Pushrod question... Will it cause damage???

-
1970dartcustom

1970dartcustom

of the Moore clan
Joined
Feb 1, 2016
Messages
776
Reaction score
184
Location
Broken Arrow, OK
My Dad is done assembling and installing the motor and has begun working on all the accessories, and happened to mention to me that he is not really sure if he put the right length pushrods in, and that he'd know right away once the motor ran cause it would run like crap.
Now, my old man is not really a mechanic per se, but he's built some nice Mo's in his life that ran well. My concern is that maybe some damage could occur with the wrong size push rods???
 
Put the right push rods in or you can do major damage if a valve hits a piston...
 
1970dartcustom said:
is there a stock size for my 383 or is there a setup specific rod that I need to account for things? (Sorry, I know very little of this aspect...)
Click to expand...

What kind of cam do you have? What rocker arms are you running?

Those make a difference...
 
Is your cam solid or hydraulic lifter???

Are the rocker arms stamped steel or adjustable...

Pull the valve cover off and look... also make sure that the valves are fully closed and seated with the push rods and rockers in place...
 
You need to measure to do it right. Especially with non-adjustable rockers. Over time blocks get decked, heads get milled, etc. if he THINKS he put the wrong pushrods in it, then clearly they weren't what came out of it, and/or he has doubts. He also needs to add the correct preload, which is typically .020-.050. on a hyd setup

on shaft, non-adjustable rockers, this is all accomplished with the correct length pushrod. If they're adjustable, you have some fudge factor, but i'm assuming they aren't.

say it had a .060 head gasket originally, and the replacement you went with was .020, and it was decked .005, and the heads milled. you just took your lifter pre-load from the min acceptable, to the max acceptable, or beyond... you'll know when the lifters pump up and the valves kiss the pistons.

this is a smart $20 to spend... make sure your range is correct.
Hi-Tech Checking Push Rod Competition Cams 7702-1 - Pace Performance Parts
 
Johnny Pace said:
You need to measure to do it right. Especially with non-adjustable rockers. Over time blocks get decked, heads get milled, etc. if he THINKS he put the wrong pushrods in it, then clearly they weren't what came out of it, and/or he has doubts. He also needs to add the correct preload, which is typically .020-.050. on a hyd setup

on shaft, non-adjustable rockers, this is all accomplished with the correct length pushrod. If they're adjustable, you have some fudge factor, but i'm assuming they aren't.

say it had a .060 head gasket originally, and the replacement you went with was .020, and it was decked .005, and the heads milled. you just took your lifter pre-load from the min acceptable, to the max acceptable, or beyond... you'll know when the lifters pump up and the valves kiss the pistons.

this is a smart $20 to spend... make sure your range is correct.
Hi-Tech Checking Push Rod Competition Cams 7702-1 - Pace Performance Parts
Click to expand...
Is this a good method for checking if I'm close but slightly off?
 
1970dartcustom said:
Is this a good method for checking if I'm close but slightly off?
Click to expand...

krazykuda said:
What kind of cam do you have? What rocker arms are you running?

Those make a difference...
Click to expand...

Comp Cam extreme energy 490,
Hydraulic lifters, non-adjustable rockers, and the heads were milled .004. He put in a stock gasket, and stock-sized push rods, so the only difference is the .004 milled. So, we should be pretty darn close aye?
 
Johnny Pace said:
You need to measure to do it right. Especially with non-adjustable rockers. Over time blocks get decked, heads get milled, etc. if he THINKS he put the wrong pushrods in it, then clearly they weren't what came out of it, and/or he has doubts. He also needs to add the correct preload, which is typically .020-.050. on a hyd setup

on shaft, non-adjustable rockers, this is all accomplished with the correct length pushrod. If they're adjustable, you have some fudge factor, but i'm assuming they aren't.

say it had a .060 head gasket originally, and the replacement you went with was .020, and it was decked .005, and the heads milled. you just took your lifter pre-load from the min acceptable, to the max acceptable, or beyond... you'll know when the lifters pump up and the valves kiss the pistons.

this is a smart $20 to spend... make sure your range is correct.
Hi-Tech Checking Push Rod Competition Cams 7702-1 - Pace Performance Parts
Click to expand...
The entire motor was just freshly built by my Dad from an empty block and new parts.

Comp Cam extreme energy 490,
Hydraulic lifters, non-adjustable rockers, and the heads were milled .004. He put in a stock gasket, and stock-sized push rods, so the only difference is the .004 milled. So, we should be pretty darn close aye?
 
1970dartcustom said:
Comp Cam extreme energy 490,
Hydraulic lifters, non-adjustable rockers, and the heads were milled .004. He put in a stock gasket, and stock-sized push rods, so the only difference is the .004 milled. So, we should be pretty darn close aye?
Click to expand...

There is still some fudge factor considering not all aftermarket "stock" replacement components are identical to oe spec. But if you just put the factory pushrods back in..then u r prob close....but close is for horseshoes and hand grenades...not engines.

1. with rockers loose, Rotate engine until lifter is on back side of cam lobe.

2. Slowly tighten rocker shaft until zero slop remains in the pushrod. (All 5 bolts)

3. When you reach zero lash (no more slop) on the pushrod. You should still be able to tighten the rocker arm bolts a "little" this would be your "pre load"

4. With a flashlight...you should be able to look and see how many threads are left on the rocker arm bolts when u hit zero lash.

This is the horseshoe/grenade method to see if u are even close. It wont be perfect bc the bolt "turns" wont be 1 for 1 to pushrod length due to geometry. ..but should tell u if the p-rods are so short..that u cant get zero lash....or soo long that u are opening the valve.

Or...spend the $20 and get a length checker and do it the right way.
 
.004 ?....there is at least that must difference in the deck height from front to back of the block if it was not squared.....sometimes this **** over engineered...but we will have 50 pages of what you should or should not do...lol
 
If the rockers are stock, and the lifters are stock, and the cam was ground with a stock base circle, and the heads and/or block were not milled "much", and you use stock thickness head gaskets, and the valves are stock length, you can get away with putting stock pushrods in it. If one or two of the above items are off, you can probably use stock pushrods. If you have no idea what is stock and what is modified, and by how much, you really need to check the pushrod length and get the right ones.
 
Completely correct. The original question sure left alot to interpretation. Especially when implied that the wrong ones were possibly installed....

"Can I reuse stock pushrods if only decked .004?"

Is a completely different question than

"My dad found some mystery pushrods on the shelf in the garage and installed them in "Engine X"...and I now need to know... will it smash 16 valves on fire-up?" Lol
 
I bet it was decked "forty" meaning .04, or .040 not .004 which is "4 thousands"
 
67Dart273 said:
I bet it was decked "forty" meaning .04, or .040 not .004 which is "4 thousands"
Click to expand...
IDK that's what he said "4 thousandths"
Just a wee bit. I assume they had a reason for such a tiny bit...

After speaking to my dad more about it, he just said that he has some slightly shorter rods he can put in, but the stock rods, stock gasket, not too big cam, stock-sized stealth heads, hydraulic lifters, etc... seem to indicate a very stock length with a bit of tolerance in the mix...

Also, I assume the 0.004 milling was just to square it up?
 
1970dartcustom said:
IDK that's what he said "4 thousandths"
Just a wee bit. I assume they had a reason for such a tiny bit...

After speaking to my dad more about it, he just said that he has some slightly shorter rods he can put in, but the stock rods, stock gasket, not too big cam, stock-sized stealth heads, hydraulic lifters, etc... seem to indicate a very stock length with a bit of tolerance in the mix...

Also, I assume the 0.004 milling was just to square it up?
Click to expand...
Anyways, thanks for the input guys, and patience. I don't get to talk with my Dad a whole lot, so I am limited on the info I can glean from him.
 
hydraulic lifters have plenty of play to deal with heads cut .004"!! what head gaskets did U use-most likely not thinner than stock. was valve to piston clearance measured-most likely plenty of clearance for heads cut .004"! was piston to deck measured-probably "down the hole" enough for no problems. thousands of people have been doing what U have done without problems for decades before the interweb was here to scare U
 
You must log in or register to reply here.
-

Back
Top