Stock Magnum 5.2/5.9 camshaft w/carb?

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cudak888

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Title pretty much says all - despite the myriad of threads online about Magnum swaps, I've yet to find a discussion that determines whether the stock Magnum camshaft can be used in conjunction with a carburetor (as opposed to the 1992+ stock MPFI beer keg and TB).

That said - is it inadvisable to run a Magnum - either 5.2 or 5.9 - with a carb and the stock roller cam, assuming one simply wants stock streetability?

-Kurt
 
Interesting question! I really don't see that there would be a significant difference between EFI and carb as far as the camshaft and valvetrain are concerned. But, I'm subscribed.
 
I put a bone stock 5.2 magnum in my work truck 10 years ago, with a m1 dual plane intake and a thermoquad, works great....Only reason the hoods been open is for oil changes. Plenty of power, very good fuel economy.
 
300 HP Magnum crate motor came with a mild cam and M1 dual plane. Instructions say 750 carb and 1 5/8 headers.
 
The 5.2 cam is a little better.
 
I have a '00 5.9 in my car topped with a 650 Thunder on top of a RPM. Hooker Super Comps (1-3/4) into Dyno Max VT's. Chrome box ignition. I'm tuning it a slight lean.
It awaits a cam swap in the future, but for now it is a stock 5.9 cam.
Jet it, set it, forget it.

The factory FI keeps the inside of these engines really clean. Cross hatch hairs still visible after 80K. The carb running on the rich side and an ignition not getting all the fuel burnt will shorten engine life.
 
Interesting question! I really don't see that there would be a significant difference between EFI and carb as far as the camshaft and valvetrain are concerned. But, I'm subscribed.

From the comments I'm seeing, apparently not (and that's a good thing!)

My fear (and assumption) was that the factory Magnum camshafts may be ground with a short duration and wide lobe spacing, thus timed to capture a more accurate air/fuel mixture from the multi-port injectors vs. a longer duration to ingest the less-accurate atomization of fuel traveling through the runners from a carburetor.

Thing is, one of my neighbors - a Mopar ASE Master Tech of 30+ years - and the former owner and self-restorer of 3 Hemi cars and a few others - insists that a Magnum swap-to-carb requires a different cam. Not to say that he hasn't been wrong in the past, but his knowledge is not to be scoffed at (when someone can correctly relate all the necessary requirements of mating the externally-balanced Magnum 5.9 to an A904 off the top of one's head without the need to double-check a single book for reference, I tend to listen. You have to give the man some credit).

And - on the other hand - I must have read every single Magnum w/carb swap success story that exists on FABO, FBBO, and the Jeep forums out there, and not one stocker-to-carb swap that I've seen out there has involved a cam change - and they've all been successes (in fact, the only cam-related issue I can recall has been rtee007's Magnum 5.9 crate - and his cam failed due to a missing lifter dogbone, not due to the fuel delivery choice).

I put a bone stock 5.2 magnum in my work truck 10 years ago, with a m1 dual plane intake and a thermoquad, works great....Only reason the hoods been open is for oil changes. Plenty of power, very good fuel economy.

I believe it. I dare say the Thermoquad may also give you an advantage, as it may emulate the leaner mixture of the MPFI system.

300 HP Magnum crate motor came with a mild cam and M1 dual plane. Instructions say 750 carb and 1 5/8 headers.

Is the purple 300-horse crate cam identical to any other Magnum 5.9 sold off the dealership floor in a Ram/GC?

I have a '00 5.9 in my car topped with a 650 Thunder on top of a RPM. Hooker Super Comps (1-3/4) into Dyno Max VT's. Chrome box ignition. I'm tuning it a slight lean.
It awaits a cam swap in the future, but for now it is a stock 5.9 cam.
Jet it, set it, forget it.

The factory FI keeps the inside of these engines really clean. Cross hatch hairs still visible after 80K. The carb running on the rich side and an ignition not getting all the fuel burnt will shorten engine life.

That has to be the most comforting comment here in this thread, along with replicaracer43's.

I don't intend to run anything larger than a 600cfm Carter AFB/Edelbrock or a Summit M2008, and I'd like to run the '92/93 stock manifolds into a 2" or - at max - a 2.25" exhaust. Nothing earthshattering - I wound up with a pair of Flowmaster 2.5" exit pipes in this deal, and they are just too overwhelming for a stock look - even with turndowns.

All I want is something streetable with a bit more efficiency and internal reliability - which somewhat negates going through the trouble of doing an engine swap for yet another choked-up '60s 318.

-Kurt
 
That has to be the most comforting comment here in this thread, along with replicaracer43's.

I don't intend to run anything larger than a 600cfm Carter AFB/Edelbrock or a Summit M2008, and I'd like to run the '92/93 stock manifolds into a 2" or - at max - a 2.25" exhaust. Nothing earthshattering - I wound up with a pair of Flowmaster 2.5" exit pipes in this deal, and they are just too overwhelming for a stock look - even with turndowns.

All I want is something streetable with a bit more efficiency and internal reliability - which somewhat negates going through the trouble of doing an engine swap for yet another choked-up '60s 318.

-Kurt

IF you choose the Edelbrock carb, it is IMO you will like the Thunder over the AFB. Seriously consider this.
On the Summit carb, I have had the Holley version before Summit picked it up. Worked well enough I suppose. I had the small spread bore version. IMO, I thought it lack luster.

I also suggest a 2-1/4 inch pipe, NOT a 2 inch pipe for your dual exhaust. The engine can use it.
Muffler wise it is hard to decide on on what will be a quite enough muffler for anybody since it is so very objective. Though a good sounding muffler that is quite at cruise with exhaust manifolds that I have personally used and would do so again in a heart beat flat was the Thrush Turbo mufflers. I used them @ 2-1/4 off exhaust manifolds on a 360 engine. Now do keep in mind that the car had Hwy. gears @ 2.76 and a 26 inch tire.

What does that mean? It means low RPM's at Hwy. speeds that also translates into an engine spinning easy and not jamming the exhaust note out. We all know it's quitter at cruise than wide open throttle and 90+ mph.
 
IF you choose the Edelbrock carb, it is IMO you will like the Thunder over the AFB. Seriously consider this.
On the Summit carb, I have had the Holley version before Summit picked it up. Worked well enough I suppose. I had the small spread bore version. IMO, I thought it lack luster.

I also suggest a 2-1/4 inch pipe, NOT a 2 inch pipe for your dual exhaust. The engine can use it.
Muffler wise it is hard to decide on on what will be a quite enough muffler for anybody since it is so very objective. Though a good sounding muffler that is quite at cruise with exhaust manifolds that I have personally used and would do so again in a heart beat flat was the Thrush Turbo mufflers. I used them @ 2-1/4 off exhaust manifolds on a 360 engine. Now do keep in mind that the car had Hwy. gears @ 2.76 and a 26 inch tire.

What does that mean? It means low RPM's at Hwy. speeds that also translates into an engine spinning easy and not jamming the exhaust note out. We all know it's quitter at cruise than wide open throttle and 90+ mph.

Is the Thunder's adjustable secondaries that much of an improvement to balance out the mix on the Magnum?

What Summit carb was that? The one I'm thinking of is essentially an Autolite 4100 (Holley-produced-for-Ford) modified to support Holley jets and internals; thus allowing for tunability without bowl gasket leak concerns (and I've had it with 4160's and the leaky 1920 single-barrel on my Valiant):

sum-m08750vs_w.jpg


As for mufflers: Quiet like an Imperial is what I want. I used to have a pair of Lincolns with Ford's lousy smogged-up 400's and single exhausts, but both cars ran as silent as you could ask with nothing more than a basic turbo muffler with a resonator just before the tailpipe. Worked wonders to shut 'em up.

Exhaust is the factory 2" single right now, so anything is a step up. I'll still need an additional hanger bracket under the rear seat (not much of an issue). Stepping up to 2.25" hangers isn't a big deal though, as new ones are all over eBay.

Not sure what to do with my two spare 2" mufflers now that came with the car now. More expenses...yippee!

-Kurt
 
When you get your hands on the Thinder AVS you will see it is basically a modified top for the AFB. The adjustable door is a really good improvement over the counter weighted AFB door that can produce a bog. Also, the 650 rating, I think it is an Edelbrock marketing thing.
I maybe wrong.

Sorry, my bad on the carb description. It was a Holley spreadbore. Just like the pictures one above. I believe it was a 4010.

On the exhaust, use what ya got if price is of concern. It would be a improvement over a stock single 2 inch. Win win!
 
Rumblefish is absolutely dead on, on every comment. Have a Magnum 5.9 given to me, tossed the "barrel intake" set up. I love fuel injection, didn't fit the way, I wanted the car to run.
 
My fear (and assumption) was that the factory Magnum camshafts may be ground with a short duration and wide lobe spacing, thus timed to capture a more accurate air/fuel mixture from the multi-port injectors vs. a longer duration to ingest the less-accurate atomization of fuel traveling through the runners from a carburetor. -Kurt

Perhaps think of it this way... with the MPFI, the fuel is just being added into the air at a different point and in a different way and with more accuracy with the O2 sensor enabling the computer to manage the A/F more accurately. But the engine as a self powered air pump works the same, with an intake throttle plate used for power control; the carb interacts with this in the same basic way as the MPFI.

There MAY be considerations to optimize the cam a bit for taking advantage of the MPFI for economy or emissions, or to compensate for the carb operation, but you are still using the cam to manage cylinder filling, and balancing that against operating CR (DCR) over RPM.

BTW, your questions are good; I am following them as I help my son into his 1st V8 build experience. After us working on his 4.7L Dakota engine and us racing TBI turbo'd engines, he wants the relative simplicity of a carbed engine.
 
Perhaps think of it this way... with the MPFI, the fuel is just being added into the air at a different point and in a different way and with more accuracy with the O2 sensor enabling the computer to manage the A/F more accurately. But the engine as a self powered air pump works the same, with an intake throttle plate used for power control; the carb interacts with this in the same basic way as the MPFI.

There MAY be considerations to optimize the cam a bit for taking advantage of the MPFI for economy or emissions, or to compensate for the carb operation, but you are still using the cam to manage cylinder filling, and balancing that against operating CR (DCR) over RPM.

BTW, your questions are good; I am following them as I help my son into his 1st V8 build experience. After us working on his 4.7L Dakota engine and us racing TBI turbo'd engines, he wants the relative simplicity of a carbed engine.

Once again - makes sense. Feeling good about the swap now.

You know, I wouldn't mind leaving the factory MPFI on the engine (we had a '98 Dodge Ram Van with the little wheezer Magnum 3.9 in it; spent way too much time with that thing, and it turned out that the P/O had never done an oil change on it. Oh well, it was free), but I'm not a guy for EFI, nor do I care for the added expense and fustration of swapping to a different fuel tank and lines.

All things considered, swapping the intake and mounting a carb on top is probably the simplest way to get the engine to run reliably.

-Kurt
 
I have a 2002 360 out of a dodge ram. Has crosswind intake and 750 holley vac secondary. Thing is very very fun to drive and runs well. My .02 is run what you have you will be happy with the stock cam if you just want a street car.
 
I have a 2002 360 out of a dodge ram. Has crosswind intake and 750 holley vac secondary. Thing is very very fun to drive and runs well. My .02 is run what you have you will be happy with the stock cam if you just want a street car.

Good to know, though I've decided against the carb swap, strangely enough (for me, that is). After crunching numbers for the conversion vs. keeping the MPFI, I realized I'd be better off spending the extra cash towards a Tanks Inc. EFI tank and sender rather than swap manifolds and front accessories.

All I have to worry about now is whether the A904 holds up.

-Kurt
 
Is it worth putting in a 5.2 stock cam into a 5.9? Looking at cost of the entire vehicle build.....finished verses high hp lol
I own the 5.2 extra cam, but will it make a noticeable difference? I'm just not looking to but springs, retainers, new cam etc....
Maybe a regring mild if the 5.2 makes little difference.
Opinions please
 
I have heard/read that the 5.2 cam is a little "Hotter" and will help the 5.9 wake up a little. BUT, I do not know first hand.

I'd work it in conjunction with other HP parts.
 
just skimming through this, I thought I'd throw out that the original magnum cams don't have the nose for a mechanical fuel pump eccentric. You have to run and electric fuel pump or get the kit from Hughes (which has some complaints). Or........
Or....... you could get a cam from a 1989 or so LA 360. It's a roller cam and has the mechanical fuel pump eccentric.
 
Just put a high mileage 5.9 in my 70 Dart. Topped with and Edelbrock AFB 750. Headers, deep gears, Mallory ignition. Runs great! Never opened the motor up. Cam works just fine.
 
just skimming through this, I thought I'd throw out that the original magnum cams don't have the nose for a mechanical fuel pump eccentric. You have to run and electric fuel pump or get the kit from Hughes (which has some complaints). Or........
Or....... you could get a cam from a 1989 or so LA 360. It's a roller cam and has the mechanical fuel pump eccentric.

Funny you should mention this, as fate threw me a 1989 LA 360 out of the junkyard. The thing was in such perfect shape that I didn't even have to touch the bottom end...and indeed, it's running a mechanical fuel pump off the factory cam eccentric. Top end are a pair of stock Magnum heads off Craigslist (from a fellow who seemed to grow Dakota Sport 5.9's in his backyard).

The engine is done now and it runs great (looks great, too). Plus, I did an (warning: shameless plug alert) awesome build video including the junkyard pull and the installation:



fm6vwy.jpg


-Kurt

P.S.: Love your low-buck 318 horsepower build. Man after my heart. You rock!
 
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