360 Magnum building on an existing bottom end

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65TTCuda

65TTCuda

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I have a 96 360 magnum engine with less than 100,000 miles on it and the engine runs good. Can I just build on the existing bottom end? My plane is a big Muta Thumpr hyd. roller cam, stage 2 EQ heads 2.02 in. 1.6 ex., roller lifters and rockers, Offenhauser tunnel ram intake, dual Holley 450cfm or Edelbrock 500cfm carbs, MSD distributer and 6AL ignition box, A-833 4spd and an 8.75 sure grip rear end. Do you think the existing short block will hold together in this setup. Welcoming all reasonable info and comments.
 
At a bare minimum, check the bearings- you'll have to replace the pan and pickup anyways.
Do a compression/leakdown test before you tear down the engine to verify ring seal.
Under 100k miles is nice, but doesn't speak to how the engine was treated during those miles.
Make sure the Offy tunnelram will fit your magnum heads- Magnum and LA intakes have different bolt angles.
Edit:
And remember that you can't use ANY LA (273,318,340 or 360) flywheel on a 5.9 Magnum. You need to either get an aftermarket flywheel or rebalance the LA flywheel to 5.9 specs. Lots of threads on this in the Magnum Swaps forum.
And make sure your crank is prepped for a pilot bushing/bearing.
 
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I would, i got a stock bottom magnum with a upgraded cam with matching springs .520 lift. runs very quick those motors are tough. Just pick up a spare bottom end 5.9 to have on the side just in case, You can build it as you go along and if needed you can swap all your top end stuff right over.
 
I plan to remove the oil pan and replace the stock oil pump and pickup with a high volume, and to check the condition of the cylinder bores. The EQ heads come in a version that accept the LA style intake bolt angles. I bought the engine used from a ram pickup, so I don't really know how it was used, but I did hear it run a while before I bought it. Only paid $250 for the whole engine.
 
Do it right the first time, cruise instead of working in it. Otherwise you will always have a question mark in the back If your mind.
 
I'm looking at purchasing a Leod flywheel and clutch kit capable of at least 500HP. and since the engine was an automatic I would have to get a proper pilot bushing for it. I have a Lakewood scatter shield for it and plan on using a hyd. slave cylinder and clutch master cylinder for throughout bearing actuation.
 
So I have the intake and carburetors and the ignition bits. Does anyone have a preference on head or cam choice for this build. keep in mind that budget is a factor. I saw close to what I want to build on a web page called Dyno proven 360 packages, Package 9 is kind of where I want to be.
It states (360 rebuilt with 10:1 compression flat top cast pistons, original crank turned .010"/.010", rebuilt factory rods. Factory windage tray installed. 2.02" heads with competition valve job and ported to flow 260 cfm. Intake, port/gasket matched. Holley H.P. 750 (.076" front, .080" rear jets). Large 1 3/4" primary tube headers. Comp Cams 305AH-8 camshaft with .525"/.540" lift and 305/312 degree advertised duration, 253/260 degrees @ .050", 110 lsa, installed at 108 intake centerline. 495 h.p. @ 6,000 rpm 500 lbs. of torque @ 4,500 rpm)
I realize this isn't exactly what I'm building, but with the motor being almost full roller with the tunnel ram and dual carbs, I think I can hit or exceed those numbers. I also planed for 3.73 gears in the rear end. Do you think they are to low or not low enough, considering it will be mostly a street show car. I am building it in a 60's Gasser fashion.
 
65TTCuda said:
The EQ heads come in a version that accept the LA style intake bolt angles.
Click to expand...
Not any more, they quit making those a number of years ago. Maybe someone still has a set stashed away that they'd be willing to part with, but that's a longshot. Stock pattern magnum heads can be redrilled to LA pattern, though; if you can find a shop willing to do it. A member on here has a jig he loans out to do the job yourself, but don't know the status of it at the moment. A quick search on the Magnum Swaps forum should tell.
 
On a budget....Get the cam reground by Oregon Cam Grinders. Give him your goals. Inspect, clean and Re-use lifters. CR is more like 9.2:1 with thin head gasket and stock pistons. Inspect bearings. As the Professor said.....Heads are a question mark. Home port factory heads if in good condition (no cracks) but will have smaller valves. Use Hughes 1110 valve spring kit. Stick with factory (non magnum) ignition.

Edit....I believe Indy makes a 2x4 Modman intake with carbs and linkage for Magnum.
 
Whether or not a high mileage engine stands up to the listed modifications will depend on how well the engine was treated in it's previous life, regular oil/filter changes etc.
I can see a lot of Hail Marys being involved....
 
New rod and main bearings would certainly be in order being the engine is 25 years old. Time is just as hard on those bearings as is an easy life.

There is acids and contaminants in the engine oil that work to degrade those bearings over time. The real question is what are the cam bearings going to look like?

If it is still available to run, an oil pressure test with a gauge will be a good thing to do to tell how tight the bearings are yet.

Bring the engine up to temp and see what the oil pressure reads at an idle, that will tell a lot.

Rock the crank back and forth and watch the distributor rotor to see how much slack is in the timing chain. That can give a clue too on the life the engine has had and how frequently the oil was changed.

20200608_195334.jpg

90,000 miles on this engine. Still pulled a few rod caps and one main. Bearings looked good, rear main not leaking.

So it got put back together with a new stock oil pump, fresh stock heads with the original lifters and roller cam and new roller timing chain.

Still running good to this day, got away with it on this one. Others may have had a tougher life, so you have to check them out.

Certainly what the lobes on the cam look like can tell quite a story too. Flat tappet cams will start going flat after that much time, just from normal wear.
 
65TTCuda said:
So I have the intake and carburetors and the ignition bits. Does anyone have a preference on head or cam choice for this build. keep in mind that budget is a factor. I saw close to what I want to build on a web page called Dyno proven 360 packages, Package 9 is kind of where I want to be.
It states (360 rebuilt with 10:1 compression flat top cast pistons, original crank turned .010"/.010", rebuilt factory rods. Factory windage tray installed. 2.02" heads with competition valve job and ported to flow 260 cfm. Intake, port/gasket matched. Holley H.P. 750 (.076" front, .080" rear jets). Large 1 3/4" primary tube headers. Comp Cams 305AH-8 camshaft with .525"/.540" lift and 305/312 degree advertised duration, 253/260 degrees @ .050", 110 lsa, installed at 108 intake centerline. 495 h.p. @ 6,000 rpm 500 lbs. of torque @ 4,500 rpm)
I realize this isn't exactly what I'm building, but with the motor being almost full roller with the tunnel ram and dual carbs, I think I can hit or exceed those numbers. I also planed for 3.73 gears in the rear end. Do you think they are to low or not low enough, considering it will be mostly a street show car. I am building it in a 60's Gasser fashion.
Click to expand...
Sound Good, I have a similar
JoePole1 said:
On a budget....Get the cam reground by Oregon Cam Grinders. Give him your goals. Inspect, clean and Re-use lifters. CR is more like 9.2:1 with thin head gasket and stock pistons. Inspect bearings. As the Professor said.....Heads are a question mark. Home port factory heads if in good condition (no cracks) but will have smaller valves. Use Hughes 1110 valve spring kit. Stick with factory (non magnum) ignition.

Edit....I believe Indy makes a 2x4 Modman intake with carbs and linkage for Magnum.
Click to expand...
Ckeck retainer to valve guide clearance, my magnum has only .20 thousandths clearance with Hughes springs/ retainers from the bottom of the retainer to the top of the valve guide.
, with A 512 lift cam
 
Ckeck retainer to valve guide clearance, my magnum has only .20 thousandths clearance with Hughes springs/ retainers from the bottom of the retainer to the top of the valve guide.
, with A 512 lift cam[/QUOTE]

What heads? I have EQ's and they look good but didn't measure.
 
I put a Oregon Regrind Cam in my 198,*** mile 5.9 with Hughes spring kit. I didn't even pull the pan, runs great. It's good to look at the bearings, but if it's a KNOWN good engine, then I might not even bother, and I'd use the original oil pump in a heart beat. The bearings to worry about are the cam bearings, seems the magnums like to chew on them a bit.
 
JoePole1 said:
Ckeck retainer to valve guide clearance, my magnum has only .20 thousandths clearance with Hughes springs/ retainers from the bottom of the retainer to the top of the valve guide.
, with A 512 lift cam
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What heads? I have EQ's and they look good but didn't measure.[/QUOTE]
Stock Unmolested 92 magnum
 
Post the flow numbers of the stage 2 eq's.

Heads are what the 360 needs the most .

I put ported heads on my bone stock 5.9 and its whole different motor...way more power.
 
At the vey least, check the upper rod shells. On account of the plenum plate under the intake, the Magnums detonate by pulling oil into the intake charge. Almost every Magnum I've torn apart, the uppers show a little copper because of this. Crank is usually OK with a polish.
 
408 swinger said:
At the vey least, check the upper rod shells. On account of the plenum plate under the intake, the Magnums detonate by pulling oil into the intake charge. Almost every Magnum I've torn apart, the uppers show a little copper because of this. Crank is usually OK with a polish.
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I also found this with the high-mileage 5.9 I pulled from the yard. Replaced the rod bearings, left everything else as-is and bolted on all my power parts; still runs great after 8,000+ miles. I also agree with @318willrun on checking the cam bearings, mine looked pretty bad but I was too lazy/cheap to change them out. Nothing to lose sleep over as like I said mine runs great but "while you're in there" and all that...

@65TTCuda check your block, if there is a passage drilled on each bank going from the cam up to the deck surface you can just bolt on and use LA heads (stock or aftermarket) and intake manifold, factory rockers as well if you please. If the passages aren't drilled you could still use LA-based heads but you'll need to use rockers that oil through the pushrods or plumb some type of external rocker oil feed, or have a machine shop drill the passages out. With the EQ heads no longer around there isn't really a good budget option for putting fresh heads on a Magnum. Might be more expensive overall but I'd go with some cheap bare aluminum heads like the Speedmasters and build them up to suit your combo.
 
You can still get magnum heads from EQ…they just don’t have the great ports like the older castings
 
67autocross said:
You can still get magnum heads from EQ…they just don’t have the great ports like the older castings
Click to expand...

Right, I've *heard* they have some quality issues too? They do still exist they just aren't the bolt-on performance and reliability improvement they used to be.
 
67autocross said:
You can still get magnum heads from EQ…they just don’t have the great ports like the older castings
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Are they a better platform than the OE head.
Please don’t go into cracks, just the facts on the ports.
 
rumblefish360 said:
Are they a better platform than the OE head.
Please don’t go into cracks, just the facts on the ports.
Click to expand...
I have no idea if they are a better platform over the stock heads… they look like good replacement type heads… but the are certainly not on the same level as the EQ heads from 5 years ago…

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4D004183-1685-4683-BC82-F6A76C18D3F3.jpeg
 
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