| From | Message |
jd
Dodge Dakota
JOIN HERE
1/25/2004
23:35:38
|
 Subject: rockers!!
IP: Logged
Message:
question for all i am rebuilding a 98 318 and was wondering what kinda rockers i should go with and whats a stock ratio whats gonna perform well for a running the cam , what cam will run well, if i go with 1.7 rockers plus a head shave how much clearance will i have between the piston and valve.....would stronger springs be a good idea... one more question what will the stock computer handle in engine mods (i dont want permium guzzling moper perf. pcm)
any help would be awesome
jd
|
gen1dak
Dodge Dakota
JOIN HERE
1/26/2004
20:21:07
| RE: rockers!!
IP: Logged
Message:
Too many parameters. How much clearance will you have? I don't mean to sound snotty here, but it really does depend on the lift in the cam, and if you're using the stock 1.6:1 ratio, or if you move to 1.7's, not to mention how much you shave off the heads. Roller rockers are much more accurate in their ratios, and free up power through reduced friction. You'll run into a need for premium as soon as you crank it if you shave those heads much. Unless you run some rediculously high overlap cam, it'll rattle like hell with more compression. You can get away with a little, but that's all. Then it's premium fuel or else! The Mopar Performance Magnum RT cam is a great cam...pulls hard through 6000rpm with good low rpm power and good manners. My prefs lean towards CompCams. Some like KRC's stuff. You can pretty well get a good grind from any reputable cam grinder. It's all in what you want. Better springs? Ya think? Come on, that's a no-brainer. Yes, get better springs. The Mopar Perf. Magnum RT springs slide right in and will handle any street cam, up to .525 lift. That's plenty. Better retainers and locks should also be used. I snagged a set of SuperStock NOS 426 Hemi retainers for $25 and they work perfectly. (The Magnum RT springs aren't conical like the OEMs, so you'll need new retainers). Just remember, if you go with 1.7:1 rockers, you have to factor that into your cam selection.
|
heh_heh
Dodge Dakota
JOIN HERE
1/26/2004
21:40:56
|  I'm off me rockers!!
IP: Logged
Message:
|
Greg
Dodge Dakota
JOIN HERE
1/26/2004
22:02:15
| RE: rockers!!
IP: Logged
Message:
OK I'm about tired of seeing the dancing face everywhere I go!!!
Back to subject now... I wouldn't go much over .020 head shave because of compression... Also keep in mind that you will have to shave intake for the same amount you are your heads... Also keep in mind that you are extending the lift of your pushrods by whatever you shave your head to if you don't shave your pushrods as well which means that you really wont need a highperformance cam... The stock cam in the mag is one fine cam, but could use low end improvements, but if you go with high lift cam, most companies say to use reg 1.6:1's rockers for better lowend performance and takeoff... Evident vacum problems have been listed for overperformance cams and lifters... Like gen1dak said, might want to change springs and retainers and opt for best rocker kits... Look into crowler rockers for reliability if you wish... Might as well do port and polish while your into head work to really free up some air:)) AND one thing most don't think about as far as performance replace exhaust with headers, high flow cats and muflers, and replace o2 sensors... Will help with idle and freeing up some more of those hidden ponies ; )) Hope this will help you a little more with you decissions on what you want to do...
|
jd
Dodge Dakota
JOIN HERE
1/26/2004
22:57:36
| RE: rockers!!
IP: Logged
Message:
so alrightey then the engine im using when i got it still had "factory installed" written on the oil filter. i got it from a guy that worked at a wreking yard and was goin to use it in one of his own projects but ran outta time...... the only reason i wanted to shave the head was to up the comp. a tad im goin to use the stock pistons so i will only take off perhaps 10 thou will it still be necissary to shave the intake?
it was mentioned that better retainers are a good idea will i have to change or make changes to teh stock valves, i am in the process of polishing the heads dont want to port much for fear of going to far.
also what will the stock pcm handle for cam upgrades
oh yea i live in canada so pollution control is not a concern for me, cat is already long gone
|
janesy
Dodge Dakota
JOIN HERE
1/27/2004
15:07:53
| RE: rockers!!
IP: Logged
Message:
if you don't need to pass a sniffer, like i do here in Ontario, don't get the R/T cam. It is a good cam for an emission controlled vehicle, but you will likely end up disappointed with it as it doesn't produce all that much power. It is a good replacement cam but not performance cam. I have just over 5000km on my new motor and i am swapping the R/T out for a krc before my dak hits the summer again.
|
Greg
Dodge Dakota
JOIN HERE
1/27/2004
19:51:46
| RE: rockers!!
IP: Logged
Message:
Yes it is my understanding that you must shave intake to your head shave exactly or there abouts... Make sure to also port match your intake if you really wan't to feel the difference from your head job... AND exhaust if you wish... You oughta be able to port out as much as your gasket matching and even then some with these heads :))
I don't know if I would had gotten rid of cat completely, but instead put high flow one on due to o2 sensors being ruined from this... Trust me I am going to have to spend nearly $80 apiece for my o2 sensors so I can replace them... Idle is affected be backpressure loss as well... AND a gas engine unlike a diesel needs some backpressure to run like it is suppost to... You will lose torque and fuel mileage from cat gutting or replacing, but the same applies for too much backpressure as well, so it's got to be just right nearly...
|
jd
Dodge Dakota
JOIN HERE
1/27/2004
22:03:28
|  RE: rockers!!
IP: Logged
Message:
so okay what diff does it make to the o2 sens if or not theres a cat or not?
and the faster the air in the faster the exh. out the more power:):)
does any body know how the pcm will respond to different cam grinds????????????
|
Greg
Dodge Dakota
JOIN HERE
1/27/2004
22:09:27
| RE: rockers!!
IP: Logged
Message:
It gives them the wrong exhaust readings, causing rich running, rough idling, and premature o2 sensor failure and possibly overfuelling causing oil cleansing of cylinder walls resulting in needing rings replaced earlier as well ; ))
|
gen1dak
Dodge Dakota
JOIN HERE
1/27/2004
22:19:54
| RE: rockers!!
IP: Logged
Message:
JD, if you stick with the stock cam, and the 318 cam has more lift than the 360, your springs will be okay, as well as the retainers and locks. Granted, the post-'93 cams are lazier in their timing, but the lift is still there so it's not all bad. Keep this in mind regarding compression. Bumping up the cam specs to a good street performance cam that builds good mid-range power will do, in essence, the same thing. Compression ratio builds cylinder pressure. A good moderate overlap cam will build more cylinder pressure, which simulates an increased compression ratio in the midrange. With high overlap cams, you lose cylinder pressure in the lower rpms and even the lower midrange until the engine speed is sufficient to take advantage ot the cam. You've already said you don't want to run premium. A lower compression engine running full ignition advance will whip a higher compression engine with a crippled ignition advance every time, and you'll have to retard the timing to run lower octane gas if you go far at all with the CR. Add a better cam, that builds even more cylinder pressure and you're gonna have a mess. The engine will be less than it could be. It's your deal. If you want to try it without milling everything, just use the 1/2 thickness head gaskets. Their compresssed thickness is about .020" thinner than standard. Cheaper, and not a permanent mod, but it'll give you an idea. Get it hot, see if it pings. A little more work, but worth it. Here it is, direct from the MP Magnum Engines bible:
The best solution, time and money allowing, is to lower the compression ratio to 9.0:1 or less. A compression ratio of 9.5:1 could be used with "blends" (octane booster, etc.) but would only be recommended for engines that are raced exclusively. Blending is troublesome and offers many opportunities for error. The 9.5 engine will also "carbon-up" to an actual 10:1 or 10.5:1 in a few thousand miles. Now you're in trouble and there isn't a good solution, except less spark advance, and that's not good for performance.
|
jd
Dodge Dakota
JOIN HERE
1/28/2004
00:36:39
| RE: rockers!!
IP: Logged
Message:
sorry greg i really should have told you the pcm i plan on using is before the started running the second o2 sensor for sampling.... so my truck will only use 1 o2 sensor..
1994 magnum:))
and gen1dak wow thanks for all the info im gonna read it again to take it all in:()
it really seems we have nobody that wants to answer my computer vs. camshaft question ?!??
is there a site that explains the workings of a 1994 dakota pcm ????? like the parameters it runs on .... will a cam change push the map sensor past the limits and make it run in limp???
|
gen1dak
Dodge Dakota
JOIN HERE
1/28/2004
20:36:54
| RE: rockers!!
IP: Logged
Message:
In the OBDII systems, the downstream O2 sensor measures the efficiency of the CAT, and when it deteriorates to the point that emissions exceed legal limits, the MIL (check engine light) comes on so it can be serviced.
Cam vs PCM. How will it react? Well, on the OBDII's, it'll take a little time, but the PCM will learn the new airflow and fuel requirements as it runs and new O2 sensor inputs are received...up to a certain point. If the cam and other mods are so great that they exceed the ability of the PCM and injectors to provide the appropriate mixture, you'll run lean and cook the converter, and will be down on power, pinging as well. For example, you can run the Magnum RT cam with stock PCM, but as you move to improve beyond that, you start reaching the upper limits of the stock injectors and limits to what the PCM can adapt to. Some cam groups will mention where their cams fall in stock PCM-friendliness or the potential need for computer mods.....Competition Cams being one. On '92-'95 PCMs, essentially, you have a built-in set of parameters that it will adjust to within the limits....simpler than the OBDII, but you run into the same situation....stock to a point, then HiPo PCM or PCM mods in some other fashion.
|
jd
Dodge Dakota
JOIN HERE
1/29/2004
01:12:12
| RE: rockers!!
IP: Logged
Message:
my truck is PRE OBD11 no second o2 sens.......
thanks anaways
do you know of what kind pcm mods can be done.... i find the computer control aspect of my truck very interesting and want to understand what does what and why..... i am also experienced in electrical and electronics and just bought the factory 1994 service manual from chrysler.... 90 bones but the wiring diagrams are the best ive seen, theyre great
is there a web site that a guy could look this stuff up in????
also whats the difference in specs of the 318 magnum camgrinds over the years?????
did they change much if any?
thanx in advance
jd
|
gen1dak
Dodge Dakota
JOIN HERE
1/29/2004
11:24:47
| RE: rockers!!
IP: Logged
Message:
Okay, with pre-OBDII, removing the converter won't upset the computer, just the smog police.
http://www.allpar.com is a good site for Mopar engine history.
This next link takes you to some more detailed info relating to cam specs, etc.
http://www.dodgeram.org/tech/gas/specs/index.html
Basically, the cam specs were milder after 1993, though the lift figures stayed the same. Note that the 318 had .432 lift, while the 360 had .410 lift. Adding 1.7 rockers kicks up the 318 cam ti some decent lift, but the timing events, especially the later cams are pretty lazy. Higher ratio rockers will help, but a better stick to start with is a better bet.
Good move getting the FSM. When I got into the whole engine swap deal, I snagged one from '89, '93, and '98 to compare changes. It's like getting the secret code book. All the questions with answers. Really makes me mad when I see that some questions I've asked could've been answered, but they just shoveled me a load instead.
Mods involve custom burning of the chips...that gets expensive quick. Typically, running the PCM for a 360, if you have a 318 with mods will work. Also, the MP PCMs have better fuel curves and quicker ignition curves. The custom burning basically does the same thing. Another alternative is to use the infinitely adjustable controllers from Accel or Holley. They are tunable with a laptop and you can set it up exactly as you want, and re-tune as mods are made. They're $teep, but you get flexibility in the deal.
|
Tnjones
Dodge Dakota
JOIN HERE
1/29/2004
13:03:15
| RE: rockers!!
IP: Logged
Message:
Be careful there JD, lower restriction exhaust doesn't ALWAYS equal more power. As previously stated, 4 stroke engines often operate more efficiently with some back pressure than with none. Too open and you also lose any scavenging benifits. There's a tork vs Horsepower trade off with reducing exhaust restriction. I stayed with a single exhaust (split after the second cat for looks and sound :) to maintain low-end tork. My KRC cams reduced low end tork and added top end horsepower. Going to true duals would have cost me even more low end tork. I'm not trying to build a motor for peak HP at 5000 RPM though. My Dak is a daily driver and I built for peak HP around 3500 RPM and shifts around 4500-4800. Within these parameters I'm VERY happy with the way it turned out.
|
Greg
Dodge Dakota
JOIN HERE
1/29/2004
19:13:53
| RE: rockers!!
IP: Logged
Message:
Thankyou, like I said this isn't a diesel, which is better off with less backpressure, but for lowend torque like I and Tnjones said, you need just the right amount of backpressure, which is ussually what the cat supplies... BUT as stated if you want a high revving get up and goer then you did the right thing in this case :))
|
| | P 1 |
|
Post a reply to this message:
Username Registration: Optional
All visitors are allowed to post messages
|
