Need Help on Magnum 360/380 hp Crate Motor Tech Info

Need Help on Magnum 360/380 hp Crate Motor Tech Info

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fatazzchuck said
Hey guy's,

I have a tech question about the p5249499 Magnum 360/380 hp crate motor with this roller cam .501/.513 lift with .230/.236 duration @.050 with a 108 lobe ..
Are the heads on this motor plain stock heads? If not what's been done to them?
I'm thinking of buying the heads/cam and installing into a Magnum 5.2 with Holley 750.. 904, Hooker super comp fenderwell headers in a 65 Dart 2 dr sedan weekend driver...with power brake and vacuum assist
What size stall converter and gear ratio would be needed?

Thanks

This cam,(288/292) ,in a 9:1-5.9, in at 104 makes a Dcr of 7.0@135psi. In a360. Check out the torque graph;about 360# at 3000. it makes 410# but not until 4500. The bottom end is somewhat (being kind) weak. I ran the 292* cam in my 360 @11.3Scr and the bottom end was so weak I had to install 4.30s and a 3.09 low gear set to get off the line,( that's a starter of 13.29), and I had a Clutch!
Now put same heads and cam into/onto 9.0 -5.2,with a 2.76 gear; I dare you. A Dcr of 6.96@133psi and 2.76s and no valve springs, no matter how you look at it "is a very bad idea".
That 904 will want a 1-2 shift rpm of well over 6500, probably about 6800 to come in at 4000. If you shift it at 5400say, the Rs will drop to 3200, and there just ain't no power down there. Well there is but it's feeble. The 5.9 has about 210 there, compared to 380@5400, and maybe 340@6800
You will want to gear that combo to hit 65 at about 6000 in second gear, to be fun on the street from zero to 60. This would take 5.13s and at least a 3000TC, to be close to optimum. Sure you can run less. But then the soggy bottom end shows up, and the OH-CHIT moment.And to blast off from 32mpg downshifted into first, you'd want 4.30s or a bit more.

But if you've moved on while I was typing, then I'll try to catch up.

In the mean time ponder this; How many times a month do we see a fella come on here needing help cuz his stock lo-compression 318-LA and 268* is gutless off the line, even with 17% more gear and 48% more TC,than what chuck is contemplating.
So let's see the new combo then, so I can get back to harrying Rumble,lol.