Max rpm 360 magnum ???

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Brooks James

Brooks James

VET, CPT, Huey Medevac Pilot
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1992 360 magnum

Stock block, crank,heads., pistons, rods,lifters
Hughes cam, Springs, rated to 6500,locks, retainers
Im thinking 6300 max rpm ??? (Safely)
 
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Brooks those stock heads are going to run out of breathing room well before that. If I remember correctly A totally stock 5.9 could be safe up to 5500 even though the ECM was good to 6500. At 6300 you’ll be way past the power band and on the decline anyway and in my opinion in an unsafe range with potential valve float. Not sure what you have there for other goodies or how you use your car. If it’s completely stock with the mild Hughes higher lift cam and no head work or head upgrade I wouldn’t bring it above 6000. My 5.9 retains the stock heads with probably the same Hughes cam you’ve got and an edelbrock air gap with a demon 625 carb. I don’t bring it past 5800 but think it could be safe to 6000. Smarter guys than me will chime in.
 
Rev it till it grenades then report back with your findings. :lol:

Why do guesses for a Max rpm number matter anyway?? Run it without a tach and learn to tell when to shift by sound and feel. Or, Take it out on the interstate and mat it until you hear clanking and let up a smidge. Note the rpm @ clanking and there ya go :realcrazy:
 
Mine don't have any power after 5 so I never saw the point in revving any higher
 
When cash for cluckers happened we had a ton turned in to the dealership I work at. We were send instructions and silica sand from the government on how they wanted us to permanently disable the engines. "Put the silica sand in the oil and Rev in neutral until the engine stops". The magnums, 360s and 3.9L V6s were the hardest ones to kill. The magnums would sit there and scream at there max rpm for over 10 minutes with sand in the oil. All other the engines never lasted more than 3 minutes with the sand in them.
 
Northern Grit said:
When cash for cluckers happened we had a ton turned in to the dealership I work at. We were send instructions and silica sand from the government on how they wanted us to permanently disable the engines. "Put the silica sand in the oil and Rev in neutral until the engine stops". The magnums, 360s and 3.9L V6s were the hardest ones to kill. The magnums would sit there and scream at there max rpm for over 10 minutes with sand in the oil. All other the engines never lasted more than 3 minutes with the sand in them.
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That doesn't surprise me, the magnums are tough. I still hate to hear how so many good cars/engines were destroyed.
 
how much tuning did you have to do to the demon 625? Planning on picking up a new carb this week.

67dartgtgo said:
Brooks those stock heads are going to run out of breathing room well before that. If I remember correctly A totally stock 5.9 could be safe up to 5500 even though the ECM was good to 6500. At 6300 you’ll be way past the power band and on the decline anyway and in my opinion in an unsafe range with potential valve float. Not sure what you have there for other goodies or how you use your car. If it’s completely stock with the mild Hughes higher lift cam and no head work or head upgrade I wouldn’t bring it above 6000. My 5.9 retains the stock heads with probably the same Hughes cam you’ve got and an edelbrock air gap with a demon 625 carb. I don’t bring it past 5800 but think it could be safe to 6000. Smarter guys than me will chime in.
Click to expand...
 
Brooks James said:
1992 360 magnum

Stock block, crank,heads., pistons, rods,lifters
Hughes cam, Springs, rated to 6500,locks, retainers
Im thinking 6300 max rpm ??? (Safely)
Click to expand...
Hey Brook! What cam is it?
If the springs are rated to 6500, that’s a good thing. Is you know according to the manufacture that valve float will happen at about that RPM, you know where to let off. After that, valve control may become an issue. Since max RPM is a function of ether or both the springs and the cams profile. (AKA What the duration is cut for RPM wise.)

Most builds of this type your doing find max power on and around the cams profile are now limited to the heads flow capacity. Since the heads are stock, this will be around the 5800 mark. There could be a 200 RPM + or - here. Cam profile dependent.

Most racers will find best ET’s shifting past peak power at some point. This a variable mostly based on bore and stroke combo along with the cam and spring package and the heads ability to flow air.

Post the cam specs or card. It’ll give us all a better idea of what the engine may do.
 
12many said:
Rev it till it grenades then report back with your findings. :lol:

Why do guesses for a Max rpm number matter anyway?? Run it without a tach and learn to tell when to shift by sound and feel. Or, Take it out on the interstate and mat it until you hear clanking and let up a smidge. Note the rpm @ clanking and there ya go :realcrazy:
Click to expand...

Great advise. Im trying to calculate the rpm in the traps
rumblefish360 said:
Hey Brook! What cam is it?
If the springs are rated to 6500, that’s a good thing. Is you know according to the manufacture that valve float will happen at about that RPM, you know where to let off. After that, valve control may become an issue. Since max RPM is a function of ether or both the springs and the cams profile. (AKA What the duration is cut for RPM wise.)

Most builds of this type your doing find max power on and around the cams profile are now limited to the heads flow capacity. Since the heads are stock, this will be around the 5800 mark. There could be a 200 RPM + or - here. Cam profile dependent.

Most racers will find best ET’s shifting past peak power at some point. This a variable mostly based on bore and stroke combo along with the cam and spring package and the heads ability to flow air.

Post the cam specs or card. It’ll give us all a better idea of what the engine may do.
Click to expand...
No card, got it from a guy who used to work for crane cams
Int 498/274
Exh 512/286
LSA 113.5
I wanted estra dur/ lift on exh for the nitrous and non lopey idle
 
Are you sure it’s a huges cam. They normally don’t give “Advertised numbers, only the .050 numbers. The duration numbers @ .050 would have been great. Do you know what series cam it is. I’m going to the Hughes site now to poke around.
 
Brooks James said:
Great advise. Im trying to calculate the rpm in the traps
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Gotcha, I know reving a little beyond peak is for shift recovery so there’s that to take into account as well up to crossing the line at peak
 
rumblefish360 said:
Are you sure it’s a huges cam. They normally don’t give “Advertised numbers, only the .050 numbers. The duration numbers @ .050 would have been great. Do you know what series cam it is. I’m going to the Hughes site now to poke around.
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Actually its a Grind from a guy who used to work for crane Cams
Im hoping for Round 370 hp and 450 with 150 hp nitrous which would put me at 11.5 et. But im thinking the heads will limitea the the hp from the nitrous and only produce 75 estra hp
 
Brooks James said:
Actually its a Grind from a guy who used to work for crane Campus
Im hoping for Round 370 hp and 450 with 150 hp nitrous which would put me at 11.5 et. But im thinking the heads will limitea the the hp from the nitrous and only produce 75 estra hp
Click to expand...
I had a Crane cam a while back with the advertised numbers of 272/284 which were 218/224 (IIRC) @050. The lift was shorter. .454/.484. It was on a 112.

The more you can create cylinder pressure with that cam the better it’ll perform. It should have some good top end pop.
 
rumblefish360 said:
I had a Crane cam a while back with the advertised numbers of 272/284 which were 218/224 (IIRC) @050. The lift was shorter. .454/.484. It was on a 112.

The more you can create cylinder pressure with that cam the better it’ll perform. It should have some good top end pop.
Click to expand...
I hope so, im hoping the nitrous and a 3500
Converter will help out mid range an low end torque
 
If your cam lobes are the same as I had on mine, then expect max power around 5800 max.
 
I had a feeling that would be where it is at.
IF! And when you get to the heads, a bowl porting and some pushrod pinch point work would be helpful. Most of the power at this point is in the valve job.
 
rumblefish360 said:
I had a feeling that would be where it is at.
IF! And when you get to the heads, a bowl porting and some pushrod pinch point work would be helpful. Most of the power at this point is in the valve job.
Click to expand...

Thanks, the motor Is together, i have another Block which will be an all forged 408. Will be needing some advice for heads for it
 
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