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Discussion Starter #1
I have a ZZ4 which I pulled the heads and cam and am installing a set of Brodix IK200 heads and a Doug Herbert roller CC6PJ cam w/1.52 roller rockers. The cam specs from the box are:

Adv. Dur 284 Int 292 Ex
@ 050 223 Int 233 Ex
Valve Lift .500 .500
Lobe Center 112
Centerline 108
@ 050 Int Open 3 Close 40
Ex Open 51 Close 1

I haven't done this in a really long time so I clayed the engine without a head gasket to check the valve clearance (using my original pushrods and new rockers) adjusted lifters, tightened head w/several bolts around the test piston.
Pulled the head and measured the clay to be about .280 for both intake and exhaust. I thought it sounded a little large for a gap especially w/o head gasket (.093).

I reinstalled the head adjusted lifters and measured the top of the valve spring height above the head casting when the valve is closed and measured it again with the valve fully open to see what the travel is. I get about .347 for both intake and exhaust.

So now I'm really puzzled............I was expecting to see somewhere around .506/.509 that reflects the lift of the cam.

Does the .506/.509 refer to something else or am I doing something wrong here??? With a .093 gasket the valve clearance will be around .373 does that sound correct??
 

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Random thoughts, in no particular order ...

It sounds like the lifters aren't actually touching the camshaft base circle.

You didn't accidentally order the smaller base circle option from them, did you?

Are you measuring valve lift at the valve or at the pushrod? If the valve is actually moving 0.500", then you would expect the pushrod to be moving approximately 0.333" (1.5 X 0.333" = 0.500").

I don't recall off the top of my head the correct piston to valve clearance, so I'll not comment on the 0.280" value you saw with the clay.

Steven
 

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Discussion Starter #4
Thanx for reply.

Looking at the lifters sitting in the block they appear to be at the same height when "at rest" as they were before. I never took a measurement before so I could be mistaken but I would think being off that much it would really be noticable.

By the way, since this motor only has 1000 miles maybe on it I thought I'd use the original roller lifters, after reading a bunch of stuff that looks like a bad idea.

"Smaller base circle"??? Sorry, I don't know what you mean. Help!

Yes, I'm measureing from the very top of the valve retainer. I picked a spot when the valve was closed then used the same exact spot when the valve was open.
 

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Discussion Starter #5
Random thoughts, in no particular order ...

It sounds like the lifters aren't actually touching the camshaft base circle.

You didn't accidentally order the smaller base circle option from them, did you?

Steven
I understand what you mean, I did a little research and found this:

retro-fit cams are reduced base circle, they have to be to accomodate OEM type hyd. roller lifters, due to the location of the oil hole. Non roller blocks have shorter lifter bores, and the OEM lifter oiling system just doesn't match up, unless the lifter can somehow be lowered in the bore. To do this, the cam is made with a smaller base circle, which lets the lifter sit lower.

Since this is a hydraulic roller block, I wonder if this cam is not correct?
 

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Thanx for reply.

Looking at the lifters sitting in the block they appear to be at the same height when "at rest" as they were before. I never took a measurement before so I could be mistaken but I would think being off that much it would really be noticable.
It seems unlikely, but it may be worth checking out. One of my theories was that the lifter isn't touching the cam until the lobe shows up.

By the way, since this motor only has 1000 miles maybe on it I thought I'd use the original roller lifters, after reading a bunch of stuff that looks like a bad idea.
In the old days, GM stated that if the bottom of your lifter still had sufficient crown, you could re-use it. I would think (although I don't KNOW) that you could re-use roller lifters with only 1000 miles on them.

"Smaller base circle"??? Sorry, I don't know what you mean. Help!
Think about this ... imagine a cam lobe. On the opposite side of the cam lobe is a circle. Now extended that circle all the way around the cam (ie, no lobe). That circle is the "base circle", and the lobe is then "added" to it. Sometimes, you need a smaller than standard base circle. If you have a cam with a smaller base circle, then your lifters will sit lower in the block. Generally, you have to special order a smaller base circle. When I looked up the cam you specified, I noticed that a smaller base circle was an option. A smaller base circle is used in stroker engines and some high lift cams. I've added an image that should illustrate it better than words!

Yes, I'm measureing from the very top of the valve retainer. I picked a spot when the valve was closed then used the same exact spot when the valve was open.
I had to ask - sometimes in the desire to figure something out, we overlook the obvious. I mistook a Torx head screw for a rubber grommet for 15 minutes yesterday while I was LOOKING for the Torx head screw! Once I left the job and came back, I spotted it immediately.

There is also a chance that the camshaft was built wrong, especially if you've been measuring at the retainer (and given your large valve to piston clearance).

You may wind up having to pull and measure the cam.

Have you called Doug Herbert and asked them for their opinion on what you're up against?

Steven

 

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Discussion Starter #7
Steven,
Thanks for all these good ideas and details!
One thing I didn't do was measure the actual travel of the lifter alone in the block. According to your previous post that should be approx .333, can't imagine that it will be given the measurement at the valve but anythings worth a look at.

I tried to call Herbert yeaserday when I ran into this but they were closed, if I can't find anything today I'll try first thing in the morning.

I agree about pulling the cam and taking a look. It's a real pain getting the clearance up front with the A/C condensor.........have to pull the vacuum cans for the headlights to get enough room. But I have an idea it may come to that.

Spending another coouple of hundred on new roller lifters was not in my plans, I'd really like to re-use these if I can.

Bill
 

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Steven,
Thanks for all these good ideas and details!
One thing I didn't do was measure the actual travel of the lifter alone in the block. According to your previous post that should be approx .333, can't imagine that it will be given the measurement at the valve but anythings worth a look at.

I tried to call Herbert yeaserday when I ran into this but they were closed, if I can't find anything today I'll try first thing in the morning.

I agree about pulling the cam and taking a look. It's a real pain getting the clearance up front with the A/C condensor.........have to pull the vacuum cans for the headlights to get enough room. But I have an idea it may come to that.

Spending another coouple of hundred on new roller lifters was not in my plans, I'd really like to re-use these if I can.

Bill
Bill -

I'd measure at the lifter first, call Herbert second, and only pull the cam as a last resort.

I haven't found a consensus on whether or not roller lifters shoud DEFINATELY never be re-used or not.

This link indicates that you can ...

http://www.aa1car.com/library/engine2t.htm

Good Luck!

Steven
 

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Discussion Starter #9
Steven,

Good link..... Thank you.

I figured out what's going on:

Measured the lifter travel at .326--330, pretty close to your number so it would indicate something in the pushrod/rocker area. I reinstalled the head, adjusted the rockers and rotated the engine and noticed the top of the lifter being pushed down by the pushrod quite a distance before the pushrod actually starts to move up. I went around and pushed on them by hand and found some were very rigid and didn't move much while others I could easily push down.
Do these hydraulic rollers need engine oil pressure to work properly?? Many of them are really easy to compress.

Just in case, here's how I adjusted them:

With the lifter at it's lowest point opposite the cam lobe I tightened the rocker nut while spinning the pushrod with my fingers. When I felt the resistance of the lifter pressing on the pushrod, I stopped, then added 3/4 of a turn more. At that point you can see the top of the lifter compress slightly.

If I'm doing it right I don't know how anyone could use the clay method with these lifters to check valve/piston clearance>

Bill
 

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Steven,

Good link..... Thank you.

I figured out what's going on:

Measured the lifter travel at .326--330, pretty close to your number so it would indicate something in the pushrod/rocker area. I reinstalled the head, adjusted the rockers and rotated the engine and noticed the top of the lifter being pushed down by the pushrod quite a distance before the pushrod actually starts to move up. I went around and pushed on them by hand and found some were very rigid and didn't move much while others I could easily push down.
Do these hydraulic rollers need engine oil pressure to work properly?? Many of them are really easy to compress.

Just in case, here's how I adjusted them:

With the lifter at it's lowest point opposite the cam lobe I tightened the rocker nut while spinning the pushrod with my fingers. When I felt the resistance of the lifter pressing on the pushrod, I stopped, then added 3/4 of a turn more. At that point you can see the top of the lifter compress slightly.

If I'm doing it right I don't know how anyone could use the clay method with these lifters to check valve/piston clearance>

Bill
I had given some thought to whether or not your lifters were collapsing under the spring load. Hydraulic lifters do need engine oil pressure to operate properly. My engine building days were almost exclusively solid lifters, so I never ran into that problem.

That could well be it.

Steven
 
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