Moparchat - Home of MOPAR enthusiasts worldwide!



Go Back   Moparchat - Home of MOPAR enthusiasts worldwide! > Technical Forums > Performance Talk

Click here to search for Mopar cars and parts for sale.


Reply
 
Thread Tools Display Modes
  #1  
Old 02-21-2009, 11:32 PM
Tarrbabe Tarrbabe is offline
Inactive User
 
Join Date: Jan 2002
Location: Cumberland Plateau
Posts: 1,972
Question Small block Magnum RPM?

I think the normal max rpm for the average stock LA motor is around 5000. That has been what I have seen most often. What I want to know is, what is the normal max rpm for the average magnum small block? It seems that I heard somewhere that it was several hundred rpm lower. And if this is so? Why?
Reply With Quote
  #2  
Old 02-22-2009, 12:11 AM
70AARCuda 70AARCuda is offline
Inactive User
 
Join Date: Jan 2000
Location: las vegas nv
Age: 70
Posts: 522
Default

weak valve springs and heavy hydraulic roller lifters is probably why...
Reply With Quote
  #3  
Old 02-22-2009, 01:20 AM
Tarrbabe Tarrbabe is offline
Inactive User
 
Join Date: Jan 2002
Location: Cumberland Plateau
Posts: 1,972
Exclamation So ,,,,,,,,,,,,,,,,,,,,,,

Are you saying that the magnum small blocks turn less rpm in stock form? If so this is something that needs to taken into account when building a magnum.
Reply With Quote
  #4  
Old 02-22-2009, 01:37 AM
70AARCuda 70AARCuda is offline
Inactive User
 
Join Date: Jan 2000
Location: las vegas nv
Age: 70
Posts: 522
Default

i have no first hand info...but the lifters are somewhat heavier then a hydraulic lifter...
Reply With Quote
  #5  
Old 02-22-2009, 12:15 PM
passing you passing you is offline
Banned
 
Join Date: Dec 2008
Location: ca
Posts: 731
Default

I have a 360 magnum 4x4 truck and yes it don't like to rev and makes peak torque around 28-3000rpm or so.
So stock magnum max rpm 4500rpm.
They have next to no camshaft in them and the spring pressures are a testament to that. The lifters, being roller, weigh a lil more.

Oiling is the same in relation to potential max rpm capability.

Yes this should be accounted for when building one being that the factory tends to match cam,comp,heads,exhaust to work together which is why the swirl port was designed for low air speed mixing of the fuel, not really aimed at big flow@max rpm /max race effort, hence the fact that there are no finned bulged wall swirl port crap in w series, eddelbrock, or even indy/brodix heads.

See when air is moving as fast as it does when buzzing high rpm's down/around the track all that finned swirl crap just gets in the way and ends up being removed with a grinder by the poor soul who was stuck having to use them in a high/max output app in the first place and when he hits water trying to really get the flow he needs, well thats probably why mag head proponents who race have no hair left.lol

As for max rpm in an stock LA small block, thats 1st determined by the amount of cam/comp, 318=48-5000, 340=6-6200rpm, 360=48-5000rpm.

In both LA/mag if the cam/comp is there about 8000rpm then you need to modify the oiling system.
Reply With Quote
  #6  
Old 02-22-2009, 12:36 PM
passing you passing you is offline
Banned
 
Join Date: Dec 2008
Location: ca
Posts: 731
Default

The above is my opinion and based on my experience so hopefully no one will take it as a personal attack on there combo and go on a crusade.
Reply With Quote
  #7  
Old 02-22-2009, 08:46 PM
bulldog426's Avatar
bulldog426 bulldog426 is offline
Registered User
 
Join Date: Apr 2008
Location: sippi
Age: 37
Posts: 868
Default

3.9 magnum in my truck which is same stroke and bore as 318, basically a 318 with two less cylinders and redline on it is about 5100rpm...
Reply With Quote
  #8  
Old 02-23-2009, 12:45 PM
pcrmike's Avatar
pcrmike pcrmike is offline
Inactive User
 
Join Date: May 2003
Location: Lawrenceburg, TN
Age: 48
Posts: 2,215
Default

Passing You, dead on. It gets ground out at first opportunity. As to a magnum revving, needs several things.

Heavier springs (preferably beehives for better harmonics)
Ganged and upgraded rockers to prevent stud pullout
Lighter lifters and lighter PR's
More cam.

These things can make a Magnum rev like anything else, but stock bottom end may be good for about 6, and not much more. The pistons are a little on the brittle side.
Reply With Quote
  #9  
Old 02-23-2009, 03:30 PM
TK TK is offline
Banned
 
Join Date: Jan 2005
Location: not here anymore
Posts: 8,876
Default

Quote:
Originally Posted by passing you View Post
The above is my opinion and based on my experience so hopefully no one will take it as a personal attack on there combo and go on a crusade.
Oh yeah? Got any proof to back up your claim?

LOL, OK,......... joking.......... Your 100% correct, other than the 318 MAG is the total opposite of the 360......... (They ruined both when they went to magnum, IMO)


To add, the 318 in my plow truck simply has a R/T 360 cam in it, and it runs great up to 5600, where the rev limiter is set on the MP computer.
Of course, I haven't done that in 100,000 miles or so....... Once i gave up trying to make a 3:55 gear, 318 power 5680 pound 4x truck move faster than your average 4 cylinder car..................
Reply With Quote
  #10  
Old 02-23-2009, 03:38 PM
cageman's Avatar
cageman cageman is offline
Inactive User
 
Join Date: Dec 1999
Location: Bismarck ND
Age: 46
Posts: 5,544
Default

Thats what my 95 318 ram revs limits at too, but it seems to run good to that point.
My valiant has bone stock magnum heads on it, my shift light is set at 6 grand, and it pulls real hard to that. 580 lift with the 1.6's. its a 273.
Reply With Quote
  #11  
Old 02-23-2009, 06:07 PM
rumblefish360's Avatar
rumblefish360 rumblefish360 is offline
Moparchat Bronze member
 
Join Date: May 2000
Location: C
Age: 57
Posts: 11,120
Default

MAx rpm on a Magnum engine before racce like mods?
6600 - 6800. Oil feeding is the issue.\
Stock for, LOL who the hell cares..................BWa ha ha ha ha
Reply With Quote
  #12  
Old 02-23-2009, 08:28 PM
pcrmike's Avatar
pcrmike pcrmike is offline
Inactive User
 
Join Date: May 2003
Location: Lawrenceburg, TN
Age: 48
Posts: 2,215
Default

Magnum 318 sure, but the 360 will stretch or break stock rods at 6500+. I have not dealt with too many 318's. I just got my third one in the dump truck. Drove it today for the first time. :-) PCRMike
Reply With Quote
  #13  
Old 02-23-2009, 10:13 PM
Tarrbabe Tarrbabe is offline
Inactive User
 
Join Date: Jan 2002
Location: Cumberland Plateau
Posts: 1,972
Question So because of the heavy lifters..........

They are hampered in revving up like an LA? And to match that the factory created the magnum heads that are designed to perform at lower rpm? Part of reducing emissions by reducing rpm and fuel consumed? But if the reduced flow is designed, shouldn't the 360 heads increase the flow and the rpm in street driving with the stock engine?
Are the magnum lifters and rockers capable of turning 6500-7000 rpm with a proper bottom end?
Reply With Quote
  #14  
Old 02-23-2009, 11:09 PM
DonCarr DonCarr is offline
Inactive User
 
Join Date: Oct 2003
Location: Prescott, Canada
Age: 59
Posts: 242
Default

Good question.

Not proof by any means, hughesengines shows hydraulic rollers going past 6600rpm. Even mention 8500rpm. These numbers seem high but .....

http://www.hughesengines.com/TechArt...rollercams.php

Their larger regrinds use 135 pound seat pressure, inverse ramp design with lots of lift.

Just click on the HER2836ALN and read. Says 8500 !?!?

Maybe give them a call ?
Reply With Quote
  #15  
Old 02-24-2009, 01:26 AM
passing you passing you is offline
Banned
 
Join Date: Dec 2008
Location: ca
Posts: 731
Default

Over 6000 or so I doubt they are talking stock lifters.
Reply With Quote
  #16  
Old 02-24-2009, 03:22 AM
TK TK is offline
Banned
 
Join Date: Jan 2005
Location: not here anymore
Posts: 8,876
Default

Quote:
I have not dealt with too many 318's. I just got my third one in the dump truck. Drove it today for the first time. :-) PCRMike
I have never seen with my own eye's, a 318 with a hole in the block, broken rod, or a LA 318 with a broken crank.

Heard of them, but never have been able to lay my hands on one. 340's? Shit, they blow like Big Blocks.........
Reply With Quote
  #17  
Old 02-24-2009, 11:06 AM
passing you passing you is offline
Banned
 
Join Date: Dec 2008
Location: ca
Posts: 731
Default

I haven't seen any factory 318's lose their guts, but have a 318 in my yard, that some knuckle head built, it ate a rod and trashed the lower half of a cyl.
Spun no.6 or 7 rod on a 440 before
I haven't ventilated any 340's so far, then again the difference between tossing rods and smooth sailing is who's building/machining it and what parts go into it.
Reply With Quote
  #18  
Old 02-24-2009, 05:46 PM
cageman's Avatar
cageman cageman is offline
Inactive User
 
Join Date: Dec 1999
Location: Bismarck ND
Age: 46
Posts: 5,544
Default

and if it had oil in it, that will kill a 318 in a hurry. That is the only way I have seen a 318 die. Shame too.
I almost killed a 318 a few years ago, another couple burnouts it would have been a goner, the spirolock came out, and the wristpin was gouging the cylinder wall, I pulled it out and put the diesel engine in it. Pulled the 318 apart to see what I had, and it was almost a goner. I couldnt believe it ihad a good pistons in it and spiro locs, I always thought it wa s apocrap motor that ran like a raped ape, but it had some work done to it. Since it gouged the cylinder wall, It is going to become a 340 whenever I get spare money. yeah right. It can sit in the corner and wait till then.
Reply With Quote
  #19  
Old 02-25-2009, 12:50 AM
pcrmike's Avatar
pcrmike pcrmike is offline
Inactive User
 
Join Date: May 2003
Location: Lawrenceburg, TN
Age: 48
Posts: 2,215
Default

My dad had a 318 that snapped the crank in half in the #2 main at an angle. The motor still ran, just made racket. Drove it another fifteen miles till we got to a payphone (before cells). It had 318K on it! LOL! My brother put a crank in it and all was good, I drove it for another 80K.

The stock magnum lifters and rockers are also limited by the stock 5/16 rocker studs. Light springs too. IF you gang the rockers with a 3/8 stud kit and run lighter lifters, stouter springs, and lighter pushrods, yeah you can turn it harder with a little more cam. It is not a glass bowl design, but it then succumbs to some of the Chevy weaknesses/flaws. The Magnum heads flow better in the exhaust (important for emissions, less overlap/re-burning) and the emissions part comes in with the high swirl design. It is a good performance design, in the chamber, chintzy in the casting between the valves and thin walled, and flawed in the rocker department.
Reply With Quote
  #20  
Old 02-25-2009, 12:08 PM
passing you passing you is offline
Banned
 
Join Date: Dec 2008
Location: ca
Posts: 731
Default

Ok... but the chevy flows good in the exhaust too but what was the LAST car manufacturer out of the big 3 mandated by the federal government to run smog pumps? CHRYSLER.

Who were the first? chevy. ha ha

The deal with the chevy, besides the poor intake flow, is that the exhaust flowed too good and over scavenging pulling intake charge out the tail pipe.
Reply With Quote
  #21  
Old 02-25-2009, 12:12 PM
passing you passing you is offline
Banned
 
Join Date: Dec 2008
Location: ca
Posts: 731
Default

notice the mags run hotter then LA's.
combustion/exhaust gas temp has a lot to do with emissions crap.
Reply With Quote
  #22  
Old 02-25-2009, 12:19 PM
pcrmike's Avatar
pcrmike pcrmike is offline
Inactive User
 
Join Date: May 2003
Location: Lawrenceburg, TN
Age: 48
Posts: 2,215
Default

Yupper. Smooth/polish teh cc face and the effects of the heat have less impat on the head. :-) PCRMike
Reply With Quote
  #23  
Old 02-25-2009, 04:00 PM
cageman's Avatar
cageman cageman is offline
Inactive User
 
Join Date: Dec 1999
Location: Bismarck ND
Age: 46
Posts: 5,544
Default

broke the crank and it still ran? how did the cam turn?
Reply With Quote
  #24  
Old 02-25-2009, 05:57 PM
Tarrbabe Tarrbabe is offline
Inactive User
 
Join Date: Jan 2002
Location: Cumberland Plateau
Posts: 1,972
Question So if you want to turn a SB Magnum............

More than 4600 rpm to say 6000, you need to change the rockers for lighter units and a hotter cam. Then you have to change the head studs to the larger Chevy size and Chevy? rocker arms? Plus re-engineer the oil system for the added rpm?

Do the Magnum Crate motors take this approach? I'm having trouble accepting that Chrysler would not engineer into these engines the ability to simply increase these engines for performance. They get bigger numbers pretty easily but what if you want 450 hp?
Reply With Quote
  #25  
Old 02-25-2009, 06:01 PM
pcrmike's Avatar
pcrmike pcrmike is offline
Inactive User
 
Join Date: May 2003
Location: Lawrenceburg, TN
Age: 48
Posts: 2,215
Default

It was broke at an angle, and it was inside the #2 main, held straight by the bearing. When he took it out, we could not believe it. Dad kept the pieces for years, as he had built engines for about 40 years at that time, and never seen anything like it. I haven;t either. Granted it chewed up teh bearing real good, but never made it to the saddle! He might still have that around here somewhere. I will see if I can get a snapshot of it. :-) PCRMike
Reply With Quote
  #26  
Old 02-25-2009, 06:05 PM
pcrmike's Avatar
pcrmike pcrmike is offline
Inactive User
 
Join Date: May 2003
Location: Lawrenceburg, TN
Age: 48
Posts: 2,215
Default

Just talked to Dad, (he walked in as I hit send) and he still has the rear part. It broke in the #4 main though, not #2. He said it was "the one behind the thrust bearing". he was gonna make a lamp stand out of it, but hasn't. I was only 17, I didn't remember right on which main it was. He is gonna dig it out so I can snap a shot of it. Prolly tomorrow if it is not raining. :-)PCRMike
Reply With Quote
  #27  
Old 02-26-2009, 02:16 AM
TK TK is offline
Banned
 
Join Date: Jan 2005
Location: not here anymore
Posts: 8,876
Default

Quote:
Originally Posted by cageman View Post
broke the crank and it still ran? how did the cam turn?
had a 400M Ford that did the same thing........
Reply With Quote
  #28  
Old 02-26-2009, 02:53 AM
rampage_82 rampage_82 is offline
Inactive User
 
Join Date: Dec 2007
Location: Mountainair NM
Posts: 657
Default

Quote:
Originally Posted by TK View Post
I have never seen with my own eye's, a 318 with a hole in the block, broken rod, or a LA 318 with a broken crank.

Heard of them, but never have been able to lay my hands on one. 340's? Shit, they blow like Big Blocks.........

Hey man leave the big blocks out of this... Now I will give you that the 318's were tough little buggers, but no need on pickin on the big blocks. I've yet to see one with a rod hanging out the side... bearings knocked out yeah, spun bearings yeah, but they will usually seize before throwing the rods.... Now I can show you about 50 both big and small chebby's dead with a rod or more hanging out of the pan.
Reply With Quote
  #29  
Old 02-26-2009, 10:25 PM
pcrmike's Avatar
pcrmike pcrmike is offline
Inactive User
 
Join Date: May 2003
Location: Lawrenceburg, TN
Age: 48
Posts: 2,215
Default

I have hauled off at least 5K pounds worth of ventilated Blowties. The ONLY blown up Mopar I ever saw was a tutu that was hevily used, and had a HG replacement and never replaced the bolts, and hydrolocked the #4. Never ventilated. :-) PCRMike
Reply With Quote
  #30  
Old 02-26-2009, 10:41 PM
john briggs's Avatar
john briggs john briggs is offline
Inactive User
 
Join Date: Sep 2007
Location: flippin arkansas
Posts: 417
Default

Ever notice when you tear down a 318 that there is never any ring ridge in the cylinder walls.
every 340/360 i take apart takes a ridge reamer just to get the piston out!
Makes me wander if the geometry of the 318 block is better than the 340/360

Ive been toying with stroking a 318 just to see what it would do.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Starter Info: Small Block LA / Magnum dust Performance Talk 15 11-19-2006 04:53 PM
Horsepower specs on small block magnum vanderkwv Performance Talk 7 11-14-2006 08:22 PM
I need a motor. 360 magnum small block Marc 99 R/T Trucks - Parts Wanted 0 11-19-2003 07:56 AM
Small Block, pre-Magnum, Roller Rockers PatrickT Rear Wheel Drive - Parts for Sale 1 12-21-2001 05:58 PM
going from Magnum to LA small block, will everything else bolt up? XJGPN Performance Talk 10 02-06-2000 02:29 AM




All times are GMT -4. The time now is 06:57 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
. . . . .