#7---Junkyard Jewel / Make Mine a 5.9 | 7/23/2015 |
Junkyard Jewel / 5.9L Magnum Engines –Make Mine a 5.9
Dave Hughes , July 2015
We have seen some interest in the two articles that ran in Hot Rod magazine about building up 5.9 Magnum engines. We are disappointed in the build-ups to say the least. We respect Hot Rod Magazine (I personally started my subscription in 1955) but these two build-ups have not treated the 5.9’s very well. It looks like they just needed to fill some space in the magazine and they threw together some parts that were just laying around. I’m sure they would not treat an LS Chevy that way!
Never-the-less, we charge ahead for the Mopar faithful. The idea of making a carbureted engine out of a fuel injected junkyard engine is very viable and can easily be done with the right parts. The problem with the Hot Rod article from 2008 with the 448HP engine (See dyno chart below) is that it would be a very uncomfortable engine to drive on the street. It had 129hp more than the stock engine but you had to wind it up 1400rpm more to get it. Up to 4000 rpm the stock engine had a better horsepower curve.
On the street torque is king, big time, and in the Hot Rod article the “stock” engine had more torque than the “good” engine up to 4,000 rpm, again. It’s a safe bet that an engine like this would be best with a 4.86 gear and a 4 speed or a 4,000 stall and a trailer to get it to the track. Can you say, NOT STREET FRIENDLY? Sure, I knew you could. The Hot Rod engine appears to be a race only set up. The cam used is typical of first time engine builders who ask, “What’s the biggest cam I can put in it?”. Well, this is the result. Top end power that is not driver friendly. In fact, a smaller cam, a street friendly stall and gear and you could probably blow the doors off of the Hot Rod engine in many situations and still go street cruising.
Here is what we choose to make a “Junkyard Jewel” of our own.
1. Heads: The original equipment heads are more likely than not cracked. We estimate that about 90% of these heads are cracked. It is possible to repair the cracks but we do not think these heads are good candidates for the repair. Our choice for a replacement head is the EQ (EngineQuest) Iron Ram head (Part #4670B). This head is available with either the LA or Magnum intake bolt pattern. There is a 2nd choice for more of a mixed family (not blended family) of engine parts. The INDY LA-X head (Part #20300A). This is the head that looks like a magnum head. It uses Magnum sized valves and Magnum parts and a Magnum style combustion chamber but it uses the LA shaft mounted style rocker arms with the shaft oiling system. It also uses LA style intake and the LA style valve covers. So you could use all of your LA parts on a Magnum block with the INDY heads as long as you have the block drilled for LA type oiling. Some of the early Magnum blocks are already drilled. Either of these heads are available with oversized valves and porting. You can see all of the options in the Magnum section of our website. Keep in mind that you can use the 5 bolt LA style valve covers on heads with the 10 bolt Magnum valve cover bolt pattern.
2. Intake manifolds: I don’t know how many times this has to be proven but if most of your driving is below 5,000 rpm there is only one type of manifold to use, a dual plane. If you are living at the drag strip and you live for a quicker E.T., then maybe a single plane. We use and recommend the Edelbrock RPM AirGap # 7577. Mopar Performance seems to be out (or wants out) of the high performance market for the older (Non Gen 3 Hemi) V8 engines so their intakes can be hard to find, like a lot of their parts. There are only 2 manifolds of note available with the Magnum bolt pattern, The RPM Edelbrock # 7577 and the Mopar Performance P5007380, which has a spread bore carb flange. If you order our EQ (Iron Ram) heads # 4668-4675B-4680-4680SP or any of the Indy LA-X heads, they will all use the LA intake bolt pattern of which there is a multitude of manifolds to choose from.
3. Camshaft: The original 5.2/5.9 Magnum engines used hydraulic roller cam and lifters and we see no reason to change to a flat tappet cam. One of the most important things to remember when choosing a cam for a carbureted engine is that the LSA (Lobe Separation Angle) should be tightened to 110º or tighter, as opposed to 114º+ for OEM fuel injection. The tighter the LSA the more torque the engine will produce and the more cylinder pressure it will have (which also helps torque). A street cam duration will be in the 208º to 224º @ .050” lift on the intake. A hot street cam duration would be in the 224º to 236º @ .050” range. If you think you need any more that that give us a call.
4. Ignition: Any high performance aftermarket distributor, like MSD, Pertronix, Accel, etc…. would be a better choice than the Mopar distributors. The old Mopar OEM distributors have a poor design in which they have a double advance curve that must be corrected. Now days with so few shops doing distributor work, you would be better off with a true performance distributor. And no, the Magnum distributor cannot be, cheaply, converted to work and that’s a good thing.
5. Timing Cover: Say what? Who cares about the timing cover? Well, you do if you are going to run a carburetor and a mechanical fuel pump, The Magnum timing cover has no provisions for a mechanical fuel pump. So now you must choose between an electric pump and regulator or switch to the LA timing cover, #1824 or P5249930AB (if available) and a mechanical fuel pump. But, with the short snout roller cams there is no room for a fuel pump eccentric, but don’t worry, Hughes Engines has your back. We have cam snout extensions (#7013) and the eccentric (P4120484) that you will need to get the job done. The LA timing cover cannot use the Magnum water pump for 2 reasons. #1 is that it won’t fit and #2 is that it turns the wrong direction. So, if you want to use the Magnum water pump and the serpentine belt system you must go to an electric fuel pump. Or, we’re not finished yet, you can use the LA fuel pump, water pump and timing cover and a March # MPP10300 serpentine pulley set up.
So, think you’re done now, think again blowby breath. If you are planning on switching your Magnum truck over to a carb with the idea of using the original in tank electric pump be advised that it pumps nearly 50psi and will require a return line along with a pressure regulator.
The bell housing bolt patterns are the same on both blocks as are the crank flange bolt patterns.
Links to articles:
Hot Rod Magazine May 6th, 2008 “Small Block Mopar Engine- Junkyard Jewel 5.9L Mopar Magnum –Engine Build-up”
Hot Rod Magazine February 2nd, 2015 “ 5.9L Magnum Engines –Make Mine a 5.9”
Hughes Engines #4--- Building-Up Magnum Truck Engines (1993-2003)
Dyno Results*
Mopar Magnum 360
SuperFlow 901 engine dyno
STP correction factor
|
RPM
|
Base TQ
|
Mod TQ
|
Base HP
|
Mod HP
|
|
3,000
|
398
|
37.31
|
228
|
212
|
|
3200
|
410
|
373
|
250
|
227
|
|
3,400
|
419
|
390
|
271
|
253
|
|
3,600
|
424
|
402
|
290
|
276
|
|
3,800
|
420
|
408
|
304
|
295
|
|
4,000
|
412
|
412
|
314
|
314
|
|
4,200
|
396
|
420
|
316
|
336
|
|
4,400
|
381
|
431
|
319
|
361
|
|
4,600
|
362
|
432
|
317
|
378
|
|
4,800
|
346
|
434
|
317
|
397
|
|
5,000
|
328
|
434
|
312
|
413
|
|
5,200
|
298
|
433
|
295
|
429
|
|
5,400
|
274
|
426
|
282
|
438
|
|
5,600
|
-
|
417
|
-
|
444
|
|
5,800
|
-
|
406
|
-
|
448
|
|
6,000
|
-
|
361
|
-
|
412
|
*Dyno results as shown on HotRod magazines website.
Strip only combo.
Hughes Engines suggested combo
Heads - 4675B
Intake - 7176
Cam - SER2630ALN-10
Carbeurator - QFT HR680 VS 680CFM
Headers - 1 3/4"
Distributor - D7141710
Rockers - 1550
This should produce:
415 hp@5500 rpm
460 tq@4000 rpm
420 tq@4000 rpm
350 hp from 4000-6000 rpm.
400+ from 3200 to 5600 rpm
This is a nice hot street combo!
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