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Would like some sage advice on 360 Magnum build

Tom Frost

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Getting ready to build a 360 Mopar Magnum carbed engine for my 73 Challenger.
Not looking for a drag car...just a dependable cruiser with a bit of an attitude.
Would like somewhat of an old school “lopey” idle if possible.
Will have PS/AC, pro built 904 trans with 2200 stall and 27” tires.
3.23 to 3.55 rear end gears posi. Mainly a weekender/car show ride.

Here's a rough idea of what I am considering> Need some input as I am as old as dirt and not very tech-savvy.
Looking for 375 to 400 HP

Will use ported Monster iron heads from PIE. Harland Sharp 1.7 rockers, ICON Hyper pistons (9.5-10 CR, Comp 270 hydraulic roller cam, Air gap dual plane with 625 (or 750 Street Demon if it's not too much carb), Pertronix ignition and Flamethrower coil. Doug's mid-length headers and 3-4 4 core Champion radiator with dual 12" Spal fans.

This is just my best guess right now, and I'd like some input from you guys. Thanks.
 

Chryco Psycho

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Well if it was my build I would do a 408 stroker with all new parts Vs rebuilding old parts , the cost is not much more than rebuilding with a used crank & rods .
I Never use Hyper pistons , for less than the cost of a gasket set you can upgrade to forged I know the engine will take anything , even if you increase power later which many people do over time .
OK I will ask again WHY Comp cam ? Check with Lunati or Engle for a cam that is a better design for Mopars , Comps are not good in Mopars ! You will need a cam that starts working around 1800 RPM with a 2200 stall .
I prefer Bushed stainless steel rockers such as PRW brand , over alum with roller brgs for long term street use , they have a larger contact area with the shaft being bushed . Be careful with 1.7 ratio & piston to valve clearance as the magnums 1.6 from the factory .
I would use a 750 carb , you will get more bang for the $$ with a Proform carb & make sure it has adjustable air bleeds , a number of years ago Demon carbs were one of the most problematic carbs but I know Holley bought them out .
If you use a mechanical clutch fan & shroud it will be far more efficient than electric fans . if you still decide to use electric you will need a Alternator bypass wire to the start relay & relays to power the fans as well as a 100+ amp alternator to make enough power .
Not trying to make you feel bad but I disagree with almost every one of your choices having built numerous engines over my entire life [probably more than 25 between 2000-2010 alone]
If you want to discuss this more send me a PM with your phone # & we can talk this over in more detail .
Neil
 

Tom Frost

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Neil, Thanks for your observations and expertise, I really appreciate it. You have a lot of experience with Mopars...and I have none. Just getting up to speed on this so I truly appreciate your input. Just may do the 408 stroker, use forged pistons...and will certainly look into all your suggestions. Just the sage advice I was searching for. Thanks.
 

Chryco Psycho

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Glad to help , let me know if you want to talk over anything , I am happy to call if it will help .
 

DrEamer

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As someone that is deep into my 408 Magnum based stroker, I can save you some pain from this experience. If I were to start over I would just get a 408 short block from Blueprint Engines and save the hassle finding a good block, and dealing with a machine shop. Then consider talking to Chris at PIE and going with one of his top end kits. If you are using his heads, he can suggest a cam for your needs. He uses Bullet Cams that he has developed over the years. In my case, Blueprint did not have the Magnum short blocks at the time. My combination is using Trick Flow heads, LA style duel plane intake, with a custom Howards cam spec by B3 Racing. It will be a fairly hot street car, and most likely more then I will ever use. Keep it simple and just enjoy it.
 

70chall440

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A stroker is the easiest and quickest way to make reliable power. Use a good set of heads and decent cam and you are about there. I disagree with the statement that Comp cams don't work in Mopars; not saying that they are "the best" per se but they certainly work just as many others. The cam is the heart of the engine and as such needs to be matched to the overall engine build. Probably the best advice I can give you is once you decide what CI you are going with (stock or stroker), induction system, exhaust system (type of headers or manifolds) and how you intend to use the vehicle contact the cam manufacturers and talk to them about their offerings rather than rely on forums. Not saying guys on forums are incorrect but they/we have a narrow base of experience with a variety of cams in comparison to the people who make cams for a living. Having said that, if you find someone who runs a dyno shop and has swapped in a variety of cams, then so be it but they still are not going to have the depth of experience.

Biggest problem I have seen when it comes to cam selection is that many guys/people look at peak HP and torque numbers and let them drive the selection. The problem is that in most cases this is not where you engine lives or even sees especially in a street car. If you are building a race car, then its very relevant but of you are building a driver then it isn't, you want the low and mid range numbers. I usually don't give a crap what the engine makes at 6500 as I seldom will ever push a engine to that; I am much more interested in what power I am making at idle to 4500 or so. Many times what you get on the top end you lose on the bottom end to a degree.
 

Tom Frost

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Doc, That sounds like a pretty good plan. Thanks for the great advice/input...I will check them all out. Keeping it simple sounds great.
 

Tom Frost

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SF...Thanks for the great advice...I just may go with the stroker as I am not having much luck finding a good core. I do plan on the good heads from PIE...and will follow your advice about the cam guys knowledge base...makes sense. Again, thanks for the input.]
 

Chryco Psycho

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I agree with above , the cam is the single most important part of the engine combo , I have always been very particular about cam choice & matching the rest of the drivetrain including gear ratio , I also believe in a strong midrange over peak power I was building custom grinds for most of my builds to get exactly the result I planned for .
For example I built 1 512 stroker , it made over 400 ft lbs tq at the wheels on a Mustang dyno which is very hard to do all the way from 2200 rpm to 5300 rpm with a peak around 4500 rpm of 465 ft lbs , so it didn't matter what rpm you hit the Throttle at it would pull like a freight train all the way to 6000 rpm ! The Bonus was it also got 17.9 MPG at 75 mph !
Having dynoed numerous engines Comp cams have always disappointed in my real world experience .
 

Chryco Psycho

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Yes it will , the left mount is different tho
Be careful of the Dakota blocks tho they have the mounts cast in a different place , if you go with Blueprint engines they should be aware of this .
 

Tom Frost

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So, the Dakota blocks won't work? I am sourcing through a private party...and I think it's from a 1999 Dakota. Had 138k on it...but std bore. If I bore to .030 over what will the Cubic Inches be?Thanks for your help as I am a newbie to Mopar.

00L0L_6LGSd4FF76j_0CI0t2_300x300.jpg
 

70chall440

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I am very confident that any Magnum will work in your application. I am not sure about the Dakota engines being different; not impossible but doesn't make a lot of sense but stranger things have happened. Even if this is the case, a Dakota 360 can be used in your car.
 

DrEamer

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The only difference is the Dakota used the mid mount provision. It only an issue with the exhaust manifold, or headers hitting them. They can be ground down if clearance is a problem.
 

Chryco Psycho

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in your picture you can see the 3 bolts around the center frost plug for the mid mount but that block also still has the front mount provision , I am not positive all do have the front mount also . If the front mount is not there it will not bolt into your car using the mid mount .
The Ram truck 360 would be fine , the .030 over bore would only gain you 4 ci approx & if you go to a stroker I would keep the bore as small as possible to retain wall thickness .
 

Tom Frost

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Thanks again. Yes, will only bore as little as needed. My engine guy is very gifted and has several bad Grand Nationals that are record-holding cars. He'll do me right.
 
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