Push rod length question.

Posted By: jhkintx

Push rod length question. - 04/25/09 02:12 AM

If my pushrods are too long what behavior can I expect from the engine?
Currently I have a vacuum leak that I can't locate and when I turn off the engine you can hear the valvetrain clicking. Also, with a 2400 stall converter and 3:91 gears the car is a little weak out of the hole and idles rough (rougher than one would expect). Below is a list of mods.

1) Stock 70 318 short block
2) Magnum heads milled .040
3) Mopar thin head gaskets
4) Mopar 7.625 pushrods
5) Mopar cam 280/474 (lift is 505 with 1.6 rockers)
6) Edelbrock Perf intake
7) Holley 600 vac sec

Posted By: Magnum

Re: Push rod lenght question. - 04/25/09 02:37 AM

Too long and the hydraulic lifters will be at the bottom portion of their range. The worst case scenario is they will be bottomed out and you will have no compression.

Posted By: MR_P_BODY

Re: Push rod lenght question. - 04/25/09 02:46 AM

If the lifter pumps up it can hold the valves open
(maybe just a touch) that would give you the rough
idle and the lack of performance. Also the intake
leak can give you both the idle issue and lack of
power
Did you use a push rod length checker to determine
the length needed

Posted By: HealthServices

Re: Push rod lenght question. - 04/25/09 05:46 AM

You can burn a valve if the it is incorrect for too long of time.

Posted By: jhkintx

Re: Push rod length question. - 04/26/09 01:58 AM

I was told to add rocker shims and see if the lifters quit clicking. Does this make sense as a starting point for trouble shooting?

Posted By: MoparforLife

Re: Push rod length question. - 04/26/09 02:15 AM

Quote:

I was told to add rocker shims and see if the lifters quit clicking. Does this make sense as a starting point for trouble shooting?

I don't understand the clicking when you turn the engine off. Are you real sure of what you are hearing????
If you have lifters clicking the push rods are to short not too long.

Posted By: jhkintx

Re: Push rod length question. - 04/27/09 05:37 PM

Quote:

Quote:

I was told to add rocker shims and see if the lifters quit clicking. Does this make sense as a starting point for trouble shooting?

I don't understand the clicking when you turn the engine off. Are you real sure of what you are hearing????
If you have lifters clicking the push rods are to short not too long.

I'm 100% sure the clicking comes from under the valve covers; it is very distinctive "click, Click, Click" for about thirty seconds to a minute on both sides of the valvetrain.

Posted By: MoparforLife

Re: Push rod length question. - 04/27/09 05:53 PM

Quote:

Quote:

Quote:

I was told to add rocker shims and see if the lifters quit clicking. Does this make sense as a starting point for trouble shooting?

I don't understand the clicking when you turn the engine off. Are you real sure of what you are hearing????
If you have lifters clicking the push rods are to short not too long.

I'm 100% sure the clicking comes from under the valve covers; it is very distinctive "click, Click, Click" for about thirty seconds to a minute on both sides of the valvetrain.

New one to me. Any one else heard of this????

Posted By: BELVEDERE67

Re: Push rod length question. - 04/27/09 06:59 PM

That clicking could be cooldown from headers or exh manifolds. I have heard that before. It is close to vc. Otherwise I'm baffled (make the home Improvement sound oah)

Posted By: jhkintx

Re: Push rod length question. - 04/28/09 06:10 PM

It is not cooldown from headers, you can feel the clicking with a hand on the valvecover. I'm shocked that with all the experience and wisdom I have a symptom that's unique...

Posted By: patrick

Re: Push rod length question. - 04/28/09 07:03 PM

with the engine off, as you state in the first post???!!!

Posted By: jhkintx

Re: Push rod length question. - 04/29/09 12:42 PM

As soon as you shut down the engine, the clicking will last 30 - 60 seconds.

Posted By: JohnRR

Re: Push rod length question. - 04/29/09 01:38 PM

Quote:

As soon as you shut down the engine, the clicking will last 30 - 60 seconds.

Kind of makes no sense , once you turn the engine OFF nothing is moving , so what's clicking ???

You could throw shims under it I guess , but if your rocker to valve tip geometry isn't off it may be so don't use them as the cure. But you have MAGNUM heads , they don't have a shaft mount system do they, shims go where? I'm lost on new smallblock stuff .

Posted By: patrick

Re: Push rod length question. - 04/29/09 02:29 PM

yeah, when the engine is turned off, nothing is moving, so I don't get where the noise would come from unless it's just the ticking of hot parts contracting when cooling? or maybe lifter bleed down closing open valves?

magnums are pedestal mount. shims could go between the pedestal and the head....

Posted By: Topher

Re: Push rod length question. - 04/29/09 04:48 PM

It's cooldown from the exhaust.

Now start chasing why the car isn't performing as it should. First thing to do is run a cylinder leakdown test, that will tell you many things about your engine.

Posted By: dgc333

Re: Push rod length question. - 04/29/09 11:39 PM

The 7.625" long push rods on a LA/magnum hybrid tend to be on the short side. I had to go to 7.650" long ones to get proper preload on the lifters.

You can check how much you are preloading the lifters by loosing the bolts that hold the rocker pedastels to the head. Then turn them back down while spinning a push rod in your fingers felling for play. Once all the play is gone the bolt should turn between 1/2 and one turn before the pedestal bottoms on the head. The bolts are 5/16-18 so 1/2 turn is 0.027" of preload and one turn is 0.055". If you are in that range the pushrods are not to long.

I agree with the others that a clicking noise after shutting down the engine is not the valve train.

Posted By: jhkintx

Re: Push rod length question. - 04/30/09 11:51 AM

Quote:

It's cooldown from the exhaust.

Now start chasing why the car isn't performing as it should. First thing to do is run a cylinder leakdown test, that will tell you many things about your engine.

As stated earlier; the clicking is NOT cooldown from the exhaust. Wish I could fiqure out a way to post a video clip to validate my issue. After reading the responses so far; I could describe the clicking as possibly the sound of metal hitting metal under pressure. It is not easy to discribe unique sounds with text.

Posted By: scratchnfotraction

Re: Push rod length question. - 04/30/09 12:50 PM

lifter bleed down and the valves clicking shut,IMO

runs like poop cause they are hanging open

Posted By: JohnRR

Re: Push rod length question. - 04/30/09 01:24 PM

Quote:

lifter bleed down and the valves clicking shut,IMO

runs like poop cause they are hanging open

This would be the only plausible answer other than the sound the exh makes cooling down .

As far as the frustration of the thread starter , WE collectively are not in front of your car so there are only 1 or 2 possible answers since the engine is NOT RUNNING when this happens. no matter what we say you are going to have to get your hands dirty and start ripping into it because it appears you do not like the answers you are getting .

Posted By: jhkintx

Re: Push rod length question. - 04/30/09 02:02 PM

No frustration with any responders to my question. I truly value the experiece of this forum and appreciate all that respond.

So, If I target lifter bleed down as a starting point would this indicate pushrods that are too short or too long?

Thanks,

Posted By: scratchnfotraction

Re: Push rod length question. - 04/30/09 02:04 PM

I have had more than a few hot and have the ticking sound "metalic sounding" pinging sound from the heat cycle cool down the engine its self is ping not the valves

same as headers would make noise the inside of the engine will do the same thing

check for the right pr IMO

Posted By: cjs69mope

Re: Push rod length question. - 04/30/09 02:57 PM

IMO .025 or even .100 differance in push rod length could be adjusted for with the adjustment screw of most aftermarket roller rockers . if i am wrong ,maybe some one could chime in and explain why .

Posted By: JohnRR

Re: Push rod length question. - 04/30/09 03:18 PM

Quote:

No frustration with any responders to my question. I truly value the experiece of this forum and appreciate all that respond.

So, If I target lifter bleed down as a starting point would this indicate pushrods that are too short or too long?

Thanks,

The pushrods would be too long , think about it if they were too short they wouldn't hold the valve open when they were supposed to be closed .

How many miles on the lifters , they shouldn't all be bleeding down that quickly as some valves are supposed to be open when the engine is shut off so that will tell me there is a lot of clearance in the plunger to body ???

Posted By: JohnRR

Re: Push rod length question. - 04/30/09 03:21 PM

Quote:

IMO .025 or even .100 differance in push rod length could be adjusted for with the adjustment screw of most aftermarket roller rockers . if i am wrong ,maybe some one could chime in and explain why .

Yes it could if they are too short , too long the .025 yes but not the .100 , typically you want 2 to 3 threads of the adjuster below the rocker body , more the pushrod is too short , less it's too long and will cause issues including blocking the oil path to the pushrod adjuster contact point.

Posted By: patrick

Re: Push rod length question. - 04/30/09 03:47 PM

Quote:

Quote:

IMO .025 or even .100 differance in push rod length could be adjusted for with the adjustment screw of most aftermarket roller rockers . if i am wrong ,maybe some one could chime in and explain why .

Yes it could if they are too short , too long the .025 yes but not the .100 , typically you want 2 to 3 threads of the adjuster below the rocker body , more the pushrod is too short , less it's too long and will cause issues including blocking the oil path to the pushrod adjuster contact point.

where did he say he was using aftermarket rockers? he's using magnum heads, OEM (non adjustible pedestal mount) rockers are 1.6 ratio.

Posted By: jhkintx

Re: Push rod length question. - 04/30/09 03:56 PM

Quote:

Quote:

No frustration with any responders to my question. I truly value the experiece of this forum and appreciate all that respond.

So, If I target lifter bleed down as a starting point would this indicate pushrods that are too short or too long?

Thanks,

The pushrods would be too long , think about it if they were too short they wouldn't hold the valve open when they were supposed to be closed .

How many miles on the lifters , they shouldn't all be bleeding down that quickly as some valves are supposed to be open when the engine is shut off so that will tell me there is a lot of clearance in the plunger to body ???

The lifters (comp cams) were new when installed, they have less than 2000 miles on them. When I finished the head converstion I took the car to a mopar shop in Texas for a tune up. The mechanic (an old time mopar guy) said all was good except for the timing; he couldnt get the timing marks to show up so he set be feel. I assumed since this guy had a great reputation that I had the best tune for what I had. I'm not to sure anymore and just want to get the most out of the mods. This set up on a hot humid Texas day dynoed at 237 RWHP. I was told that was respectable and left well enough alone. At this point I just want to be sure all is good inside.

Posted By: FlyFish

Re: Push rod length question. - 04/30/09 05:32 PM

Why not just pull a valve cover and take a peek?

Posted By: JohnRR

Re: Push rod length question. - 04/30/09 05:45 PM

He couldn't get the timing marks to show up so he set it by FEEL ??? That wouldn't be giving me a warm and fuzzy feeling .

Posted By: JohnRR

Re: Push rod length question. - 04/30/09 05:47 PM

Quote:

Quote:

Quote:

IMO .025 or even .100 differance in push rod length could be adjusted for with the adjustment screw of most aftermarket roller rockers . if i am wrong ,maybe some one could chime in and explain why .

Yes it could if they are too short , too long the .025 yes but not the .100 , typically you want 2 to 3 threads of the adjuster below the rocker body , more the pushrod is too short , less it's too long and will cause issues including blocking the oil path to the pushrod adjuster contact point.

where did he say he was using aftermarket rockers? he's using magnum heads, OEM (non adjustible pedestal mount) rockers are 1.6 ratio.

I was thinking the same thing , I left out at the end of reply ...

This is all well and good but doesn't help the thread starter since he didn't say he had adjustable rockers ...

Posted By: jhkintx

Re: Push rod length question. - 04/30/09 06:48 PM

I, the thread starter never claimed to have adjustable rockers. I have Magnum heads with STOCK ROCKERS.

Posted By: scratchnfotraction

Re: Push rod length question. - 04/30/09 06:57 PM

it is a slider cam and you better look at the lobes and lifters maybe

might be the quik bleed down of the lifters and valves shuting

could explane down on power and rough idle

but again if it did not line up...a damper could have sliped

what kinda chain and gears it got for timming?

are they set up correct? reatrd..advanced...striaght up?

what springs ya runnin on the mag heads?

whats the spring seat rate?

Posted By: jhkintx

Re: Push rod length question. - 05/01/09 10:34 AM

Quote:

it is a slider cam and you better look at the lobes and lifters maybe

might be the quik bleed down of the lifters and valves shuting

could explane down on power and rough idle

but again if it did not line up...a damper could have sliped

what kinda chain and gears it got for timming?

are they set up correct? reatrd..advanced...striaght up?

what springs ya runnin on the mag heads?

whats the spring seat rate?

As for the timing chain; it is a generic Auto Zone item "straight up". I cannot answer the spring and spring rate question, when I had my heads done I gave them the cam specs and they said it would be taken care of.

Posted By: scratchnfotraction

Re: Push rod length question. - 05/01/09 11:53 AM

vauto zone china crap straight up

have you tryed pulling the vc and chcking it with them off?

sound like that would be my next trick

maybe alittle messy if the engine is clean,but would rather have an oil stained engine than a broke one

I cant figure the "can feel it" part and 30 sec is a long time to "feel" the vc ticking

I would just check to see if all the rockers are moving about the same,give the springs a looky see for any broke ones maybe

do you trust the machince shop that said it would be taken care of?

if they left stock mag springs on that cam they might be a prob in Houston

I would also pull #1 plug and bring it up to TDC and check dist/cap/rotor/wires/damper to see if its off time...I dont like the cant line it up thing....junk t-chain and gears could be off

it could be the damper has slide and marks not lining up

I guess by feel he ment "feeling the piston down the plug hole" and setting the dist/oil drive in fase with the cam

IMO..get it up to temp and then pull the vc,run and shut down and

Posted By: edbux

Re: Push rod length question. - 05/03/09 11:11 PM

Quote:

I turn off the engine you can hear the valvetrain clicking

Does it sound like a spring compressing? I can't think of the correct way to define the sound. I get it also on my Mag headed LA motor after I first shut if off. I just figured the springs are too weak and I am going to upgrade the valve springs soon. Another theory of mine is that the spring is pushing the rocker arm up and compressing the lifter on a cylinder or two, I'm running 7.650" long pushrods, the MP conversion rods left me with about .025 preload.