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#458139 - 09/03/09 06:56 AM 340 Engine... How to determine pushrod length??
cuda_tim Offline
mopar addict

Registered: 04/08/04
Posts: 557
Loc: Waynesboro, PA
Guys!

I'm preparing my 340 for reassembly and I've been searching (somewhat casually) for the proper method in determining push-rod length. (BTW: I've been known in the past to skip this step and just slap an engine together and see what happens... )

I didn't see anything in the tech area, and even many of the guys at the machine shops aren't sure (unless it is a chevy ).

My 340 has the stock cam, lifters (hydraulic), and non-adjustable rocker shafts/arms. They all mention using a black or blue felt marker to mark the tops of two valves, assembling with two push rods & rocker arms/shaft and rolling the engine over a few times.

Then check the affect that the rocker arm has on the top of the valve.

I can't see how affective this method is with non-adjustable rocker arms, although I think I understand the intent of the procedure.

They also mention using a solid lifter & the adjustable push-rods, to determine the proper length. But they say that the stock lifters can be used (some-how) also.

Basically you lengthen and shorten the adjustable push-rod to achieve the correct imprint on the top of the valve. (Then use that length to order new ones of that length).

Has anyone used this method with non-adjustable rockers?

Any advice would be appreciated.

Thanks!

Tim...
_________________________
"Robots building robots.... now that's just stupid!" - Will Smith in the movie "I, Robot". '71 Demon (340/727)/'69 Charger (383/727)/'65 Barracuda (273-2V/904)/'66 Coronet (340/727)/'86 Dodge Aries (2.5L)/'78 Dodge Aspen (318-2V/904)

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#458140 - 09/03/09 07:06 AM Re: 340 Engine... How to determine pushrod length?? [Re: cuda_tim]
mopars4ever Offline
master

Registered: 01/20/03
Posts: 7727
Loc: md
Did you have machine work done to the block? If not and everything is stock I personally would not bother but that`s me.

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#458141 - 09/03/09 07:08 AM Re: 340 Engine... How to determine pushrod length?? [Re: cuda_tim]
JohnRR Offline
I Win

Registered: 01/20/03
Posts: 71046
Loc: U.S.S.A.
Yep sounds like chevy builders doing that will tell you if your rocker to valve tip geomerty is correct but the length of the pushrod will NOT do anything for it since you have a SHAFT MOUNTED system and once you bolt it down and torque to spec it is what it is. You have to use spacers under the shaft OR remove material from the cast stands to change that relationship.

Has the block been decked alot ? heads shaved alot , head gasket thickness vs. original ? These are things that aeffect the pushrod length on big block and small block mopars .

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#458142 - 09/03/09 07:11 AM Re: 340 Engine... How to determine pushrod length?? [Re: mopars4ever]
cuda_tim Offline
mopar addict

Registered: 04/08/04
Posts: 557
Loc: Waynesboro, PA
Quote:

Did you have machine work done to the block? If not and everything is stock I personally would not bother but that`s me.




Yes, heads were shaved significantly. In fact, I need to use a shim...

But more importantly, I think I'd like to know the best way to do this...

Tim...
_________________________
"Robots building robots.... now that's just stupid!" - Will Smith in the movie "I, Robot". '71 Demon (340/727)/'69 Charger (383/727)/'65 Barracuda (273-2V/904)/'66 Coronet (340/727)/'86 Dodge Aries (2.5L)/'78 Dodge Aspen (318-2V/904)

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#458143 - 09/03/09 07:15 AM Re: 340 Engine... How to determine pushrod length?? [Re: cuda_tim]
JohnRR Offline
I Win

Registered: 01/20/03
Posts: 71046
Loc: U.S.S.A.
Quote:

Quote:

Did you have machine work done to the block? If not and everything is stock I personally would not bother but that`s me.




Yes, heads were shaved significantly. In fact, I need to use a shim...

But more importantly, I think I'd like to know the best way to do this...

Tim...




what do you mean ... I NEED TO USE A SHIM ????

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#458144 - 09/03/09 07:46 AM Re: 340 Engine... How to determine pushrod length?? [Re: cuda_tim]
RapidRobert Offline
Too Many Posts

Registered: 11/20/03
Posts: 25553
Loc: Lincoln Nebraska
From Dave Hughes & co: At 60% of total valve lift (50% if BB) the centerline thru the pushrod and adj screw should be a straight line viewed from the front of the eng. Shorten/lengthen the pushrod and or saddle shims (or milling) to achieve it. 1-2 threads showing and include the lash if it's a solid cam/lifters & if hyd use a junk hyd lifter w the cup welded solid. Then rocker tip side alignment & shims on the shaft to correct that then check the wipe pattern.
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live every 24 hour block of time like it's your last day on earth

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#458145 - 09/03/09 08:18 AM Re: 340 Engine... How to determine pushrod length?? [Re: JohnRR]
cuda_tim Offline
mopar addict

Registered: 04/08/04
Posts: 557
Loc: Waynesboro, PA
Quote:

Quote:

Quote:

Did you have machine work done to the block? If not and everything is stock I personally would not bother but that`s me.




Yes, heads were shaved significantly. In fact, I need to use a shim...

But more importantly, I think I'd like to know the best way to do this...

Tim...




what do you mean ... I NEED TO USE A SHIM ????




Ok, my machine shop performed a valve to piston clearance check for me and they advised using a 0.020 shim, in addition to the normal Fel-Pro head gasket.

I don't remember the numbers exactly (I'm at work), but I think that the numbers fell out like this:

Using the Clay method, the clearance between the intake valve and the piston valve relief was 0.036. They recommended 0.100 on the exhaust side.

If you figure that the Fel-Pro head gasket compresses to 0.039 and the shim is 0.020, this should get me to 0.095.

0.036 + 0.020 + 0.039 = 0.095.

Anybody?

Tim...
_________________________
"Robots building robots.... now that's just stupid!" - Will Smith in the movie "I, Robot". '71 Demon (340/727)/'69 Charger (383/727)/'65 Barracuda (273-2V/904)/'66 Coronet (340/727)/'86 Dodge Aries (2.5L)/'78 Dodge Aspen (318-2V/904)

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#458146 - 09/03/09 08:30 AM Re: 340 Engine... How to determine pushrod length?? [Re: cuda_tim]
Challenger 1 Offline
Too Many Posts

Registered: 02/05/05
Posts: 24842
Loc: Cincinnati, Ohio
Quote:

Quote:

Quote:

Quote:

Did you have machine work done to the block? If not and everything is stock I personally would not bother but that`s me.




Yes, heads were shaved significantly. In fact, I need to use a shim...

But more importantly, I think I'd like to know the best way to do this...

Tim...




what do you mean ... I NEED TO USE A SHIM ????




Ok, my machine shop performed a valve to piston clearance check for me and they advised using a 0.020 shim, in addition to the normal Fel-Pro head gasket.

I don't remember the numbers exactly (I'm at work), but I think that the numbers fell out like this:

Using the Clay method, the clearance between the intake valve and the piston valve relief was 0.036. They recommended 0.100 on the exhaust side.

If you figure that the Fel-Pro head gasket compresses to 0.039 and the shim is 0.020, this should get me to 0.095.

0.036 + 0.020 + 0.039 = 0.095.

Anybody?

Tim...




Never heard of a head gasket shim?
_________________________

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#458147 - 09/03/09 08:32 AM Re: 340 Engine... How to determine pushrod length?? [Re: cuda_tim]
repad Offline
super street

Registered: 05/15/04
Posts: 679
Loc: N.E Indiana
I had the same problem when I had the heads shaved .070. The machine shop could not tell me how much shorter my pushrods needed to be. You would think there would be a formula similar to the one used in shaving the intake to fit. I found it easier to get new custom cut pushrods and adjustable rockers.

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#458148 - 09/03/09 09:03 AM Re: 340 Engine... How to determine pushrod length?? [Re: repad]
65vert Offline
member

Registered: 02/13/07
Posts: 31
Loc: Shoreview,MN
End result on 69 340-Chrome moly pushrod through chrome moly rocker arm. Hamburger sells or used to sell adjustable rocker arms which was my net result.

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#458149 - 09/03/09 09:19 AM Re: 340 Engine... How to determine pushrod length?? [Re: RapidRobert]
JohnRR Offline
I Win

Registered: 01/20/03
Posts: 71046
Loc: U.S.S.A.
Quote:

From Dave Hughes & co: At 60% of total valve lift (50% if BB) the centerline thru the pushrod and adj screw should be a straight line viewed from the front of the eng. Shorten/lengthen the pushrod and or saddle shims (or milling) to achieve it. 1-2 threads showing and include the lash if it's a solid cam/lifters & if hyd use a junk hyd lifter w the cup welded solid. Then rocker tip side alignment & shims on the shaft to correct that then check the wipe pattern.




doning my firesuit ...

That's some BAD info from Hughes , I'm surprised ... really , I am ...

Hughes bootlickers , don't waste your energy ...

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#458150 - 09/03/09 09:21 AM Re: 340 Engine... How to determine pushrod length?? [Re: cuda_tim]
patrick Offline
I Live Here

Registered: 01/20/03
Posts: 16102
Loc: Grand Haven, MI
Quote:

Quote:

Quote:

Quote:

Did you have machine work done to the block? If not and everything is stock I personally would not bother but that`s me.




Yes, heads were shaved significantly. In fact, I need to use a shim...

But more importantly, I think I'd like to know the best way to do this...

Tim...




what do you mean ... I NEED TO USE A SHIM ????




Ok, my machine shop performed a valve to piston clearance check for me and they advised using a 0.020 shim, in addition to the normal Fel-Pro head gasket.

I don't remember the numbers exactly (I'm at work), but I think that the numbers fell out like this:

Using the Clay method, the clearance between the intake valve and the piston valve relief was 0.036. They recommended 0.100 on the exhaust side.

If you figure that the Fel-Pro head gasket compresses to 0.039 and the shim is 0.020, this should get me to 0.095.

0.036 + 0.020 + 0.039 = 0.095.

Anybody?

Tim...




use the standard fel-pros (Q8553PT) they're actually .054" compressed. that'll get you .090" clearance. if you're still concerned, try retarding the camshaft 2 degrees.
_________________________
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2006 Inferno Red Dodge Caravan SXT 2011 Toxic Orange Dodge Charger R/T

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#458151 - 09/03/09 11:23 AM Re: 340 Engine... How to determine pushrod length?? [Re: repad]
DUFFMAN Offline
I Live Here

Registered: 03/14/05
Posts: 10331
Loc: Land of Beer and Cheese
Quote:

You would think there would be a formula similar to the one used in shaving the intake to fit.




P2 = 7.500 - D/Cos(14)

P2 - Desired (new) push rod length
7.500 - Stock small block pushrod length
D - Amount of height removed; Amount milled from heads + Amount shaved of the block deck + head gasket compressed height difference
_________________________
Disclaimer: The opinions contained within are solely based on my perspective.

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#458152 - 09/03/09 03:42 PM Re: 340 Engine... How to determine pushrod length?? [Re: DUFFMAN]
Anonymous
Unregistered


YOU DO NOT ADJUST PUSHROD LENGTH BASED ON VALVE TO PISTON CLEARANCE!!!!!!!!!!!!!!!!!!!!!!!!

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#458153 - 09/03/09 08:38 PM Re: 340 Engine... How to determine pushrod length??
cuda_tim Offline
mopar addict

Registered: 04/08/04
Posts: 557
Loc: Waynesboro, PA
Quote:

YOU DO NOT ADJUST PUSHROD LENGTH BASED ON VALVE TO PISTON CLEARANCE!!!!!!!!!!!!!!!!!!!!!!!!




Ok, so when does the pushrod length need to be considered? And how it is verified without adjustable rockers?

My original post only suggests that I would like to determine the length... since I want to make sure it is correct.

Especially since I know that when using the stock cam, (per my machine shop guy) I need to add a shim, since the valve to piston clearance is already tighter than normal.

And especially since I know that (when I disassembled the engine) the intake manifold mounting holes had previously been "hogged out" a great deal in order to get the intake to fit correctly.

Anybody?

_________________________
"Robots building robots.... now that's just stupid!" - Will Smith in the movie "I, Robot". '71 Demon (340/727)/'69 Charger (383/727)/'65 Barracuda (273-2V/904)/'66 Coronet (340/727)/'86 Dodge Aries (2.5L)/'78 Dodge Aspen (318-2V/904)

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#458154 - 09/04/09 07:17 AM Re: 340 Engine... How to determine pushrod length?? [Re: cuda_tim]
JohnRR Offline
I Win

Registered: 01/20/03
Posts: 71046
Loc: U.S.S.A.
Quote:

Quote:

YOU DO NOT ADJUST PUSHROD LENGTH BASED ON VALVE TO PISTON CLEARANCE!!!!!!!!!!!!!!!!!!!!!!!!




Ok, so when does the pushrod length need to be considered? And how it is verified without adjustable rockers?






when you deck the block and the head A LOT , which sounds like the case here since you don't have enough piston to valve clearance now , take one of your old pushrods put it in place with head on the block and pick a spot in the valley that you can easily get at with wrenches and cut about an inch and half out of it , thread the inside ... FINE THREAD .... get a piece of threaded rod and 2 nuts , wala ADJUSTABLE PUSHROD ... find out the length you need with it .

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#458155 - 09/04/09 09:39 AM Re: 340 Engine... How to determine pushrod length?? [Re: JohnRR]
Anonymous
Unregistered


Some of you guys are confused. PUSHROD LENGTH is adjusted to maintain VALVE CLEARANCE "lash" when adjusting valves AND to maintain decent rocker arm geometry. IT HAS NOTHING TO DO with piston to valve clearance. Pushrod lenght is set WITH THE VALVES CLOSED

Piston to valve clearance is determined by cam lift, by valve timing, by the type and height of pistons and deck. Unless I mis--read the type of cam you posted you have very little valve/ piston clearance.

If you need more valve / piston clearance you need to

go to a lower lift cam

go to lower ratio rockers which also lower the lift

Buy different pistons with deeper reliefs

Figure a way to cut deeper reliefs--not a backyard project for the usual shadetree--these must be milled, the pistons re--balanced and quite possibly the engine rebalanced


I'm starting to wonder if this entire question is not mis construed. Maybe you have more piston / valve clearance than you were told?? In any case pushrod length is NOT the answer


Edited by 440sixpack (09/04/09 09:44 AM)

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#458156 - 09/04/09 10:28 AM Re: 340 Engine... How to determine pushrod length??
patrick Offline
I Live Here

Registered: 01/20/03
Posts: 16102
Loc: Grand Haven, MI
Quote:

Some of you guys are confused. PUSHROD LENGTH is adjusted to maintain VALVE CLEARANCE "lash" when adjusting valves AND to maintain decent rocker arm geometry. IT HAS NOTHING TO DO with piston to valve clearance. Pushrod lenght is set WITH THE VALVES CLOSED

Piston to valve clearance is determined by cam lift, by valve timing, by the type and height of pistons and deck. Unless I mis--read the type of cam you posted you have very little valve/ piston clearance.

If you need more valve / piston clearance you need to

go to a lower lift cam

go to lower ratio rockers which also lower the lift

Buy different pistons with deeper reliefs

Figure a way to cut deeper reliefs--not a backyard project for the usual shadetree--these must be milled, the pistons re--balanced and quite possibly the engine rebalanced


I'm starting to wonder if this entire question is not mis construed. Maybe you have more piston / valve clearance than you were told?? In any case pushrod length is NOT the answer




another way to change valve to piston clearance is to change the cam timing. moving the ICL around can drastically change V-P clearance.
_________________________
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2006 Inferno Red Dodge Caravan SXT 2011 Toxic Orange Dodge Charger R/T

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#458157 - 09/04/09 10:31 AM Re: 340 Engine... How to determine pushrod length??
B G Racing Offline
master

Registered: 03/28/06
Posts: 9501
Loc: Eighty Four, PA
Using stock non-adjustable rockers and hydraulic lifters you need only bolt on the rocker assembly,find the distance(adjustable pushrod ball&ball ends)and at rest,valve 100% closed add your desired preload(start the plunger downward)Lock your adjustment on the pushrod and you have your proper length.Make sure you are on the(bottom) of the cam lobe at true basecircle.
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#458158 - 09/04/09 01:11 PM Re: 340 Engine... How to determine pushrod length??
JohnRR Offline
I Win

Registered: 01/20/03
Posts: 71046
Loc: U.S.S.A.
Quote:

Some of you guys are confused. PUSHROD LENGTH is adjusted to maintain VALVE CLEARANCE "lash" when adjusting valves AND to maintain decent rocker arm geometry. IT HAS NOTHING TO DO with piston to valve clearance. Pushrod length is set WITH THE VALVES CLOSED






The only person confused here seems to be YOU , no one said anything, anywhere, in this thread about adjusting piston to valve clearance with the length of the pushrods till you brought it up .

If you go back and reread you'll see he was told to use a HEAD GASKET SHIM to regain his piston to valve clearance .

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