To shim or not to shim

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P

Problem Child

Guest
I have a LA 36 block that I had decked when all my machine work was done,. Havent started it yet, but think I may have a problem that needs attention before I start the motor.
I have mag heads on it, so I used Mopar Perf push rods (can't remember the part num) as used in a Mopar magazine to do the head conversion. The heads were cut .0015 and the block was cut enough to change the piston TDC from .0070 down to .0020 down in the hole.
Long story short, if I start the motor like this I think I will wipe out the cam??????? So, do I need to shim my rockers back up so they don't create so much pressure? I am thinking around .0045. Help!!!!! Thanks Guys.
 
Sorry i dont have my engine book in front of me. The thing you need to look for/up is how to check lifter pre-load. Someone on here may be able to tell you the method.
 
You want .010/.015 lifter preload and thats it regardless of what it sounds like (tappet wise) the best way to do this is with adjustable rockers and a custom set of pushrods and your done.
More RPM's and Torque/HP ........................any questions?........................lol


old mopar thing, ya know.
 
first of all I think that you have your numbers all wrong. I'm sure that .015 (fifteen thousandths) was taken off, not .0015 (fifteen tenthousandths). Please double check your numbers. If the deck was cut down only .005 its not a problem. But .050 would make a change.

don
 
You are correct sir. I went to school in Mississippi, and we didn't have no math classes. I added an extra zero. The heads were cut fifteen thouandths,,,,,and the pistons are now down in the hole twenty instead of the stock number of seventy. Please tell me I didn't ruin everything and spend a lot of money doing it. Thanks guys.
 
Problem Child said:
You are correct sir. I went to school in Mississippi, and we didn't have no math classes. I added an extra zero. The heads were cut fifteen thouandths,,,,,and the pistons are now down in the hole twenty instead of the stock number of seventy. Please tell me I didn't ruin everything and spend a lot of money doing it. Thanks guys.
Click to expand...

Hey PC, don't be so hard on the fine Mississippi educational system. I'm a
"gradjeet" myself, and as long as I can get my shoes kicked off in time I can
"calkeylate" with the best of 'em. LOL!
 
Ok, so at least I caught this early. I do have a set of adjustable rockers from a 273 or 340, will they work? On the push rods, how do I know which new set to buy, or even if I need them? What did you do to find out the hard way Jack? Maybe I should just stop with the Magnum heads......thoughts!

Used to have an uncle that lived in Brandon, I was from just south of Meridian,,,,,Was.
 
PC,
If you have magnum heads the older 273 and 340 rockers won't work as they are shaft style and the magnums are stud mount, so you'll have to use a set up like the small block chevy's, I think that comp cams and Crane have them, but they are somewhat pricey.
 
Will stock type from a 350 work? These mag heads are looking worse as I go along.
 
P.C.

I know because I have wiped 2 cams. I know what the problem is and I won't wipe another one. The adjustable rockers are the best solution. Don't give up on those Magnum heads, they flow real good and if worked properly are light years ahead of J's.

Jack
 
Thanks Jack. Should I get one of those adjustable push rods or whatever to figure out what length pushrod I need? Any other suggestions as to how to figure it out?
 
I have to stop short as to how to determine the best way to figure out that measuement. I don't want to steer you in the wrong direction. BJR, moper or Mrmopartech are much more qualified than me to give you the best advice.

Jack
 
PC,
Adjustable pushrod or a pushrod length checker is the easiest and quickest, then call Smith Bros. pushrods if there isn't pushrods in that length already avaliable. Make sure that the rocker pad or roller is in the center of the valve stem tip and 90* or parallel to the head width or the checking will be wrong.
 
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