Help settle an arguement!!

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dustoff440

dustoff440

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I have a 360 magnum I built for my Dart and I have come up with an "estimate" of the horsepower and my buddy says I am way off.

360 Magnum
stock heads, pistons, rods, block, crank
windage tray
9.1 to 1compression ratio
496/512 276/286 LSA 112 cam
1 3/4 tube headers
850 Thermoquad
Air Gap knockoff

differences between mine and 380 horse crate Magnum
10 to 1 CR
501/292 106 cam
M1 single plane

I say that between the cam difference, intake difference, and 1 point of CR I am only 30-40 horsepower behind the 380 horse......approximately 340-350 horse power

what do you say???
 
dustoff440 said:
I have a 360 magnum I built for my Dart and I have come up with an "estimate" of the horsepower and my buddy says I am way off.

360 Magnum
stock heads, pistons, rods, block, crank
windage tray
9.1 to 1compression ratio
496/512 276/286 LSA 112 cam
1 3/4 tube headers
850 Thermoquad
Air Gap knockoff

differences between mine and 380 horse crate Magnum
10 to 1 CR
501/292 106 cam
M1 single plane

I say that between the cam difference, intake difference, and 1 point of CR I am only 30-40 horsepower behind the 380 horse......approximately 340-350 horse power

what do you say???
Click to expand...

Tell your buddy he is off, your estimate is very close, your not going to loose that much HP from a loss of 1 point in compression (at that level). One thing i do not see working well on that mild build is the 1.3/4" headers, you will be leaving some low-end torque on the table, you should be useing 1.5/8", unless in the future you'll be building a stroker.
 
What does your friend say?
I think if the parts are stock, meaning you took a good running 250 net hp Magnum 5.9, stuck a cam and Cross Wind on it, and ran it, that you are not as high as you would like it to be. If it was rebuilt and done with performance in mind (like fit-to-fit rings, blueprinted long block, great valve job, etc) you could get closer to it. But factory they just weren't that good IMO. The intake is costing you more than the headers IMO too.
The real answer will be known when you run it so you'll have to let us know.
 
Aside from a couple of issues, I'd think you're in the ballpark.

Leave the windage tray off if you can, you're much better off with a baffled pan.

That Air Gap knockoff is a piece of crap. I'm guessing I found 10-15hp switching to the real thing. Ports are mismatched, runner shape is bad and small, casting is not good.

The Thermoquad is a confusion factor over the holley. Who knows on that?

My Ford 302s went faster with 1-3/4 headers than 1-5/8. I think the bigger motor can handle the bigger header too.

If you're rating the compression at 9:1 because that's what the factory rated those engines at, its somewhat optimistic. The heads are a couple cc bigger than the claimed 59 cc, and the pistons are about .050 in the hole. You can pick some of that back up by going with the skinny head gaskets that Mopar and Mr. Gasket sell. Worth taking the heads off to check for cracks anyway. My magnum was under 80K miles and both heads were cracked between the seats.

I'd say you can't be too far off, at least with the real Air Gap, unless the thermoquad costs you horsepower over the race carb mopar no doubt used to get those numbers.

The calculators rate mine about 420 @ a race weight of 3400 lbs (through the Super Turbo mufflers), but I know there's more ET in the car with the right gears. Sometimes those calculators are optimistic though...

Mine is probably too different to make a reliable comparo but here's the combo.
I've got the EQ magnum heads, a kevko pan, 1-5/8 headers, Eddy Air Gap (LA), Quickfuel 750, 224/230 .536/.544 cam. My shortblock is around 70K miles, straight out of the junkyard - never even checked the bearings.

Good luck with your Magnum!
 
Steve, i thought you said your race weight was right around 3200
 
Its 3280, plus me, plus or minus gas. I weigh 140-150 depending on the time of year - LOL.

I've been confused about it for a while 3280 with me? without me?), but I got my logbook when I got the Challenger out of storage. Logbook could be wrong of course, but unlikely.

All steel car, full interior including bench, AC crap still under the dash, factory sound deadener. Iron headed magnum, mufflers, tailpipes, 8.75 and subframes.
 
You are probably pretty close. The older magnum crate engine mopar rated at 320 HP was basically a stock 5.9 with aluminum intake & carb instead of stock beer barrel fuel injection intake & throttle body. 360 magnum in my 98 Dakota R/T with just a ported throttle body, tuned PCM & electric fan pulled 229 rwhp on a mustang dyno which is about 280 crank horses give or take.

Oldschoolcuda
 
dustoff440 said:
I have a 360 magnum I built for my Dart and I have come up with an "estimate" of the horsepower and my buddy says I am way off.

360 Magnum
stock heads, pistons, rods, block, crank
windage tray
9.1 to 1compression ratio
496/512 276/286 LSA 112 cam
1 3/4 tube headers
850 Thermoquad
Air Gap knockoff

differences between mine and 380 horse crate Magnum
10 to 1 CR
501/292 106 cam
M1 single plane

I say that between the cam difference, intake difference, and 1 point of CR I am only 30-40 horsepower behind the 380 horse......approximately 340-350 horse power

what do you say???
Click to expand...

I have a Mopar Performance 380 HP crate motor in my Demon, the compression ratio if I am not mistaken is 9.3 to 1. I have a M1 intake with a holley HP 4150 750 cfm DP. Your estimate is probably closer than you think.
 
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