67 289 Pushrod Length

[BDT 1967]

I have a 67 289 that I have rebuilt, has a Comp Cams Xtreme Energry flat tappet hydraulic lifter cam. Has the comp cams high energy lifter kit.
Currently I have sealed power 6.801 in. pushrods in the engine. I am getting quite a bit of lifter noise from the engine. Noise is coming from both sides of the engine best I can tell. Engine runs strong, doesn’t miss or have any apparent issues aside from the noise. We have set the lifters 2 times with no change. Curious if maybe our pushrods are too short. From my research it sounds like spec for the engine is 6.825 is that correct? Being off .024 on a hydraulic lifter setup I wouldn’t think that would make much if any noise. Comp Cams recommends a heat treated (cant imagine that matters) 6.800 pushrod for the cam and lifter setup I have. The heads have been rebuilt with factory spec parts. Pushrods are not bent. So my questions


1: What size pushrods are you running?

2: Is factory spec 6.825 for pushrod length?

3: Is there a way to measure pushrod length requirements without replacing a lifter with a solid lifter?


As always any help is appreciated!

 

[tos]

First what is the lift on that cam?
is the noise always there or does it change (come or go) at diff rpms?

Ill answer #3 for you- since you have run this cam and pushrod already then you can check to see how your geometry is and go from there. Remove one of your rockers and look at the top of your valve for the wear pattern. You should be able to see a wear spot forming that will indicate if your geometry is correct. The pattern should be centered on the valve stem. If it hasn't worn a pattern yet then you can mark it up with some ink or magic marker and run it again to check pattern. This will tell you if you need to spend the time measuring for length. So I wouldn't worry so much about what the stock length is because you are not using a stock spec cam.
As for the hardened pushrods I would do as they suggest, because one isn't bent now doesn't mean you wont bend one later. Any performance cam with more lift than stock should really have hardened rods, threaded studs and guide plates.

 

[BDT 1967]

Thanks for the reply, the specs on the cam are as follows,
Valve Timing: .006
Duration Intake:268
Duration Exhaust: 280
Duration @ .050 Lift: 224 Intake 230 Exhaust
Valve Lift Intake: .509
Valve Lift Exhaust: .512
Lobe Lift .319 Intake .32 Exhaust
The noise is always there, it increases with RPM. I will pull one of the valve covers this weekend to see if I can track down how its wearing. When reviewing the mark on the valve stem I am guessing you want the mark as small as possible, my assumption would be if the mark is on the top part of the valve stem the rods are too short, if its on the bottom of the valve stem the rods would be too long. Would that be correct?

 

[tos]

That's a lot of lift for stock rebuilt heads. You definitely need hardened rods, screw in studs, guide plates and springs heavy enough to handle that lift.
And yes you are correct on the position of your wear pattern.

Also can you explain the procedure you used to get your valve lash?

 

[BDT 1967]

Good morning,

I pulled the valve covers and removed one of the rocker arms to take a look, it appears that I have a very large wear pattern that nearly swaths the entire valve stem. I have pretty much decided purchase a measuring device from comp, measure what I need then purchase hardened pushrods. Attached are pictures of what my situation looks like. You may or may not be able to see what I am referring to after the upload. If I go 0 lash at 0 lift with the engine cold will that give me enough of a measurement to purchase the rods or do I need to pull out a hydraulic lifter and replace it with a solid lifter to get my measurement. I would rather not pull off the intake but will if needed.

Thanks again for the help

 

[tos]

What ever pattern its leaving should be centered on the valve stem. I guess I thought you had roller rockers, they would leave a more confined pattern but these stock rockers are a lot more forgiving when it comes to push rod length. I would still blacken them up somehow on the valve and on the bottom of the rocker just to see it clearer.
A couple things in your pics concern me though. It looks like the valve is not smooth on top and it also looks like the rocker has a worn are off the side of it like it rubbing. Maybe these are shadows in the pics? The only contact should be on the valve stem and little pad under the rocker. See the edited pics Im posting.

 

[BDT 1967]

I agree, its clear that it did rub on that shoulder, however, I think that may be due to the slop in the valvetrain. I did the test you mentioned by marking the valve stem with a marker, the pushrods appear to be the correct length, it left a nice mark pretty much center on the valve stem. I went through again and checked the valve lash, my method is outlined below.

Roll the engine over by hand until the exhaust valve begins to close, set the intake valve to zero lash then apply 1/2 turn preload. Roll the engine over by hand till the intake valve begins to close, set the exhaust valve to zero lash and apply 1/2 turn preload.

 

[tos]

Ok, sounds like you got the length resolved. Just make sure that your rocker where I circled does not make contact at any time. During operation the only contact should be the valve stem and the pad on the bottom of the rocker.

Also consider what I said in my earlier post about your lift versus stock heads. Those springs aren't strong enough for that kind of lift and you will also likely yank out a rocker stud or three unless they're threaded.

 

[BDT 1967]

Yeah, something isn't right in the heads, still makes racket when running, I am going to have to see what we put in for springs in the heads I can't recall exactly what we put in there. I am beginning to think I have a lifter not pumping up. I know I do not have screw in studs, I may also need to pick up some guides.

 

[Realmongo]

Looking at the photos, I think you are trying to mix incompatible valve train components together. The rocker looks like the rail style with the (I'm guessing) large push rod slot, while the valve spring side looks like the close tolerance push rod slot style that uses the conventional rocker arms. If so, you are about to drop a valve into the engine.

 

[tos]

Looking at the photos, I think you are trying to mix incompatible valve train components together. The rocker looks like the rail style with the (I'm guessing) large push rod slot, while the valve spring side looks like the close tolerance push rod slot style that uses the conventional rocker arms. If so, you are about to drop a valve into the engine.

Realmongo is right. As I said earlier it looks like your rocker is contacting the valve spring washer. THis is probably the noise you are hearing. Those valve stems are too short for rail rockers. You might want to try conventional (early) style rockers. Here's a pic of some 289 heads I have for sale on Craigslist. Notice the stem height.

 

[BDT 1967]

Thanks for the input, definitely makes sense, I will order a set and throw them on, worth a shot for sure,

 

[Realmongo]

As tos pointed out above, with that much lift you need screw-in studs.
Also, if you don't have the earlier heads, you can't just throw on the early style rockers, as there is nothing to keep the rocker arms aligned. You will either have to swap heads to the early style, or use push rod guide plates with the hardened push rods.
Good Luck!

 

[BDT 1967]

Yeah thanks again for the advice, I thought that my heads were the original 67 heads, but looking at them they have 65 stamped on them. I planned to use pushrod guides to keep them from walking off the valvestem. Picture attached.

 

[BDT 1967]

No more valve tick!


View: http://youtu.be/g2HSKiCPdZ4


I replaced the pushrods with the hardened 6.801 comp pushrods, then installed standard comp cams rocker arms without the rails. Doesnt tick anymore thank God! I still have to do a final lash adjustment. I did not pull the heads to have press in studs installed or guide plates. I am still trying to decide if I should just put aluminum heads in. But it's running good now, that will be a project once I pay off Christmas.

 

[tos]

Sounds good.