LA 360 budget build ideas

Small Block Mopar Engine

  1. Dan the man

    Dan the man Well-Known Member

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    Looking for 360 horsepower at the flywheel. Would a 9.0:1 compression ratio be enough? Thoughts, ideas on what cylinder heads, cam,etc would I need to get to the power level that I'm looking at. I think that this would make for a nice winter project.
     
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    • AJ/FormS

      AJ/FormS 68 Formua-S fastback clone 367/A833/GVod/3.55s FABO Gold Member

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      For what application?
      Tow-truck , or race car two different engines.
      C-body or A, need torque?
      Manual trans or automatic? need powerband?
      Daily-Driver or weekend warrior? Need fuel economy?
      Do you have a limit on what rear gears to run, or TC stall?

      You can build a 360hp 360 in several different ways, but if you don't match it to the combo, results can quickly become disappointing.

      9/1 might be enough, it really depends on too many things to commit to. And especially on your budget.
       
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      • Murray

        Murray FABO Gold Member FABO Gold Member

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        I am going to stick my neck out in the face of so many knowledgeable people here and give you my opinion. 10/1 compression, ported heads (at least well breathing), four BBL carb and modest headers, stock ignition, modest cam.
         
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        • Max1196

          Max1196 Well-Known Member

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          You can do lots with 9-1. This alone in a dirt circle track "rule" locally, gives you the 500 cfm benifit. "Collins" car, 355 inch.

          098 (3).JPG
           
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          • rumblefish360

            rumblefish360 I have escaped the evil Empire State! FABO Gold Member

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            I’m a bit with @AJ/FormS on this.

            9.0-1 is certainly enough! Oh yes!
            So you have an engine now?
            This is what I would do;

            Once your block has a balanced assembly in it….
            The stock letter heads (J. Z, O, etc..) with back cut valves and a competition valve job should be done. 750 carb, Edelbrock RPM (air gap a plus) & headers.

            Camshaft wise, (it’s just simply hard to get them now,)
            1; It will depend on what it’s going in,
            2; How heavy the vehicle is,
            3; gear ratio and tire size,
            4; if you willing to change converters or not. If not, the smallest cam I’d run for this endeavor would be ether of these below;
            Howard’s cams;
            DODGE Howards Cams 711451-08 Howards Cams Hydraulic Flat Tappet Camshafts | Summit Racing
            DODGE Howards Cams 711651-10 Howards Cams Hydraulic Flat Tappet Camshafts | Summit Racing

            These cams will get the job done. A larger duration cam moves the power band up.

            If the stock OEM heads are not suitable for some reason, then I would use Edelbrock heads. If you have the coin, roller rockers would be a plus for there accurate ratio over the stamped steel OEM offerings.

            2-1/2 “H” piped exhaust. Summit turbo mufflers or Hooker Aero Chambers

            Your over building. Not a bad thing!
            10-1 is where most people would go. Not a big deal.
            Ported heads aren’t needed. BUT!!!!! More flow doesn’t hurt. The thing is here is the camshaft needed doesn’t need a high lift. At best, a OEM head can use a bowl porting. Most of the lift will need a good valve job and a better valve… or at least a back cutting.

            Stock ignition? Perish the thought!!!
            If you have an electronic ignition, use at the minimum, the Chrysler Chrome box or a FBO box.
            Modest headers? WFT is modest headers? (LOL!)
            Modest camshaft? Again as above. There are dozens smaller than what I listed.

            A bit of a FWIW…. A long way back when Dodge entered the Craftsman cup truck series…. The small block engines made 750hp @ a rule limited 9.0-1 ratio.
             
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            • MOPAROFFICIAL

              MOPAROFFICIAL FABO Gold Member FABO Gold Member

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              Plenty.
               
            • Dan the man

              Dan the man Well-Known Member

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              Car is going to be a semi daily driver as weather permits. My goal for the car is strictly a cruiser ( looking at getting a 1973 duster ). Gas mileage isn't a huge concern but yet I'm for better than 5mpg. Rear gearing, I thought about either a 3.23 or a 3.55 gear ratio. I don't want the engine spinning at 3,500 rpm's at 70 mph. If I need to change the torque converter that's okay. Are mopar small blocks known for coil bind with cams over a 0.515" lift? I thought about running the pistons at zero deck height, with a head gasket that has a 0.039" compressed thickness and 1.880" intake valve's, will I have piston to valve clearance issues? Do I need to run closed chamber heads? I'm wanting to select the right parts so that my combination will work well. Also, if I was to buy bare cylinder heads are the seats already cut for a certain size valve? Since my goal isn't 400+ horsepower I was thinking of using 1.880" intake valve's and 1.600" exhaust valve's with a comp valve job and back cutting the valve's, bowl clean up. Am I going in the right direction or am I totally wrong?
               
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              • 273

                273 Well-Known Member

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                • 273

                  273 Well-Known Member

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                • 273

                  273 Well-Known Member

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                • rumblefish360

                  rumblefish360 I have escaped the evil Empire State! FABO Gold Member

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                  Lots of questions…. Whew! Your on the right path.
                  Zero decking the pistons will not be needed. However if you went that route with a set of KB-107’s & a older letter head which fall in around 72cc’s, you’ll have a 9.8-1 ratio with that .039 head gasket. In order to drop that .8 in ratio, you’ll need a pretty thick gasket.
                  Don’t zero deck it.

                  You’ll have no issues with a 1.88 or 2.02 valve and clearance. The OEM heads can take more lift. Don’t worry about how much lift you’ll need. The cams I listed will do the job. You don’t need to run closed chambered heads. Aftermarket heads are cut to run bigger valves, so they need to be matched.

                  Oddly enough, I just seen the new engine masters where they make 360-365 hp from a 5.9 Magnum. Those stock heads are a little better than stock LA heads. That engine is @ 9.0-1.
                   
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                  • QuickDart360

                    QuickDart360 Well-Known Member

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                    3.91's would be most fun! But you don't want to spin 360 up high. So that limits your choices I guess.
                     
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                    • rumblefish360

                      rumblefish360 I have escaped the evil Empire State! FABO Gold Member

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                      Oh, I forgot, IMO, you won’t need a converter change with the cams I listed and with a stock tire size, they will work with a 3.23 gear. An upgraded (higher stall) converter would be helpful for street performance acceleration. You’ll only need a few hundred rpm more. A good converter will drive like a normal one and serve you well.
                       
                    • 66fs

                      66fs FABO Gold Member FABO Gold Member

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                      Pretty much a quality build with 9:1 compression ratio. 340-360 milled .020 LA heads with bowl clean up, very good valve job, tight guides, viton valve seals, back cut intakes, 1.88 intake valves are fine 2.02 better, 340 or equivalent valve springs. Good intake, 750 cfm carb, Hone with torque plates, balance the rotating assy, file to fit rings, windage tray, high pressure oil pump spring, double roller timing chain, 268-276 duration, .450-.500 in lift cam. 323- 3.21 gears, That is all it takes.
                       
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                      • JoePole1

                        JoePole1 A dude in a B body FABO Gold Member

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                        Define budget build. Machining, balancing and porting work alone can be $2k. Stock bottom end magnum would give you close to 9:1. Add .028 head gasket and pocket port replacement heads plus Oregon regrind Weiand or air gap and you are there.
                        Of course if you already have the LA I would follow @273 post 9 Holdener route.
                         
                      • rumblefish360

                        rumblefish360 I have escaped the evil Empire State! FABO Gold Member

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                        A stock bottom end Magnum w/an LA (Weiand) intake…. what heads are on top now?

                        I took my ‘00 - 5.9 and added Hooker 1-3/4 headers into a 2-1/2 exhaust, LA distributor, Edelbrock’s Magnum style RPM A-G and a Edelbrock carb. It is not 360 hp, but these bolt on parts work very well. I will be ordering a Howard’s cam later. It is followed up with a 727 & 3.55’s riding on 245/60/15’s.
                         
                      • JoePole1

                        JoePole1 A dude in a B body FABO Gold Member

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                        You are correct rumble. Weiand won't work with magnum heads. Would need Air gap or knock off.
                         
                      • AJ/FormS

                        AJ/FormS 68 Formua-S fastback clone 367/A833/GVod/3.55s FABO Gold Member

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                        Are you saying that you do not yet have a car, but are looking at purchasing a 73 Duster?
                        That would be a good thing because they have enough rear wheel housing to receive reasonable-sized rubber, for their short wheelbase. Cuz without rubber, 300hp is already overkill.
                        Strictly a cruiser sorta means gears around 2.94/3.23 and 275/60-15s at 28" tall for low-rpm hiway cruising.... in lock-up, and that points to
                        a hi-torque engine.
                        With the LU convertor, you have two options of gears;
                        1) 2.45-1.45-1.00 running 3.23s your starter is 7.91, and 65=2520
                        2) 2.74-1.54-1.00 running 2.94s your starter is 8.06, and 65=2290
                        Without LU add about 4 to 5% so 100/250 rpm; 200 is typical.
                        These cruise rpms are high enough to run almost any cam and still get reasonable fuel mileage. But, I have found that a lot of this fuel economy depends on a couple of things, namely; CCP (Cranking Cylinder Pressure), and the length of the Power extraction cycle, and your engine may ask for massive ignition cruise-timing.
                        So then, it sorta behooves you to aim high on the CCP, and Long on power extraction; or some combo of the two.
                        Now, going back to the Hi-torque engine, Lots of CCP is again the target. We can get that in about three ways; 1) design, 2) a short period hydraulic cam, 3) a shorter period solid lifter cam. Short period cams have little to no idle lope.
                        Put that on hold for a bit.
                        With tall tires and tall gears, and a starter-gear of say 8.0 we have a bit of a problem. Namely, your roadspeed is 10.4mph per 1000 rpm plus compensation for convertor slip. Lets fix the slip at a straight-up 10%; so then; 2500 is 23 mph, 3500 is 33mph, 4500 is 42 mph, 5500 is 52 mph, 6500 is 61mph; you see where this is going right. As for Performance, and a city car, for practical purposes; you have a ONE-GEAR car. To make something of it, will take some fancy engineering.
                        But;
                        you said strictly a cruiser, and you're ok with as low as 5mpg, and it's a budget build.
                        So then, none of this matters; slap it together with a 318 cam and call it good.

                        But, if yur like me, you still want to spin tires occasionally; am I right?
                        Well then, the 28s gotta go or the gears gotta go, or the engine will need some serious CCP. Or you just up the stall.
                        Upping the stall is the easiest and fastest way to get tirespin off the line. And with a LU convertor, it makes the most sense. It will Not affect your fuel economy. If you go this route, say a 2800 to 3200, you can sacrifice a lot of CCP, meaning you can up-cam a fair bit, cuz that CCP was mainly making low-rpm torque/power, to help get moving with the very modest ~8/1 starter gear. By 2800/3200 that CCP is no longer a major player in torque-production.
                        Now then, you have a choice; Move the power up to a higher rpm , which will suck gas around town, or increase hi-rpm breathing in a different way and keep the cam modest.
                        With KB167s, the piston will fall in at around .012 below un-machined decks. You can run the .039 Fell-Pros and closed-chamber heads but the Quench is starting to get baggy (.051). Some guys, have successfully run .028 gaskets for a Q of .040, about middle of the road. But if you run open-chamber iron heads (budget) then it won't matter. So now your total chamber size is climbing to
                        2.5 deck +5 in the eyebrows, + 8.6 in the gasket, +72 in the heads, totals ~88cc, for a Compression Ratio of ~9.5
                        So at 9.5Scr with iron heads and no quench, to run on say 91 gas at WOT, will allow a maximum CCP/cylinder pressure of ...... say 155psi. At a mean elevation of 800ft in Missouri this allows a MINIMUM Ica (Intake closing Angle) of ~60* Badaboom.
                        Since it's a One-Gear car, we can run any LSA we want, so lets tighten it up to 110*, to get a lil power in the midrange, but still be able to rev it out a bit. And I get a hydro of something like;
                        262/270/110, which has 119* of compression, 115* of extraction, and 46* of overlap, with the specified Ica of 61* when installed straight up at 110*..
                        As for that 115* of extraction, this, together with; the 155psi CCP, and a cruise rpm of 2290, points to fairly thrifty fuel useage at steady state cruising. And not too bad around town if yur taking it easy. IMO; this is the smallest cam to run with 9.5Scr and 155ps, with iron open-chamber heads and no quench. If it was me, I would just do a simple valve job and call it done because this 262 cam has a fairly modest powerpeak of around 4800/ maybe 5000 installed "straight up".
                        As for the 46* overlap, this will idle like a 340.
                        As for the 270* of exhaust duration, this allows you to run cast-iron manifolds.
                        As for the 262* intake duration, this will allow you to run any old dualplain intake or very small-runner/small plenum single-plain.
                        Very budget friendly.
                        One of your biggest expenses would be the hi-stall LU convertor. To that end, I would just install the complete A999, as found with it's factory LU, and try it, You may find it to be reasonably satisfactory, with the 3.23s... even more budget friendly.

                        The point id this;
                        you said strictly a cruiser, and you're ok with as low as 5mpg, and it's a budget build. This is practically a bolt-together engine with the only expense being the tall pistons.

                        For the ultimate in cheapness,
                        you could run the stock 360 2bbl cam (252/260/112) with an Ica of 56* when installed at 110, but the CCP rises to about 161psi, so you might have to run 91gas at WOT; you can still cruise on lesser gas. With the extra pressure, you can run any old A904 with any old TC, but with the 3.23s, and for cruising 65=2620 @4* slip with the 28s. Can you get any more budget friendly than that?
                        At this point, I gotta say something else.

                        This car will really like a lil more gear; 3.55s will get you close to 3500 at 30 mph on the kickdown into First gear and 65=2850
                         
                        Last edited: Nov 21, 2021
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                        • PRH

                          PRH Well-Known Member

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                          With a basic 9:1 360, getting into that 1hp/cu range is quite easy.
                          It just depends on what you’re willing to live with in terms of cam, gears, stall.
                          The milder you want it, the better the heads/induction need to be.

                          You can get there with basically stock heads if you run enough cam, but then you need more gear and converter to go with it.

                          True 9:1, bowl ported refurbished heads(honest 210-220 cfm@.450 lift), rpm style manifold, headers, mid-220’s-230@.050 cam....... should get you there.
                           
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                          • Dan the man

                            Dan the man Well-Known Member

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                            I may have listed the wrong mileage, I'm wanting the gas mileage to be in the low to mid teens
                             
                          • Dan the man

                            Dan the man Well-Known Member

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                            With budget, I mean to use pretty much what I already have such as the block, if rebuilding the stock heads isn't cost effective then I would be willing to buy aftermarket heads. 2nd, to not buy the same part twice like the carburetor, cam etc. I was thinking that $5,500 should get me a decent engine.
                             
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                            • Dan the man

                              Dan the man Well-Known Member

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                              Why you say not to zero deck it? I figured that would help improve the compression ratio, flame travel, quench. Isn't a good quench distance better for preventing detonation?
                               
                            • Dan the man

                              Dan the man Well-Known Member

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                              I plan on having the block bored and honed with tork plates as well as having the rings file fitted while the torque plates are still on the block, what do you think?
                               
                            • Dan the man

                              Dan the man Well-Known Member

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                              Factory heads
                               
                            • PRH

                              PRH Well-Known Member

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                              For $5500 I’d be aiming higher than 1hp/ci........ but then you might still end up trying to walk the line between HP and civility.

                              With that budget, I’d do a zero deck and some aluminum SM heads combo.
                               
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