Ok, so I am actually putting this in a RWD converted 99 Intrepid, but since it`s a Magnum, I kinda figured this would be the best place to discuss the engine build. No need to school me in trans tech, I come from the diesel side of things and know full well the inside of the 727 based OD transmissions and how to make them hold up to monster tq (because we all know tq is what breaks things).

Now, I have had my hands in building some older LA engines and know that they are tough. But I`m new to Magnums and where their weak points are. I know older rods can handle 525 NA hp and 7500rpm, the proof is in our last 340 we built, though they were balanced and shot peened. My question is are the Magnum rods just as strong as the LA rods? Or should I throw them in the scrap heap and find some good forged I-beams? Also, is the production crank cast or forged? If cast, I would like to know for sure that they interchange from LA to Magnum since I have a forged 360 crank at the shop... Last, using 2-bolt forged main caps, what kind of power can the stock Magnum block withstand? Is 550 turbocharged hp out of the question, or will I have a live grenade under my hood?

 

you'd definetly want a new set of slugs for it (the magnum pistons don't hold up all that great to boost)

not sure about the rods, but i'm about dead sure the crank is cast, not forged

 

Wouldnt push the block past 6500rpms na, 6k rpm w/boost. Buddy split his 408/360block down the middle buzzing 7k. Bottom end is ok, cast cranks seem to hold up fairly well, rods are forged from my understanding, pistons semi crap, heads are garbage (crack between valve seats) & the steel plenum under the alum kegger is just down right idiotic.
52-55mm tb with some EQ (Hughes HD) heads with good gaskets under them & either an m1/2bbl or Hughes F1 if you want to splurge. Know of a couple guys with Daks that were making mid/upper 400rw for years without splitting the block or popping windows in it.

 

Oh the stock slugs are getting tossed in favor of a set of .030 over Sealed Power coated hypertuetics and a set of barrel faced chome-moly rings. I think I`ll just save myself some hassle and get a set of Eagle SIR-I beams with floating pins anyway... I was wrong on that crank at the shop, it`s just a stocker

So now I`m torn, if I spend that kind of money for a Forged crank I may as well go 4" stroke. I think the extra torque potential would come in handy with such a heavy car, and the turbo should help push the extra air through stock (ported) heads.

BTW for future reference, I`m setting up the heads with 2.02/1.60 SS 11/32 stem +.100" chevy valves and .550" spring pockets. Also, I`ve had decent sucess with a VGT turbo on my old 12 valve cummins, so I`m gonna give it a shot on this build. Should be fun...

 

post pics...

 

indy.. this is your game... lol, but definatly, post pics, i had a 94 intrepid, diff boyd, but still, very cool if ya can pull it off....

 

Already have it`s twin done with an old mid 60`s 318/727 combo out of a truck with an 8 3/4 out of a Fury III out back. It was all stuff we had laying around. Always thought about doing it, just couldn`t justify hacking up a perfectly good car until one came into a buddy`s salvage yard with major hail damage and he decided $350 would take it home... Surprisingly, there isn`t much fab work, so I managed to steal an almost mint 99 for $500

The plan for now is a simple rebuild and shift kit for the 46RH and dropping a 5.2 Magnum in with a ported TB and the keg with 2" cut off the bottom of the runners at a 60* angle. But that`s just to get it moving because I really need something gas to drive instead of my diesel on these short trips in the winter. The 360 will sit on the engine stand as I gather parts until it`s ready to drop in the hole. Then the 318/46RH will come out so I can put some goodies in the trans and swap it to the 360.

Just so you guys know, the 360 end of this project may take some time... I plan to get my truck to the 500rwhp club bare minimum before starting on it. All while working on a disabled veteran/college student budget lol

 

I'm not a well read FI guy, so I figured I may as well ask. The fuel pressure range for the Magnum engines in the trucks is 35-45psi, whereas the range for the Intrepids is 44-54psi. My question is if the fuel pump in the car is pushing the high side, will that extra 9psi put a strain on the stock injectors? Also, will it throw the PCM for a loop?

Before I forget I need to ask about how I plan to set up the exhaust, I am going to put an x-pipe in almost imediately downstream and use this as a point to put the upstream O2 (to mimick the 2in 1out style cat). Now the question is, do I have to worry about not having a downstream O2? If so is there a way to remedy the problem (O2 simulator)?

BTW- The PCM is out of a 95 1500 rcsb and I will have the complete wiring harness to play with. Which also brings up another question, does anyone know if B&G can work with the older style PCMs? Or will it hold me back? If so, I'll look for a PCM/harness out of a 96 or later truck for the performance build and run this one in it for now...

Oh, and for when I get this 360/408 (whatever I end up with) project going, how do I get the boost into the engine? Is there a bolt on adapter/elbow for the TB? I was looking at how to make one and it looks simple enough. Or is there a certain aftermarket TB that I will need???

Say, RM_Indy, do you think parallel 60/60/VGT turbos will be a little much? I guess my thoughts are if I'm pushing one to 45psi on my diesel to get 422rwhp/903ft-lbs (and still feel safe about trying for the 500hp mark), that pushing two to produce a much more modest 15-20psi will still net about the same flow? Or am I asking too much of the block/heads/headgaskets to handle that kind of boost? Plan is for CR in the 8.5-9:1 area and to run it on E85...

 

Since the car is completely custom why don't you just get a standalone ECU like megasquirt to run everything it would be easier and better than adapting a stock ECU. Also don't worry about the downstream O2 because 95's didn't have them. B+G can also work with the older PCM's or at least they say they can on their website.

 

LOL you must not have caught the "working on a disabled veteran/student budget"? I could only imagine the dyno time required to dial the megasquirt in with let alone the cost of buying one... I have access to really cheap parts off of wrecked trucks, so dealing with stock style PCMs is more in my budget. Though if it comes down to it there will be an Edlebrock RPM Air Gap and a blow through Holley sitting on top... But I would rather have the driveability/ease of cold weather starting of the MPI.