Cut heads .025 thousandths...do I need different pushrods?

Black1987Stang · Dec 19, 2008

So I had some Edelbrock Performer RPM heads cut about .025 thousandths from overheating/warped issues.....Would I need different length pushrods to keep the rocker tip on the center of the valve stem? They're stud mounted rockers....

347HO · Dec 19, 2008

"IF" your pushrods were the correct length to begin with... I say RUN them!
I say this because OTS pushrods come in .050" increments.
If you need some more specific... you'll have to buy custom ones.

BlownFiveLiter · Dec 19, 2008

I agree. Set your valve lash and see what, if any action is necessary. You may luck out and have the roller make a good pattern across the valve stem.

PAzYearazzUP · Dec 19, 2008

It is going to be a pain, but now how much is left from the squish to the top of the ring? That should be about .150 thousands so you do not cook or warp the ring.
Now that you took off .025" for the warp, that is less material for heat-transfer is they sure made the head light is not enough meat for head dissipation. So, with the assembly about to start, you can just use one cylinder is set up one rocker arm assembly in the cylinder, check to see of the rocker arm follows the valve(s) tip and if it does, you do not need new rods. Being that is the only reason you want new is solid lifters could take up the .025" if you ran adjustable push rods or the rockers were adjustable for lash.

Black1987Stang · Dec 19, 2008

What's the best way? cover the valve stem in permanent marker set up a rocker and rotate the motor a few times and look at the pattern?

As for adjustable pushrods? They're only to check the length so you can order the right ones in solid form....and I wouldn't need new rods....it's going to increase my compression but that's fine by me, I'm running premium octane anyway.

347HO · Dec 19, 2008

PAzYearazzUP said:
It is going to be a pain, but now how much is left from the squish to the top of the ring? That should be about .150 thousands so you do not cook or warp the ring.

What are you talking about

PAzYearazzUP said:
Now that you took off .025" for the warp, that is less material for heat-transfer is they sure made the head light is not enough meat for head dissipation.

So you think removing .025" off the deck is going to create an overheat condition?
In your experience... what is the deck material thickness on RPMs?

PAzYearazzUP said:
So, with the assembly about to start, you can just use one cylinder is set up one rocker arm assembly in the cylinder, check to see of the rocker arm follows the valve(s) tip and if it does, you do not need new rods.

Is it not more important to ensure the rocker tip is mostly centered on the valvestem, with not greater than .060" of witness mark?

PAzYearazzUP said:
Being that is the only reason you want new is solid lifters could take up the .025" if you ran adjustable push rods or the rockers were adjustable for lash.

What solid lifters are .025" taller on the buttom than the lifters "BlackStang" has... which he hasn't told us what he has in the first place?
Would you please post up "who" runs adjustable pushrods in their "running" engine?

lang williams · Dec 19, 2008

i had .040 taken off my gtp heads. i was told that was the max for keeping stock length push rods. i did run into ptv clearance issues though.

Maryland Stang · Dec 20, 2008

lang williams said:
i did run into ptv clearance issues though.

That was what I was going to point out too. .025 is a good bit to take off and the whole setup needs to be rechecked. Let me point out too that although most pushrods come in .050 increments you can get custom length pushrods made to any length that you like.

old_blue · Dec 20, 2008

agreed with above. I dont think the pushrods would be your biggest problem. YOu need to definitely check PTV clearance as .025 is a good chunk and you might have some unexpected noise when you fire it up.

oh9mustang · Dec 20, 2008

If you cut .025 off the heads wouldn't that lower them .025? Because heads are located on a block that is 45degrees apart, lowering each head by .025 would bring the heads .050 closer to each other.
If they are lower wouldn't that create a gape on the inside of the intake manifold area that contacts the head? So I would guess you would need to take .025 off the top area of the intake that contacts the head.

Ron

795.0pacecar · Dec 20, 2008

oh9mustang said:
If you cut .025 off the heads wouldn't that lower them .025? Because heads are located on a block that is 45degrees apart, lowering each head by .025 would bring the heads .050 closer to each other.
If they are lower wouldn't that create a gape on the inside of the intake manifold area that contacts the head? So I would guess you would need to take .025 off the top area of the intake that contacts the head.

Ron

I had my heads milled .020 last year, and the machine shop also milled the intake side the same to keep the intake where it should be.

Cougar5.O · Dec 20, 2008

347HO said:
What are you talking about

Whew! I knew I didn't smoke any crack tonight!

bluevenom867 · Dec 22, 2008

Assuming the push rods were correct befor you had the heads milled,just shim/adjust the rocker arms for the differance (i.e heads milled .025,add .025 shim to the rockers or adjust the poly lock about 1/4 turn out) to get correct valvetrain geometery again.

Where the heads flat milled or angle milled? If they were flat milled definitly check piston to valve clearance,if its close you got two options,have the pistons fly cut,or a thicker head gasket. I'd opt for the first one.

If it was angle milled,you may actualy have gained some clearance,but make sure you check. Always check. The only real down side to angle milling is that parts may not fit up quiet right.

You may also need to mill your intake manifold,check first as its possable that only a change to thinner manifold gaskets would be required.

(Btw,I'm back!)

Black1987Stang · Dec 22, 2008

Well since it's stock pistons with 1.6 rockers and not a Huge cam, (F cam) I'm not worried too much PLUS I am using the 9333 gaskets which have a .047 thickness rather than the normal .039 thickness so that makes .025 equal out to .017 thousandths....which makes it not nearly as bad..(correct me if im wrong please)

347HO · Dec 23, 2008

You should still check all your clearances.
In my experience, increasing quench to "fix" other issues is not the best way to do it. I don't suggest you use a thicker gasket... but it is your engine in the end.

Black1987Stang · Dec 23, 2008

Well I'm still going to double check everything just in case....but as for the head gasket that's how thick it comes in stock form and it's what a HUGE amount of people, especially the boosted guys are running without any problems at all.

martyd · Dec 23, 2008

I hate to hijack but what happens by way of compression ratios and valve to piston clearence when doing something like this. I know in general terms that 1.90 valves are about the largest you can go without fly cutting the pistons. But what about after you do something like this?

Black1987Stang · Dec 23, 2008

It's going to increase the compression and increase the piston to valve contact chances...which is what most people are saying to do is to double check for the p to v clearances...and if you cuts heads too much then the intake ports wont line up enough and I would have to get the surface of the intake cut also....

Basically what I'm trying to get at is since I'm using a .08 thousandths thicker gasket than normal isn't that basically like having the heads only cut .017 thousandths?

martyd · Dec 23, 2008

I'd say it would be something like that. I was wondering about the compression and such because I plan on doing all I can do with a set of stock heads worked to their max. abilities. Seems like a decent little way to jump compression a tad bit making it a better setup for a slightly more aggressive cam.

Modular2v · Dec 23, 2008

bluevenom867 said:
Assuming the push rods were correct befor you had the heads milled,just shim/adjust the rocker arms for the differance (i.e heads milled .025,add .025 shim to the rockers or adjust the poly lock about 1/4 turn out) to get correct valvetrain geometery again.

Where the heads flat milled or angle milled? If they were flat milled definitly check piston to valve clearance,if its close you got two options,have the pistons fly cut,or a thicker head gasket. I'd opt for the first one.

If it was angle milled,you may actualy have gained some clearance,but make sure you check. Always check. The only real down side to angle milling is that parts may not fit up quiet right.

You may also need to mill your intake manifold,check first as its possable that only a change to thinner manifold gaskets would be required.

(Btw,I'm back!)

DING DING DING! We have a winner

Cut heads .025 thousandths...do I need different pushrods?

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