LA 360 budget build ideas

Small Block Mopar Engine

  1. AJ/FormS

    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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    With the 262 type cam , I'd be surprised if you couldn't tune 65@2250 into the hi teens/low 20s. That 262 cam will run and make mileage down to 1800 no problem, if you give her the timing she wants.
    When I read 5mpg, I was pretty sure it was a typo... lol. So I more or less ignored it, but high-lighted it so you could catch it.

    Five thousand is a nice budget, and you can build a nice dual-purpose engine for that. Just slam some closed-chamber alloy heads onto it, pump the pressure up to around 185psi, up cam a wee bit, and now you got a tire-frying powerhouse, that still gets hi-teens for hi-way fuel-economy, with 3.23s.
    More pressure translates to more low-rpm torque, which translates to a smaller required throttle-opening, at no matter what load the engine is seeing. And that means less rear-gear and especially less stall, is needed.
    =====================
    I had a hi-pressure (185psi) 360 combo back in the early 2000s, with a manual trans mind you. It didn't much care what starter gear it had, and at one point I had it geared down to 3.23 x .71 x .78=1.79 final drive, that on the hiway, turned 65=1450 in double overdrive. But I couldn't give her the timing that she wanted. so I switched to 3.55s, for a final-drive of 1.97 and 65= 1600, and bought/installed a dash-mounted, dial-back, spark-box with a range of 15*. With this and a V-can modded to 22*, I was able to find 48+15= up to 63* of cruise timing; which was just a lil more than she needed. This engine combo made 32mpgs, on point to point hiway cruising, with a Hughes HE2430AL cam, that is ;
    270/276/110 and 223/230@.050; in a 68 Barracuda weighing ~3800 with passenger and gear.
    That combo was very sweet, but the cam lost lobes right after an oil-change, back when they took the zinc out of the oil and failed to memo me, lol. So the next cam was one size bigger, still a FTH and I got rid of the Mopar overdrive box. But the 3.55s are back in, and still with the GVod. .
    The point is; that with the 360HO as a base, lots of things are possible.
    Btw
    at one point, that 2330 Hughes cam was running on 11.3Scr, tickling 195psi, and still running 87E10, from idle to WOT, at any load-setting.
     
  2. rumblefish360

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

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    Because the KB-107 slugs come in decently high and the usage, as you said, is f a .028 head gasket on a zero deck engine and iron heads @ 72 cc’s, IF you have a 72cc head, is 9.8-1 or better. With a small cam, the cylinder pressure is very high and no amount of quench will solve your pinging problems. You’ll have to dial back the timing in order not to ping even with 93 octane and you’ll end up loosing a lot of power.

    File fit the rings without a torque plate on.

    What heads?
     
  3. Dan the man

    Dan the man Well-Known Member

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    Head gaskets will be either 0
    0.039 or 0.041 compressed thickness. Is it better to do the rings with out the torque plate installed than that's what I'll do.
     
  4. Dan the man

    Dan the man Well-Known Member

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    The heads that are currently on the engine, if it's going to cost as much to redo the factory heads I'll get a aftermarket pair
     
  5. rumblefish360

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

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    I answered that above.
     
  6. Dan the man

    Dan the man Well-Known Member

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    Yes you did, my bad
     
  7. Dan the man

    Dan the man Well-Known Member

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    It'll be awesome when it's done. Hopefully it be fun and enjoyable to drive
     
  8. AJ/FormS

    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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    What ^^^^ he said

    The Scr we build to is to achieve a Dcr which is very much affected by the cam, and the whole thing has to run on pump gas, without pinging. It's no fun to take the engine back out to lower the compression, nor even just taking off the top.
    This is why in an earlier post I wrote MINIMUM Ica of 61* for 9.5Scr IIRC. That 262 is the SMALLEST cam I would run in your combo with iron heads. It will make a good amount of pressure (was it 155psi?) for iron heads and pump gas. The Dcr that goes with that is ~7.8. You can run perhaps as high as 8.0 but yur gonna have to have all yur ducks in a row, and you may be stuck running best pump-gas ALL the time, which gets kindof pricey for a DD type of cruiser.
    If you stay below 7.8 Dcr, you can vary your other engine parameters any way you want to and it should be fine with mid-grade gas at 800 ft elevation. As soon as you try to get over 8.0Dcr with open-chamber iron heads, yur looking for trouble.
    When I ran that small cam at 11.3Scr, with closed-chamber alloy heads, the Q was ~.028, and the Dcr was 9.2 . That is the biggest, OK one of the biggest, advantages of the alloy heads. But IMO, that is overkill for a combo like what you are contemplating. Alloy heads will destroy your budget. and I question their use for a cruiser, that is seldom gonna see rpm because of the cruiser gears. You will likely be better off sticking to iron.
    ------------------------------
    But I suppose a closed chamber iron head might work, but getting the compression LOW enough with what's out there, to run with a cruiser-cam, well that's another can-O-worms.
    the next bigger size cam would get you to a Dcr of 8.0 at about 10/1 Scr....... which would be a total chamber volume of 82.7cc@4.02 bore. With 2.5cc in the decks and 5cc eyebrows and a tight-Q gasket of .028 being about 4.8cc, that totals 12.3cc leaving 70.4cc for the iron closed chamber heads. I don't think that's doable, so then the .028 gasket has to be sacrificed, in favor of the .039 Fellpro, and the new closed-chamber iron head comes to ~66.4cc . Doable maybe but the Q is borderline high at .051.... risky business.
    So then if we add another cam size, we can make it work, but now the Dcr is down to 7.8 again, and the Ica is up to 67*, and the pressure is back to 155, and it just become very frustrating to find the sweetspot.
    Easier it is with the stock iron heads and no Quench. And you can mill those to make whatever you want Scr, as long as the Quench remains over about .080, which should be doable.
    Rumble said;
    One of the fastest ways to lose power, especially between stall and ~3600, is having to compensate with retarded timing for too much pressure. Having to gas up with best gas, just to stay out of detonation in this tiny window really sucks. She might be fine until 80% throttle, and over 3600; but you gotta gas up with best gas ....... just in case you floor it at the wrong time. It's better to give up some pressure, and maybe delay the secondaries.
    Part of the problem is the 3.23 or similar gear and the lo-stall, which will force your engine, even in First-gear, to not get to 3500 until ... what was it? I think 33mph? Sounds about right. And with a cruiser-car, your engine might spent 60/70/80% of it's life in that, stall to 3500rpm window, so you just gotta play it cool in the pressure department.
    Hope that helps

    Oh I guess I didn't finish the comparison; Zero to 3500/33 mph at WOT might be say 4 seconds. At an average rpm of 2800rpm, that would be say 188 revolutions . If she's detonating because of the load, and you can't hear it; firstly the power will be down, and secondly; the KBs are pretty tough, but they will eventually break.
    But if you installed 4.30s, 3600 rpm becomes 24mph. Your new time from zero to 3600 might be a second faster, say 3 seconds at an average of 2800 is 140 revolutions, but the load will be reduced 21%. So maybe she escapes detonation. .
    Or you could just install a 3000 stall convertor, ant the tires will light up reducing the load even with the 3.23s, and thus escape detonation in that way
    Another thing you can do is to install a 2bbl, lol, and reduce the load in that way. But all/most, of these things cost money, destroying your engine budget.
     
    Last edited: Nov 21, 2021
  9. rumblefish360

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

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    OMG AJ. Could you carry on any longer?

    :rofl:

    The aluminum head option, though expensive, would help a lot, but I also don’t see the worth. It’s just not there. Even more so at the performance parameters and cam sizes being looked at. Stock heads will get you there. If you had no heads, fine. I’d still tell you not to zero deck it so fast. With the pistons down the hole some and closed chambered heads, you could easily end up with a 10.5-1 ratio.
     
  10. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    My replies in red.
     
  11. j par

    j par Well-hung Member

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    Budget $5500.....
    You have 360 block...
    $1.550 scat Stroker kit...
    $1.200 for machine shop to prep block and install Stroker kit..
    $700 on Black Friday for Speedmaster fully assembled aluminum small block heads to the door...
    $350 cam & lifters...
    $150 Black Friday Speedmaster air gap intake...
    $50 Summit billet double roller timing chain and gears...
    There's 4K spent and you pretty much have $1,500 to buy a carb and some of the small stuff like head bolts and whatnot... oil pump etc...
    You should be able to fart on the gas pedal and get 360 horsepower out of that combo....
     
  12. Dan the man

    Dan the man Well-Known Member

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    I've been trying to research as much as I can on performance modifications. I'm understanding that port velocity is important for throttle response and low to midrange torque?So my question is since I'm not looking for high horsepower would 1.780" intake valve's and 1.600" exhaust valve's give good port velocity in stock 360 heads?
     
  13. Ted265

    Ted265 Member

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    Port volume will affect velocity more than valve size, I don't see the point in spending $$ on seat inserts and machining to choke the 360 port up with a 1.78" valve.
    If your after velocity over flow stick with the iron 360 heads (smaller runner than aftermarket alloy heads) and 1.88/1.6" valves, do some bowl blending, get a decent valve job and back cut the intakes to help low lift flow.
     
  14. 273

    273 Well-Known Member

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    maybe under 2000 rpm at the most 2500 rpm, but I think your over thinking this. Most mild builds cam porting bigger carbs etc.. will make more torque from 2500 rpm and up, might be small loss 2500 rpm and under but probably nothing you can feel. There's not much you can do to add under 2500 rpm other than CR and or displacement. Maybe super tuned intake and headers and cam with no regarded for above 2500 rpm. For a daily driver type street engine goals to me is to extend the power and rpm range much as sensibly possible with out altering the under 3000 rpm much or at all, especially if low stall and high gears and heavy car.

    The valve is the most restrictive part of the port why restrict it more ?
    the rest of the intake tract will be the same size can't see it changing the velocity much or at all. yes you don't want ported W9 with a dominator or two on a mild 360 but can't see how something like 750 eddy heads, intake and a mild 215 ish cam is gonna make much noticeable difference under 3000 rpm.
     
  15. rumblefish360

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

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    Over thinking this for sure.
     
  16. 273

    273 Well-Known Member

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    Also remember most of these theories, rule of thumbs etc.. are originally from race engines not mild - hot street engines. Not saying velocity isn't important but when talking low power stock parts it's being over used, 360 was never meant to be a high power engine so if smaller valves and ports would improve idle to 4500 rpm they would of used 318 heads if it would of increased power. Most stock low power engines suffer from being over restricted thats why bigger carbs cam intakes headers better heads all add power and torque through out the 2500-5000+ rpm power range.
     
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    • Bighead440

      Bighead440 Well-Known Member

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      My budget build from the '90s, was a 360 bored .030" with KB167s (SpeedPro H116CP will also work) and 2.02" J-heads (double springs). I found a 284*/.528"/112LSA NOS Direct Connection Purple Shaft cam and lifter kit at a swap meet for $100 so I went with that and 273 rockers and Crane cup/ball pushrods. Made my own baffling for the stock oil pan and ran a M72HV pump, and a factory windage tray. I took 2 sets of stock .010" main bearings and made full groove bearings by relocating the notch in the cap per the MP manual. Got the crank turned on the loose side and ended up with .002" on the rods and almost .003" on the mains. Did not block off or restrict the oil to the lifters in any way, as I was street driving and idling a lot. Put the cheapest Hedman Hedders and H-pipe 2.5" exhaust with FlowTech Afterburner mufflers (this was before the cheap straight thru Jones, Salute, etc.) and a Torker II 360 intake (swap meet $100 item) with a 750 Edelbrock (later a 750AED DP Holley $$). This was a cheap, dynamite running combo for the street. Pulled 15" vacuum, gave no issues with pump premium (91+octane), and ran high 12 second 1/4s at 109mph in my '71 Demon (3.91 gears, 904 3000stall). Later I reconfigured this motor for a '68 Dart with a 727 and 4.30 gears, and I used a bigger REED solid cam and lifters (252/260*@.050", .540/.557" lift, 107LSA), 1.6 Crane roller rockers and some Hooker 1 3/4" headers and 3" exhaust with Aero Chamber Hooker mufflers. Now it runs high 11s @113mph with literally the same long block assembly. The 360 is definitely the budget choice and only performs better with more money/goodies applied!!
       
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      • Bewy

        Bewy Well-Known Member

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        A 1.78" valve is pretty small to feed 360 cubes. Chrys introduced the B engine in 1958 & I am not sure what the valve size was, but it was larger than 1.78". The 'standard' Ford 351 Clevelands had 2.04" valves [ 4V had 2.19"]; AMC 360 had 2.025"; Pontiac 350 1.96" & the 350 HO had 2.11" valves.
        Bigger valves would help & offset any loss due to reduced velocity.
         
      • RustyRatRod

        RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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        You'd be hard pressed to listen to anybody else with the experience and knowledge of this dude^^^^ He doesn't respond a whole lot, but when he does, listen up. He's a local friend whose been there done that and still doin it.
         
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