Change in plans... Anybody used a "retro-fit" roller cam in a Magnum?

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MopaR&D

MopaR&D

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So originally I was planning to rebuild the 1970 318 I pulled out of my Duster just to get it back on the road but in light of the fact that I have a 5.7L Hemi I plan to swap in the car later I decided to take the least-cost approach to getting my Duster running again by just getting a used running Magnum engine for the short block so I can save more money for the Hemi conversion. I already have a good set of factory iron Magnum heads which I am thinking of getting ported and definitely a valve job done, also already have all the rocker gear and whatnot. Thing is I would like to keep the roller cam if possible but I know that requires an aftermarket cam with a longer snout to drive the mech. fuel pump, like one of the retro-fit style roller cams (I'm looking at specifically the Lunati Voodoo hyd. roller line). My main concern is, is it risky to try reusing the stock roller lifters which will surely have lots of miles on them for the sake of saving $300+ on a set of new lifters? Another question, how thick of head gaskets came on factory Magnum engines and would it be beneficial to use thinner ones if possible, since I will be replacing the heads anyway?
 
Hughes sells an adapter that goes on the cam for it to drive a mechanical fuel pump if that is your
plan. Yes why not reuse the roller lifters. You can have the cam in the engine now reground for
a mild performance application. I have done this before and it worked out good.
 
Cool thx guys, @66jim how much did it cost for a regrind? I'm looking at this cam from Lunati: Voodoo Retro-Fit Hydraulic Roller Cam - Chrysler 273-360 270/279 - Lunati Power I think their Voodoo roller line is pretty new, like released less than a year ago... I'm looking at them for now as I've ran the 256/262 Voodoo hydraulic flat-tappet before and it was awesome. Lunati lists MSRP for one of those cams around $300 so unless it would be a lot cheaper to get the Hughes adapter and regrind the stock cam I'd rather just get a new one...

@Lelo Dart was just reading Magnum-Swaps.com looks like they had similar success with that Mr. Gasket .028" head gasket. Stock is like .050" thick so that's a pretty good improvement. I also CC'd the chambers in my heads and they came out to 66cc, 3 bigger than factory spec but gotta run the calculator first and see what I get. Regardless as long as it's over 9:1 I'm happy, 9.5:1 would be ideal but kinda splitting hairs in this scenario.
 
That comp cam looks way better for a teen.
 
Just a heads up... The cam you showed has valve lift listed with 1.5 rockers. With Magnum rockers I get
INT- 0.549 EXH- 0.565
 
Yes add some lift for 1.6 rockers.
Comp retro series work fine in a mag.
They also make some smaller ones, pick one for your build.
 
I figure if I'm going with another engine it might as well be a 5.9L. 5.2s are cheaper and more plentiful around here but not by much and I'd rather have the extra torque than fuel economy. My Duster is more of a weekend-warrior road-race type build fyi.

I have a set of Hughes 1110 springs and their retainers, last I checked there was at least .560" clearance to the valve seal on the guide.
 
Stock original magnum roller lifters that are in good shape with no roughness or binding of the roller wheel and no rust or pitting/flaking of the roller wheel have worked well for me. A regrind cam is a good option to have but also requires new longer pushrods, evening up the cost a bit after all shipping and cam snout extension is factored in. I am not against them because you can get a nice custom grind that way too. Also, just for information, I installed one of those cam extensions on a 360 magnum about 10 or 12 years ago along with a Mopar short snout cam and it's still going strong to this day. I filed it a little to make sure it went together smooth and used red Loctite on the cam bolt threads and it has never come loose with a mechanical fuel pump the whole time. It's in my brother's car and gets driven plenty on summer weekends.
 
Make sure to check the piston to valve clearance while you have the heads off. I have .534 lift on the exhaust valves (regrind cam around 150$ or so after shipping), and I believe they might have hit the pistons because all the exhaust valves leaked when I replaced the valve springs with Hughes 1110 springs. They for sure weren’t leaking that bad when I put the engine back together. I don’t have any issues with the retainer to guide clearance with the 1110 springs and matching retainers. I’m running mr gasket .28 head gaskets, and the Hughes mech. fuel pump extension with it too and I haven’t had a problem with them after many hard miles.

I’m running the stock lifters with probably over 150k on them (junkyard engine). I checked them out before putting them back in the engine though. I’ve ran it past 5k rpm quite a few times and had it in traffic a buncha times. Ive heard them make noise during cold starts sometimes, but the engine runs strong to this day. But for sure, if you have the money I’d replace them with maybe some sealed power units. With advance auto discounts you can get them for probably less than 160$.
 
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I doubt the valves hit the pistons on a 360 magnum at .534" lift, even without knowing the rest of the cam specs and whether it was installed advanced, retarded, or straight to suggested spec. Every one I checked so far had plenty of extra valve to piston clearance in that lift range, especially on the exhaust side, when using stock pistons, heads, and valves. They all ran out of retainer to guide clearance well before piston to valve clearance was too close. Probably just needed a valve job, or at least a good lapping, and now the sealing issues are showing up. But always double check these clearances on each build, just to be safe.
 
Also, if you decide to go regrind and it’s the correct length for your application, Magnum Pushrods +.036 longer than stock here’s a set of cheap pushrods if you’re wanting to keep the cost down of the cam swap. As I’m sure you know there’s more expensive hardened options on summit racing or similar. I’m running the same length pushrod with mine.
 
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