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V8 Installation.., '08 GXP

21K views 66 replies 8 participants last post by  Morningside 
#1 · (Edited)
The donor body for this project started life as a red, 2008 GXP convertible. The motor is an Ls7 crate (Corvette), differential is a Gertrag 3.73 and the transmission gear ratios will be: 1st 2.66, 2nd 1.78, 3rd 1.3, 4th 1.00, 5th .74 and 6th .50. Transmission selection is in process but leaning to the Ford Tremec Magnum XL.

Motor mounts were obtained from Wade Linger along with a welding jig he kindly provided. The Ford specific transmission will get its input shaft exchanged for a GM style, and along with an Ls aluminum bell housing and GM hydraulic clutch unit, fitment to the back of the Ls motor should be possible.

A distance of 33 inches is needed to reach the OEM, 5-speed shift column location (center), from the bell housing mating surface on back of the motor. OEM GTO, Tremec F-body with extension and the OEM 6060 with remote shifter (modified) will all work. I am hoping the XL will be close enough to be fitted with a crooked shift column, precluding cutting the tunnel, using articulated extenders or modifying the remote shifter length.

The pictures show the tacked motor mounts after removing the OEM ones that spanned the cross members.



Front covers will be fitted to the mounts. They are not in place because the front of the mounts need to be exposed in order to reach the inside during final welding.
 
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#3 ·
Looks like fun. Will be following along.
 

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#4 ·
The TR6060 is probably the best trans of those choices, but may not be the best fitting.

Looking forward to more progress.
 
#5 ·
Initial pricewise, the 6060 at $2680, with bell housing and clutch hydraulics, no doubt is the cheapest. After much consideration, I am not sure I can fit the XL in there. May be just a tad too long. One thing is for certain, fitting the 6060, at least as far as positioning the shift column is concerned, will be possible. On the XL it will fit where it falls. On the F-body trans, it will be closer to where it needs to be, but a cut of the tunnel will be required.
 
#6 · (Edited)
Selected ratios and ideas. Tremec has produced variety of ratios for OEM applications (TR6060) but in the aftermarket (T56 Magnum) for GM appliactions, only two are available.

1st 2nd 3rd 4th 5th 6th rev
3.01 2.07 1.43 1.00 0.84 0.57 3.28 SSR Truck
2.97 1.78 1.30 1.00 0.80 0.63 2.90 Camaro
2.66 1.82 1.30 1.00 0.77 0.50 3.98 Corvette
2.26 1.58 1.19 1.00 0.77 0.63 ? Viper

Using experience and ratio information from three of my cars (1986 Mustang 5.0, 1994 Nissan 300zxTT and 2007 Honda Civc Si), I selected the Corvette ratio above. Let us consider the Civic. Weighs about the same s the Solstice, 3000 lbs, and has a 2.0L NA engine the spins to 8500 rpm (with Hondata flash). 1st is circa 3.3 and diff ratio is over 4. 80 mph RPM is 3500+. The 200HP engine is very weak at the low end with anemic torque, just over 100 ft. lbs. This low gearing combination works well with a weak, high revving engine that can still get the car moving fast by spinning up the motor.

The Nissan has 400 HP (with some mods, boost, intake and exhaust) but engine is little at 3.0L and a max RPM of 7500 (with reprogrammed ECU chip). Weight is a porky 3400 lbs. 1st is 3.3x and diff is 3.69. 5th is .6x with cruising rpm at 80 mph under 3000 rpm, but close. In this case there is a heavy car (relatively speaking, about the same as a corvette) and a smallish motor that revs respectably. Having a turbo has benefits running revved up, as it keeps the car responsive, at the expense of wear and fuel consumption.

Come the Solstice. OEM weight with the 4 cyl was circa 3000 lbs. Let us estimate 3250 with the Ls7 and Tremec T56 Magnum. The engine is modestly revvy, 7100 (not bad for a pushrod V8) and produces over 400 HP and 400 lbs of torque. With this combo there is little need for the transmission to help the engine. The combination of gear ratios (2.66 ... .5), diff ratio (3.73) and car weight, resembles the factory configuration for pre 2015, Z06 Corvette.

The Ls7 has titanuim rods and a 30% lower weight reciprocating assembly. The reduced mass of its internals should allow it to change rpm quicker than a comparable motor with heavier internals. I also replaced the OEM flywheel with a Fidanza aluminum unit, seeking torque reduction off the line to reduce wheel spin. These are all fact based theoretical estimates, but non-the-less just good guesses. We shall see how this all works when put together.
 
#8 · (Edited)
The motor area is progressing nicely. The motor mounts have been finish welded and the "noses" of the OEM mounts added to the front for a bit more strength and better looks. The tunnel brace flange had been cut, about 6 inches on each side but the bell housing was still too close. We added another 1/4 inch on each side and ground of a pair of casting protrusions that may have something to do with the casting process or mold fitment of the bell housing. Since the spot welds were on the flange that was removed for clearance, the edge was welded to fuse the two pieces of metal that comprise the tunnel brace. The black shape seen on the rear cross member, is the spot where the Ls7 sump drain is located. There is about 3/8 of an inch of clearance between the oil pan and the rear cross member. Unfortunately the the drain plug has a collector valley that protrudes about 1/2 below the pan. Until I cut a hole for this to fit the engine just rests on the rear cross member and will not accept the transmission input shaft.







 
#9 ·
Christ, I wish I had the talent to pull this off...
 
#10 ·
Sly.., you buy what you can ready made and hire a welder. Painting was made with rattle cans. Not too big a deal. The financing is perhaps the most challenging, knowing full well, that the market value of your creation will be less than 1/2 of your expenditures.
 
#12 · (Edited)
Plastic engine with exhaust manifolds installed. Motor bolted to the mounts and bell housing. The manifolds are from Performance Motorwerks. Fit against the car is acceptable, but only one O2 sensor bung was provided on the right side manifold and the motor flanges need to be modified to clear the coolant temperature sensor in the front right side head, and the plug in the rear of the left side head (same head is used for both sides). I should have not requested jet hot coating. After mods headers will need re-coating. Engine swaps in most cars are not this tight, requiring living with very close clearance tolerances. I am trying to stay to no less than 3/8 of an inch. Notice right manifold side is closer to frame. Left side was made tighter to clear steering shaft/u-joint.

Engine on lift sitting on original crate. The hydraulics on my Chinese lift do not hold pressure for extended periods of time. If motor were to be left hanging, it would reach the floor overnight.

I am having the transmission mount modified. The way it was made allowed no front-to-rear adjustment of the transmission location. The motor mounts have slots about 1 inch long, but even all the way to back I still could not reach the bell housing. I could see the isolators deflect when I forced the union of the motor/trans. This is a moot pint though, because in order for the headers to fit the motor has to be at the extreme front of the slots. Even at that spot the isolator pads overhang the mounts just a hair.









 
#18 ·
On a test fit, the belly of my engine is only 3/8 of an inch above the rear cross member. Are you using the stock motor mounts that are taller? My son has a car with reduced suspension travel (lowered) and urethane motor mounts. I have to wear a kidney belt when I ride with him.
 
#20 ·
What will you be using to control the engine? OEM LS ECU?
 
#23 · (Edited)
This is the part I'd like to see explained and documented more because it seems to be the most intimidating part of the entire process. Especially if you want keep as much of the OEM systems and options working as possible. For examle; having air conditioning and cruise would be important to me, along with TC/ABS on a V8 car.
 
#24 ·
I will be using a MegaSquirt 3, which will take the traction control out of the OEM equipment's hands (fully tuneable, because the OEM TC is a bit too stingy). The ABS will work with a few added wires (power, ground, and brake light output). Cruise control, kinda sucks that I will essentially forfeit that, but I can likely hook up an aftermarket box down the line and integrate the steering wheel controls to it. ESC is the only thing I will lose completely, but that's no biggie to me, honestly. I drove around with it off the majority of the time anyway (unless it was rainy, and I don't drive in the rain intentionally).

Looking good JMartz! I am keeping a close eye on this build as I will be undergoing mine soon, though I will be taking a slightly less OEM approach.
 
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#25 · (Edited)
mkriebs

I'd like to mention a mistake a I made so you can avoid it. I trusted the trans mount I got, cutting the tunnel bracketry as needed to fit the bell housing. When I mounted the motor, I realized the exhaust would not fit, and the isolators were hanging off the back of the motor mounts. i had to modify the tans mount and move its attachment points 7/8 of an inch forward. Have the motor and trans attached and the exhaust installed before you finalize mount locaions.

The tunnel bracket has flanges used by GM for spot welding its sandwich shape. They only need to be cut and the exposed joint rewelded. This does not weaken he structure. The flange is there for the robots to have access to. The engine can indeed fit the 7/8 inch more backwards than I placed it (and would be better for overall balance) but I would have needed to fabricate my own exhaust and motor mounts.

I got those commercially as I am trying to reduce fabrication to a minimum. When you are about to begin, contact me for a discussion. Do keep in mind aftemarket parts NEVER fit w/o some modification. This car is especially problematic as a swap subject, since tolerances are close all over. No surprise putting a V8 into an L4 space.
 
#26 ·
Thank you for the tips! I am going to utilize the OEM trans for the time being, just to save some cost. I can't quite swing the cost of the TR6060, but when the time comes, that will be my choice. But, this also simplifies the swap.

I own all of the fabrication equipment that I need to fully fabricate almost everything I would need to use, so thankfully, the engine mounts will be a non issue. The trans mount, for the time being, will be a stock trans mount from the early cars that do not have the torque arm set up.

For the rear end, I plan on utilizing a brace that will be coming to market soon (more on that hopefully before summer). If that doesn't come to fruition, I will use a Ford 8.8 IRS with a custom fabricated bracket, its a pretty easy swap.

The engine I am using is the iron block 6 liter (much to the dismay of many people), I wish I could use the LS7, in near stock form the LS7 is kicka$$.

Your build is awesome and I am glad I can follow along with you!
 
#27 ·
What accessories are you planning to use?
 
#28 ·
I got them from Pace. Kit comes complete with all brackets, fasteners and belt. The PS oil pump sits high on the drivers's side. The generator under it. The a/c bracket is from a 2000 Corvette. This mounts a compressor with the refrigerant connections in the back. The PS rack needs the left side oil inlet rotated 90 degrees, to clear the engine pulley and a 1/2 inch of clearance on the right side cross member vertical reinforcement bracket, must be provided, to clear the compressor against the frame.
 
#29 ·
Awesome, same essential set up I am looking at, however I have no experience with A/C and lines and all that stuff, so I will forego A/C for the time being just to get the car on the road in a more timely fashion. The Pace stuff seems so expensive!!!
 
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