How does this 360 Magnum combo sound?

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sharpie

workin' stiff
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I know you have all seen and replied to these threads before, but I have a little different situation. In another thread I showed my recent acquisition:

DSCN2760.jpg


A 1998 Jeep 5.9L (360) Magnum long block. It was pulled with low compression at 149,*** miles, but I haven't pulled anything apart to see what the cylinders or pistons look like. It doesn't have an oil pump, oil pan, intake, carb, distributor, or any of the belt drive accessories.

This motor will be the eventual replacement for my Demon's slant. I'm going to convert it to an LA-style everything including a carb and LA accessory drive, so here's what I am looking for:

Daily driver motor
350-375 horsepower
375-400lbft torque
Low compression ratio for 87 octane (hopefully?)
Mild duration cam for street use

Here you can see I have done a little research:

DSCN2766.jpg


From this research, I've come to some conclusions. I am going to run:

KB107 Hypereutectic Pistons (or stock if they're in good shape)
Federal Mogul std bore rings/gaskets (comes in a re-ring kit)
Edelbrock RPM Air Gap Intake
Holley 650 Street Avenger
MP Timing case
MP Hi-Po Oil Pump
MP Electronic Ignition Distributor

What I'm still unsure about are the heads and cam.

With the heads, I am unsure what attribute is more advantageous: the larger intake runner of the stock cast-iron magnum heads (I've read 180cc?) vs the Edelbrock RPM head's 174cc, or the lightweight aluminum construction of the RPM heads vs the stock heavy cast-iron construction.

With the cam, I have read good things about the Comp XE268H, but will that keep me streetable? The police in my town already look awry at my car, and it only has the slant in it now. More unwanted attention is very bad.

Anyway, I'll update tomorrow with a screenshot of my full parts list and see how that goes, but does this sound good right now?

Oh, last question: is it going to be at all possible to run the motor on 87 octane? Would it require too low advance? Thanks
 
YES, you will be able to run 87 octane, even at 10.6:1 compression. Those big quench areas in the heads help the fuel/air burn way faster. It'll give you even more insurance if you round out (not just smooth) all the edges in the combustion chambers and clean up the port bowls. dgc333 built a Magnum 360 for his 'Cuda, he runs low-octane gas just fine and has his mechanical advance around 32-34*.
 
If the goal is 87 Octane, then I would definately go with the alum Edelbrock units, for their heat shedding / ping resistant design.
 
It's the dynamic compression ratio that determines octane need. That is a calculation that takes inot account the closing event of the intake valev, and the rod length. You want to run at max 8.25:1 dynamic for good power and no issues with 86 octane with iron heads. If you go aluminum, you can bump that up to 8.6:1 dynamic. If you need power brakes (vacuum), you'll want to build using the aluminum heads and a lower static ratio with a smaller cam. That will be all torque. Also bear in mind, hydraulic roller cams are different, and I would stay hyd roller in this build.
 
MOPEkidD-3 said:
YES, you will be able to run 87 octane, even at 10.6:1 compression. Those big quench areas in the heads help the fuel/air burn way faster. It'll give you even more insurance if you round out (not just smooth) all the edges in the combustion chambers and clean up the port bowls. dgc333 built a Magnum 360 for his 'Cuda, he runs low-octane gas just fine and has his mechanical advance around 32-34*.
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I would never try to run 87 octane with 10.6 compression, especially with iron heads and a 268 degree cam. That would not even run well on 91 octane. The intake size of a head shouldn't be a concern when comparing 174 to 180 cc stock. The edelbrocks can flow alot more air and will make alot more power and be more resistant to preignition and they're lighter too.
 
If you only want 350-375 hp. the stock heads will be fine.
You won't need 10.6 compression. I would build something similar to the 380hp crate motor specs.
 
Michaeluser said:
I would try a cam more like http://www.hughesengines.com/partDetail.asp?partID=10057&eTypeID=10
For the head I would go with the EDDY magnum with the magnum manifold. I like the vertical manifold bolts. Lastly the Magnum serpentine belt is WAY better then any v-belt. Less drag, less headaches. V-belt conversion on a magnum is a pain. IMHO.
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I don't know if you realize that the 98 Jeep block was MPI and reverse rotation accessories? Because of this, I am definitely not going to be able to keep the magnum manifold (though the motor came without a manifold anyway).
 
Yep! my LA/magnum hybred has 10.6:1 compression and runs on 89 octane just fine. I have 180-190 psi of cranking pressure with the Comp XR268 cam which I think is a great street cam, it pulls hard from 1500 rpm to over 6000 rpm and I can pull away without bucking or loading up the motor down to 1000 rpm. It idles comfortably at 600 rpm.

You will actually have more detonation resistance with the pistons at zero deck than you will with them down in the hole 0.030 or so. A better choice in pistons if you want a lower compression is to go with a step dish over a flat top. You can keep the good quench of a flat top and have enough chamber volume to get the compression down to the high 9's.

I recently tried a few tanks of 87 octane and under normal driving it's just fine but under hard acceration I got some detonation until it got well past 3000 rpm. I could likely tune it out but the car perfroms great with the timing I have and at a $1.60 additional per tank I will stick with 89.

BTW, my engine is making approximately 370 HP based on 102 mph trap speeds I get in the 1/4.
 
sharpie said:
I don't know if you realize that the 98 Jeep block was MPI and reverse rotation accessories? Because of this, I am definitely not going to be able to keep the magnum manifold (though the motor came without a manifold anyway).
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Yes I know it, but I meant the carb flange manifold.

P5007381 Aluminum Dual Plane Intake — 4-bbl Carb (5.2L/5.9L Truck Magnum/Jeep® Engines)
 
dgc333 said:
Yep! my LA/magnum hybred has 10.6:1 compression and runs on 89 octane just fine. I have 180-190 psi of cranking pressure with the Comp XR268 cam which I think is a great street cam, it pulls hard from 1500 rpm to over 6000 rpm and I can pull away without bucking or loading up the motor down to 1000 rpm. It idles comfortably at 600 rpm.

You will actually have more detonation resistance with the pistons at zero deck than you will with them down in the hole 0.030 or so. A better choice in pistons if you want a lower compression is to go with a step dish over a flat top. You can keep the good quench of a flat top and have enough chamber volume to get the compression down to the high 9's.

I recently tried a few tanks of 87 octane and under normal driving it's just fine but under hard acceration I got some detonation until it got well past 3000 rpm. I could likely tune it out but the car perfroms great with the timing I have and at a $1.60 additional per tank I will stick with 89.

BTW, my engine is making approximately 370 HP based on 102 mph trap speeds I get in the 1/4.
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Oh man thank you for the info! Any chance you have a detailed parts list? I am confused about which one: LA/Magnum to go with for lifters, timing case, chain, etc etc.
 
Insuring the life of your motor is worth alot more than $1.60 per tank. I still have my doubts you are at an actual compression ratio of 10.6 and not pinging with iron heads and a 268 cam. I run 10.7 with edelbrocks and a 286 solid roller, 32 total timing and have made it ping on 91 octane on a really hot day. If you are getting away with it that is great, but I wouldn't recommend having somebody else try it.
 
Sharpie said;
I'm going to convert it to an LA-style everything including a carb and LA accessory drive,
Click to expand...

If you run LA heads on a Magnum engine, you will need to drill the block for oil to the head. This passage is not drilled on Magnum engines.

Keep it simple and use Magnum heads and a Hyd. roller cam since you are allready set up for it. You can get mello grinds via request to Comp Cams, Crane cams, huges engines, etc.........

vioperblue72 If you only want 350-375 hp. the stock heads will be fine.
You won't need 10.6 compression. I would build something similar to the 380hp crate motor specs.
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Excellent Idea IMO, but probably more cam than you need for what you describe.
Though I'd skip the Edelbrock heads and just spend some of that money on preping the Magnum head at best and most. The OE head can deliever the power your asking for without porting. The smaller valve size of the OE head will keep velocity up and quick. This will provide a snappier throttle.

YES, you will be able to run 87 octane, even at 10.6:1 compression.
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No way, no how, unless you retard the heck out of the timing, at which point you'll dial out any performance.

I am confused about which one: LA/Magnum to go with for lifters, timing case, chain, etc etc.
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Pick one and run it. IF it were me, I'd run LA style stuff up front. Timing chain doesn't matter. There the same.
 
Well, I'd imagine it wouldn't be too bad with about 32* mechanical advance and around 10* initial. The whole point is that the chamber is efficient enough that you will need to run less timing in order to get the best performance.
 
Edelbrock has a RPM Magnum head and RPM Magnum intake.I would look for a Hyd roller cam in the 220* @.050" range on a 110lsa.
 
rumblefish360 said:
Sharpie said;


If you run LA heads on a Magnum engine, you will need to drill the block for oil to the head. This passage is not drilled on Magnum engines.

Keep it simple and use Magnum heads and a Hyd. roller cam since you are allready set up for it. You can get mello grinds via request to Comp Cams, Crane cams, huges engines, etc.........


Excellent Idea IMO, but probably more cam than you need for what you describe.
Though I'd skip the Edelbrock heads and just spend some of that money on preping the Magnum head at best and most. The OE head can deliever the power your asking for without porting. The smaller valve size of the OE head will keep velocity up and quick. This will provide a snappier throttle.


No way, no how, unless you retard the heck out of the timing, at which point you'll dial out any performance.


Pick one and run it. IF it were me, I'd run LA style stuff up front. Timing chain doesn't matter. There the same.
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If I was going to go with Edelbrock heads, they'd be the Magnum heads for a Magnum block. As fort the cam, what's the difference between grinds, and what's a "mello grind?" I am really new to this stuff so pardon the ignorance.

Would porting the heads be less expensive than the aluminum Edelbrock heads? That might be an option. However, because the Magnum heads are limited to .52 lift, aren't I limiting the HP? That was my main concern, because if I went with the Edelbrock heads and a comp cam, I could be in the zone where I want without a lot of other parts bought, I'd think.

On to the lifters/rods. I don't quite know how to pick them out. Hydraulic flat tappet? Solid? Hardened pushrods? I am lost.

And then my final question is about timing case vs. timing cover. Is this a timing 'case?'

http://store.summitracing.com/partdetail.asp?part=DCC-5249930&autoview=sku

Or do I just need one of those chrome covers? Hmm, maybe Borders Books will have one of those small-block books that I can go pick up...
 
As fort the cam, what's the difference between grinds, and what's a "mello grind?" I am really new to this stuff so pardon the ignorance.
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Mello? Thats on the other end of the scale of radical.

Each and every grind you see in a book/catolog is different in some way even if they seem to have the same numbers. They could have exactly the same numbers and a different grind/part number. When you think of the major headache you can have from this, STOP, do worry, theres a simple way that you can do this and still make a good choice without knowing nothing about cams.

I'll get into this with you in a minute.

Would porting the heads be less expensive than the aluminum Edelbrock heads?
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Yes, but you won't need to at the HP level you asked about. You can use the head as is. I mentioned "Prep the heads" before. This would be making sure the valves are right in the guides and the same height uptop the springs. Then furtherly, the "Prep" work would included a valve job with 3 angles and back cutring the valves.

That is more than enuff for what you want to do.
However, because the Magnum heads are limited to .52 lift, aren't I limiting the HP?
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No, not at all. Your limited in HP more so with the ports abilty to flow more air. True, valve lift has a lot to do with making HP, but at this level your asking for, you'll have no need to go that far with lift.

You could make 400 HP with a cam that lifts only .480 or less.

And then my final question is about timing case vs. timing cover. Is this a timing 'case?'
Click to expand...
Timing cover.

On to the lifters/rods. I don't quite know how to pick them out. Hydraulic flat tappet? Solid? Hardened pushrods?
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Lifters go with the cam and order them with the cam. Most times, there included.
IF your staying with the roller set up in your engine, just order the cam because you can reuse the roller lifters without a problem.

Cams come in few flavors.
Hyd
Solid
Then rollers in Solid or Hyd. The lifters are a Solid body for solid cams and Hyd. Bodied for Hyd. cams.

Keep the pushrods as well. No need to change them unless your going to make some real heavy duty power.

Or do I just need one of those chrome covers? Hmm, maybe Borders Books will have one of those small-block books that I can go pick up...
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The Chrome covers are nice eye candy, there smoother finish is to aid oil drain back. Skip Boraders, they probably won't have it, but I guess it is worth a check. Or, click here http://www.manciniracing.com/ and order up a Magnum engines book from MoPar and How to rebuild my small block MoPar from SA Design.

I am lost
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Read the books first and that will help light up the way. Then you wont feel so out in left feild.
 
A basic way to select a cam is by way of the RPM driving range you want to be in. READ the pages of Comp Cams, Crane cams, Huges engines, for there descriptions next to there cams.

Read the first pages of the catolog, they speak volumes and should be read at least once. They will tell you alot about how they do things and how things work.

IF you have some type of idea on the driving RPM range you want to be in, the listings next to the cams in the catolog will give an RPM range in which they operate in. The cams cruise range is somewhere in the middle area of the RPM range given.

Cranes listings clearly show this. Click here for an example page of a cam;
http://cranecams.com/?show=browsePa...=318 C.I.&partNumber=693941&partType=camshaft
Crane home page;
http://cranecams.com/

Knowing how well your head flows as per info given by a flow bench will also help you select a cam better. Knowing where the heads flow is best and where it stops flowing well would be great. Stock heads have a "Give me" to a degree and suggestions are limited unless port work is done.

Lets say we did some prep work to the heads and it flow well up to .480 lift. Well, guess how much lift your cam should be about. Thats right. .480.

Could you go past .480 lift if the head doesn't flow that well past that point, welllllll, yes, but lets not get crazy on this and just keep it simple. Get the cam that lifts as close to .480 as possible for max bennifit from the head.

The duration is were the RPM range, (Operation range) comes in. Note what the grinder says about the duration of there cams. It very well may not be the same as the next grinder, but you can count that is where it works.

Often, the grinder or shop will list what other parts should be used with a particular cam.
The basics are, Cam Compresion, carb. They also work with the cars weight, gear ratio and stall converter.

IF THERES ANY DOUBT IN SELECTING A CAM SPEAK WITH A PRO FROM THAT COMPANY!

Better to error on the side of caution and pick a smaller cam than one to large. Better to ask a pro than take a blind stab!
 
vioperblue72 said:
Insuring the life of your motor is worth alot more than $1.60 per tank. I still have my doubts you are at an actual compression ratio of 10.6 and not pinging with iron heads and a 268 cam. I run 10.7 with edelbrocks and a 286 solid roller, 32 total timing and have made it ping on 91 octane on a really hot day. If you are getting away with it that is great, but I wouldn't recommend having somebody else try it.
Click to expand...

Well the engine is at 10.6:1 compression, I measured everything when I built it. The block was machined so the KB107 flat tops sit at zero deck. The heads were cc'd at 64 ccs. The bore on the head gasket was 4.150 and had an advertised compressed thickness of 0.039". I didn't measure the valve reliefs in the pistons and went with the 5cc advertised by Keith Black. I did not account for the gap between the piston and the top of the rings but with the KB pistons it less than a cc. With the Comp XE268 cam I get a cranking pressure of 180-190 psi in all my cylinders, that is high but within the limits for pump gas.

There are other folks on this forum with essentially the same build and compression levels that also have no issues running 89 octane so it's not a matter of getting away with it, its how you build the engine. The key is the excellent design of the magnum head and a very tight quench which makes the engine very detonation resistant. Drop the piston down in the hole for 9.x:1 compression and you will have more detonation issues than at the higher compression.

FWIW, the top three competitors in the Mopar Muscle sb engine shoot out used iron magnum heads and they all had compression levels in the 11's to low 12's and ran on 93 octane pump gas. That's certainly pushing it but mid 10's is not an issue.
 
Well said Dave! I am one of the others on this board running a similar combo to Dave. I have a little bigger cam than Dave but not much. My pressures are at 180 give or take 5 lbs. I can run on mid grade pump gas with no problems, even when it's hot. This combo moves my Demon very nicely.

Jack
 
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