GMT900 408/80e conversion
12-30-2009, 12:22 AM
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GMT900 408/80e conversion
Well, it's time to start modding the '07 GMT900. Right now its a bone stock 4.8L/60e worktruck. I have a 408/80e/3500 stall I'm refreshing from my previous project truck, 93 ECSB. I had a 58x reluctor wheel installed on the Eagle 4" stroker crank and bought a Rollmaster CS1190 so I can continue to use the 3 bolt camshaft. Below are the parts used to refresh the engine. All machine work done by a very competant machinist in Lavon, TX.
KING Aluminum racing main bearings, MB5013HP 020, +.020 oversize.
Clevite rod bearings, CB-663 HN10, +.010 oversize.
Rollmaster single row timing set CS1190, allows use of 3 bolt cam in Gen4 engines according to Scoggins Dickey.
SpeedPro Hellfire file fit piston rings, R-19100 35.
Cam bearings, deburred, radiused and installed.
4" Eagle 4340 crank, polished.
6.125" Eagle rods, resized and narrowed on small ends
4.030" Wiseco Pistons -8cc K394A3
58X reluctor wheel 12586768.
New Spiral locks for the piston pins.
GM head gaskets 12589227
ARP main studs 234-5608
ARP head studs 234-4317
cam retainer plate 12589016
Bores brushed and cleaned, no previous wear after 30k miles.
Line-bored main bearings, were .002 too tight.
Replaced factory cam bearing previous builder failed to replace. Shop found metal shavings from the GM machining process in the oil galleys. A good reason to replace factory cam bearings even on a new block.
Narrowed small end of rods .040" to prevent scuffing of the rods on the piston bosses caused by use of a crank with excessive crank bearing side clearance.
Balanced entire rotating assembly.
Surfaced heads
I assume I am going to have to tap the bosses on the pan rail drivers side of the engine to fit the E38 PCM's knock sensors onto the block.
80e was refreshed not long ago with all new BorgWarner clutches and plates, 4l80e-HD2 Transgo shift kit, Transgo 80e vacuum mod for the pressure control, many numerous HD parts in the trans plus the front pump was modified per the PI/Vig instructions. I found an 80e controled Suburban and got a TCM with the 80e program in it.
Hopefully the ECM and TCM will talk to each other. I will keep you updated if successful. I have all the wiring mods figured out to rewire the 80e. 
First step on this build was installing a Detroit Truetrac, I love it over the G80.
Anything I need to watch out for? I'm keeping my eyes open for a 92mm 6.2L electronic throttle body.
I'm sure I'm going to have to upgrade the fuel pump. What do you guys recommend over the Walbro? Since they're petered out from 500+ HP, what's a better pump to go intank?
KING Aluminum racing main bearings, MB5013HP 020, +.020 oversize.
Clevite rod bearings, CB-663 HN10, +.010 oversize.
Rollmaster single row timing set CS1190, allows use of 3 bolt cam in Gen4 engines according to Scoggins Dickey.
SpeedPro Hellfire file fit piston rings, R-19100 35.
Cam bearings, deburred, radiused and installed.
4" Eagle 4340 crank, polished.
6.125" Eagle rods, resized and narrowed on small ends
4.030" Wiseco Pistons -8cc K394A3
58X reluctor wheel 12586768.
New Spiral locks for the piston pins.
GM head gaskets 12589227
ARP main studs 234-5608
ARP head studs 234-4317
cam retainer plate 12589016
Bores brushed and cleaned, no previous wear after 30k miles.
Line-bored main bearings, were .002 too tight.
Replaced factory cam bearing previous builder failed to replace. Shop found metal shavings from the GM machining process in the oil galleys. A good reason to replace factory cam bearings even on a new block.
Narrowed small end of rods .040" to prevent scuffing of the rods on the piston bosses caused by use of a crank with excessive crank bearing side clearance.
Balanced entire rotating assembly.
Surfaced heads
I assume I am going to have to tap the bosses on the pan rail drivers side of the engine to fit the E38 PCM's knock sensors onto the block.
80e was refreshed not long ago with all new BorgWarner clutches and plates, 4l80e-HD2 Transgo shift kit, Transgo 80e vacuum mod for the pressure control, many numerous HD parts in the trans plus the front pump was modified per the PI/Vig instructions. I found an 80e controled Suburban and got a TCM with the 80e program in it.
Hopefully the ECM and TCM will talk to each other. I will keep you updated if successful. I have all the wiring mods figured out to rewire the 80e. First step on this build was installing a Detroit Truetrac, I love it over the G80.
Anything I need to watch out for? I'm keeping my eyes open for a 92mm 6.2L electronic throttle body.
I'm sure I'm going to have to upgrade the fuel pump. What do you guys recommend over the Walbro? Since they're petered out from 500+ HP, what's a better pump to go intank?
Last edited by Red Heartbeat; 01-02-2010 at 02:35 PM. Reason: fixed reluctor to 58x
12-30-2009, 12:17 PM
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Should be good to go but its 58x not 52. Just plug the rear cam sensor and use the front one. And tap of the side knock sensors.
The L92's TB are only 87mm. The LS3 is 90mm.
The L92's TB are only 87mm. The LS3 is 90mm.
12-30-2009, 03:37 PM
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Oh, I thought the 6.2L in the Denali and newer trucks was a 92mm. Cool, I'll save a little money by not having to do the swap.
Fixed reluctor to 58x. Thanks.
Fixed reluctor to 58x. Thanks.
12-30-2009, 11:21 PM
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Put the rotating assembly together tonight, it turns so smooth. I've seen the specs on the ARP main studs to be 50 ft/lbs on the inner bolts and 60 ft/lbs on the outer bolts. My machinist spec'd out 65 on the bolts since he had them at that setting when he line-bored the block with the bolts torqued at that setting. It took 85 ft/lbs of torque on the ARP rod bolts in the Eagle rods to get .0055" of stretch. 
The coolest part was the assembly lube he sent home with me was a spray can of PTFE, WINZER poly-lube 250, to be used on everything except pistons/cylinders. 
I used 20w50 oil on the piston skirts and rings. You need to oil the rings and the grooves they ride in inside the piston before assembly. The SummitRacing 4.030" piston diameter tapered ring compresser worked so nicely, I wish I would have bought one for every engine I've ever built. 
One word of wisdom if you have set of stroker pistons that cut into the oil ring groove... there is supposed to be a ring in the bottom of the groove to retain oil rings and also take of some of the width of the groove. Without with ring you will have issues. There is a dimple in the ring and the exposed side of it should fit in the open area of the oil ring where the piston pin is located. The design is to keep this ring from spinning on the piston.
I've seen the specs on the ARP main studs to be 50 ft/lbs on the inner bolts and 60 ft/lbs on the outer bolts. My machinist spec'd out 65 on the bolts since he had them at that setting when he line-bored the block with the bolts torqued at that setting. It took 85 ft/lbs of torque on the ARP rod bolts in the Eagle rods to get .0055" of stretch. The coolest part was the assembly lube he sent home with me was a spray can of PTFE, WINZER poly-lube 250, to be used on everything except pistons/cylinders. I used 20w50 oil on the piston skirts and rings. You need to oil the rings and the grooves they ride in inside the piston before assembly. The SummitRacing 4.030" piston diameter tapered ring compresser worked so nicely, I wish I would have bought one for every engine I've ever built. One word of wisdom if you have set of stroker pistons that cut into the oil ring groove... there is supposed to be a ring in the bottom of the groove to retain oil rings and also take of some of the width of the groove. Without with ring you will have issues. There is a dimple in the ring and the exposed side of it should fit in the open area of the oil ring where the piston pin is located. The design is to keep this ring from spinning on the piston.
Last edited by Red Heartbeat; 01-20-2010 at 12:08 AM.
man what happened to the 93??? did you have a custom wiring harness on it? are you using that or your GMT900 harness on this motor?
12-31-2009, 10:53 AM
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The 93 is getting demodded and a 2006 4.8L engine is in it now. Originally I shattered the 9.5" rear end in it. While gathering parts to repair it I ran across this 2007 GMT900 and decided to buy it. I haven't had a newish vehicle for myself in a really long time and decided I deserved one, so I bought it with the intentions of putting all the performance parts from the 93 into it. I have a modded 1998 fbody harness in the 93 and its now hooked up to the 4.8L engine. I have a stock 60e and a stock 80e and am trying decide which one to put back into the 93, will probably go for the 80e for the reliability though the truck will be down on power pulling that big boss transmission around. I rebuilt the old 8.5" rear that was originally in the 93 and am ready to put it back in. When its all said and done my daughter wants it for her first vehicle. She had a choice of it or our old BMW 325i and she chose the truck, what a good choice IMO.
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12-31-2009, 01:02 PM
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ahh i see! my fiance' took my 01 over my 94 bc of the speed :thumbsup: but i got rid of it an bought my CC an had to buy her an 02 camaro 
now she wants a forged 5.7 lol
i think your daughter made the right choice! post up some pics of the 07 soon an dont forget to take install pics
now she wants a forged 5.7 loli think your daughter made the right choice! post up some pics of the 07 soon an dont forget to take install pics
01-01-2010, 03:17 PM
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Sounds like your buildup is going nicely, Greg. Are you planning on lowering that nnbs any more than what you did with those drop shackles? I installed the 2" GF's, but now I feel like I wanna go a couple inches lower in the back and the front. Post some pics, bud
youve got a ton of projects going on..i have 2 but minor stuff compared to you.