5.9L Magnum questions

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MechNerd said:
I'd like to get others input too, but from the perspective of what they would do if the $$ was coming out of THEIR pocket.
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That is the biggest crack I have ever seen on a Magnum head so far.
If you are not in a big hurry, you could wait and see if Speedmaster does their 40% off sale for black Firday or cyber Monday and grab a pair Magnum new replacement castings.
 
And the saga continues...anyone have any issue with getting Comp 901 springs to sit down on the stock seats? I kinda thought that these springs were drop in's on stock 5.9 iron heads. I measured the stock spring base dia. at about 1.316, the 901's are 1.494. Anyone have to take a grinder to open up the "ledge" created by the seat cutter to get their springs in? Looks like what it's gonna take. Any answers appreciated. Thanks.
 
you are 1000% not going to want to hear it, but i'd just spring the $700 for new iron heads or if budget/timeline allow, speedmasters or eddies.

how many sets of used up iron heads do you want to buy and dick around with till you get a set that'll work for you?
 
Waste of time to do a valve job on a cracked magnum head. That crack WILL open up, and eventually it will cause sealing issues. I'm ok with running them if it's a used engine with no obvious problems, but 100% against trying to repair that.
 
Yeah, I'll get another head- what really irritates me is the new Comp 901 springs don't fit. Every post I've read said they are "drop ins". Did I misunderstand?
 
When I search "Comp 901 spring magnum" this old Moparts post is one of the results. One guy says the 901s will work, another guy chimes and in and says they won't work without machining, another guy steps in and says they will work... Yup, that's the internet alright.

I bought the Hughes springs # 1110P when I did my build (I actually bought the entire HUG 1199 kit) because I couldn't find any other brands whose marketing specifically said their springs would work on a Magnum head.

Just doing some checking right now, Hughes says their springs are 1.440" outside diameter, and as you mentioned the Comp springs spec out at 1.494" OD. So I guess you would need to grind off half of that that 0.054" difference all the way around. Doesn't sound like much, but multiply that by 16 and it doesn't sound like fun.

Maybe you could sell your 901s and get the Hughes springs? The whole kit from Hughes is $240, or you could just buy the springs for $144.
 
If you do choose to grind or cut the spring seats, do not go any deeper. There is not much material thickness under that area. The easiest fit is the Magnum specific spring kits available like the Hughes Engines kit mentioned by @autopar3000 in the previous post.
 
For anyone that is considering using Comp 901 springs on 5.9 iron heads, they ABSOLUTELY DO NOT drop in to the stock machined seats. Ask me how I know...
 
the benefit of the hughes kit-- besides the springs fitting-- is that you get the retainers/locks that allow for more lift without machining the head.

if you're gonna machine the head for more lift, then just cut the spring seat and run the 901's
 
Are any of your stock pistons gonna be saveable? I tore down my 5.9 (similar build as yours that kept snowballing as more damage was uncovered) and found 1 damaged piston, so I’m looking to buy 1 or 2 stock pistons from someone.
 
macdrew77 said:
Are any of your stock pistons gonna be saveable? I tore down my 5.9 (similar build as yours that kept snowballing as more damage was uncovered) and found 1 damaged piston, so I’m looking to buy 1 or 2 stock pistons from someone.
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Yeah, I think 5 or 6 are fine. Let me know.
 
I had to go with the KB 107's, couldn't get the other pistons. While I have everything apart, what parts do I have to give the machine shop to get the rotating assembly balanced? Pistons and rods? Crank? I was trying to keep everything away from the shop. Damn.
 
MechNerd said:
I had to go with the KB 107's, couldn't get the other pistons. While I have everything apart, what parts do I have to give the machine shop to get the rotating assembly balanced? Pistons and rods? Crank? I was trying to keep everything away from the shop. Damn.
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When the shop did my 5.9 with KB107s, they wanted a set of rings, rod bearings, flywheel and balancer.
 
MechNerd said:
I had to go with the KB 107's, couldn't get the other pistons. While I have everything apart, what parts do I have to give the machine shop to get the rotating assembly balanced? Pistons and rods? Crank? I was trying to keep everything away from the shop. Damn.
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One of everything and anything that rotates and reciprocates.
Crank, rod, piston, rings, bearings, pin, locks, nuts, bolts, flywheel, harmonic balancer.
 
if your interested in a set of magnum heads I pulled a set off of a 2000 5.9 I bought the van for the motor for my dakota and when I pulled it someone had replaced the heads I bought eq heads and refigured them but the heads that were on it aren't cracked (YET) and I don't know where they were bought but I do know this motor ran perfectly so if your int in them $100 you ship i'll pack them and box them
 
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