Paul Deasy

Hi,
I have just installed the head after it was milled due to a blown gasket and now have some serious knocking noises coming from the top end and don't know what it is. The shop also re-seated the valves.

The car is a 1966 6 Cylinder Convertible.

I took the head off again today to check the valves and cylinders and they were all ok. I took some of the hydraulic lifters out (they came out really easy).
The knocking noise sounds like the base of the lifters are banging off the cam shaft.

I don't really know what to do next !!! I don't know a lot about hydraulic lifters. I don't think they should bang off the cam shaft and make a noise like that but I don't know how to fix it.

Could it be the timing is way out ?

Also the rockers aren't adjustable, do I need to get shorter pushrods because the head was milled ? Or is there another way of adjusting the rockers/pushrods ?

Did I damage the lifters with the original pushrods installed ?

Any help and advice would be greatly appreciated.

Paul.

Gun Jam

1) Did you check piston to valve clearance using something like clay?

2) Did you roll the engine over by hand with a ratchet and breaker bar? How does it feel?

3) Did you check for coil bind? The valve spring coils should have nice space between them when fully compressed (valve open)

4) (very important)Did you set preload on the pushrods by rolling the engine over until the lifter is on base circle of cam and then setting the proper amount of preload on the pushrod? usually .50 turn past zero lash.

5) (very important) did you check the rocker arm contact pattern on the valve stem? it should be right in the middle of the valve stem if its favouring the inside or outside by much you'll need to purchase longer or shorter push rods to accommodate this.

Let me know which numbers you've never heard of and have no idea what they are and ill try to find more info for you because thats probably where you went wrong.

-Gun

Paul Deasy

Thanks for the reply Gun,

1 - Piston to valve clearance is ok.
2 - I rolled over the engine by hand and everything feels ok.
3 - I think the coil bind is ok too. Everything looks fine and uniform.
4 - Em, this is where you loose me. After I installed the push rods and rocker I rolled over the engine by hand 4 or 5 times and that's it. I haven't a clue what you're talking about with .50 turn past pre lash.
5 - Again I'm a little lost, I'm new to trying to rebuild an engine etc. it's my first project.

Thanks again,
Paul

Gun Jam

Okay its possible that you are having problems because of 4 and 5 but I have limited experience with I6.

lets just start with 4 let me know if im on track here I see where I may be off track.

I was under the assumption that like the v8s the i6 also has an adjustable rocker arm. I tried to look up some pictures but it appears that they are non adjustable. This could be an issue.

How much did you mill off the head?

What you'll want to do is pick any valve (start at the front for ease i guess) rotate the engine over by hand until the valve closes. keep rotating the engine and attempt to rotate the pushrod like it were a drill bit and you were trying to hand drill something. with the lifter sitting on the base circle you should be able to rotate that pushrod with little effort but it should not have noticable up and down play it should be snug but not bound up either.

The rocker arms on the I6 appear to be captured on that guide rod that makes me think push rod length it quite critical even more so than with a v8 setup. Especially since I cant see a way to adjust them. Im guessing they will feel bound up and very tight

here is a picture of base circle.

Gun Jam

and thats assuming that for some reason the pushrod isnt captured i would think it can free spin inside the rocker arm....the push rod should have a ball machined onto the end of it...do you remember seeing that?

Paul Deasy

Hi Gun,
There is a lot of tension on the push rod and can't rotate it at all.
The rockers aren't adjustable.
The push rods are properly seated in the hydraulic lifters. The banging/knocking seems like the base of the lifters are bangin off the cam shaft.

There's a ball on both ends of the push rod, 1 seats into the lifter and the other into the rocker.

I phoned the shop today to see what he milled off, he said the head was pretty bad and he has to look up his diary to see what he milled off. still waiting for him to call me back.

Oh, the engine is also shaking pretty bad.

Thanks again
Paul

Gun Jam

is the firing order correct?

Which cylinders aren't firing??...you can check by seeing which exhaust headers are cool... use water drops (which headers dont boil right away after start up?)

From your initial post it sounds like you might not have a timing light...you'll need to barrow one and make sure the timing is about 12(ish) deg BTC at idle.

Are there massive vacuum leaks from maybe around the carb...did a hose not get reconnected?

The push rods are't captured right...with like a set screw or something goofy? when you pulled the head they just fall right out correct? so they should spin if they weren't crushed into the lifter and rocker arm right?

-Gun

Paul Deasy

Hi Gun,
It's firing on all cylinders but I will do the water check tomorrow just to be 100 %
I'll buy a timing light tomorrow and check the timing too.
There's no vacuum leaks either but again I'll double check tomorrow.
When I pulled the head they just fell out. After the head was milled and reinstalled, when I torqued down the rocker arm the pushrods tightened into the rockers really tight with no movement, can't spin or rotate them at all.
Do you think I'll have to buy shorter pushrods when I find out how much was milled off the head ?
Thanks again Gun,
Paul

Gun Jam

Yeah I think he mill a bunch off of those heads and it caused the head to become shorter so the rocker arm guide rod literally sits closer to the cam making the pushrods longer in relation to the head height. Chances are you'll end crushing lifters and they'll collapse with much run time....hopefully not already.

On the v8s you just adjust and if the pushrod is too long is just causes the rocker arm to slide out and push on the ouside of the valve stem (I think...maybe it was inside..whateves) the rocker arms are not captured and can slide in an out and can be adjusted for too long of a pushrod (but the side effect is poor contact pattern on valve stem)

with your setup rocker arm appears captured on the guide rod with nowhere to move in and out an no way at all to accommodate any change in push rod lenght...So I would imagine that push rod lenght need to fall within +-.010 to run right.

hopefully an I6 pro can join in...also might be worth asking the mechanic who did the work about this...but if he really knew about this setup I suspect he would have mentioned it.

-Gun

Paul Deasy

Would that cause all the knocking I can hear (the banging sound off the cam shaft) ? Do you think I could put a shim between the head and rocker arm to raise it up a fraction, or would that affect how much the valves open ?

Thanks again Gun,
Paul