Head or Valve Train Geometry

[Flash]

I had a lot of doubts before actually deciding on going with shimmed rocker arms. When I found it would be ok I went ahead and got them but now that everyone is talking about correct geometry its concerning me. I called Hesco and told them my situation, how I would be decking .060 exactly from the block and head total and I had .060 shims. I told them I was concerned about oiling and geometry but they said it was good to go, and that while they did offer shorter pushrods, they wouldnt be necessary. Now either its ok to shim, or they have some really bad salespeople/tech help. But now that Ive thought about it, it would seem that the shorter pushrod can cure both block and head decking, but the shim can only cure head decking without throwing the geometry off. Is this right? Heres my logic: If you take off .010 from the head but shim the rocker arm .010, the relationship between the pushrod, rocker and valve has stayed the same. Now if you take another .010 off the block and shim the rocker another .010 so it is now up to .020, the relationship between the pushrods and rocker stays the same, but the rocker and valve angles have changed. Is this correct?

If you take .010 off the head or block..........it will still make the pushrod two long and require a that amout of shim under the rocker arm.

flash

[seanyb505]

Yeah I could always see whats needed before I turn the engine on for the first time with the adjustable pushrod. Im debating on whether to have the machine shop complete the build cause I dont want to have to buy all the tools and make sure it all goes together correctly, and risk screwing up 3000 dollars worth of stuff. If the machine shop does it they can tell what steps need to be taken, and I will have the peace of mind knowing that my engine was put together well and with quality.

[seanyb505]

If you take .010 off the head or block..........it will still make the pushrod two long and require a that amout of shim under the rocker arm.

flash

I know that, Im thinking that if I only were to deck the head a shim would fix the lengths and geometry, but if I deck the block too, the shim wont be enough to fix the geometry, Ill have to get the shorter pushrod. Summary:
Deck head - shim or shorter pushrod
Deck block - shorter pushrod only

Maybe?

[Flash]

Yeah I could always see whats needed before I turn the engine on for the first time with the adjustable pushrod. Im debating on whether to have the machine shop complete the build cause I dont want to have to buy all the tools and make sure it all goes together correctly, and risk screwing up 3000 dollars worth of stuff. If the machine shop does it they can tell what steps need to be taken, and I will have the peace of mind knowing that my engine was put together well and with quality.

You have learn plenty enough to do the build you self. (If you have a good torque wrench, service manual and so plastic gauge.....to double check there work).............If you build it, you can beside how much gray area you are will to do................If the machine shop does it, you reallying on them to make the gray desision...........which may no be a bad idea.

My self the most important decision is a clean dirt free area to build it!

IF you don't have it, the machine shop is a way better idea..................


Flash

[Flash]

If you take .010 off the head or block..........it will still make the pushrod two long and require a that amout of shim under the rocker arm.

flash

I know that, Im thinking that if I only were to deck the head a shim would fix the lengths and geometry, but if I deck the block too, the shim wont be enough to fix the geometry, Ill have to get the shorter pushrod. Summary:
Every .010 that you put under the rocker are pedestal will change the Geometry for its factory designed(will affect rocker arm to Valve tip relation ship.....How ever slit it may be)
So......Deck head - shim or shorter push rod (Push rod GREEN, shim Gray)
Deck block - shorter push rod only ( same as above. push rod = stock geometry, shim starts to alter the factor geometry design)

Maybe?

I havn't here of any body that has galled up there rocker arms by using a .060" shim.....so oil lube must still be adequate for the rocker arm/push rod tip/valve tip.
So the only concern with a shim,.........is it will ware the valve guide faster..............does that mean that it will ware excessively in 10,000 mile............or that it will only get 100,000 instead of 2 or 300,000......

Flash

[seanyb505]

I havn't here of any body that has galled up there rocker arms by using a .060" shim.....so oil lube must still be adequate for the rocker arm/push rod tip/valve tip.
So the only concern with a shim,.........is it will ware the valve guide faster..............does that mean that it will ware excessively in 10,000 mile............or that it will only get 100,000 instead of 2 or 300,000......

Flash

Thats not a question I want to be the guinea pig for. Ill look into some diff length pushrods.

[gradon]

I haven't searched hesco yet, sean, so let me know what you find and prices(I have a feeling they'll cost >2x over my $16 mopar performance ones). I'll be looking for pushrods that are .030" shorter than stock. And I'm gonna go with new stock rockers for the time being(boo).
Edit: Our stock pushrods are 9.640", I didn't see 9.610" on hesco's site(they sell 9.639" as stock length) but I emailed them and asked. I will be buying Comp cams 7401-1 pushrod checking tool to get the exact length before I order the shorter rods. So If anyone wants to buy it/rent it after I'm done with it, let me know. Oh yeah, hesco's pushrods are $3.33 so x 12=$40, so they are >2x the other ones(3x with shipping--figures, huh).

[John]

Let me add one more link to the discussions on valve train geometry, http://www.thedirtforum.com/pushrodlengths.htm
Shimmed rockers have likely been used since the 2 or third valve train was built. It is a tool to make adjustments, within reason. Another variable to consider and possibly correct for, economical, reduces engagement of the bolt securing our rocker. Pushrods, if you have the right size, the geometry is correct and the preload is correct. Sounds simple, but often builds will use both techniques, The most important thing here is to insure the geometry is what you want, not what just happened. The link I just posted gives a example of why you might want to vary slightly. The difference between a designer/builder and good mechanic lies in these subtleties.
Adjustable pushrods, if you buy one, get one that matches the design/diameter as the motor you are working with. one with larger or smaller ends will give you a error in measurement.
Lifter, save a old one, disassemble. clean thoroughly with solvent, reassemble and squirt the oil passage full of glue, when it dries, paint the top of the housing red. The issues with our motor is the requirement to remove the stock head.
John

[Flash]

Yet another grate link THANKS,

That last statement of the link is vary interesting to me............I haven't fully grasp it .......But I will


Flash

[gradon]

Alright John, so I've been reading and re-reading the dirt and comp cams site. The dirt site used chevy as a reference(of course) so I don't know if this will hold true. So there is hydraulic pre-load(from the oil pressure) and lifter pre-load (1/2 turn of the 5/16 stud"--dunno if it is 24 threads per inch like the 3/8"in the example so I'll have to find that out). Anyhow using Dirt's example(even though is probably different with the Jeep, but just for explanation), I would take .600lift-.45 lift(30ab cam)=.15/3=.050" of hydraulic pre-load. Then I figure out how many threads per inch the 5/16 studs have and divide that number into the inch to find out the height of each thread. I would then divide that # by 2 for the amount half a turn is to get the lifter pre-load. So using the 3/8's specs 1/24 divided by 2=1/48(.021). I then add the hydraulic preload--.050" with the lifter preload .021 and get .071" I use a .071" feeler guage b/t the valve stem and rocker(dirt called them checkers) and then adjust the adjustable pushrod until it touches the rocker. Correct? Also the 30ab's centerline happens to be 108*(just like dirt's example, right?), so to adjust the geometry for best power, I want the valve stem to be centered on the rocker @ 2/3 lift(.30"), I would rotate crank until it was ~75*ATDC and make sure that the valve stem is centered on the rocker(adjust adjustable pushrod until valve is centered). Am I on the right track? Is there somewhere I can find hydraulic preload values and without having the 5/16 stud in front of me find out the # of threads per inch(I can find out on Wednesday)? Also I didn't understand gluing the old lifter and painting it--could you explain(I'm thinking too much and it's late).

[seanyb505]

I think the glueing might just be to eliminate any error due to the lifter not being solid. Once its glued there is less chance of error, and if its painted red theres less chance of throwing it back into a running engine. Seems a little obvious, but hey, mistakes happen.

[John]

Your bolt is .0625 inch for each full revolution, The lifter info is how to make a solid lifter for testing, one night very late I saw the red top showing on a motor I was assembling. Bad thing, just makes it obvious. And yes you are getting the setup figured out.
John

[Flash]

gradon, I just when and look up spec to adj rocker arm(If every thing was stock and un changed)

Ours bolt are torqued to 21 ft pound.......so it is in-fact not like the suspended pivot of GMs

Which means, that every thing that you figures up in your last post.......Pretty much works the same......EXCEPED, too get the valve tip exactly correct(or to change it).........you would Have to loosen the rocker bolt, add shim, and lengthen the adj push rod........or shave the pedestal down and shorten the push rod

In other words.(and i have no idea, as no one has tried it) A shim my improve from the Factory's Designed spec..........Or it could go the other way and require pedestal shaving to get that perfect rocker arm to valve tip relation ship........Every head and cam lift would require something different......as well as valve install hight variance.

Thanks John, i have learned a lot that i didn't even know there was to learn.
sense my next motor for my 340 is going to be a hi compression Big Cams 7500 RPM motor...........This info is vital to the life of that motor ...........It'S still year a way, but in the planning and parts collecting stage now.

Flash

[John]

Flash, it doesn't matter what motor we are working on, Check everything, and again everything we change causes ripple effects, trace them down, bring things to where you want them. Valve train issues can really eat up some parts, usually not the one causing problems. Kinda like the redhead that caused the bar brawl will be the only one not arrested.
John

[Flash]

That's to funny!!!!!! But vary true on both instances


Flash