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#1
07-20-2006, 01:02 AM
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340 or 360
what would you guys build a 340 or a 360 and why would you build the one you chose? i am looking to get 475 to 500hp from one of the two that i have.the 360 is a 1972 the 340 is a 1971 with a forged crank.
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#2
07-20-2006, 01:34 AM
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If you want torque, 360. If you want RPM, 340. For the horsepower, you want I would consider a stroker. You have a good core for a stroker since your 360 is pre-1974/75. You would get more cubes by stroking a 340 (416 vs. 408 w/4" crank). Personally, I would build a 408 w/alum. worked heads and save the 340 for a resto project.
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#3
07-20-2006, 01:39 AM
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360 is the only way to go. No substitute for cu. in. to start with. THe 360 will make 400 hp easy with bolt ons. With more work you can get 500 without stroking it. Stroked, it will just make more hp. The 360 will turn just as much rpm as the 340 will. We use 365's in our race engines and turn them to as much as 6500 on stock reworked rods with ARP bolts, so rpm is not an issue.
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#4
07-20-2006, 01:46 AM
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#5
07-20-2006, 02:34 AM
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well the 340 came with ported X heads and i have 2.02 J heads,torker II manifold 800 holley.can you guys give me a recipe for a 475 to 500hp 360.i dont wont to stroke it.
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#6
07-20-2006, 04:04 AM
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Yep. Use those heads and cc them and use a flat top to get you at least 10.5 to 1 cr. Windage tray,valley baffle. Stock oil pump with Mp pressure spring. Maybe a KEvko oil pan. The intake is o.k. I'd rather use an 800 Thermoquad than the holley, but you already have it. THe TQ would be much better though. Pick a dual pattern cam in the 280* range and you should have what you want. Go forged and hit it with the bottle for some extra if you like that stuff. I just build all engines though. THey last longer. Oh, internally balance the 360. That way you have more choices in balancers and converters too.
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#7
07-20-2006, 09:21 AM
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DW, that is not enuff cam for much over 450 HP on a great day. The stock heads would need some serious serious posting to make that power with that cam on a magical day. That part list is for 400 - 425 HP at best.
Theres great arguments to both engine blocks. The 340 has smaller bearing surface as to not rob power from friction. A bigger bore to push HP up top the rpm range. But it'll use more stall on the converter, bad for the street for some people. Smaller engines need more cam for the same track effect. Not really an issue here. But it's true. Aparent in a larger spread of cubes. Expensive. (If you don't have a 340 block. Which could be sold for more money than 3 - 360 engines complete. That'll help fund the project.) Otherwise, same cost really. The 360's natural extra stroke is a bennift. But will have about a 500 rpm less ceiling than a 340 in equally built engines. Replacement blocks at the junk yard are cheap cheap cheap in a Lord forbid problem. I would save the 340 block if OE to the car. Otherwise, I'd sell it off. Later 360 blocks are roller cammed. Now think........
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#8
07-20-2006, 01:25 PM
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All this in theory of courseĀ
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#9
07-20-2006, 04:25 PM
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Sorry dust, wrong on both counts. With the bearings, the greater surface area does equate to a lower load per square inch. But that doesn't mean they wear less, because that lower load is cancelled out by the greater amount of crank surface passing over that bearing area because of the larger diameter. I have never observered a noticable difference in bearing wear between identically built, used (abused?), and maintained 340s and 360s.
The same goes for ring wear. Even though the 340 is turning higher RPM, the stroke is shorter, so the distance traveled by the piston is identical. This assumes that the engines are built to produce equal horsepower, which they do by burning identical amounts of fuel, which requires that they draw in equal amounts of air, which they do by moving the pistons identical distances. One at a shorter stroke and higher RPM, the other at a longer stroke and lower RPM. But the piston speed and distance traveled stays the same.
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#10
07-20-2006, 06:47 PM
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Use the 360 block.......
Parts are everwhere and you can build it just the same as the 340. The 72 360 block was the same casting as the 340 and can be bored to the 340 size and still have the thickness of the 340 when it was new. The only physical difference is the bearing/crank size. And like was mentioned, the 340 block would be better for a restroration because of it's value.
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#11
07-21-2006, 02:29 AM
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340 or 360
Thanks to all but, I still have not got a recipe to make 475 to 500hp for the 340 or the 360.
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#12
07-21-2006, 03:51 AM
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The heads are the key to making the power. Professionally ported stock heads can do the job, but it's cheaper and easier to use an aftermarket head.
The Edelbrock heads will work, but I think they now have a vector series head? and Indy cylinder heads has small block heads also that will make it easier to get big power numbers. In theory, to make 500 HP you need a head that flows about (or better than) 245 cfm @ 28". To use that much airflow, the 340 would have to rev about 6,900+ RPM for the peak HP number, add about 10% on top for the likely shift RPM. The 360, needs to rev aboutt 6,500+ RPM, and a 412 stroker about 5,700+ RPM (+ the 10% factor). As cheap as it is to build a stroker these days, I would go that route for 500 HP. Also the lower RPM of the stroker engine could allow the use of a milider cam. For the 340 and 360, you would need a pretty radical solid cam, but a roller cam is fairly common for an engine like this anyhow.
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#13
07-21-2006, 03:52 AM
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340 or 360..........
Single plane manifold. 750 Holley/Edel/Demon................... 10.5-1+ Forged pistons HD shot peened rods. Windage tray, oiling mods, Hi Vol pump, (DOnt listen to the suck all the oil out of the pan snore) Balanced, ect................. Cam? Well, IMO Solid flat tappet?? 300+ adv duration Solid Roller? (OH YEAH!) 280+ @50............ Heads? Ported (Heavy) Iron heads, or some cool aluminums. Some bigger headers, and 2 1/2" exhaust, X or H, or no, if likey..........
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#16
07-21-2006, 11:26 AM
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What dodgetruckboy said. Except the following changes;
flat top zero deck pistons 3 inch exhaust heads flowing 250 cfm @ a min. Hyd. cam (?) Comps 305 Magnum will make the power MoPars M-1 single plane intake And what 451 said............
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#18
07-21-2006, 01:16 PM
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Yea, it'll need to breath a little better IMO for a max result.
The X heads can be milled a tad. But I wouldn't go far at all. An iron head can go to 10 -1 with a big cam and work fine. After that, I'm not so sure if 93 octane on a iron headed engine with a cam like I listed will work. (As in no detonation. ) It would be more harmful, HP output wise, if you retard the timing so it could work rather than not have enuff to make it work at peak. In other words I'd rather run a 1/2 3/4 point down than 1/2 over and be able to run on 93. Notice race gas isn't in the thoughts. I can get 100. But why bother when big power can still be made on 93. Why pay extra for something that could have been built to run on 93 vs 100. The 100 octane I just spied was $5.99 a gallon vs the $3.39 I just paid for 93.
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#19
07-21-2006, 07:53 PM
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And I do agree, the 3" is too big.
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#20
07-22-2006, 03:50 AM
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Dunno, must be the 2.02 valves.............. Zero deck 340, with flat tops................X heads................. What was the stock compression? Of course, a 360 has more cylinder volume.................so who knows. MAybe the extra few CI's make the compression a point and a half higher.
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#21
07-22-2006, 04:05 AM
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Actually, you're both right. The way you get 10.7 with flat tops (you can even have 5 cc valve reliefs) is to use the 360. With .030 overbore, a .039 gasket, zero deck, and the 64 cc chamber, it works out to 10.69:1.
But TK is basing it on a 340. With the same specs in a 340, it's only 10.15:1.
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#22
07-22-2006, 04:08 AM
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What is a 75cc headed 360 with flat tops?
I forget how many cc's the flatop is.............but i have just had a major malfunction with the engine in my dually, and ma looking for a quick fix....................
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#23
07-22-2006, 04:22 AM
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All the same specs as before, but with a 75 cc head in a 360 = 9.5:1. (9.48:1 if you want to get picky)
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#26
07-23-2006, 02:35 AM
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sell the 340 and the 360 and get a R block with some w'8 heads ,500 hp is pushing both those blocks to the limit. is this a street car/street strip/race only ?Their are lots of ways to get their but how long it will last is the problem ,for instince just the cam hydrolic street rollercam solid cam ,pistons ,are you going nitrous ? what type of gas do you wont to use ?how much do you plan on spending?mopar don't even sell a small block crate motor that comes close to 500 not stroked .lots of things to consider need more information on its usage.
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#27
07-25-2006, 01:49 AM
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Quote:
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#28
07-25-2006, 04:27 AM
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I had a duster, with a 318 built kinda lke your 340/360 will be, it had some nicely ported X heads, a 590/615-290 @ .050 solid roller cam (Isky), Port O Sonic intake, and a 750 Edelbrock, ran a 11.53 on the fourth try.........then I was told I needed a cage. Never went back, and never found a ricer who would even look at me...hehe, of course, ricers weren't popular ten years ago.
Rumble is right, the M1 manifold, and the 3" exhaust should work nice, I had 3" on my 318, and it ran too good to complain. IMO, Here we go. I really don't like 340's............I really have no reason why, other than it is a 22 inch difference from a 318. Not worth the extra piston weight. Sure, you can get light pistons for a 340, but the 318 piston will be smaller (lighter). I also believe, that smaller bore engines have a cleaner, faster, more efficient combustion, because the the fire has less distance to travel, plus less friction from less cylinder to piston surface. So, in the 3.31 stroke department, I am a 318 advocate. If you go 340, might as well go 360. Yes, I don't care a whole bunch for the big bearings, but, with the right clearances, and oiling, it isn't an issue. More drag IS more drag, but there was never a substitute for cubic inches. The 360 also has a smaller bore advantage over a 340, not by much, but enough to make a minoot (sp) difference, IMO. For me, wanting 500HP in the small block engines, those are my thoughts. I built my 318, mostly because I like them, LOL. Give 99% of the 400+ inchers a run for the money. So, IMO, go with the 360, I really don't care for them a bunch, but facts are facts, and, the fact is, the engine I am putting together for my one ton is a 360, LOL...............give me something to complain about, other than dwc's 2.02 valves, and thermoquads............ 
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#29
07-25-2006, 09:43 AM
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#30
07-26-2006, 04:30 AM
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With that much gear and duration on the cam, being fed by the big Holley this engine should last at least two weeks. Gas for this thing will be cost prohibitive unless you have mucho cash, because you said it will be driven regularly. A stroker motor with about 400 Hp and some 391s gears would be a better combination because the X heads will not flow any more than a standard set of magnums. A blower motor would be an awsome driver with the power levels you seek.
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