340 Engine... How to determine pushrod length??
#458139
09/03/09 08:56 AM
09/03/09 08:56 AM
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Joined: Apr 2004
Posts: 589 Waynesboro, PA
cuda_tim
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mopar
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OP
mopar
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Posts: 589
Waynesboro, PA
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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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Re: 340 Engine... How to determine pushrod length??
[Re: cuda_tim]
#458141
09/03/09 09:08 AM
09/03/09 09:08 AM
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Joined: Jan 2003
Posts: 74,962 U.S.S.A.
JohnRR
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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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Re: 340 Engine... How to determine pushrod length??
[Re: cuda_tim]
#458143
09/03/09 09:15 AM
09/03/09 09:15 AM
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Joined: Jan 2003
Posts: 74,962 U.S.S.A.
JohnRR
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I Win
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Quote:
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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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Re: 340 Engine... How to determine pushrod length??
[Re: cuda_tim]
#458144
09/03/09 09:46 AM
09/03/09 09:46 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Posts: 36,040
Lincoln Nebraska
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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.
live every 24 hour block of time like it's your last day on earth
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Re: 340 Engine... How to determine pushrod length??
[Re: JohnRR]
#458145
09/03/09 10:18 AM
09/03/09 10:18 AM
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Joined: Apr 2004
Posts: 589 Waynesboro, PA
cuda_tim
OP
mopar
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OP
mopar
Joined: Apr 2004
Posts: 589
Waynesboro, PA
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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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Re: 340 Engine... How to determine pushrod length??
[Re: cuda_tim]
#458146
09/03/09 10:30 AM
09/03/09 10:30 AM
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Joined: Feb 2005
Posts: 28,312 Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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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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Re: 340 Engine... How to determine pushrod length??
[Re: RapidRobert]
#458149
09/03/09 11:19 AM
09/03/09 11:19 AM
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Joined: Jan 2003
Posts: 74,962 U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 74,962
U.S.S.A.
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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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Re: 340 Engine... How to determine pushrod length??
[Re: cuda_tim]
#458150
09/03/09 11:21 AM
09/03/09 11:21 AM
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Joined: Jan 2003
Posts: 16,123 Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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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!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: 340 Engine... How to determine pushrod length??
[Re: DUFFMAN]
#458152
09/03/09 05:42 PM
09/03/09 05:42 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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YOU DO NOT ADJUST PUSHROD LENGTH BASED ON VALVE TO PISTON CLEARANCE!!!!!!!!!!!!!!!!!!!!!!!!
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Re: 340 Engine... How to determine pushrod length??
[Re: cuda_tim]
#458154
09/04/09 09:17 AM
09/04/09 09:17 AM
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Joined: Jan 2003
Posts: 74,962 U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
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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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Re: 340 Engine... How to determine pushrod length??
[Re: JohnRR]
#458155
09/04/09 11:39 AM
09/04/09 11:39 AM
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Anonymous
Unregistered
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Anonymous
Unregistered
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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
Last edited by 440sixpack; 09/04/09 11:44 AM.
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Re: 340 Engine... How to determine pushrod length??
#458158
09/04/09 03:11 PM
09/04/09 03:11 PM
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Joined: Jan 2003
Posts: 74,962 U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 74,962
U.S.S.A.
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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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