Okay,
So I took the advice from my last post and looked into a swap for my 95 5.2L. Took it to a custom engine guy and he put in a 2002 5.9L magnum. Direct swap. Of course after reusing the 5.2 intake manifold and put in the 5.9 flywheel. It runs good. However im still running it on my 5.2l computer. It runs fine with very little vibration. May not be a good word but basically it purrs along just fine. At 3/4 throttle or even more so WOT it falls on its face. I used to be able to squeal the tires for a few seconds before taking off with the 318 w/ full bolt ons minus a tune. Now it wont even chirp the tires. Very sluggish but after about 40 mph it starts to come to life.


My thought is that it will indeed run fine with the 5.2L stock pcm but it will run lean and I wont be taking full advantage of the power (TQ mainly) difference in the 360. Also I have a comp cams 20-744-9 cam installed. After seeing it was a Super strong TQ cam for a 318 installed in a 360 I got worried but saw others have use this cam to reap the low to mid range benefits. After seeing the stock 360 and 318 cam specs this is still a vast improvement from factory. This may also attribute to the stock tune and it falling on its face. It has great power putting around or mild (50 percent) throttle. 75% or more and its a rolling turd until about 40plus mph then pulls great. What happened to the low and mid range? I feel like ive stepped backwards. I have a 50 mm tb that probably could use some porting to 52mm down the road. Its a fastman and still better than factory.


Ive read a few forums and plan on calling B&G. Am I way off or could I be really toning down my tuning that bad with the 5.2 pcm. I know the 360 makes more power at a lower power band. It feels like ive got all the air I need but maybe my fuel is minimal. As a side note. It runs much better currently with 90 octane vs 87. Im also running the 318 manifold with the 318 injectors. Its a 46 rh so my beefier TQ converter and trans don't give me any issues. Ive successfully maintained OBDI (hence my lack of tuning options) Any suggestions from experience here guys? Thanks!

 

Also as an extra side note- between 40 - 52ish if I step on it from cruising it will pop once(sounds like backfiring) and after the hesitation take off just fine. Another reason im thinking it may be running extremely lean with the 5.2 pcm. I know I could run a 94-95 mopar pcm as well if I am correct but 90 is the highest we have here. MMT (octane booster every fill up) will probably foul my plugs much more often than needed and I don't imagine it being "great" to run every fill up.

 

See if you can find a mopar performance PCM for your truck and the 5.9 engine. That will help, not sure if it will solve all your issues though...... How do you feel like upgrading to OBDII?

 

hmm strange, my 360 does the "pop" also. its backfiring out of the throttle body. i have narrowed it down to the cam being a bit out of time, or the fuel sync being off a tad.

i have the 20-745-9 cam, along with 1.7 roller rockers, and a few other goodies.

im still running my 5.2 pcm, but have a custom 5.9 tune from hemifever.

 

Being OBD1 i also would go with the Mopar performance 5.9 pcm. The 5.2 in it now isn't supplying the 5.9 with enough fuel. As far as the "pop", Did you check the plenum gasket?

 

The plenum gasket isn't going to cause a backfire out of the throttle body. It would just cause a vac leak, and oil consumption.

I have an m1, so I won't ever have that problem with the motor ever again.

I also have a Hemi now also, so the 2nd gen just sits around doing nothing til the snow melts.

 

Yes it will! Especially under hard throttle. I had this exact issue with mine before i was educated of all the issue a leaking plenum can cause. How i know is i put a timing light on the coil wire and pointed it on the crank. Put the truck in drive(blocked up e brake on) gave it some throttle until it acted up. the leak throws the pcm into fits and it fire the coil when it's not supposed to (causing the a backfire out the intake). I seen it first hand by watching the timing light. Replaced the gasket with the Hughes kit and problem solved.

 

Ok so of course I bought a Hughes plenum plate when the 360 donor was overhauled. My guess exactly that the 318 pcm wasent giving enough fuel under heavy acceleration. I really don't think I'll go to obdII. The 94-95 mopar 5.9 pcm will work but will octane boost every fill up hurt? We have 90 as premium here. Also what about having b&g flash for a mild 360. And the backfire is actually 45-55 and feels like the header meets the y pipe area. Maybe my exhaust has too much back pressure or too little? Thanks for the replies!

 

See which option is less expensive. I know B&G is right about 250-300, aren't they??

 

Yeah I wanna say around 400-450 or so. I'll call them tomorrow. Just want my low end back. It's gotta pull over 3000rpms to really pull. Do these systems get plagued by torque management as well? Also the stage 3 patc trans build doesn't like the rev limiter at stock settings either