# Pushrod length changed



## Willshire (Jul 14, 2011)

i am in the middle of installng new scorpion rollers on my 389 and it appears my p/r's will need to be .220" longer. Is this common when going from standard stamped steel to billet rollers. i used a p/r length checker (comp 7902 note the locknuts dont fit past the guide plates) and ended up with 8.940" could go 8.950" for ease of purchasing. but, i have a question... when i tightened up the pushrod and added a half turn, the valve went down instead of the lifter is this normal? does it relax off the spring once the oil is flowing? i guess if there is no oil in the lifter the cup has bottomed out so the only thing to move is the valve right? do i still add the half turn after snug or do these adjustments after it is running. willl my geometry change once the lifter pumps up?


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## BearGFR (Aug 25, 2008)

Howdy Willshire...
Couple things jump out: One is that the procedure for determining correct pushrod length is usually done with a solid lifter at zero lash to avoid the problems you ran into. You can also take one of your hydraulics apart, remove the spring, and flip the internal plunger over upside down and accomplish the same thing. It's also easier if you use lightweight checking springs instead of regular valve springs, but that's not absolutely required. 

When I measured mine I used a length checker like this one. It doesn't have lock nuts so guide plate interference isn't a problem and it reads like a micrometer, making it really easy to know what length to order. All the reference materials I've located say that you don't need to allow for hydraulic lifter preload distance during the measurement process. I guess if you get the length correct for a lifter that's 100% pumped up, it'll still be good for normal operation.

I'd think it's normal to need different length pushrods when changing rocker type, ratio, or anything else that could affect the location of the rocker ends and/or fulcrum.

Bear


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## Willshire (Jul 14, 2011)

Thanks Bear.

I looked at one of the old lifters i took out (original) and up till a few minutes ago i thought i was missing the guts of the lifter. I did not realize the p/r cup sat on a steel housing above the spring. I looked in the end under the cup and just saw an empty cavity and thought wtf? :lol: now i realize there is more to remove (i guess i assumed the plunger would just fall out duh). i gotta get some assembly lube for the valve train. do i use 30wt oil on the threads of the head bolts too? (getting mixed advice on this one). Thanks for your help, as this is my first build these forums are a great place for advice. Also the comp 7902 p/r that i have is a 8.5 - 9.8" or there abouts. i used a caliper to measure the distance between the nuts and added them to the full closed (8.5") distance. .440 + 8.5= 8.940. before i restart the engine should i drizzle oil over the entire valve train?


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## Mr. P-Body (Jan 20, 2011)

Wilshire,

A drop of engine oil (30 is fine) on the threads of the head bolts. DO NOT use "sealant". That's a Chevy thing. Pontiac head bolt holes are "blind". 

We often discard the jam nuts on the length checkers because of guideplates (not just Pontiacs...). As long as you're careful when you remove it, the length won't change. You must measure the checker "end to end". Your method MIGHT be accurate, but I never tried something like that... -

Definitely prime the system.

Jim


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## Willshire (Jul 14, 2011)

Mr. P-Body said:


> Wilshire,
> 
> A drop of engine oil (30 is fine) on the threads of the head bolts. DO NOT use "sealant". That's a Chevy thing. Pontiac head bolt holes are "blind".
> 
> ...


Jim,

i got you jumpin on two sites answering my question here. i figure if i put it in multiple pllaces get multiple answers :lol: feel free to hit hpp to and add .02. :rofl:i had the engine running before, once i put the heads back on can i just lube the top end with assy lube and engine oil and fire it up? i don't see it being any different than starting it after a month or so or am i talkin out the side of my mouth again.


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## BearGFR (Aug 25, 2008)

Measuring pushrod length directly isn't as simple as it seems. The reason is the measurement is affected by the oil holes on the ends of the pushrods. There's a good explanation of it all on the Comp Cams web site here. That's why I really like their "Hi Tech" checking pushrods: you get the correct length directly by "reading" the pushrod instead of having to try to measure it.

Using a good assembly lube is important on the valve train, especially on the cam lobes. More wear will occur on the first fire-up than on the many miles of operation thereafter. It's also why you don't let an engine with a new flat tappet cam idle for the first 20-30 minutes after assembly. You want to make sure all those surfaces are getting plenty of oil until they've had a chance to "get friendly" with each other for awhile. Thorough priming of the oiling system prior to startup is mandatory. Pull the valve covers and spin the oil pump with a drill (running "backwards" for Pontiacs) until you see a good bit of oil squirting out of all 16 pushrods. You can buy a special priming tool or improvise your own. I use a 1/2" drill and an old distributor I've gutted (and removed the gear), and I've also used a wood cutting 'spade' bit that's narrow enough and long enough to fit down into the oil pump drive shaft slot (break/grind the point off of the spade bit first so it winds up resembing a big screwdriver).

You definitely want to use some sort of thread lubricant on head bolts (and all torque to measurement fasteners) otherwise you can't get an accurate torque reading during installation. Depending on who you choose to listen to (like many things you'll find opinions all over the map on this one), the specific lubricant used can matter a great deal. ARP recommends their own "Ultra Torque" lubricant (of course) - you can read about it on their web site..

Just take your time, be meticulously clean with everything - you'll be fine.

Bear


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## Willshire (Jul 14, 2011)

Does the drill need to spin very fast it has been my luck that any flathead screw the thing jumps around i don't want to jump it off the oil pump rod. again, could someone please explain how tearing the heads off the engine differs from the drain back experienced when you don't start your car for a month?


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## BearGFR (Aug 25, 2008)

Willshire said:


> Does the drill need to spin very fast it has been my luck that any flathead screw the thing jumps around i don't want to jump it off the oil pump rod. again, could someone please explain how tearing the heads off the engine differs from the drain back experienced when you don't start your car for a month?


No, it doesn't have to spin fast. You're really just making sure all the oil passages are full of oil with all the air purged out of them so that oil will flow more or less "instantly" when you start the motor. When you see oil coming out all of the pushrods, you're golden. It doesn't have to shoot across the room or anything 

The difference is that removing/reinstalling pieces creates an opportunity for things to move from their original locations, even if only by miniscule amounts, and that can change the wear patterns.

Bear


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## Willshire (Jul 14, 2011)

BearGFR said:


> No, it doesn't have to spin fast. You're really just making sure all the oil passages are full of oil with all the air purged out of them so that oil will flow more or less "instantly" when you start the motor. When you see oil coming out all of the pushrods, you're golden. It doesn't have to shoot across the room or anything
> 
> The difference is that removing/reinstalling pieces creates an opportunity for things to move from their original locations, even if only by miniscule amounts, and that can change the wear patterns.
> 
> Bear


Excellent. Thanks Bear. lastly, do/should i copper spray felpro 1016 head gaskets? one side? both sides? still confused about why geomtry is so far from stock


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## BearGFR (Aug 25, 2008)

On gaskets I always follow the recommendation of the gasket manufacturer.

As far as the difference, double check everything. Forgive me if I'm telling you things you already know, but fr'instance, I assume you noticed that the rocker trunions do have an up and down side - one side is rounded by the bolt hole and the other side is flat. The flat side goes "up" next to the poly-lock. 

Did you replace rocker studs too or are they still original? If original you might try re-installing one of the factory ball-type rockers and checking it. Being able to see it correctly installed and sitting right next to one of your new ones on the same head ought to really highlight where the differences are. 

Bear


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## Rukee (Feb 8, 2007)

I use the copper coat on both sides of every head gasket job I do.


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## Willshire (Jul 14, 2011)

BearGFR said:


> On gaskets I always follow the recommendation of the gasket manufacturer.
> 
> As far as the difference, double check everything. Forgive me if I'm telling you things you already know, but fr'instance, I assume you noticed that the rocker trunions do have an up and down side - one side is rounded by the bolt hole and the other side is flat. The flat side goes "up" next to the poly-lock.
> 
> ...


Trunions good new screw in studs and guideplates. I mean if you think about it, if your rocker was .020 away from centre at mid lift, how much p/r length would be required to move it that .020? i guess that is why it is called valve train GEOMETRY. Angles, fulcrums etc. etc. Anyway, i wonder if the ol' stamped steels weren't on the money either. I am gonna go home and play around a little i got one gasket to put on (darn backorders) then i can check it again. I will let you know what i found. to be sure i will set the rocker on, tighten by hand until i feel the p/r drag slightly, add 1/4 turn, rotate, check, check, check, be sure, done.


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## 66tempestGT (Nov 28, 2009)

you say the pushrod length changed. but did you ever actually check it before or just assume all the stock stuff was on the money?


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## Willshire (Jul 14, 2011)

66tempestGT said:


> you say the pushrod length changed. but did you ever actually check it before or just assume all the stock stuff was on the money?


I did it guys. Thank you Bear for the suggestion of side by side rocker comparison. Turns out the valve tip contact points are different. With the stock p/r, the stock rocker was bang on but the roller was closer to the intake side. New p/r length 8.880-8.900" I love old car restoration!


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