| From | Message |
Satakieli
Dodge Dakota
JOIN HERE
7/13/2005
10:12:50
|
 Subject: Magnum or non magnum
IP: Logged
Message:
Ok i got the oh so wonderful 360 magnum in my 88. I am wondering about raising the compression ratio, in comparison to the non magnum head. Ive arleady got a 10.6:1 ratio (shaved head and head gasket) and i have to run premium. I would like to know about what can get me the most out of 93 octane fuel in power. Thought about a stroker kit but the raise to 12:1 compression in a magnum scares me a little. any numbers or figures would be great. dont really know to much about the workings of a magnum head either so and explanation about them would be great
|
gen1dak
Dodge Dakota
JOIN HERE
7/13/2005
12:19:29
| RE: Magnum or non magnum
IP: Logged
Message:
The LA head has had the same hi-quench heart-shaped, so-called swirl-port chambers as the Magnum....since 1985! The Magnum is an evolutionary development. How much ignition timing are you running with that 10.6 CR. Stock cam or aftermarket?
|
Satakieli
Dodge Dakota
JOIN HERE
7/13/2005
17:34:43
| RE: Magnum or non magnum
IP: Logged
Message:
thanx much so theres really no diffrence im assuming. its aftermarket 502/502 by comp cams. i didnt do the tuning myself. Afraid of breaking it by causing detonation. The guy who did it at this rice boy tuner shop said he retarded the timing about 8 degrees to 4 degress btdc. Doesnt spark knock though so im thinking im good so far. if i could advance it a little to get more power and still avoid knock let me know.
I want to run higher compression because i want it naturaly aspirated.
|
t-racy
Dodge Dakota
JOIN HERE
7/14/2005
00:48:36
| RE: Magnum or non magnum
IP: Logged
Message:
If you've already had to retard the timing so it don't detonate you won't gain anything by raising the compression unless you don't mind running airplane fuel. Generally 10.5-1 is the upper limit for 93 octane but there are variables that can raise it slightly higher. Another thing to consider is the smallest chamber head is 58 cc before milling. The only way to get more compression is by a piston swap and or milling the block. If you want more power port and polish the heads and port match the intake to the heads.
|
gen1dak
Dodge Dakota
JOIN HERE
7/15/2005
00:33:20
| RE: Magnum or non magnum
IP: Logged
Message:
Well, I hate to say it because there's no way to un-mill those heads, but you could use double thickness head gaskets. Reason being, dropping the CR will allow full, or nearly full advance of the ignition timing. The Mopar Smallblock likes around 34 degrees total advance. If you're down to 4 degrees initial, that means your total is only coming up to the mid-20's total advance. The lower CR engine with full ignition timing will make more power, usable power "under the curve", than a high CR engine with a hobbled ignition timing curve, especially when all else remains equal. Other than thicker gaskets with your current setup, your options are pretty limited. You could go with a higher overlap cam, thereby reducing cylinder pressure til somewhere above 3500rpm, but you're again giving up a lot of real-world low rpm power with that. If you want street-able power, get back to no more than 9.5:1 CR, and do whatever you can to improve airflow. Heads! Port, polish, bigger valves. Crank up the total ignition advance to around 34 degrees. This watered down tripe they call gas just won't allow much. After that, increase displacement, either by blower, or more cubes.
|
Satakieli
Dodge Dakota
JOIN HERE
7/15/2005
09:08:45
| RE: Magnum or non magnum
IP: Logged
Message:
Basically it means i would have to run a more "exoctic" fuel. I dont mind considering im building this truck for drag racing only. I know where i can get some alcohol fuels, they're just expensive. So that will allow total advance in a 10.6-1 or higher, right?
|
gen1dak
Dodge Dakota
JOIN HERE
7/16/2005
00:33:47
| RE: Magnum or non magnum
IP: Logged
Message:
Okay, for racing only, it's a different game. Yeah, the more exotic fuels will allow higher CR and maintain optimal ignition advance tolerance. Just remember that with alcohol fuels, you'll need to ramp up that fuel curve, since alcohol has only 60% the BTU capability of gasoline.
|
IntenseDak39
*GenIII*
7/16/2005
08:09:34
| RE: Magnum or non magnum
IP: Logged
Message:
what's the thickness of your current head gasket on the motor right now?
|
IntenseDak39
*GenIII*
7/16/2005
08:35:42
| RE: Magnum or non magnum
IP: Logged
Message:
Satakieli,
man, i hate to be the bearer of bad news but there's no way you have 10.6:1 compression from thinner head gaskets and shaving the heads down to 58cc (that's what you told me in another post)
You need to throw away your compression calculator or hurt the person that told you that figure.
The stock 5.9 magnum is 8.9:1 compression with the following dimensions;
Flat top pistons w/o valve reliefs
Head gasket thickness: .042
Head gasket bore dia.: 4.06
Combustions chamber: 60cc
Piston deck height: .115 below 0 deck
that right there would get you 8.96:1 compression
now if you shaved the heads .010 to get 58cc chambers, then you'd have 9.14:1.
now let's make the head gasket smaller. If you put .000 (as in no head gasket), you'd only get 10:1 compression, and i doubt you're gonna run without a head gasket so let's put a .020 shim gasket in there and see what it is: 9.6:1
now if you can get me the actual gasket thickness, we can get a more accurate answer for you. But now here's the problem, just because you think you have 10.6:1 compression doesnt mean you have to run premium gas. You need to look at your static compression.. get a compression gauge and see what each cylinder's compression is. You could have a 10.6:1, but with a cam that opens it's early enough to bleed off some of the compression. If i changed my cam from the xe262H that i have now and went for the little bit hotter xe274, i'd be loosing about 15 cranking psi out of each cylinder because of the valves timing.
after you get the compression ratio figured out, you should really think about getting someone to tune that truck
|
Satakieli
Dodge Dakota
JOIN HERE
7/18/2005
10:14:23
| RE: Magnum or non magnum
IP: Logged
Message:
Thanx so much intensedak! That equation is exactly what i needed! i just measured the gasket and its a .030 so im running a little lower than i was told, about 9.3:1 roughly calculating.(thats what i get for having a ricer shop do my tuning). so i can safely reset my timing, without creating spark knock then right? will that allow me to stuff in a stroker kit to increase my displacement and CR and still run 93 octane fuel?
|
Satakieli
Dodge Dakota
JOIN HERE
7/18/2005
10:32:44
| RE: Magnum or non magnum
IP: Logged
Message:
Btw Tips on tuning for a higher cr would be great. In all honesty i dont know much about performance tuning
|
IntenseDak39
*GenIII*
7/18/2005
14:43:54
| RE: Magnum or non magnum
IP: Logged
Message:
if you build up a stroker motor, nothing with the motor how it is now matters.
you'll be replacing your crankshaft and you pistons, possibly your rods. Depending on the deck height, the piston being flat, domed or dished, and overbore, your compression ratio will change.
best tuning would be to call a place like www.krcperformance.com and telling em what you have and what kind of tuning options you want.
|
Satakieli
Dodge Dakota
JOIN HERE
7/20/2005
21:53:40
| RE: Magnum or non magnum
IP: Logged
Message:
ok ill try that site and see what happens, btw you were right about the idle being a vaccum leak. got it purring at 800 rpm idle now thanx.
|
IntenseDak39
*GenIII*
7/20/2005
22:40:23
| RE: Magnum or non magnum
IP: Logged
Message:
good to hear man..
still wanting pix though.. lol
|
| | P 1 |
|
Post a reply to this message:
Username Registration: Optional
All visitors are allowed to post messages
|
