Crate 360 vs DIY Built
I saw in a catalog they have crate Magnum 360's for about $6k. granted I may save a few bucks just rebuilding my current engine, would I be better off with a brand new Dyno tested 0 mile Magnum over a 40 year old LA motor? The Magnum would likely get better mpg over the LA, right?
On top of that, what would you do about the transmission? new or used?
Thoughts? I appreciate the input!
Here's my thoughts:
Are you sure that they dyno test the Magnum crate engines? I've never heard that..
No, the Magnum may not get better MPG than your Cordoba engine. My father had a 76 Charger with a 360 2 bbl. It had a 20 gallon gas tank and would get 20 MPG on the highway - 500 mile range between fill ups. We had to stop to pee before we needed gas on long road trips...
The 360 - 380 horsepower Magnum engines have big cams and single plane intake manifolds. They are more for top end power than low end power and economy. A dual plane intake is better for a street engine going for performance and economy.
I would recommend building the engine that you have (77 360).
In one of my engine building books by Larry Shepard (the Mopar engine guru from back in the old days - and he's good), Larry says that the best cam for the Mopar SB is the stock 360 2 bbl cam that is 252°/256° duration and .410"/.412" lift. I myself am going to build a 360 for my 66 Valiant wagon and am shooting to get 20 MPG, and that is the cam that I'm going to try, along with a set of Rhoades lifters.
I did build a 318 many years back with the stock 340 cam and Rhoades lifters. It was 9.2 compression and a stock 69 340 dual plane intake. In my 68 Barracuda fastback with 2.76 gears got 17.75 MPG more than once when I checked it. Not quite 20, so I think my next econo build will use the smaller 360 2 bbl cam with Rhoades lifters.
My old 318 idled at 24" vacuum with 318 heads on it, but I had overheating problems as I had 10.5 pistons in it. I replaced the 318 heads with a set of 77 360 heads and it only dropped down to 22.5" vacuum. I was able to run a 10.5" power valve and with the vacuum gauge in my dash was able to still accelerate on the highway and keep it above 11" vacuum to keep the power valve from kicking in - better fuel economy. It did perform well, but is no street racer. I once was pulled over by a cop after turning a corner and nailing it (no tire spin) and he commented that my car was pretty fast. I told him that this was just spare parts that I threw together and could do better...
Maybe a lock up trans and converter would help. I believe that the 77 Cordobas had the lock up trans. Did you happen to get the trans with the engine?
Here's how I would build your next engine (and how I'm building my Valiant engine):
Try to get 9.2 - 9.4 compression pistons, file fit the rings at minimum end of the tolerance for ring gaps. The stock 360 2 bbl cam with Rhoades lifters. Rebuild the heads and go with either 1.88" or 2.02" intakes (you can have them installed in the 77 360 heads), you don't need to go to 2.02" intakes if you don't want to, 1.88" will work for an economy engine. Edelbrock LD340 intake or Wiand Stealth intake part number 8022 for square bore carb, Holley 80457 600 vacuum secondary carb. If you want to run a spreadbore carb like a Thermoquad, then use the Waind Action Plus intake part # 8007. Then use stock 68-70 340 exhaust manifolds or headers, whichever you choose. Then run a 2 1/4" dual exhaust with an H-pipe.
Here's some info on the Rhoades lifters. They bleed down at idle and take out .015" lift and about 10° duration at idle, then "ramp up" and give full lift and duration of your cam by 3500 RPM. They help low end and mid range torque and horsepower, increase idle vacuum, and improve fuel economy. For the SB Mopar you will want Rhoades lfiters part # 2018. Here's an article on how they work, look at the second one half way down the page:
http://www.rhoadslifters.com/Pages/Articles.html
Here's where you can buy a set:
http://www.summitracing.com/search?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=rhoades 2018
I would recommend rebuilding the '77 360 that you have. I feel that you would get better fuel economy than with the Magnum crate engine, they are built more for power than economy.
For your trans, I would have the original trans for your 77 360 rebuilt if you got it with the engine. It's difficult to find good trans builders, I found a guy in Detroit that does them right where the kickdown works properly. Some trans guys, the kickdown either shifts too early or too late and the trans don't last as long or perform as well. Find a good trans guy and rebuild the stock trans and have the original converter checked and run that if it is still good.
I prefer stock low stall converters over high stalls as they slip less and are better for economy than high stalls... But that's just my opinion - I'm more of an engine guy than a trans guy.
Good luck, we're all counting on you...
[ame]http://youtu.be/aB2yqeD0Nus[/ame]
