LS3/4L60E 1968 Chevelle
 

Just completed the LS3/4L60E swap into a long time friend's 35000 mile rust free 1968 Chevelle. The paint is still original except for the right rear quarter panel that had some minor damage. One of the requirements for this swap was no trans tunnel mods and no driveline vibrations. As most LS swaps into the Chevelles that I've seen had the trans tunnel cut open and or severe driveline issues. I'll try and answer any questions.

Russ Kemp

This is what we started with

Then C4 brakes were installed from Performance Online. Also to fix the bumpsteer & backwards camber curve of these cars, tall lower ball joints & extra tall upper ball joints from SC&C were installed. Next to be able to get 6-7* caster, SC&C adjustable upper control arms replaced the stock A-arms. Also a Lee 670 Delphi 12.7 steering box was installed.

Wheels are American Racing Torque Thrust 18x8 5" backspace front & 18x9.5 5.5" backspace rear. Nitto NT555 245/45/18 & 275/40/18 tires.

Time to pull the 307/glide. I got the GM Performance LS3 430 engine & Corvette assy drive from Capital Pontiac in Regina. Note that the assy drive from Holley is $748.00 US, and that doesn't include the P/S reservoir, idler & tensioner pulleys or the drive belt. The GM kit is complete for $576.00 Canadian.

I installed a Cam Motion 220/234/.578/.561/115+5 cam. This cam has only -3* overlap, as my friend wanted a nice idle (700 in gear) and stock manners. Stainless Works 1.75" headers and LG Motorsports high flow 3"x2.5" cats will be used. The cats will completely eliminate the exhaust smell, and will cost no measurable power.

The Holley 302-2 oil pan was used, as it's only 1.25" deep at the front to clear the inner tie rods, and to allow the engine to be placed as low as possible. This is to improve to front U-joint angle and to increase the trans to trans tunnel clearance. The full length windage tray needs to be shorted for this pan, or use an OEM 4th gen F-Body tray.

The 4L60E was supplied by Downtown Automatic in Regina. It has the billet sunshell, upgraded clutches, wide 2-4 band, 5 pinion planets, Corvette 2-4 servo, Trans Go .500 boost valve and an 11" Trailblazer convertor. As the LS3 has no trans bolt hole for the dipstick tube, I installed a 5/8" Keensert into the trans bellhousing that allows a 3/8" bolt to hold the dipstick tune in place.

I was going to use the Hedman mount kit, until I learned that it was designed to be used with the GM H3 pan. This pan is over 2" deep at the front, so the engine would sit to high in the front. Then the trans would hit the tunnel, and the driveline angle would be very steep.

So the Energy Suspension 3.1148 LS swap mount kit was installed. This kit uses the OEM short & wide frame brackets plus the preload plates are deleted. So this allows the lowest engine location possible. And this places the bellhousing 1.25" forward of stock to help with the trans tunnel clearance. The inner tie rods clear the pan at full lock. And the transmission tunnel clears nicely.

Russ Kemp

The owner wanted to keep the stock column shift & speedo. Shift Works in Las Vegas supplied the trans extension housing & adapter to use a mechanical speedo and a shift linkage kit that fits very nice.

Airaid has a 4" u-build it air intake kit for the Chevelle, but it required a lot of trimming to fit. They said it was because it was designed for a car with plastic inner fenders. But I'm sure plastic innners would be a direct swap. But it does fit very nice after many hours of modifying.

Nice looking setup.

For the fuel system, a Tanks Inc fuel tank with the 255 LPH pump was used. Then a Corvette fuel filter/regulator with a 3/8" aluminum fuel line to the firewall just to the left of the brake booster. Russell -6 braided hose to the fuel rail, and Russell twist lock hoses from the tank to the Corvette fuel filter.

Used the Russell Powerflex -6 hose & Endura hose ends for the power steering hoses. Also used the Turn One extended AN-6 flow restrictor in place of the Corvette outlet fitting. This is so the pulley won't rub the 45* hose end.

After looking for a place to mount the ECM, I modified an S10 bracket and pop riveted it to the back of the heater housing. Note that I didn't install a rivet in the top left corner as the defrost door would hit the back of the rivet.
Although I don't have a pic, I did lower the mounting bracket 1/4" to make the bottom of the bracket flush with the top edge of the floor vent. This was because the pcm wiring plug was a bit too tight to the defroster duct.

Since the LS3 has a 58 tooth reluctor, I installed the LPE 58 to 24 conversion module in order to use the 411 LS1 PCM. This was for several reasons; the Speartech harness is cheaper, no need for a TCM for the trans, no need for a trans position switch on the shift shaft, way cheaper PCM and for ease of hooking up a GM cruise control. Also the owner didn't like the look of the available gas pedals for a drive by wire throttle.

Russ Kemp

Next up was to install a cruise control from a drive by cable 2000 Silverado. Used a Rostra cruise handle with resume that fits the oem signal switch. But the problem with this switch is it's an open circuit switch, and the GM cruise needs a closed circuit switch. So you need to use two 5 pin relays to invert some of the switch inputs to be compatible with the GM cruise module.

Also installed the Shift Works shift indicator label. But found the cable frayed, a trip to a fishing store to get a leader that was the exact same size as the OEM.

Russ Kemp

Since my friend was complaining about the gas fumes in his garage, I installed a charcoal canister from a 1997 Yukon and mounting tabs from a 3rd gen F-Body. The OEM fuel line is connected to the fuel tank vent to the canister, and the purge port of the canister is connected to the purge solenoid at the right front of the engine. Speartech added the purge solenoid wiring. Mounted the canister behind the battery. Also had to install restrictor with an 1/8" hole in the vent hose at the fuel tank.

Nice job, it looks well thought out.

Installed a Yukon posi and kept the OEM 3.08 gears. The car will never have drag tires, so anymore gear is a waste and will actually slow the car down due to zero traction. With the 275/40/18 tires, the trans will shift into 2nd gear at 52 mph, and into 3rd at 98 mph. And at 75 mph in OD, the engine is at 2075 rpm. He plans on taking the car on long trips.

As I wanted a way to adjust the pinion angle, I got the UMI control arms. Very nicely made, and at $379.00 was a great deal. With the engine mounted as low as possible, and the taller Energy Suspension trans mount, the engine and trans are only 1* down at the rear. So with the Eibach springs, the driveshaft is 2* up from the trans at ride hieght. I set the pinion to be 2* up from the driveshaft, so the centerline of the engine & pinion are parallel. This is so the front & rear U-joints cancel each other out for a smooth, vibration free driveline.

Russ Kemp

Thank-you, yes I spent hundreds of hours on this car. Good thing I'm not charging my full shop rate!

Russ Kemp

Since we wanted to keep the OEM indicator lights, I used an Autometer 16mm to 1/8" NPT adapter for the stock oil light pressure sender. For the OEM temp light, I used a Painless 12mm coolant fan switch in the right rear cylinder head. This switch will turn the temp light on at 205 & off at 190, this is perfect as I installed a 160* thermostat and lowered the fan temps.

I first hooked to charge light to the L terminal of the alternator. With the key on, engine off the charge light was on. But the light stayed on with the engine running & the alternator charging. The fix was to add a short wire from the S terminal to the main battery wire on the alternator.

The other issue was how stiff the gas pedal was. I used a Lokar throttle cable, but the problem was the negative leverage of the stock gas pedal. So I shortened the pedal rod 1.5" between the pivot & the hole where the throttle cable fits into. This changed the ratio from .83 to 1.11 and made the pedal feel just right. Also had to drill the throttle cable mounting hole 1" lower so the cable would line up with the pedal.

Russ Kemp

So Russ what your saying is that it's ok to have the rear pinion facing upward to cancel out the downward angle at the trans ? I have the same rear control arms that you have on my 68 and will be lowered all around. My trans is down 2.5 degrees so should I have my pinion up that same 2.5 ?

Really nice build BTW and your pictures are great....all 59 of them.

Thanks, Tony

Yes, if your trans is down 2.5*, then your pinion has to point up 2.5*.

Thank-you

Russ Kemp

Excellent work. :)

Very nice car. GREAT WORK !!!