Huston, we have a problem...!!!!

[Red63440]

Turned my 383 over by hand this morning and I think my valves are hitting the pistons. I loosened up my rocker arms and the problem went away but I had to back them off quite a bit. I am running stock dished pistons (1967) and factory rods. Pistons are about .023 below the deck. I have a fresh pair of 915 closed chamber heads with 2.08 and 1.74 valves. Cam is a Mopar Pn4452993 cam shaft with stock rocker arms, push rods, 848 springs (good for .540 lift) new retainers and locks amd I am using a .040 head gasket. I do notice that I have quite a bit of valve stem showing above the locks, more so than before but then this was just all bolted together. What direction to I take here???

 

[70rr-brian]

Are you sure the cam is degreed in properly?

 

[Red63440]

I just installed it on the center mark....but I realize something isn't right....

 

[70rr-brian]

You should probably use a cam degree wheel versus the dot to dot method. It sound like it is out of whack.

 

[Red63440]

The cam is not high lift which makes it hard to understand why its hitting.

 

[70rr-brian]

Just sounds like the cam is not degreed properly so your valves arent where they should be when the piston comes all the way up.

Could your pistons be installed in the wrong direction?

 

[Red63440]

The bottom end wasn't taken apart and I was running 906 heads. I was driving the car...

 

[Jonnyuma]

Anybody else here remember a time when .540" was considered a lot of lift?
Then again, I remember when 13 second cars were considered fast...such a geezer.
I think Brian's right, borrow or buy a degree wheel.

 

[Red63440]

The springs are good for that much but I am only running a .484. Guess I will tear down the front end and take a look.

 

[Jonnyuma]

Have you checked your valve to piston clearance? Like, with clay or Pla-Dough or something? The heads will have to come off at least a couple more times, but it can be very enlightening.
Don't use cream cheese, its messy.

 

[67 B-body]

Dot to Dot should be VERY close..... It would take a heck of a lot of poor quality / miss marked points on a timing set for it to be off enough to cause valve strike with dished pistons and .474" lift! How far have any of you actualy seen a cam be off when lining the dots up? 1deg? 2deg? 3deg?.... shouldn't be enough to cause valve strike......
Are you certain you have the marks lined up?

 

[Red63440]

I am going to tear it apart and check it out but I know that I checked it several times before I locked it down.
No cream cheese at all!!!

 

[Big Jim]

I noticed you commented about valve showing more stem above lock than before- first thing I would do is actually measure the length of the valve(s). If they are longer overall this coould cause interference. ( If you have .050" valve ot piston clearance and the stems are .100 longer than stock, this puts you .050" into piston. Just random numbers but you get the idea). jmho

 

[Red63440]

I was thinking about that...I know that the tops of the valves have more stem showing than what was showing on the 906's. I will have to call the machine shop tomorrow and see what they say.

 

[67 B-body]

I noticed you commented about valve showing more stem above lock than before- first thing I would do is actually measure the length of the valve(s). If they are longer overall this coould cause interference. ( If you have .050" valve ot piston clearance and the stems are .100 longer than stock, this puts you .050" into piston. Just random numbers but you get the idea). jmho

If it opened them further, wouldn't they be open at 0 lift "lobe baseline"? this is a hyd camshaft too... It would certainly make the geometry less than desireable, but I'm not sure it would increase valve lift...
This opinion is based on the lifter having enough plunger to take up that differance above the retainers "I think it would".

 

[Red63440]

If it opened them further, wouldn't they be open at 0 lift "lobe baseline"? this is a hyd camshaft too... It would certainly make the geometry less than desireable, but I'm not sure it would increase valve lift...
This opinion is based on the lifter having enough plunger to take up that differance above the retainers "I think it would".

Thats sort of what I was wondering, closed is closed. If they were to long then the valves would be open at 0 degrees...correct?

 

[67 B-body]

Thats sort of what I was wondering, closed is closed. If they were to long then the valves would be open at 0 degrees...correct?

Yes,,,,, if they were long enough to increase lift at full open, they would be long enough to keep them open at baseline too.... The lifter would have to have all of it's adj used up before this would happen. Completely collapsed...

 

[67 B-body]

Anybody else here remember a time when .540" was considered a lot of lift?
Then again, I remember when 13 second cars were considered fast...such a geezer.
I think Brian's right, borrow or buy a degree wheel.

Sure do!!!!!
When I got all my stuff around I choose the MP .590" lift cam and 1.6 ratio rockers.... I thought this was big at around .600" even after lash! Some of these rollers are HUGE and NO valve strike..... :icon_pray:

 

[MoparBill]

Some timing chains have multiple sets of 'dots'. Double check to be sure there is only one set. I have seen a set that had circles and triangles for different centerlines... just a thought.

 

[67 B-body]

Some timing chains have multiple sets of 'dots'. Double check to be sure there is only one set. I have seen a set that had circles and triangles for different centerlines... just a thought.

Good point,,,, Some do have the advance / retard keyways and dots accordingly.