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/advice would be greatly appreciated.

Thank you.

They will NOT drop on, the spring seat locator is too big and they will not go over it, secondly you can not machine the spring seat itself down or you will hit water, this means you can not get enough installed height for the taller LS1 spring. In order to use an LS1 spring you have to have the spring locator machined smaller to fit inside the smaller diameter spring and you have to find a longer (probably custom length)valve to get the proper installed height.

If you are carefull however, you may be able to run a chevy V6 valve spring for the 3.1 3.5 engines. If the .506 lift is with the 1.6 rockers you can probably get away with them but you need to check real carefully for coil bind. If the lift is .506 with a 1.5 and you are useing 1.6 factory rockers it will get into coil bind. I am running them right now on my 360 with a comp XE268 cam that has .320 lobe lift and factory 1.6 rockers. Those springs drop right on and work great to 6000+ a little more, I have not found valve float yet

A couple more things, you need the LS1 or V6 retainer, they are both the same, you need the magnum keepers, the V6 springs work great with the stock valves.