Mast Motorsports L92HO/6L90E Powered 1968 Short/Wide---Hot Rod Power Tour Long Hauler

[MastMotorsports]

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Overview

We are creating this build thread to hopefully help those that are performing a similar swap.

For the past few months, we have been building a test truck for our development of GM 6L80E/6L90E 6 speed automatic transmissions. Our M-90 ECM is able to communicate with the transmission controller (TCM) that is inside the transmission. This means that there is no additional controller that you have to buy.

The truck is a 1968 Chevrolet Short/Wide that came to us with a carbureted SBC, TH350 transmission, and an open 12 bolt diff. The truck first got one of our L92 TI crate engines that use our M-90 ECM and wiring harness. Once we got the transmission sorted we installed a Mast Motorsports VVT Camshaft and valve springs to essentially make it one of our 525HP L92 TI HO crate engines. As stated above, the transmission is a GM 6L90E and the diff is an Eaton limited slip with a 3.08 gear.

We have just gotten done long hauling it on the Hot Rod Power Tour and plan on racing it at the LSX Shootout in Memphis this year. The truck ran great over the entire tour and got up to 17 MPG!!! (Depending on who was in the driver’s seat)

Here is an engine dyno plot of the first engine (Mast Motorsports L92 TI) that was in the truck.

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After running this engine for a short time we swapped in a Mast Motorsports VVT camshaft to make this engine the same setup as our L92 TI HO crate engine package. The first 450HP setup we had was no slouch by any means, but after the cam swap this truck was an absolute beast. The 75HP increase from the cam was pretty impressive to everyone here that had driven or ridden in the truck before and after the cam swap. The dyno plot below shows the power gains seen between the L92 TI and L92 TI HO. Notice that it makes WELL over 400 ft.-lbs. way down at 2500 RPM thanks to the VVT!

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Engine Installation

After the SBC was removed, the engine bay was cleaned up and the L92 was dropped in. We used Early Classic Enterprises engine mounts (911-GenIII). These required drilling just a few holes in the front cross member and use the stronger clamshell style engine mount. This was our first time using these mounts and we were very pleased with the quality and engine placement. One nice thing about these mounts is that we used the stock truck pan that came on the L92. That saved $250-$300.

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The L92 almost looks like it should have come in the engine bay from the factory. We used Pacesetter F-Body headers (72C2256). These have 1-3/4 primaries and fit after reasonable dimpling and frame notching. Doug Thorley released a set of swap headers designed for this truck after we bought ours (THY324Y-C), so that is another option.
http://67-72chevytrucks.com/vboard/showthread.php?t=287231

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[MastMotorsports]

Continued...
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We routed the wiring harness trough the firewall on the passenger side and mounted the M-90 ECM in the glove box.
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Below is a picture of the drive-by-wire pedal placement. We were really pleased with how stock appearing this came out. The stock stainless trim fits the pedal perfectly!
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Transmission details next...so stay tuned!!!

[oestek]

Great timing... we're just finishing editing our video interview / feature on this truck... the truck is killer! We'll post the vid here when it's ready.

[BossaNova]

:jawdrop:

[WILWAXU]

Met a couple of you guys (and the truck) on power tour. Very cool setup!

[MastMotorsports]

Great timing... we're just finishing editing our video interview / feature on this truck... the truck is killer! We'll post the vid here when it's ready.

Sweet Kevin!...Thanks.

[MastMotorsports]

Transmission Installation

The 6L90E required using a 4x4 transmission tunnel pan. It is very easy to swap to this tunnel. Once the old trans. tunnel hump is cut out and the 4x4 piece is installed, it is a bolt in installation. The best part is that you can get carpet out of a catalog!

After this modification, the 6L90E fit beautifully. One thing to note is that we did not modify the transmission cross member to get the 6L90E to fit. Holes were drilled into the frame to accommodate the new transmission length. A spacer was made out of 1 ¼” square tubing to raise the transmission pan up.

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The factory column shifter was retained by using a Lokar cable shift linkage kit (ACA-1804)

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We ran the transmission oil to an external cooler. Stock GM lines off of an Escalade were modified to accommodate the aftermarket cooler.

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The driveshaft yoke is stock 6L90E yoke. It takes a 1410 u-joint. To make this work on the truck we just had a driveshaft made with a 1410 yoke on one end and a 1350 yoke on the other end. We chose to upgrade to a 1350 on the rear axle while we were at it. We could not find any conversion u-joints to get around having a custom driveshaft built.

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Hope this information helps someone else on their build.

Fuel System Installation is next so stay tuned!!!

[MastMotorsports]

Fuel System Installation

We bought a fuel cell for this specific application. It gets the fuel out of the cab and relocates it and the filler neck to the bed of the truck. The fuel cell was a really nice piece with a straightforward installation. However, the fuel runs away from the pickups if the tank is below ½ full. The tank has doesn’t have the proper baffling inside, so it a lean condition when you get on it and are running below a half a tank of fuel. It really leaves a lot to be desired.

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Our fuel system is a Mast Motorsports AN fuel system that is an option with our crate engine packages. We send it as a universal kit that has to be finish fit to your specific chassis and routing preferences. It uses anodized fittings and braided stainless line from the fuel cell all the way to the fuel rail. The pump (can be in-tank or in-line) is a 67 GPH and the filter/regulator is a GM unit. We have tested this pump setup on all of our engine packages that we offer thus far and it has supported the high power levels just fine. This includes our LSX 454 HO engines. Everywhere on our fuel system that has a GM push connect line uses an anodized quick connect with a 6AN outlet. This makes for a nice solution for a complete, low cost fuel system solution for the LS series swap. Below are some pics of the fuel system layout.

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We haven't figured out what our solution to our fueling problem is going to be. We may just cut the tank open and put in the correct baffling or get a new tank. For now the fix is to run it with at least a half a tank of fuel.

[ScotI]

Where (who) did the fuel cell come from?

[MastMotorsports]

Where (who) did the fuel cell come from?

It came from Classic Performance Products.

Hope this helps!!!

[MastMotorsports]

CAN Gauge Installation

For the gauges, we used our Mast Motorsports CAN Gauge Package. These gauges hookup to the M-90 ECM’s CAN network over two wires and essentially act as a scan tool. In addition to having analog readouts on the “master” and “satellite” gauges, they allow the user to scroll through other engine parameters such as: engine hours, RPM, battery voltage, engine coolant temperature, oil pressure, fuel level, intake air temperature, throttle position, roadspeed, DTC’s, and odometer. All of these parameters come over only 2 wires!!! They require a 7 wire hookup for the master gauges and the satellites are plug and play with quick connectors.

The gauge panel is made from a modified glove box door. This made for a more stock appearing look using the new technology gauges.

You can see in this pic how the satellite gauges are plug and play from the master gauges.
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Panel Front
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Intro. screen that shows when the gauges are turned on.
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We were really pleased with how this turned out. Still retained an older look with new function.
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[BossaNova]

Good grief, Shaun. Is there anything you guys can't do?

[Motown 454]

Awesome truck. I would love to do this to my 99 Tahoe. But the Camaro comes first.

[MastMotorsports]

Good grief, Shaun. Is there anything you guys can't do?

We can't seem to get the traction we'd like with the street tires!:)

Thanks for the compliments. The real fun thing about this truck is the drivability. It drives like a 530HP Escalade. That is what most people are blown away about that drive this truck.

[MastMotorsports]

Cooling System Installation

The cooling system was pieced together out of relatively inexpensive components but still yielded excellent results. The radiator is a Jeg’s universal fit (555-52009) with Summit fans (SUM-G4852). The bottom of the radiator sits factory heavy duty radiator mounting brackets and pads that are welded to the core support. We had some aluminum bent at a local sheet metal shop to attach the fans and radiator to the core support. The aluminum plate bolts to the core support and to some bungs that were welded to the top of the radiator. When bolted together the fans are trapped in and don’t move at all. The fans are wired directly into the Mast Motorsports Engine Harness, no other fan relays are required!!!

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The lower hose is NAPA P/N: 8025, while the upper hose is a Gates P/N: 22436. If we had it to do over again we would try a Jeg’s double pass radiator (555-52039). This would put both the inlet and outlet on the passenger side and eliminate the upper hose from having to go all the way across the vehicle.

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[BossaNova]

Hey Shaun. Have you guys checked gas mileage on the truck since you swapped in the VVT?
Just curious how it compares.

[MastMotorsports]

The truck gets up close to 17.5 MPG and makes 530HP.

This past weekend we got runner up at the LSX Shootout in Memphis, TN. The truck went a best of 12.83@109MPH. This was with over a 2.0 60 foot time. We are confident that it has very low 12s in it with a converter change and a drag tire...and still get 17.5 MPG.