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Discussion Starter · #1 · (Edited)
Hi all, despite being my first post, I've been an avid G8 fan. I've read every TSB, and even got a chuckle out of Mark Reuss once talking about (okay, pleading for) CNG G8s in a chance encounter. I'm finally in a position to buy one.

Anyways, I know talk of LLT swaps has been dismissed in the past. Since those threads, GM added the LLT as an engine option on the Caprice PPV. The PPV's ECM pegs it at 302 horsepower and 30 mpg highway. This is what I wanted from a 2010 G8. Thank you Presdential Auto Task Force... I digress.

But I love the G8. And, I can't find a Caprice PPV LLT for under $25k.

You've probably figured out my plan. Get a high-mileage G8 at a bargain. Wait for the G8's LY7 to die, and swap in the LLT using PPV's setup, and swap in any parts that differ between the two.

There are potential roadblocks, of course:

* The ECM differences (if any... and really, there may few if any) between Caprice PPV and G8
** I am buying a '09.5 with the updated DIC, so hopefully there's less risk of that being an issue
* Transmission and TCM differences
* Possible engine mounting differences between LY7 and LLT
* Scarce part supply for Caprice PPV parts stateside to do the swap
* I'm in California, CARB loves to ruin people's days/months/years even when they're helping the environment with a more efficient engine

That all said, I'm optimistic, and I'd love to hear thoughts on the swap. I'm hoping I can pull the trigger on a G8 V6 and get it to 300k without a transmission or engine swap, but I'm trying to make the worst-case scenario on the eventual engine replacement be a realistic 300 hp, 30 mpg G8 too.

After all, who would put a replacement LY7 in a G8 if we could get something a bit better for very little more? I'm surprised L76 swaps haven't been spec'ed out, hopefully this swap is a bit more viable.
 

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Well, if you do source a LLT engine, it would need to come with all harnesses, ECM's and TCM (along with transmission, of course). Not sure what the LLT ECM is, but the LY7 is the Bosche ECM which is hard to deal with, at least in comparison to the widely-supported E38 Delco ECM found in the V8 cars.

You'd want to get the engine/tranny combo, as the 5-speed that comes with the LY7's wouldn't be up to the task, I'm afraid. I've read several reports of the 5-speeds burning up with stock horsepowered 3.6 V6's, it would be quite a faster timetable with a more potent LLT block.

Plus now you're also needing to source a new fuel delivery system, as the direct injected cars have high pressure fuel systems to help atomize the spray. Maybe you can source parts from a 3.6 Caddilac or something , but if you're doing all this, keep tabs on your budget as you go, as swapping a 3.6 for another 3.6 (even if this one is more 'stout') better be worth the overall investment... most find that taking it from a v6 to a v8 might prove more bang for your buck, at least in case you ever would consider camming, supercharging or whatnot, the v8 cars thrive in that environment.

I hope this doesn't come across as anything more than contributing some details to your thought process. I'm not aware of anyone doing a LY7--LLT swap before, and hopefully if successful under a reasonable budget, you could achieve your goals. The problem is how many of the cars subsystems would need to be adjusted, replaced, or reprogrammed to make it all play nice together in the end. To me seems like too much trouble, but I'm not a mechanic by trade, so that biases my opinion.

Good luck OP.
 

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Discussion Starter · #3 ·
The fuel system was one of the parts I wanted to see. Unfortunately each and every Caprice PPV I've come close to is V8, and I'm not sure if the local PD would really be interested in me popping the hood on a V6 to see how they adapted it.

It's possible it uses a whole new fuel system, though I was hoping GM did some quick adaptation to make the LLT work, something I could pull from a PPV easily that gets junked while on police duty. It could be the deal-breaker though.

As to the 5-speed, I've heard across the board on it. Supercharged V6's use the 5-speed and so I was hoping the <40 hp increase would not be the killer.

The long-tail alternative would be to wait until the LY7 dies, replace it, and then supercharge the LY7 after the warranty runs out on the replacement... but that is hopefully *many many* miles away.
 

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The fuel system was one of the parts I wanted to see. Unfortunately each and every Caprice PPV I've come close to is V8, and I'm not sure if the local PD would really be interested in me popping the hood on a V6 to see how they adapted it.

It's possible it uses a whole new fuel system, though I was hoping GM did some quick adaptation to make the LLT work, something I could pull from a PPV easily that gets junked while on police duty. It could be the deal-breaker though.

As to the 5-speed, I've heard across the board on it. Supercharged V6's use the 5-speed and so I was hoping the <40 hp increase would not be the killer.

The long-tail alternative would be to wait until the LY7 dies, replace it, and then supercharge the LY7 after the warranty runs out on the replacement... but that is hopefully *many many* miles away.
For the record, my current (but not for long) five speed that I built myself is a lot stronger than the stock Camaro 6 speed with the V6. It obviously takes money to make it that way though. I have a thread on that.

But, to be honest- there's nothing to this swap. If you get a 3.6 LLT from a Camaro with a 6L50 (Option code MYB) transmission, along with the harness and ECM (you don't need a TCM, it is already inside the transmission), then you are pretty much plug and play electrically. You will need a transmission tune to correct your speedometer as Camaros do not come with 2.92 rear gears. The 6L50, depending what kind of car you get it from, may or may not have the linkage on the correct side of the transmission to hook up to the shifter. A Cadillac will have it on the passenger's side, and a Camaro will have it on the driver's side. You can change it over with a $5 internal shift shaft. Either way, the shifter rod in the G8 will also be too short for the 6L50. The driveshaft slip yoke will extend it to the correct length, as the 6L50 is shorter, but the driveshaft bolt pattern is not the same. I am currently working on figuring out how to adapt that. You need the rear section of cooler lines that fit a 2011 Camaro V6 car and they will adapt from the G8 front section to the six speed.

The engine is very simple. The mount points are the same, the exhaust MAY be the same but that is easy to correct, and the accessories are all in the same position so you don't have to worry about moving A/C lines around.

The direct injection system is internal to the engine. The injector pump is driven directly by the engine's internals. The only thing that I know is not the same is the fuel pump inside the tank.

Overall, the parts list is pretty small.

Engine
Transmission
Harness
ECM
Cooler Lines
Shift Rod
Driveshaft (possibly)
Fuel Pump

That's just what we can foresee, however. When you actually get the swap underway, it'll grow a little bit of course.
 

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Discussion Starter · #5 · (Edited)
If I have to swap to the 6L50, it starts getting dangerously close to the cost of an direct new LY7 + Supercharger (ballparking $7,500 for a new LY7 and then to supercharge it - about the difference between the V6 and GT today, but I'll get a new engine down the road and ~365 hp out of the deal, plus cheaper insurance).

What I was/am hoping is that GM made modifications to the LLT implementation on the Caprice PPV, seeing as (hood-wise) it's a VE Commodore underneath, same as the G8. I'd really like to hear how they made the adaptation to support LLT, if it was swapping in Camaro parts to accommodate, or if the LLT application is different somehow to leave the Caprice as-is. It would be really cool if the Caprice PPV's LLT is a drop-in replacement to the LY7 it replaces, but that may be a pipe dream.

(It's possible that the LLT is drop-in and that the V6 PPV uses the 6L50 standard, in which case this would be... ideally... pretty easy, and the driveshaft may just link up to the G8 as-is).

Theoretically, it may be cheaper/better to still go with the Caprice PPV's engine (and tranny, if needed). At this point, it's sounding like I may be better off waiting for a PPV to hit the junkyard when a cop totals it, then grab the whole engine and transmission... and everything that plugs into them out of it.

Really, I think this boils down to where I wind up (NorCal has few tuners that know this stuff, but if I wind up in somewhere like Detroit... that changes the equation) and how much the PPV will cost at the junkyard to pick from. Cost with trans and fuel lines would be too high where I am, supercharger would be cheaper here.

Either way, I'll be up for it. Going to make my final offer to the owner tomorrow, asking $10k for 105k G8 V6. Fingers are crossed, we're not too far apart right now on price.
 

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That's awesome, very good insight. Certainly above me, but if OP attempts it; document well with pictures on a build thread, it would be awesome!

I just assumed that all PPV cars (or the majority) would be flavored L77 with dod and E85.

DO IT! :)
 

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Discussion Starter · #7 ·
That's awesome, very good insight. Certainly above me, but if OP attempts it; document well with pictures on a build thread, it would be awesome!

I just assumed that all PPV cars (or the majority) would be flavored L77 with dod and E85.

DO IT! :)
From what I hear, 99% are. However, when Caprice PPV sales came in at 5% of expectations (literally), GM added the LLT option to try and spark sales. The idea was a lower starting MSRP and higher MPG would get things rolling. Edit: Forgot, the LLT option is actually the same price - way to think it through bean counters.

The LLT in Australia got added to the Caprice there too, though it appears to be different. Lower horsepower (280 vs 302) and E85 on the US unit. That's why I'm hoping the US Caprice LLT was/is a drop-in swap from the LY7 across the family of VE/Caprice/G8.

On the plus side, the LLT on the PPV is E85 (unlike Camaro), so theoretically you might be able pull the fuel pump and have an E85 SIDI V6 G8. Or we could get really, really lucky and the '08-'09 fuel pump is already E85-rated and the same part number...

I think the two walkaway bullet points I need to get some GM engineer to answer on background is:

* Will the ECU from the LLT Caprice PPV drop-in on a G8? Just program the VIN, and the DIC will work? Or will it all go to hell with flashing no-airbag, no-tc, no-esc alarms?
* Can the 5-speed transmission TCM talk to the LLT - or do you need to do a transmission swap/pull from Caprice's 6L50 to make it work?

Either one could be a deal breaker, but it's a good sign nobody has chimed in to say definitively that the wiring, TCM, ECU, etc would have to be redone.

Bad news is, it'll be awhile. I can't pull the trigger right now unless the V6 engine in my soon-to-be G8 dies. And, I'm still negotiating on said G8 (must have Stryker Blue... limited color is limited, only more frustrating is Kinetic Blue on a Solstice/Sky - my "white" whale).
 

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From what I hear, 99% are. However, when Caprice PPV sales came in at 5% of expectations (literally), GM added the LLT option to try and spark sales. The idea was a lower starting MSRP and higher MPG would get things rolling. Edit: Forgot, the LLT option is actually the same price - way to think it through bean counters.

The LLT in Australia got added to the Caprice there too, though it appears to be different. Lower horsepower (280 vs 302) and E85 on the US unit. That's why I'm hoping the US Caprice LLT was/is a drop-in swap from the LY7 across the family of VE/Caprice/G8.

On the plus side, the LLT on the PPV is E85 (unlike Camaro), so theoretically you might be able pull the fuel pump and have an E85 SIDI V6 G8. Or we could get really, really lucky and the '08-'09 fuel pump is already E85-rated and the same part number...

I think the two walkaway bullet points I need to get some GM engineer to answer on background is:

* Will the ECU from the LLT Caprice PPV drop-in on a G8? Just program the VIN, and the DIC will work? Or will it all go to hell with flashing no-airbag, no-tc, no-esc alarms?
* Can the 5-speed transmission TCM talk to the LLT - or do you need to do a transmission swap/pull from Caprice's 6L50 to make it work?


Either one could be a deal breaker, but it's a good sign nobody has chimed in to say definitively that the wiring, TCM, ECU, etc would have to be redone.

Bad news is, it'll be awhile. I can't pull the trigger right now unless the V6 engine in my soon-to-be G8 dies. And, I'm still negotiating on said G8 (must have Stryker Blue... limited color is limited, only more frustrating is Kinetic Blue on a Solstice/Sky - my "white" whale).
Define "drop in"...the answer is it will physically mount in the same location as it is the same ECU, just with different software to run the direct injection. It WILL communicate with the other onboard modules. It will need the DI harness though.

And yes, the 5 speed can communicate and would work, but in order to do it a little research would need to be done. I have the GM High Speed LAN diagrams for both the G8 and Camaro in front of me and I'd have to spend some time with them to figure out how it could be done. Its not if, but how. You would need a different flex plate as the 5 speed uses three converter bolts and the six speed uses six. No cooler line or driveshaft adaptation would be necessary in this case.

In my opinion, you would not reap the full power benefits without the six speed, as the first gear in the six speed is 4.06:1 and the five speed is 3.42:1. The six speed uses a lepelletier gear train instead of a ravignaux like the five speed and provides much better ratios since it does not have to utilize a direct 1:1 ratio.
 

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Why the LLT from the PPV and not the Camaro? I see the LLT from camaro's all over ebay and I think they are rated at 323 horsepower. This is what I am shooting for someday...along with the 6 speed as well.
 
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