good enough mark, but I think it was bigger)... (going to test that again when I get home) but what if it is truly wider? with the 6.300 I'm getting just shy of full turn on preload to hit torque as it is... So a 6.350 is going to be even worse.
That is how I'm doing the witness mark test. like you say (solid lifter, zero lash). but, only way I can go is longer, how does that change the witness?
also, what did you mean by "little tie bars" you talking about the u channle that the pedistals sit on top of? that goes between the intkae adn exhaust, if so, yes i'm using it.

I was under the impression that the only way to move the witness mark with pedistal rockers is with shims..

 

[Chuckman]

i'm hoping you're just missing a 0, because .8 is almost 7/8", the valve stem should only be around 11/32 (.343). either way, test again. try shorter, try longer, it will take some trial and error to find the sweet spot, it may well end up needing a stock length pushrod, you just need to make sure.

 

[kendawg73]

i'm hoping you're just missing a 0, because .8 is almost 7/8", the valve stem should only be around 11/32 (.343). either way, test again. try shorter, try longer, it will take some trial and error to find the sweet spot, it may well end up needing a stock length pushrod, you just need to make sure.

lol, yes .08x is what I ment....

 

[kendawg73]

i'm hoping you're just missing a 0, because .8 is almost 7/8", the valve stem should only be around 11/32 (.343). either way, test again. try shorter, try longer, it will take some trial and error to find the sweet spot, it may well end up needing a stock length pushrod, you just need to make sure.

ok i'm still not getting any smaller sweep... looks like its staying in the .081 range... this is the rod set to 6.350, I had to use the big shim in the ford racing shim pact and it would turn to between 3/4 and 1 full turn to hit 20ftlb

 

[kendawg73]

this is when I had it set to 6.300 and use the thick shim... preload to hit 20ftlb was almost half a turn

 

[kendawg73]

and this is when I had it set again to 6.300 and used the thin shim... I got almost 3/4 to hit 20ftlb


as you can see in all the pic... it starts from center and moves towards the exhaust side of the head... this are all from the intake valve.

 

[kendawg73]

ok, went to the other head this morning cyl #2... the stock push rod is off the table... I was not able to adjust to zero lash.. the rocker would still move up and down off the valve tip... so too short...

the thin shim's I'm using measure .020... (forgot to say that before)...

so with the 6.300 adjustable rod... I used the then shim... I'm getting the same .08x" sweep pattering.. so that is staying consistent... for pre-load on the cyl #2 intake with the thin shim I'm between 1/4 and 1/2 (I would say a little closer to the 1/2 side maybe) with out the shim, I just a hair shy of 3/4.

on the exhaust with thin shim, almost 1/2 turn.

on cyl #8 exhaust... almost 1/2 turn with thin shim as well. and sweep is the same...

 

[Chuckman]

that sweep may just be what it is then, though i do find it odd that every pic of the valve stem seems to have two distinct marks, and not just one fat one.

instead of setting the checker out of the motor, make as short as it will go. use the solid lifter you made and just snug up the rocker bolt (with no contact between the checker and the rocker). then just expand the checker under the rocker until all the lash is out. turn the motor over by hand a couple times, if that wear pattern is still that big, then put every thickness shim under the rocker in sequence and repeat. see if it shrinks or grows. combine shims if you have to. check both intake and exhaust valves. make sure when you're expanding the checker that you're on the cams base circle (tdc for that cylinder). the more revolutions you turn the crank, the more clear that wear pattern will be.

.080" is still a HUGE wear pattern, something may be wacky with your setup somewhere, either they just need more adjustment, the valves are too high (i.e. someone cut the valve seats very deep), valves too short (heads milled more than you think), rockers themselves could be off, maybe need some material off the bottom of the pedestal, etc.

 

[kendawg73]

that sweep may just be what it is then, though i do find it odd that every pic of the valve stem seems to have two distinct marks, and not just one fat one.

instead of setting the checker out of the motor, make as short as it will go. use the solid lifter you made and just snug up the rocker bolt (with no contact between the checker and the rocker). then just expand the checker under the rocker until all the lash is out. turn the motor over by hand a couple times, if that wear pattern is still that big, then put every thickness shim under the rocker in sequence and repeat. see if it shrinks or grows. combine shims if you have to. check both intake and exhaust valves. make sure when you're expanding the checker that you're on the cams base circle (tdc for that cylinder). the more revolutions you turn the crank, the more clear that wear pattern will be.

.080" is still a HUGE wear pattern, something may be wacky with your setup somewhere, either they just need more adjustment, the valves are too high (i.e. someone cut the valve seats very deep), valves too short (heads millehaddn'td more than you think), rockers themselves could be off, maybe need some material off the bottom of the pedestal, etc.

Sorry hadn't had a chance to try this until today, first I found out something... the old stock lifter I made solid by flipping the insides shows a .020-.021 difference when doing zero lash then the new ford racing lifters. for example on cyl 1 intake with the solid lifter I made the adjustable push rod small, put it in, and put the rocker on and tightened down the bolt, then I adjusted the push rod until I got zero lash, then I took the rocker off and measured... I got 6.206 with the old lifter made solid, with the new lifter (not modified) I got 6.227.

also, I have a .020 difference on the other head, for example cyl 5 I get 6.227 with the solid lifter and 6.248 with the new lifter, on cyl 8 6.232 with solid and 6.243 with new.

on cyl 4 6.208 with solid and 6.229 with new.

and in both cases if I torque to 20 ftlb is get just under 1/4 turn.

also, I'm getting the same wear pattern... plus I found out this weekend my brother inlaw got my sister a 87 stang which has gt40p heads too and hes putting on scorpion 1.7 rockers, and he's getting the same thickness wear pattern as me....

so, would the trickflow 6.300 push rods be the correct ones then? which if i'm figuring right, gives me average .073 on the pass head (cyl 1-4), and about average .055 on the drivers head (cyl 5-8).

but then I would have to use .020 shim on the pass side (cyl 1-4) so that would make the pre-load .055-.020=.035

so I'm going to need at least a .037 shim on the drivers side (cyl 5-8) to hit that same ball park pre-load which I think would put me at about 3/4 turn??
am I thinking this out right??? the ford racing shim pack I have has .020 and .040 shims, so putting the .020 shims on the drivers side and the .040's on the pass side, would put them all about the same pre-load.....right? god my head hurts..... lol

now why i'm showing .020 different from side to side I don't know... before I put the heads on I used the digital calibers and measured from the top of the lower head bolt mount and the bottom surface of the head and they were about the same 1.37xx and 1.38xx


**** Update 5/4*** I set the adjustable push rod to 6.300 and put the .020 and .040 shims in place... setup zero lash, and torqued to 20ftlb, I get just abut 1/2 turn on both sides...
I then set the rod to 6.350 with same shims in place... it took a full turn maybe just slightly past... I don't want to add any more shims.. so looks like the 6.300 is what I will order, which will give me 1/2 turn pre-load.