Magnum 5.9 Magnum Rebuild: What can You get away with?

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Woods74

Woods74

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Hi all after much research and obsession, I've got a few questions to ask:

Engine Info/Purpose:

Junkyard '99 5.9 Magnum In good shape, water pump went out but all bearings, cams and pistons in good shape accept one... Broke the ridge between the compression and wiper ring on # 5.

This build will be mild, home ported heads, healthy cam, touch of awesomeness. Into a '74 swinger with 3.55 gears. Would like to keep it out of the machine shop as much as possible.

The BIG Questions:

Pistons:

In intrest of keeping this engine out of the machine shop as much as possible. What is the best course of action on replacing this piston? (set)

Options:

#1 Thought about going and yanking a piston/rod from another junker, that runs a risk...

#2 I've priced stock pistons and they seem to be more costly than if the project went aftermarket...

#3 If we go performance pistons, I've read good things about:

SP H116P
H405P
KB 362

Keeping it about 9.5:1. Milling the head .20 Giving the same effect. KB107 for a little more 10:7:1. Sound about right? Willing to go 89 octane MAX. Whats good here?

If we go the performance/aftermarket piston route, Will The engine have to be re-balanced? And since we're talking machine shop time:

Rods:

How much abuse will the stock rods take? I've read good things about SCAT rods. Whats Advised? Want to keep it budget without cutting throats. What can you get away with?

Thanks for the council. :read2:
 
You want to go cheap on pistons, but use scat rods?

If you're on a budget, go to Mopar, get one piston, and re-ring it.....
Put a bit more cam in it, mill the heads .020, and have fun on the cheap. I have ran many many many used pistons, one set, had over 200K on them, stock from 1970, now they are in yet another 318, that runs up and down the road every damn day.
If you go aftermarket cheap, the good ol sealed power pistons are good...... They have a middle of the road piston, thats pretty good.

You can get away with whatever works!
 
Although I don't know for sure, it is my understanding is that the factory 360 magnum pistons are a very good unit both in terms of strength and durability. Plus they were designed to work with the magnum head in terms of flame travel and quench which is evidenced by the magnum engines running on about 3 degrees less advance versus an LA engine... I have also heard that with a magnum head the crossflow is excellent which means that unless you're running nitrous, a split duration/lift camshaft is not necessary. Unless you are going to thrash the motor unmercifullly every time you drive it, I would also just get a new piston and rings. Mask everything off with plastic and just hone that one hole. Milling the heads means milling the intake or intake side of the head to really do it right and that puts you in the machine shop which you said you wanted to stay out of. Added compression will probably increase blow by and will magnify any other sealing/ring issues you may have. On your build 2 points of compression should be about 20 horsepower or 2/10 in the quarter. To really do it right you will be laying out some bucks but if you're doing this on an extremely low budget like I am, patch it up and let if fly.
 
Magnum motors use metric rings, which makes the rings much more expensive then standard rings. If you rebuild with new pistons, you should consider using an aftermarket piston due to sheer cost of the piston and ring combo, plus parts cost down the road for rebuild. I priced a set of replacement rings throught the parts stores when installing a 5.9 into my 97 Ram, and the rings alone were 130 or so bucks.

I vote for a .030 over bore, using aftermarket pistons (hypereutectic are ok for mild and basic performance build, cast will hold up OK as well, but neither LOVE nitrous)
Resize stock rods, ARP rod bolts and clean up stock crank. Keep the bottom end SOUND, but not exotic.

Spend the extra money in stuff that helps airflow and power (cam, intake, heads, exhaust, ignition, etc)
 
Same seller has a no name dual plane manifold too......... I'm thinking we should have a FABO 360 magnum on the cheap project! Find a DYNO near you, hell, I'll chip in a few buckaroo's even................... Cheap dish pistons, no name 190$ manifold.........

DOOO IIIIT!
 
I'd try to find another 5.9 Magnum in decent shape and go from there.

I'm really pleased with my junker.
 
dodgetkboy78 said:
Same seller has a no name dual plane manifold too......... I'm thinking we should have a FABO 360 magnum on the cheap project! Find a DYNO near you, hell, I'll chip in a few buckaroo's even................... Cheap dish pistons, no name 190$ manifold.........

DOOO IIIIT!
Click to expand...

Where, all i see on his sight is 1 item, the pistons, am i missing something?


I'm with Steve, i'd just re-ring it, new bearings, polish the crank, "maybe" new rod bolts, but that can add up with re-sizeing, Then install the thinner head gasket & mill the heads .020"-.025", this will give it a solid 9.5.1 compression, thats more then enough for a stout machine on pump gas, get a roller cam in the 520-530 lift range, .230s dur. @ .50 on a 108-109. On the heads, sure you can clean them up, but i'll bet there cracked between the valves, I layed out 900.00 for a set of RHS heads, $$$$ well spent, they flow really good OOTB.

Steve LXguy has a junkyard motor & is running 11.7s with it, i'm running 12.5s with less in my junker 360 magnum, these magnum shortblocks are very stout in factory form & hold up very well, the absolute ++++ to those "meteric" rings is there alot easier on the cylinder walls, My engine has a good 130K miles on it, you can still see the hone pattern from the factory & you can't even hang a nail on the upper edge of the bore.

Oh, as for how strong are the rods, well i'm juiceing mine with a 125 & it laughs at it, the only problem i've seen with mine on the bottle is 2 cylinders will spit oil passed the rings some, plus i see signs of minor blow-by on the VC, but you can exspect this on an engine with high miles, car still gains 10 MPH in the 1/8, ET sucks cause the car WILL NOT hook.
 
dustoff440 said:
Although I don't know for sure, it is my understanding is that the factory 360 magnum pistons are a very good unit both in terms of strength and durability. Plus they were designed to work with the magnum head in terms of flame travel and quench which is evidenced by the magnum engines running on about 3 degrees less advance versus an LA engine... I have also heard that with a magnum head the crossflow is excellent which means that unless you're running nitrous, a split duration/lift camshaft is not necessary. Unless you are going to thrash the motor unmercifullly every time you drive it, I would also just get a new piston and rings. Mask everything off with plastic and just hone that one hole. Milling the heads means milling the intake or intake side of the head to really do it right and that puts you in the machine shop which you said you wanted to stay out of. Added compression will probably increase blow by and will magnify any other sealing/ring issues you may have. On your build 2 points of compression should be about 20 horsepower or 2/10 in the quarter. To really do it right you will be laying out some bucks but if you're doing this on an extremely low budget like I am, patch it up and let if fly.
Click to expand...

I think it's the magnums chamber design that means less timing,rather than the piston.Just nit picking,lol..
 
Google Junkyard Jewel 5.9 Magnum. A bone stock 360 mag with m1 low rise dual plane, 750 Demon, and headers did 300 horses on the dyno with the stock cam. However, with the stock cam it had 420 ft lbs of torque. I basically have a completely stock 360 mag with the exception of a 512 lift cam and a crosswind dual plane air gap, mp dizzy, and a 750 Proform carb body. Assuming a 20 percent drive line hp loss, I am still thinking I will come in around 285 rear wheel hp and 370 ft lbs. Which should propel the car to 13.30 I saw another member who was selling a car with an almost identical engine package except he had a Hughes cam and a little less carb and his car dyoned at 276 horsepower.
 
JoeDust451 said:
Where, all i see on his sight is 1 item, the pistons, am i missing something?


I'm with Steve, i'd just re-ring it, new bearings, polish the crank, "maybe" new rod bolts, but that can add up with re-sizeing, Then install the thinner head gasket & mill the heads .020"-.025", this will give it a solid 9.5.1 compression, thats more then enough for a stout machine on pump gas, get a roller cam in the 520-530 lift range, .230s dur. @ .50 on a 108-109. On the heads, sure you can clean them up, but i'll bet there cracked between the valves, I layed out 900.00 for a set of RHS heads, $$$$ well spent, they flow really good OOTB.

Steve LXguy has a junkyard motor & is running 11.7s with it, i'm running 12.5s with less in my junker 360 magnum, these magnum shortblocks are very stout in factory form & hold up very well, the absolute ++++ to those "meteric" rings is there alot easier on the cylinder walls, My engine has a good 130K miles on it, you can still see the hone pattern from the factory & you can't even hang a nail on the upper edge of the bore.

Oh, as for how strong are the rods, well i'm juiceing mine with a 125 & it laughs at it, the only problem i've seen with mine on the bottle is 2 cylinders will spit oil passed the rings some, plus i see signs of minor blow-by on the VC, but you can exspect this on an engine with high miles, car still gains 10 MPH in the 1/8, ET sucks cause the car WILL NOT hook.
Click to expand...

Hey Joe, gonna roll the stock heads for now, there's a couple small cracks. Some porting will be played with. "Can't even hang a nail on it." is an understatement. Everything in the engine was great. Its been completely disassembled and honed. Since you all say such good things about these engines It will just be standard rebuilt.

Thinking of just going to a junk yard, pulling a piston and rod out, slapping it in there and calling it a day. If I really wanted to be a mechanicondriac, (balance issues?) I'll mount the new found piston on the rod here and run it. BAM. If you have a better idea, all ears.

Thanks! :-D
 
PoisonDart74 said:
Hey Joe, gonna roll the stock heads for now, there's a couple small cracks. Some porting will be played with. "Can't even hang a nail on it." is an understatement. Everything in the engine was great. Its been completely disassembled and honed. Since you all say such good things about these engines It will just be standard rebuilt.

Thinking of just going to a junk yard, pulling a piston and rod out, slapping it in there and calling it a day. If I really wanted to be a mechanicondriac, (balance issues?) I'll mount the new found piston on the rod here and run it. BAM. If you have a better idea, all ears.

Thanks! :-D
Click to expand...

The only thing i would suggest if your going with a used rod/piston from another engine IS, i would at least get the rod checked & make sure it doesn't need re-sized, i would also mic the piston too (especially the squirt), all should be good you would think, especially if the bearing looks good from that other engine, but as you know, all engines are not created equal, especially "once they have been run for some time", so have that rod/piston checked, because your puting it in another slot. I wouldn't put much in those heads, not even any port work, IMHO, a "cracked" head is a "junk" head, i'm sorry if i'm being blunt, sure use them, but just clean them up a bit & go, maybe just a set of springs.

Another option is like LXguy said, find a "good" running magnum & BAM, your good to go, they can be had for 3-400.00 bucks.
 
dustoff440 said:
Google Junkyard Jewel 5.9 Magnum. A bone stock 360 mag with m1 low rise dual plane, 750 Demon, and headers did 300 horses on the dyno with the stock cam. However, with the stock cam it had 420 ft lbs of torque. I basically have a completely stock 360 mag with the exception of a 512 lift cam and a crosswind dual plane air gap, mp dizzy, and a 750 Proform carb body. Assuming a 20 percent drive line hp loss, I am still thinking I will come in around 285 rear wheel hp and 370 ft lbs. Which should propel the car to 13.30 I saw another member who was selling a car with an almost identical engine package except he had a Hughes cam and a little less carb and his car dyoned at 276 horsepower.
Click to expand...

Don't know what your dart weighs, but when i calc. all mine in with a guess race weight of 3200, it said 290 RWHP for my 12.5 ET, If its your dart that your talikng about running 13.3s, either you have the weight "off" or your a heavyweight yourself, These 70-72 darts are not heavy. If your not over 200 lbs., your car should run 12s easy with that engine in a dart.

I weigh 145 lbs., my 71 is all metal, MS & brakes, raceing seats, i'm running 12.5s with less then that junkyard mule you listed, i shift at 5100 because thats all the cam has, its also with a 650dp, an 11" 2800 PTC & 3.73 gears.
 
dodgetkboy78 said:
But a piston from mopar, and use your rod.................
Click to expand...


If you buy me a 24 pack I'll go mopar parts...... That's a little steep for a stock piston in a junkyard dog.

Thanks for everyone's input, greatly appreciated! :cheers:
 
JoeDust451 said:
...... Then install the thinner head gasket & mill the heads .020"-.025", this will give it a solid 9.5.1 compression, thats more then enough for a stout machine on pump gas, get a roller cam in the 520-530 lift range, .230s dur. @ .50 on a 108-109. On the heads, sure you can clean them up, but i'll bet there cracked between the valves, ....
Click to expand...

The magnum heads require the guide to be cut down when you get to the .525" lift range. Also, a cam with much over .450" of lift will require new springs and retainers. The magnum head uses a spring with a smaller OD than an LA head so the choices are some what limited and they cost more. None of these items make for a low cost build.

Considering the crate Magnum 360/380 typically dyno'd in the 410-420 HP range with a stock bottom end and heads I wouldn't get involved in milling the heads. Do a search over on Moparts and there is a number of threads on using GM 3800 V6 springs on magnum heads as a low cost spring upgrade good to about .5" lift.
 
dgc333 said:
The magnum heads require the guide to be cut down when you get to the .525" lift range. Also, a cam with much over .450" of lift will require new springs and retainers. The magnum head uses a spring with a smaller OD than an LA head so the choices are some what limited and they cost more. None of these items make for a low cost build.

Considering the crate Magnum 360/380 typically dyno'd in the 410-420 HP range with a stock bottom end and heads I wouldn't get involved in milling the heads. Do a search over on Moparts and there is a number of threads on using GM 3800 V6 springs on magnum heads as a low cost spring upgrade good to about .5" lift.
Click to expand...

Did you read his post, he wants a healthy cam, so that rules out the V6 springs, If i'm not mistaken, the 380 crate 360 uses FT pistons, not factory dished, so theres the increase in compression, he also mentioned about milling the heads some, Me personally, i wouldn't put a dime in a cracked head, he needs to get with LXguy for some tips on what he did with his magnum heads, i know he raised the compression some on the cheap & doesn't have a **** load in them. You can also use the 1110 springs from hughes engines, either way, i'd rather put alittle more $$ in a "good" set of Magnum heads over any LA head.

If you want to talk low cost, Its funny, out of ALL my SB builds, this ones been the cheapest & sure enough the fastest, i have about 1800.00 in the entire engine (includeing its purchase), & thats with a new set of RHS heads for 930.00 bucks.
 
Hughes offers retainers for about 60 bucks that provide an extra .125 over stock making it not necessary to cut the head with a cam over .525.
 
I was not aware that the crate engines had a different piston than the production engine. I always thought they had the same 9:1 compression as the production engine.

I did read his post and he wants to avoid the machine shop too so going past .5" lift on magnum heads is going to require a trip to the machine shop to have the guides cut down. If you stay under .5" then the GM 3800 V6 springs are a cheap option and you can use the stock magnum retainers. The Hughes spring will require retainers as well as the springs. I was just trying to provide some options so he can decide whether to spend money on the heads or pick a cam that will work without head work.

FWIW, I have stock magnum heads with the expeception of valve springs and retainers on my 360 LA block with a relatively mild Comp XE268H hydraulic flat tapet cam. I run mid 13's at 102 mph with it. If I was ever to take the time to sort my traction issues on launch and get the 60' times down under 2 seconds I would have a 12 second car too.

The RHS heads are certainly the way to go for the price compared to spending a bunch on machine work and porting of stock magnum heads. I have a fresh 30 over 340 sitting in the garage that I plan to put a 4" stroker crank in and use the RHS heads on.
 
dustoff440 said:
Hughes offers retainers for about 60 bucks that provide an extra .125 over stock making it not necessary to cut the head with a cam over .525.
Click to expand...

I believe that .125 is for the installed height of spring. The center of the retainer has to be in the same relative location in order for the locks to engage the groove on the stem properly.
 
I meant, just find a different 5.9 that's in good shape instead of rebuilding that one. They're out there.

I put the EQ heads from hughes on my engine. All the issues from the stock magnum heads gone in one fell swoop, and they flow better too.

A junkyard Magnum isn't a cheap build in absolute terms, but its a helluva lot cheaper than dragging the old 340/360 to the machine shop for a rebuild. I've got $2800 or a little less in my motor, air cleaner to pan, gaskets included. That includes the Hughes heads, Kevko pan, and custom hydraulic roller camshaft.
 
Dare I say anything or will I get flamed for being a magnum fan once more,lol? I agree with everything typed so far,only the extra expense of a magnum is out of proportion. If your smart,wait for sales,shop around etc you will spend no more on the magnum than an LA. Less if you chose to go with chevy valvetrain stuff.

Heres one way how to drill the magnum heads to accept LA intakes.

http://www.bigblockranger.com/Jig.html
 
needsaresto said:
Dare I say anything or will I get flamed for being a magnum fan once more,lol? I agree with everything typed so far,only the extra expense of a magnum is out of proportion. If your smart,wait for sales,shop around etc you will spend no more on the magnum than an LA. Less if you chose to go with chevy valvetrain stuff.

Heres one way how to drill the magnum heads to accept LA intakes.

http://www.bigblockranger.com/Jig.html
Click to expand...

You won't get flamed by me!
 
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