Purple Shaft lash question.

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Dartthunder340

Dartthunder340

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i have a .590 Purple Shaft in a 340, with Aries domed pistons, and open W2's. Lash has been set at .25/.25 cold and I'm wondering how far I can push it (.18/.20 cold?). What are you setting your lash at with these cams and does anyone have info as to why Mopar wants them set up so loose? Thanks for any help!
 
28/32 is the listed settings and I'll assume, hot. I don't know how far you can tighten it up so, it becomes at your own risk.
 
.018-.020 hot is fine. There is no reason to beat the valve train to death With hot lash that loose.

If you have to advance the cam, or loosen the lash to make the car move you need a better converter.
 
We've seen great results with the solid purpleshaft cams by advancing them, even with good custom 8" converters. I had the 590 cam in my big block, advanced to 104.
My friend kept advancing the 557 cam in his small block and the car kept going quicker, he ended up at 100. It's something you have to play around with but I think it's very safe to advance them 2 degrees, especially since the timing chain will eventually stretch a little.
 
yellow rose said:
.018-.020 hot is fine. There is no reason to beat the valve train to death With hot lash that loose.

If you have to advance the cam, or loosen the lash to make the car move you need a better converter.
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My attitude is, there is SOME reason the guy who designed that cam specified that lash IE that much
 
67Dart273 said:
My attitude is, there is SOME reason the guy who designed that cam specified that lash IE that much
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Call them and ask them. They will baffle you with a buck of techno bullcrap. Essentially, when valve springs were limp and because the entire world was dazzled by the small block Chevy, lash ramps were long and slow. A cam that used to lash at say, .014 hot was considered a lobe suitable for 50k miles adjustments, but a "racing" lobe would need more lash and frequent adjustments were considered acceptable.

Today, that same .014 lash ramp would embarrass the best ramps of the 1970's.

More than .020 hot on most of these old lobes is plenty. As long as the valve isn't being held open at temp you're fine. There is no sense in beating the valve train apart because that is how they used to do it.


Edit: I'd also say that if you are moving 2 degrees either way from a split pattern ICL the cam is wrong and more power and better performance would happen with the correct timing events that by crutching a bad cam by moving it ahead.
 
rumblefish360 said:
28/32 is the listed settings and I'll assume, hot. I don't know how far you can tighten it up so, it becomes at your own risk.
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LOL, never assume My friend, all Purple Shaft solids are lashed "cold".

Except the smallest /6 cam which is set at the stock lash.
 
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Killer6 said:
LOL, never assume My friend, all Purple Shaft solids are lashed "cold".

Except the smallest /6 cam which is set at the stock lash.
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That is incorrect. 28/32 is the 'Hot' lash setting. I set mine at 22/26 cold to get 28/32 hot.

My 451 big block ran in the high 9's in the 1/4 mile with the 590 cam and 28/32 lash.
It didn't beat parts up and it has ran 9's for years and years.
 
I set my cam at .020"-.022" warm. with a flat lifter I do not think it is a good idea to play with lash too much from a wear aspect
 
ProSport said:
That is incorrect. 28/32 is the 'Hot' lash setting. I set mine at 22/26 cold to get 28/32 hot.

My 451 big block ran in the high 9's in the 1/4 mile with the 590 cam and 28/32 lash.
It didn't beat parts up and it has ran 9's for years and years.
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Sorry Sir, that is the footnote in the catalog,.....haven't seen a mech. Purple Shaft "card" in 25 years........
 
No problem Killer6, just want to make sure people set their lash correctly.
 
I remembered them being set hot as most all are, but I read this & thought maybe they weren't or I'd forgotten,lol!!
0507172103-00.jpg
 
I assume you are running Aluminum heads? The OP is running cast iron W2's. Lash will tighten on an iron head engine.

ProSport said:
That is incorrect. 28/32 is the 'Hot' lash setting. I set mine at 22/26 cold to get 28/32 hot.

My 451 big block ran in the high 9's in the 1/4 mile with the 590 cam and 28/32 lash.
It didn't beat parts up and it has ran 9's for years and years.
Click to expand...
 
66fs said:
I assume you are running Aluminum heads? The OP is running cast iron W2's. Lash will tighten on an iron head engine.
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I have never seen an engine with iron heads have the lash close up from cold to hot. I've seen some that opened up just .001-.002 but most open up .003-.004 and aluminum grows on average .006-.008.
 
yellow rose said:
I have never seen an engine with iron heads have the lash close up from cold to hot. I've seen some that opened up just .001-.002 but most open up .003-.004 and aluminum grows on average .006-.008.
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The exhausts will close up, but You'll never catch them at their minimum, You'd have to be in the valve cover checkin' while the loud pedal's down!!
 
Yes I've always ran aluminum heads, you guys are right, iron is probably a little different. It makes sense that the lash with iron heads would be a cold lash because it probably doesn't change much at all when hot.
Now onto the next question, why are people still running iron heads these days? Lol!
Just kidding.
 
ProSport said:
Yes I've always ran aluminum heads, you guys are right, iron is probably a little different. It makes sense that the lash with iron heads would be a cold lash because it probably doesn't change much at all when hot.
Now onto the next question, why are people still running iron heads these days? Lol!
Just kidding.
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Oh no you didn't:elmer:lol . I also now run aluminum heads, but I love that old iron nothing like smoken some modern car with 40+year old heads
 
ProSport said:
Yes I've always ran aluminum heads, you guys are right, iron is probably a little different. It makes sense that the lash with iron heads would be a cold lash because it probably doesn't change much at all when hot.
Now onto the next question, why are people still running iron heads these days? Lol!
Just kidding.
Click to expand...

Mainly, they are fast enough for me. I figure they will last another 50 years...
 
yellow rose said:
I have never seen an engine with iron heads have the lash close up from cold to hot. I've seen some that opened up just .001-.002 but most open up .003-.004 and aluminum grows on average .006-.008.
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They do close up, not sure how much. I always add .002 to the hot lash on initial startup and always have to tighten them up, hot and running.
 
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