302 heads on a 360 magnum block

[TheCraigMachine]

Hey guys, i gots another question for the experts. In adding up the numbers on building another 318 shortblock to replace the one that i blew, i just cant keep myself from going back to this idea:

What IF i picked up a 5.9 magnum engine from the auto salvage, with say maybe a 100k miles or so, pulled the mag heads off and threw them in the trash (because of cracks) and slapped on my recently reworked, milled, and ported 302 heads with bigger valves and springs already installed?

I know the biggest obstacle to this swap is the oiling, but i already HAVE two sets of hollow pushrods AND rocker arms from late 80's roller 318s, which used a combination of shaft oiling and pushrod oiling.

I figure the pushrod oiling alone should be enough to oil the shafts and valve tips, right?

Id want to run the factory roller lifters with the comp cams 20-746-9 that I already have in my possesion, which will yeild a lower net lift running the 1.5:1 rockers vs the magnum's 1.6:1 rockers. Havent yet calculated what that will actually be yet, thou.

My biggest concern is the compression ratio. More specifically, the compression height of the 5.9 magnum pistions, and the CC's of the piston dishes, if any. My heads have been milled .050, which gives me an 'estimated' 60cc combustion chamber. I intend to cc the heads asa get them off my old motor.

Any thoughts on this idea? Am i crazy for thinking that this will work? In my mind, if i can keep the compression under control, I think this would make for a proverbial rocket engine in an early A body!

 

[Robbie2734]

I would think about selling the 302's and getting a new set of magnum heads, have the springs changed and bolt up and go!

 

[dustinmoran91]

They say 95% of the magnum heads on the road today are cracked and nobody knows any different. I dont see what the big deal is about it. My machinist said they dont recomend fixing it because its so un noticable. Unless its a major crack that causes coolant leaks or vacuum leaks id run them on my engines.

 

[OldmanRick]

The main issue you would have is drilling the Magnum block for rocker shaft oiling, which i understand is a tricky procedure.

Sorry, i just saw you mentioned pushrod oiling............Once the oil is pushed out between the rocker and shaft, the pressure between the two won't let much back under there just being gravity fed. I don't think i'd do it myself.

 

[rumblefish360]

What IF i picked up a 5.9 magnum engine from the auto salvage, --- I think this would make for a proverbial rocket engine in an early A body!

There, it's all fixed now. Perfect! Go for it. Install that Magnum engine in the car. Get the B&M flex plate for a Magnum to "LA" converter and be done with it. Then proceed directly to GO and burn rubber. :burnout: DO NOT FORGET to give the Chevy guys this icon ---> :finga:

 

[Robbie2734]

They say 95% of the magnum heads on the road today are cracked and nobody knows any different. I dont see what the big deal is about it. My machinist said they dont recomend fixing it because its so un noticable. Unless its a major crack that causes coolant leaks or vacuum leaks id run them on my engines.

You can buy a set of NEW heads for the cost of rebuilding the old ones..or fitting the 302 heads with the 1.5 rockers. They make a new casting that's thicker and ready to go. I just bought a bare set, they are very nice.

 

[TheCraigMachine]

There, it's all fixed now. Perfect! Go for it. Install that Magnum engine in the car. Get the B&M flex plate for a Magnum to "LA" converter and be done with it. Then proceed directly to GO and burn rubber. :burnout: DO NOT FORGET to give the Chevy guys this icon ---> :finga:

Haha, yeah that makes it pretty simple there! I just ordered my salvage 5.9 today. 90k miles and a really good price. Gettin the whole motor for the same price as it would cost to refresh my 318 shortblock. Im already having buyers remorse about it though, i feel like im abandoning my 318 heritage! Im scared im going to miss that high rpm 318 buzz!

 

[TheCraigMachine]

Why the F*** cant i find ANY drop in valve springs for the magnums??? you would think with the proliferation of LS motors and their conical valve springs, that someone somewhere would have figured out a combination of off the shelf parts that dont have to come from the mopar performance rapists! I mean, these motors have only been around for 20 friggin years now, why does it have to be such a bigass secret?

 

[66plyValiant]

Haha, yeah that makes it pretty simple there! I just ordered my salvage 5.9 today. 90k miles and a really good price. Gettin the whole motor for the same price as it would cost to refresh my 318 shortblock. Im already having buyers remorse about it though, i feel like im abandoning my 318 heritage! Im scared im going to miss that high rpm 318 buzz!

the magnum engine looks so close to the LA block you would nearly never know the difference except for the valve cover bolts; besides the magnum engines make better power stock then LA does stock

 

[Abodybomber]

Call Hughes Engines.Order 1110 springs,matching retainers.Use OE valve locks,done. Did this on mine,works like a charm.

 

[bad440]

There, it's all fixed now. Perfect! Go for it. Install that Magnum engine in the car. Get the B&M flex plate for a Magnum to "LA" converter and be done with it. Then proceed directly to GO and burn rubber. :burnout: DO NOT FORGET to give the Chevy guys this icon ---> :finga:

hats off to you rumble..rayer::supz:

 

[Abodybomber]

Lol!

 

[TheCraigMachine]

Magnum engines suck!!!

So i got my 99 model 5.9 with 90k from a truck that was running only 2 months ago delivered from one of the local auto salvage companies here in town. Everything looked good on the outside, disassembled it down to a long block, everything still looked good. Didnt want to pull the heads because i knew what id find.

Decided instead to do a leak down test on the cylinders to see IF the cracks in the heads were leaking. The very first one i tested was leaking SO bad thru the exhaust valve that the cylinder would not hold ANY pressure. At that point i went ahead and pulled the head to find out why. The number one cylinder was so full of rust from the cracked head leaking coolant into the chamber that the valve seats were too rusty to seal! The cylinder wall itself was freakin orange with oxidation. All total, 3 of the 4 chambers in that one bank had been leaking coolant from cracks in the head.

After seeing that, i reassembled the engine, and called the salvage company to come back and get it and refund my money, which they did without any fuss, thank goodness! Ive decided that used magnum engines, no matter how old or new, are worth little more than a rebuild core, and im not willing to put $700 worth of cast iron replacement heads on a 100k mile block.

Ill just do a full house rebuild on my little 318 LA block, and Ill know EXACTLY what kind of condition the motor in my car is in!

 

[Woods74]

Magnum engines suck!!!

This is nothing new man. Cracks develop in almost all of them. Magnum engines go forever, 300k negligible bore wear so 100k is just breaking in, partially thanks to fuel injection, mainly thanks to better metallurgy. Not to mention the roller cam, 1pc rear main, lighter rotating assembly, just to name a few pluses. Mine had 200k and and it was beautiful.

A few members are famous for beating junkyard high mileage Magnum blocks with good heads on here, LXguy and JoeDust451 come to mind.

To each their own. No need to badmouth. You jumped the gun on a great engine.

 

[TheCraigMachine]

This is nothing new man. Magnum engines go forever, 300k negligible bore wear so 100k is just breaking in, partially thanks to fuel injection. Not to mention the roller cam, 1pc rear man, lighter rotating assembly, just to name a few pluses. Mine had 200k and and it was beautiful. It has better metallurgy hands down, but to each their own. No need to badmouth. You jumped the gun on a good engine bro.

This I know for sure. My last company worktruck was a 2000 Ram 2500 5.9 with 300,000 miles on the clock when they sold it. The truck was driven every day, except when I had time off from work. It ate coolant, and used oil, but always ran.
If it had been a few days since it was started, it would miss and skip for a minute as it burned all the water out of the cylinder, then it would run fine. This situation is just fine for a beater that gets driven regularly, but not on a project vehicle that may sit for a month or more between starts.

Lets say youre out tooling around in your Dart/demon/duster/valiant, running her hard thru the gears and giving it hell. You go back home, park it in the garage, and then pull a three week on call schedule where you never have a chance to drive your personal vehicle, much less your project car (this is exactly how my work schedule works). Meanwhile, that cracked head is leaking coolant into the bore, rusting the rings and valve seats. Three months later, you jump in the car, twist the key, and score up the cylinder wall with rusty rings and the damn thing is missing on two cylinders because the valves wont seal enough to even build compression. This is exactly the senario that i dont want.

Dont get me wrong on my rant here, the magnums were a powerhouse for sure. Ive done two swaps myself with low mile engines that had less than 50k on the clock, both turned out great. But... These engines are over 10 years old now, they havent even been made since '03. The chances of finding a used one that doesnt need critical attention is very slim these days. You can figure in head replacement right off the bat.

Like I said, little more than a rebuild core.