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291c Heads

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69 ambassador 390 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/27/2011 at 9:56pm
One intake and one exhaust if running a split pattern cam or just one valve if running a single pattern cam.  I would not use the 70+ torque specs because those are for the bigger bolts.  Because you are using ARP bolts I would add 10 and leave it.  The clay test is not for the valve length it is because you are changing the cam and now a lot in the heads.  Nothing is stock so check it.  It takes two seconds to do because you already are doing the pushrod check.  If you are running hydraulic lifters you need pushrods that are .010 to .030 longer than the checking rod at zero lash or if running H.P. anti pump lifters and zero lash you would add nothing to the length you figure.  I like to have .100 or more piston to valve room at least so as long as it is that or more you are good.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GREM Quote  Post ReplyReply Direct Link To This Post Posted: Mar/28/2011 at 1:17am
Originally posted by 69 ambassador 390 69 ambassador 390 wrote:

One intake and one exhaust if running a split pattern cam or just one valve if running a single pattern cam.  I would not use the 70+ torque specs because those are for the bigger bolts.  Because you are using ARP bolts I would add 10 and leave it.  The clay test is not for the valve length it is because you are changing the cam and now a lot in the heads.  Nothing is stock so check it.  It takes two seconds to do because you already are doing the pushrod check.  If you are running hydraulic lifters you need pushrods that are .010 to .030 longer than the checking rod at zero lash or if running H.P. anti pump lifters and zero lash you would add nothing to the length you figure.  I like to have .100 or more piston to valve room at least so as long as it is that or more you are good.

Sorry I didn't clarify that I'm not changing the cam. Just the heads on the same 68 390 AMX motor with stock pistons so I can run a set of Headman dogleg headers. Mild RV cam (already in place with the square port heads) with the 51cc chambers & hydraulic lifters so I think you answered my questions. Ten over on the torque & .010 to .030 longer than 0 backlash on the pushrods... Thanks... 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/28/2011 at 9:55am
If you are using the same cam you are good there.
Steve Brown

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Post Options Post Options   Thanks (0) Thanks(0)   Quote amx39068 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/28/2011 at 10:07am
why would you need longer pushrods with 291C heads?  They should have the same casting height as the earlier heads.  The 70 and up block is taller but to the best of my knoweldge the heads are the same stud height as the earlier heads.
Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/28/2011 at 9:08pm
Originally posted by GREM GREM wrote:

Originally posted by GREM GREM wrote:

In the meantime can someone tell me how the QUOTE thing works?
Confused

It only took me a few weeks but I think I got the quote thing figured out.

For my next question...I'd like to add a set of roller rockers to these heads. I've got my eye on a set of Scorpion's from Summit. It's my understanding they can be installed with the addition of adjustable studs. I spent a great deal of time today with a good friend of mine who tried his best to explain to me the rocker ratio relationship. He found a popsickle stick & a marble on the workbench & showed me what happens when you move the stick off center & raise or lower the short end. I think I understand that relationship better now. If the stud is raised the roller rolls forward on the valve stem & if it is lowered it rolls backward on the stem. The ratio affects how far the valve travels into the cylinder?

So my question is this...what pushrods do I use? 

Thanks in advance
This is where the checking of pushrod length came from.
Steve Brown

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Goodare 72 SST Quote  Post ReplyReply Direct Link To This Post Posted: Mar/28/2011 at 9:50pm
69 ambassador 390 Smile
 
You are correct, don't leave anything to chance check everything.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote amx39068 Quote  Post ReplyReply Direct Link To This Post Posted: Mar/28/2011 at 10:01pm
ah yes.  With different rockers you will definitely need to check the pushrod length.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SKeown Quote  Post ReplyReply Direct Link To This Post Posted: Mar/28/2011 at 10:08pm
 
X2 Goodare, when reinverting an engine design, leave nothing to chance. Were often dealing with different cam base circle, lifter height, head & block surfacing, different rockers and valve stem height. There's too much at stake to take anything for granted. Details make the difference in you're outcome.
 
 SKeown


Edited by SKeown - Mar/28/2011 at 10:09pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GREM Quote  Post ReplyReply Direct Link To This Post Posted: Mar/29/2011 at 6:47pm
Thanks for the feedback everyone!Hug I'll heed the advice & check for clearance. I'll report back with the results in about three weeks when the motor is pulled & on an engine stand. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote beepbop Quote  Post ReplyReply Direct Link To This Post Posted: Mar/30/2011 at 5:25pm
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