5.2 magnum GT35 to S475

[Turbosmblk]

On back pressure it can be useful if you’re leaning on things from what I’ve seen. coolant pressure absolutely is helpful. They say you can see when you’re about to blow a head gaskets because you’ll get little spikes right before it goes.

 

[TT5.9mag]

I haven’t, however I’ve taken advise from some guys that tune Holley for a living and they said you can watch your VE numbers on your fuel graph and where it peaks it’s typically max torque then it will start falling off in the upper rpm range. That’s exactly what my fuel graph does between 3700-4200 range. My theory on this was further solidified when a guy on YouTube (restoreitralph) dynod a bone stock magnum with a gt45 and peak torque was at like 3100 just like the factory peak torque numbers. He then put a Hughes air gap on with no other changes and peak torque was now 3800. So my super victor probably pushed things up a couple hundred from that.

What “they” say is correct. Peak torque will always fall right at peak VE. So you pull an additional 3 degrees, in how much of the map? On traction limited stuff, (street tire) I usually keep the timing out of it down low all the way to peak torque and ramp it back when the tire has less chance to break loose. AEM infinity has tables that can be referenced to speed or gear. Boost by gear or boost by speed are two of my favorite tuning tables.

 

[Turbosmblk]

What “they” say is correct. Peak torque will always fall right at peak VE. So you pull an additional 3 degrees, in how much of the map? On traction limited stuff, (street tire) I usually keep the timing out of it down low all the way to peak torque and ramp it back when the tire has less chance to break loose. AEM infinity has tables that can be referenced to speed or gear. Boost by gear or boost by speed are two of my favorite tuning tables.

I pull the most timing at 4k and ramp the timing out starting at 3750 and put the timing back in at 4250. On street tires I’ve been using timing retards using boost vs time and it’s worked out well so far.

 

[Turbosmblk]

So youve dynod it and know where MBT is with the stock cam?
Please do measure the ring gap and let us know.

So I checked a cylinder tonight on a spare motor. .029 top ring and .034 bottom. Now… we all know we can’t say they’re all that wide but it might be safe to assume they used the same gaps as a 5.9 even though the smaller bore could take a tighter ring gap. If this is the case I don’t think anyone would ever have to really worry about butting rings together unless they got super greedy with the timing or was really making big big power. What say you?

 

[Cuprum-74]

Hey as long as it's mopar to mopar right? What gives...
Oh wait you used a GM wiring harness... Booo! Rubbish! Filth! Muck!

J/K
But this is cool, heck it would still be cool if it was a G3 Hemi, I've actually seen some good work done on those swaps to the older Mopars.
Heck, I was droolin' over a 1970 Challenger with a V10 from a totaled Viper at a car show years ago. Modified a little of course, he said he got it to push about 570HP while still using the stock Viper wiring harness tuned. Yes he said he knows he can push a lot more HP out of it but he likes it the way it is.

 

[Turbosmblk]

Hey as long as it's mopar to mopar right? What gives...
Oh wait you used a GM wiring harness... Booo! Rubbish! Filth! Muck!
View attachment 1716371513
J/K
But this is cool, heck it would still be cool if it was a G3 Hemi, I've actually seen some good work done on those swaps to the older Mopars.
Heck, I was droolin' over a 1970 Challenger with a V10 from a totaled Viper at a car show years ago. Modified a little of course, he said he got it to push about 570HP while still using the stock Viper wiring harness tuned. Yes he said he knows he can push a lot more HP out of it but he likes it the way it is.

LOL my dad said the same when I told him it had a GM tps, iac, temp sensor, and ls coils haha. In all fairness the way HCR does their harness you can literally swap between sbc, bbc, sbf, any hemi etc in 2 minutes. There’s a sub harness that branches off for ignition that’s already pinned for your different reference voltages. You buy another sub harness, plug it in and you’re good to go.

 

[TT5.9mag]

So I checked a cylinder tonight on a spare motor. .029 top ring and .034 bottom. Now… we all know we can’t say they’re all that wide but it might be safe to assume they used the same gaps as a 5.9 even though the smaller bore could take a tighter ring gap. If this is the case I don’t think anyone would ever have to really worry about butting rings together unless they got super greedy with the timing or was really making big big power. What say you?

I agree. I really have no idea why Chrysler would assemble them with that much ring gap. Maybe theyre soft and wear quickly and why the bores in magnums are always nice. Who knows.

 

[TT5.9mag]

That’s an .0075 ring gap factor. That’s a top ring gap factor most ring manufacturers spec for big boost, big nitrous, serious drag race stuff. I use .007xbore for just about everything and I’ve made big power there on boost and never butted rings. I think it’s safe to say at least that 5.2 would be ok with lots of boost.

 

[Turbosmblk]

That’s an .0075 ring gap factor. That’s a top ring gap factor most ring manufacturers spec for big boost, big nitrous, serious drag race stuff. I use .007xbore for just about everything and I’ve made big power there on boost and never butted rings. I think it’s safe to say at least that 5.2 would be ok with lots of boost.

It’s just a theory I have, and I could be wrong…. But I almost wonder if 5.2s have more boost pressure capability before blowing head gaskets than 5.9s due to the increased deck area from the smaller bore. Kinda like 4.8 and 5.3 is the “golden child” of sbe ls stuff. Smaller bore than ls1 6.0 etc so the cylinder head can clamp better. Maybe I’m wrong and it’s just a coincidence.

 

[TT5.9mag]

It’s just a theory I have, and I could be wrong…. But I almost wonder if 5.2s have more boost pressure capability before blowing head gaskets than 5.9s due to the increased deck area from the smaller bore. Kinda like 4.8 and 5.3 is the “golden child” of sbe ls stuff. Smaller bore than ls1 6.0 etc so the cylinder head can clamp better. Maybe I’m wrong and it’s just a coincidence.

Interesting theory, but I can’t say I’m with ya. The difference between a 5.9 and a 5.2 is .09 and that ain’t significant when it comes to clamp load. I use studs and cometics so I dont have head gasket problems. And BTW I just gave Richard Holdener a 6.0 LS that I plucked from a junk van and watched it make 850 on very low boost. I’ve personally made 1200 with one and I know Richard has made 1543 with one. If you offered me a 4.8, 5.3, or a 6.0 all for the same price there is no world where I’d take anything but the 6.0.

 

[TT5.9mag]

Now if you start taking about pounds per square inch and the surface area of the top of a piston and the difference in overall cylinder pressure at 20 or 30psi and the difference in load it imparts between a 5.2 and a 5.9 I might could get on board with that.

 

[Turbosmblk]

Small update. I’ve got the hot side done minus wastegate placement (I know where it’s going to go) and finish welding 2 tubes but I ran out of filler rod so it will be the weekend before I can get some shots of that. I did cut my radiator to see how everything is going to fit. I ended up taking 6” out of it and believe that will give me enough clearance even with a shroud and fan. I don’t feel like I’ll have any cooling problem whatsoever, but if I do it will probably be at idle in which case I will install a c7 vette fan. They’re 14” SPAL brushless and 600w so they move a TON of air. You can pick them up straight from GM for like $300 but require PWM- signal which won’t be a problem as I can use the Holley to control them but if others want to go this route you will have to purchase an external controller to make everything work. Snapped some shots of the rough cut on the rad and how it looks roughly bolted up. Still have to dress everything up and add the flat plate that goes on the ends to protect the fins.

 

[Turbosmblk]

Hot side is done. Everything is setup to give max clearance around the accessory drive and be low to help alleviate heat issues under the hood. Only going to run a single 50mm gate. With the priority it has I think I’ll be alright. We shall see anyway. If not I may use the BOV like a cold side gate. It’s gaining in popularity and some folks claim their stuff spools faster.

 

[TT5.9mag]

If not I may use the BOV like a cold side gate

That can be very hard on compressor wheels.

 

[Woody500]

What size are the primaries? They look small, does it spool faster, what about back pressure, etc etc .
Many questions, as I've got a GT 45 for my 65 Barracuda. I've already decided to mount it on rh side to exhaust thru rh inner & get all that extra heat out. Any accessory placement ideas welcome.

 

[Turbosmblk]

What size are the primaries? They look small, does it spool faster, what about back pressure, etc etc .
Many questions, as I've got a GT 45 for my 65 Barracuda. I've already decided to mount it on rh side to exhaust thru rh inner & get all that extra heat out. Any accessory placement ideas welcome.

2”. Forcefed86 on the turbo forums made like 1000hp with 2” fully divided hot side on a 4.8 and went 160mph to the 1/4 and said spool was much faster than 2.5 or 3”. If your not fully divided though I’m not sure how small you can go.

 

[Woody500]

2”. Forcefed86 on the turbo forums made like 1000hp with 2” fully divided hot side on a 4.8 and went 160mph to the 1/4 and said spool was much faster than 2.5 or 3”. If your not fully divided though I’m not sure how small you can go.

1-5/8 is a good size for 318 tube header primaries, so sounds interesting, however
4.8 LS doesn't really prove it. I'd like to see you build one with larger tube's & test them back to back, only changing pipes. It sounds real good for street use, which is what I need, but for 1/4 mile, will it work @ higher rpm or lay down?

 

[Turbosmblk]

Got the radiator welded up finally last night. Took me 4 different attempts before I was able to get the tank sealed without blowing holes in the tubes since it’s so close. Layed my 5” 90 on the exhaust flange and will have to get creative with the fan shroud but everything will clear. I thought I would be able to sneak a 5” between the kmember and strut rod but it’s never going to clear so I will reduce down to a 4” at the strut rod and run that the rest of the way. With it being short I think I won’t have to deal with backpressure much. All my stuff for the -12 drain came in so this upcoming week I’ll finish out the radiator side pieces/ 16AN outlet and run my oil drain line. -12 is HUGE btw.

 

[Turbosmblk]

Got everything fired up last night. I still need to finish the down pipe and the cold side isn’t the final rendition but I didn’t want the e85 to sit in the injectors any longer without pulsing (this would’ve been a month). The Down pipe flange was too thick for the vband to clamp so I got a guy from working turning it down to fit. Put it on the chip and it made 4.1psi in 3.2seconds when I lifted. Timing manipulation and fuel should allow me to make boost faster as well as more leave rpm (this was 3200). I have a very serious worry that the converter is going to be entirely too loose. But, those are minor things I can get fixed with datalogs and showing the converter place exactly what it’s doing. Overall I’m super impressed. On the datalog green is boost, red is rpm, and purple is timing

 

[Turbosmblk]

Here’s a quick vid I took on the chip

 

[Turbosmblk]

Start of dp routing. It’s going pretty smooth so far. I’m hoping I can get everything buttoned up this week and go to the racetrack next weekend. I won’t get to see the full potential due to being on a hard tire but I might can throw a decent timing retard in it and then if it mph good I’ll know what the ET potential could be on a radial.

 

[Turbosmblk]

Was able to make a hit tonight. This was on street tires and no burnout so it’s obviously very lazy. Just for a guess I added 5% to the entire map in boost and added an additional 3% from 5700 up and smoothed my 5% to 8% transition(no I didn’t use the smooth feature I know it’ll get ya) I was actually pretty close. Below 4500 to 5500 I was adding 3% and then it started removing a bit around 5700. So it’s definitely making more power as I had based my fuel map off a 40* night and coolant temp of 145 vs 65* and 180 coolant tonight. I just left at like 1800 or so and had a 15* timing retard for 1second. As you can see from the TPS reference it still spun obviously. Even with a single gate boost was VERY steady and was between 6.8 and 7.5psi the whole run. As you can see I let me feathers show( I was a chicken) and short shifted the 1-2. Timing is pretty soft as well at 20*. Overall I’m very happy and think once I can get to the track on a radial and leave on some boost it might make some bacon. I do have a 4 port Mac valve as well so I can turn up the boost and I’ve already got a decent duty cycle curve to help build boost faster. Let me know what y’all think!

 

[Turbosmblk]

Made another hit on the street tonight. Added 1 click on front rebound, 100lb in trunk, and changed the launch retard a little to get it to try to stick the tire initially and then pull the timing. SUCCESS. Dead hook. Dropped 1100rpm on the gear change so I can turn it up a good bit before I have to worry about converter slip too much. Glad I was able to see what the converter would flash to as well. Right at 3200 and it had 11deg total timing in it right there so it will definitely loosen up. My cheap eBay fan has to go. So I’ll be getting a c7 vette fan and making a shroud to hold it and PWM from the Holley. That should handle all my cooling issues I think. I’m filling my overflow so I think I have a head lifting and then resealing once the pass is over. I’ll be able to know more once I get the cooling issue sorted to see if it was pushing water from heat or combustion. The tuning side is becoming addicting to see what changes I can make to change the ET and not touch the target boost. Speaking of which. The boost overlay was darn near identical to the run the other night. Fuel flow was within 9lbs and mph was within .3 so at least the only variable that really had an effect was the 60’.

 

[DNasty777]

Do you have an open input? You could wire in a pressure sensor and put it in the coolant crossover.

 

[Turbosmblk]

Do you have an open input? You could wire in a pressure sensor and put it in the coolant crossover.

I do, I also have a spare 100psi pressure transducer and I thought about doing a quick and dirty install to see if it is in fact lifting the head under power.