GMT900 408 build summary - Gen3 to Gen4 update
I logged my build here...GMT900 408/80e conversion - PerformanceTrucks.net Forums... so that I could summarize it on LS1TRUCK once completed. If you want to read the whole saga, grab a soda and a sandwich, you're going to be here a while. :laugh:
Well, it was time to start modding the '07 GMT900, the truck was a bone stock 4.8L/60e worktruck. I had a 408/80e/3500 stall I was refreshing from my previous project truck, 93 ECSB. 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
Put the rotating assembly together, 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 a set of stroker pistons that the piston pin bore cuts 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 the 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. My engine went together with .028" piston ring gap to account for piston ring growth in length when spraying the nitrous. Be sure to check ring gaps according to the piston ring manufacturer specifications. Top and middle rings had to be filed to fit the bore using a hand operated piston ring filing tool rechecking the fit in the piston bore numerous times per ring, a very tedious operation for 16 rings.
Started working on completing the engine assy but hit a wall, the cam retainer plate has a silicone seal molded on the engine block side of the retainer plate and there was a small nick in the silicone. That will cause a leak and loss of oil pressure so I moved on to other parts of the assembly until I can pick up a new cam retainer plate at the dealership. I put the lifters and retainers in with a little loctite on the bolts holding the retainers in place, torquing them to 90 in/lbs and then bolted the heads down using ARP head studs torqued at 85 ft/lbs on the large bolts and 25 ft/lbs per the new ARP specs. This engine block is a newer model that has all 10 studs/bolts the same length.
Since the engine is the older Gen3 style engine I had to put the Gen3 valley cover on, installed the knock sensors just for a filler(not doing anything with them anyway) and installed the knock sensor harness. I figured this would be needed so that water does not pool in the knock sensor pockets in the valley pan. You sure wouldn't want moisture getting into the oil via the valley cover. I also used some gorilla tape (black duct tape, super strength) to hold the wiring down and sealing the knock sensors more seriously.
While I was assembling the heads to the block I looked in the intake runners and saw a piece of fiberglass wedged between a valve and the seat. I made a flat bar to compress the spring so I could get the piece out. I wonder where in the world that could have come from? It looked kind of like a fiberglass reed.
Picked up cam retainer plate 12589016 at the dealership. The newer cam retainers are a little thinner than the one I had from my 1998 Fbody and it uses countersunk head screws using a torx bit for installation. I've seen guys strip the torx head bolts out trying to remove them so I reused the old bolts with loctite torqued to 18 ft/lbs during the install. Next, the camshaft went in advanced 2 degrees using the new Rollmaster single row timing chain setup. The dowel pin hole in the cam gear was very tight and I had to use the cam bolts to draw the gear onto the dowel. Aligning the timing marks is different on the adjustable setups since you don't have a dot to line up on the crank gear, you use the tooth with the number on it that you setup the advance or retard. My engine has the little plastic timing chain guide that fits between the two gears. To verify I had the alignment correct I used a piston stop screwed into one of the spark plug holes and then rolled the engine forward until it stopped and then scribed a mark on the guide, then rolled it backwards until and stopped and made another mark. Measure the distance between both points and one half of the distance should be damn near TDC. I removed the stop and then moved the pointer to my halfway point and all was good. I then removed the bolts and added some loctite and then torqued the bolts to 18 ft/lbs.
Loctite is our friend, it keeps things from loosening at the worst possible times.
Added the oil pump, it is very important to get it centered so that you don't cause a wear spot inside the aluminum housing. I use two indicators, one to locate and center horizontally and one to center it vertically. I leave all bolts loose on the pump and then lightly snug one on each side of the pump. Next, move it all the way up and zero out the indicator then tap it down and check the reading, mine was .011". Do the same thing with the horizontal measurement, measure the slack from left to right. Now lightly tap on the pump until it is located in the middle of the indicated travel in both directions and tighten the two bolts that were just snug. Now remove the other two bolts, put loctite on them and torque to 18 ft/lbs and then do the original two bolts.
Install the windage tray, leaving the two nuts that hold the pickup tube off and torque to 18 ft/lbs. Again, loctite is suggested. Install a new O-ring on the oil pickup tube. Some say to put it in the pump and then slide the tube in, I prefer to put it on the tube and slide it into the pump. Something I started doing lately is putting red silicone sealer in the void area from the installed oring and up to the metal clamp before snugging the pickup tube clamp bolt to 80 in/lbs. The truck tube seems to be forgiving of misalignment due to its floating tube clamp. The Fbody tube has the clamp brazed to the tube and any misalignment can pinch the oring. BMR makes a billet aluminum clamp to help with this issue in the Fbody setup. The red silicone is a kind of 2nd line of defense in case you pinch the seal. Something to check before you do the silicone is checking the clearance of the oil pickup to the bottom of the pan. Install the pickup tube and snug all the bolts down, no seals in place. Put a 3/4" ball of clay/playdoh on the bottom of the pickup tube, wrap some cellophane around it to keep it from sticking to the pan and then put the oil pan gasket down and then put the oil pan on the engine and push to mash the clay. Remove the pan and gasket and then measure the thickness of the clay. I've always shot for 1/2". Shim or bend the tube accordingly. Mine was so far off I had to cut 1/2" out of it and braze it back together, this was due to having to shim the windage tray down for the 4" stroker. I've read in the magazines where some like to have .350" clearance for the sump tube. Get it too close and your pump will cavitate and pull in air rather than oil.
Flushed the pushrod tubes out with solvent and blew the solvent out with compressed air, then dropped the pushrods in place in the engine pushing them down to seat the lifter onto the cam lobe, being sure to lube the ends of the tubes with assembly lube. My engine has Patriot Stage 2 heads and the porting job violated the the intake valve bolt hole. If you don't address this you will have an oil consumption issue. I'm also running those cheap blue Scorpion 1.7 ratio rockers, too. To address the rocker arm bolt hole I take some thread sealing teflon paste and coated the threads on the intake bolt, only. Wipe the rockers off with a solvent soaked rag and dry with a clean rag. Don't soak your rockers in solvent unless you want to submerge them in oil for a while to get oil back into them. To install the Scorpion rockers I take a factory rocker bolt with one of the 8mm ARP washers on it and slide it into the rocker, turn the rocker upside down and slide a pedestal on it. Assemble one more arm the same way but with the sealant on the other bolt, if you have ported heads, and then assemble the pair together using the C-channel from the Scorpion rocker kit. Take the setup to the head, align the sealant coated bolt with the intake valve and bolt it on torqueing to 22 ft/lbs. Do this 7 more times, fun. LOL I like to do them all with the engine at TDC then turn the engine 1/2 turn and torque them again. I do this a total of four times. It's amazing you get a few that weren't tight the first time around.
Installed the engine covers from the factory 4.8L and torqued all bolts to spec, 18 ft/lbs I believe it was. I had to use the front timing cover, oil pan, windage tray and pickup tube from the 4.8L also because of the shape of the pan and the crossmember that runs under it otherwise there would have been a 1" interference. Since the engine is a Gen3 I have an LS6 valley cover installed plus the cam sensor is installed at the back just to fill the hole in the block. Gen4 knock sensors bolted right to the factory Gen3 block in the correct location. Oil pressure module and crank position sensor were swapped from the Gen4 block to the 408, too.
Engine installation was a simple remove and replace. Larger injectors were needed so the 42 lb Lucas/Delphis went in from the original build using spacers and longer bolts to hold the fuel rail down. Fbody/Ford style fuel injector clips were spliced into the wiring harness. Finally, the tune had to be updated for the larger engine and injectors. Thanks Allen. Once the engine was in place it fired up first try. Gotta love it when a plan comes together. :thumb:
I'm sure I left some good stuff out.
