360 magnum heads on 318 magnum engine
11-23-2023, 08:23 PM
#1
New Member
Thread Starter
360 magnum heads on 318 magnum engine
I have a 318 magnum engine that I am wondering if I put 360 magnum heads on it what would I have to do in order for it to work? Anyone can please help me I've spent my last dime into this project and this will be my 4 attempt to get a dependable way to work. I've done spent over 2500 all together between 2×360 and 1×318 engines. Reason I'm using the 360 heads is my 318 head has a Crack and I have no funds left for this project.
Last edited by Donald Fairchild (Dee); 11-23-2023 at 08:32 PM. Reason: Forgot to add some info
11-23-2023, 08:57 PM
#2
Super Moderator
Yes I believe that they are the same…
The following 2 users liked this post by Iowan:
Donald Fairchild (Dee) (11-23-2023),
RacerHog (11-24-2023)
11-24-2023, 04:45 AM
#3
Mopar Fanatic
The only thing I can say from experience is that the 273 and 318s sat separately from the 340 and 360 as far as intakes, bell housing bolt patterns, motor mounts and water pump housings. The valley, I'm almost 100% sure has a different geometric angle (wider). I'm concerned in your application if the intake from your 318 and block surface would seat properly or even at all. They look close in appearance. Take out your measuring tools and check length, width, depth and height of the 360 heads. Measure height of valve and springs to base of combustion chamber. If they're not exact your lifters won't seat properly causing them to be too loose or too tight. If it was me, I'd find 318 heads.
Last edited by Kuvasz101; 11-24-2023 at 07:13 AM.
11-24-2023, 08:45 AM
#4
Mopar Lover
AS far as i know, swapping heads Magnum to Magnum shouldn't be an issue.... Just make sure whatever Magnum heads you are going to install? You check for cracks if you haven't already. Just my 2 cents...
Kuvasz: Are you referring to the LA head via the Magnum head?
(Dee) said he was going Magnum to Magnum, as far as in know that is a direct swap? or am I missing something?
Kuvasz: Are you referring to the LA head via the Magnum head?
(Dee) said he was going Magnum to Magnum, as far as in know that is a direct swap? or am I missing something?
Last edited by RacerHog; 11-24-2023 at 11:48 AM.
11-24-2023, 09:29 AM
#5
Mopar Fanatic
Maybe the magnums are better fitted to each other. I just recall on my 340 back in 1990 trying to interchange parts with a 318. I remember using 360 parts because the 318 just was off a bit. Here's a little article from Motor trend. This article refers to swapping between same Cubic inch motors. I would just micrometer every angle, height and length before installing.
Magnum Heads On A Pre-Magnum Block
Tips on installing Magnum cylinder heads on a non-Magnum A-engine must be prefaced with the question, "why?" Sure, there's a major price difference between new castings of both types: A bare P4876256 Magnum from MP lists for $127, while the P4529269 pre-Magnum 308 counterpart is $365. But the actual costs depend on the parts you already have on hand. Performance-wise, there's little, if any, advantage to using Magnum heads-again, depending on what's already on the motor. Magnums have slightly larger intake valves (1.925 inches versus 1.880 inches) than most previous A-heads, but an out-of-the-box Magnum casting doesn't respond as dramatically to modifications as the 308 head does, particularly on the intake side.
Preliminary investigations have shown that a Mag casting flows effectively only up to 0.550 inch of lift, a factor that limits competition applications to stock-style assemblies. Displacing 65 cc, compared with the nominal 70 cc of the 308 open chambers, the Magnum's smaller chambers raise static compression by fractions of a point. But installing Magnum heads means using the retro rocker train rather than the A-motor's advantageous pivot shafts. The swap also requires pushrods of the correct length to fit between the Magnum rockers and non-Magnum tappets and still maintain proper geometry throughout the lift range.
In addition, the vertical intake manifold fasteners on the Magnum head make inlet castings especially sensitive to tightening torque and sequence upon assembly. And carbureted intake systems from earlier Chrysler A-engines are attached by bolts nearly perpendicular to their head face, making it difficult to adapt these systems. The selection of Magnum-compatible intake manifolds is currently limited to a pair of four-barrel M1 alloy castings from Mopar Performance: the P5249500 dual plane and the P5249501 single plane.
One solution for an early-to-late intake switch calls for elongating the bolt holes in an early manifold and using six drilled, angled spacer blocks along the top of each flange for the appropriately longer 5/16-inch attaching fasteners to clamp on to. A somewhat cruder approach is to redrill and tap the bolt holes in the Magnum head to suit the attaching specifications of the early manifold. Although there's not much metal for new fasteners to grab, this setup will seal if all the mating face angles are correct. With the Magnum's intake port only 0.0625 inch wider and about 0.012 inch shorter than a 308's, minor matching can make two-, six-, and eight-barrel tunnel-ram Magnums practical. And rules-restricted Magnum bullring racers will have 30 years' worth of OE iron inlet castings to pick from.
Magnum Heads On A Pre-Magnum Block
Tips on installing Magnum cylinder heads on a non-Magnum A-engine must be prefaced with the question, "why?" Sure, there's a major price difference between new castings of both types: A bare P4876256 Magnum from MP lists for $127, while the P4529269 pre-Magnum 308 counterpart is $365. But the actual costs depend on the parts you already have on hand. Performance-wise, there's little, if any, advantage to using Magnum heads-again, depending on what's already on the motor. Magnums have slightly larger intake valves (1.925 inches versus 1.880 inches) than most previous A-heads, but an out-of-the-box Magnum casting doesn't respond as dramatically to modifications as the 308 head does, particularly on the intake side.
Preliminary investigations have shown that a Mag casting flows effectively only up to 0.550 inch of lift, a factor that limits competition applications to stock-style assemblies. Displacing 65 cc, compared with the nominal 70 cc of the 308 open chambers, the Magnum's smaller chambers raise static compression by fractions of a point. But installing Magnum heads means using the retro rocker train rather than the A-motor's advantageous pivot shafts. The swap also requires pushrods of the correct length to fit between the Magnum rockers and non-Magnum tappets and still maintain proper geometry throughout the lift range.
In addition, the vertical intake manifold fasteners on the Magnum head make inlet castings especially sensitive to tightening torque and sequence upon assembly. And carbureted intake systems from earlier Chrysler A-engines are attached by bolts nearly perpendicular to their head face, making it difficult to adapt these systems. The selection of Magnum-compatible intake manifolds is currently limited to a pair of four-barrel M1 alloy castings from Mopar Performance: the P5249500 dual plane and the P5249501 single plane.
One solution for an early-to-late intake switch calls for elongating the bolt holes in an early manifold and using six drilled, angled spacer blocks along the top of each flange for the appropriately longer 5/16-inch attaching fasteners to clamp on to. A somewhat cruder approach is to redrill and tap the bolt holes in the Magnum head to suit the attaching specifications of the early manifold. Although there's not much metal for new fasteners to grab, this setup will seal if all the mating face angles are correct. With the Magnum's intake port only 0.0625 inch wider and about 0.012 inch shorter than a 308's, minor matching can make two-, six-, and eight-barrel tunnel-ram Magnums practical. And rules-restricted Magnum bullring racers will have 30 years' worth of OE iron inlet castings to pick from.
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