Foreign valve springs in a Magnum

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stryker63

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Help!

I am worked through my first resto-mod project – a 1973 Plymouth Duster and have hit a snag.

I had to purchase new heads for my chosen power plant – a 5.2L Magnum bored 0.30 over, balanced and with a hotter cam (216/224 duration @ 50, 0.506 lift) – and the local engine shop suggested using Chevy LS1 valve springs. I was told that they were heavier than the stock springs, would install with no modifications to the heads, and were considerably cheaper.

Now I am in the process of finishing the valve-train, and here’s where the snag occurred. I was adjusting the valve lash and sheared off the last (figures) exhaust rocker bolt.

I am using OEM replacement rockers and pushrods (from Mancini Racing – a good outfit to deal with). Is this my problem, do I have a defective bolt, or was I adjusting the lash incorrectly? I was following the rebuild manuals for the Magnum engine and they advised adjusting the lash following tightening down the bolts to 21 ft-lbs.

Is anyone out there running LS1 valve springs in their LA or Magnum? I was told I am the only one in this area who is – scary.

Should I bite the bullet and invest in Harland-Sharp roller rockers, or is the OEM set going to work? Will I need adjustable pushrods?

Any info/advise would be greatly appreciated.

Thank you.
 
well from what I've read stock LS1 valve springs aren't anything to get excited about. I was looking for a cheap set of beehive springs for a project and LS1 springs popped up and they don't have much pressure IMO. I realize beehives work with lower pressure but they were only about 85 lbs. on the seat and 205 open. At least that's what the website I was on showed. To know if the springs are sufficient for your cam just look on the cam card and see what pressure's it requires.

Magnum engines never used adjustable rocker arms so I'm not sure what Mancini's is calling stock OEM replacements that were adjustable? If I'm not mistaken the only SB Mopars that used adjustable rockers were solid cammed 273's and 340 T/A engines. What size is the bolt you broke off? If your referring too the stock magnum 5/16" rocker hold down bolt something was drastically wrong if 21 ft. lbs broke it. For that matter most rocker arm adjusters are 5/16" and should be strong enough to handle 21 ft. lbs. of torque, providing your torque wrench is calibrated correctly.
 
What heads did you buy? Stock Magnum? Iron Ram/EQ?

There is no adjusting the lash on stock Magnum rockers, you just torque it down to 20 ft lbs.

Hughes' 1110 valve spring should be more than sufficient for your camshaft. If you have the heads off, I'd get the pockets machined for taller springs.It opens up the possibilities immensely.
 
Thanks for replying,

As far as I know, those were the stock OEM bolts for the Mopar Performance P4876050 rocker arm set.

I should clarify, the bolt didn't fail while I was torqueing it down, but rather while trying to adjust the valve lash - which was recommended by both "How to Rebuild your Mopar Magnum V8" and "How to Modify your Mopar Magnum V8" both by Larry Sheppard and published by HPBooks.

Neither specified exactly how to adjust the lash - I had read and heard elsewhere that you tighten down the bolt per the sequence given in the manuals until you cannot turn the pushrod - then another half turn.

Is this incorrect for Magnum engines?
 
LXguy said:
What heads did you buy? Stock Magnum? Iron Ram/EQ?

There is no adjusting the lash on stock Magnum rockers, you just torque it down to 20 ft lbs.

Hughes' 1110 valve spring should be more than sufficient for your camshaft. If you have the heads off, I'd get the pockets machined for taller springs.It opens up the possibilities immensely.
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They were stock OEM replacement heads.

Wish the author had been a little clearer on this whole valve lash thing. I'm a newbee to rebuilding motors and also on a budget and bought those books in an effort to avoid making a mistake!

Live and learn, I quess. Hughes Engines a good outfit to deal with?
 
If all the parts were stock magnum parts then yes you did it wrong. As LX guy and I said the stock magnum rockers are not adjustable. If you torqued it down to 21 ft. lbs. then tried to turn it 1/2 turn more that's why it broke. It sounds like what you were reading was how to adjust a chevy, not a Chrysler. Or perhaps a Dodge magnum engine with a adjustable conversion kit installed.

You also keep mentioning "setting lash" but by your description sounds like you have a hydraulic cam if you tightened it down until you couldn't turn the pushrod then tried to tighten it more. That's pre-loading the lifter, not setting lash. Setting lash is done on a solid lifter cam and is exactly opposite of pre-loading a hydraulic lifter.

If you have a hydraulic cam and do not have adjustable rockers (which again magnum rockers are not adjustable) you just torque down the rocker bolts to 20-21 ft. lbs and leave it at that.
 
Fishy is right on the money. If you are running stock magnum rockers then they are not adjustable and you just torque the rocker bolts to pre load the lifters and call it good.

I am running Chevy springs on my magnums, but I have adjustable 1.6 rockers, comp cams guide plates and push rods. Here is my set up that is adjustable.
 
Well, both books referenced above were somewhat vague about this whole valve lash thing.

It was implied that once the rockers were installed and torqued, then the lash is adjusted. However, I may have mis-read the section. Live and learn, I guess.

So, overall, using the "foreign" LS1 springs shouldn't be an issue? I'm still a little confused about that point.

Thanks again for all your help.
 
Yes, that's them.

I'm now concerned that I may have over-torqued some of the other bolts as well - should I bite the bullet and order new sets?

I'm wondering if this is a sign that I should have gone with Harland-Sharp roller rockers?

What does everyone think?
 
stryker63 said:
Yes, that's them.

I'm now concerned that I may have over-torqued some of the other bolts as well - should I bite the bullet and order new sets?

I'm wondering if this is a sign that I should have gone with Harland-Sharp roller rockers?

What does everyone think?
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I would not order new rockers, but you will need new bolts, because the bolts will stretch when over torqued. Those rockers may work for your set up. I may have missed it, but is the block an LA or a roller? Did the engine builder spec out the pushrods? Meaning did he measure for the correct length pushrod? If the pushrods are the correct length then I would run the factory rockers. My only concern is coil bind in your spring, because if I recall those springs on magnums are only good for around .510"-.520" lift (I may be wrong). Factory rocker are 1.6 ratio and with your .506" lift cam then that will put you well over that.
 
This is a '99 5.2L Magnum bored 0.30 over stock. Cam is 216/224 duration @ 50, lift is .506

The pushrods were not custom length - I was advised that stock length Magnum replacement pushrods (ie MP P5249662) would work.
 
This was a custom grind camshaft done by a cam shop here in Washington. The specs were provided in a conversation with a Comp Cams tech a few months ago.

Although when I check out the cam you mentioned, the specs are very similar.
 
stryker63 said:
Well, both books referenced above were somewhat vague about this whole valve lash thing.

It was implied that once the rockers were installed and torqued, then the lash is adjusted. However, I may have mis-read the section. Live and learn, I guess.

Once the rockers are torqued down the "preload" is set. Not the lash. Lash is clearance needed when your using a solid lifter cam. Preload is how much a hydraulic lifter is compressed. They are exact opposites. Just so your clear on that. And the books you read are correct that once the rocker bolts are torqued down the "preload" is adjusted correctly if the pushrods are the right length.
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So, overall, using the "foreign" LS1 springs shouldn't be an issue? I'm still a little confused about that point.

I don't know why the confusion. Springs are springs. Doesn't matter what brand they came off of if they are the correct size. But again as I said earlier you need to find out the spring recomendation for the cam and make sure the LS1 springs are up to snuff.
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Thanks again for all your help.
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I would definitely replace all the bolts as it sounds like you did it wrong and probably weakened them. No need to replace the rockers. Just the bolts.

As far as your thinking that maybe you should have gone with Harland Sharp arms what I'd have to say is (and I don't mean this in a mean way) since you didn't know how to properly adjust the stock rockers why do you think you would have done better with the Harland Sharp's? They install the same.
 
You are quite correct - I probably would have ran into the same issue with the Harland Sharp's. I know better now - thanks to all who replied. It's great to have a resource like this forum in order to successfully complete my project (my first, by the way).

The reason I was looking at the Harland Sharp set is because they are full rollers and would pick me up a few extra horses. They are quite expensive, and I think this is why I finally went with the OEM set.

My original goal was 300+ horsepower, but this should still be acheiveable with the hotter cam, 600-650cfm 4-bbl and headers.
 
UOP said:
Is this the cam you're using? If so, it's the same one I'm running in my 5.9 magnum with stock lifters, pushrods, and rockers. The springs I'm using are Mopar P5249464 springs, though they're not beehive units.

http://www.summitracing.com/parts/CCA-20-746-9/
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I have a set of those sitting here on heads, but my spring compressor is out on loan. damn. I would have handed them right over.

But yes they will work with all the stock gear with these springs.
 
green1 said:
I snapped that bolt off at 15# once. replaced all with grade 8.
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Hell, I snapped a damned comp stud made by ARP trying to torque it to spec. Those things are junk because they are a flawed design.

I decided to never deal with stud mounts on a magnum again and sprung for these...and the bolts they attach with gave me no probs whatsoever...They are a shaft that bolts to the head through a hard pedestal. And they are a nice solid setup for the magnum head.

These IMO are the best thing you can do for the magnum before dropping over a grand on a jesel setup. Very happy with them.

They are 1.65 ratio.

perfectadjustmentandpushrodlength.jpg

rollerrockersandbeehivesprings.jpg

rolleronopenvalve.jpg


th_readytorun.jpg
 
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