Need to do some brain picking on locking the exhaust cam in place on the Atlas I6 engine. Would one lock it in the advanced, retarded, or some point in between. The 4.2 Jaguar has nearly an identical bore and stroke so thought about mapping a profile of it's exhaust cam and getting the split overlap reading. Then ?? could the Atlas cam be positioned the same? A possible fly in the ointment is the Jag is a 2 valve head and the Atlas a 4 valve so flow rates may be so different cam comparison is useless. Jump on board with any and all thoughts along this line. They are now offering a VVT eliminator kit for the LS3 V8 (not legal for highway use) so it must work but have no power output comparison between stock and modified. Don't want to knock a 25mpg ride down to a 12mpg one but would like to make something that doesn't scare an old pliers and screwdriver Stovebolt guy from opening the hood and getting dirty.
I would think you would find straight up zero and lock it there? Is it actuated from the cam gear hydraulically? If so it may need to be either welded in place or make a insert blocker to lock up the movement.
I like the idea of incorporating the Atlas in more of our bolts. Have you inquired with anyone from Inliners? At one time one of their members were toying with the 4200's.
Come to think of it, wasn't Jerry tearing into one awhile back?
John
Last edited by J Lucas; 04/06/20209:55 PM.
~ J Lucas 2006 GMC Envoy 4.2 I6 2023 Ram 2500/Cumins 6.7 I6 2010 Jeep Grand Cherokee (Wife’s) 2002 Silverado 2500 Gas 6.0 1941 Chevy 1/2-Ton 1942 Chevy 1.5-Ton SWB In the Gallery My Flicker Photos!
The VVT actually is at full advance at idle, no valve overlap. At around 1500 RPM it goes to around 12 degrees, which is normal run mode. At 3000-3500 RPM the VVT goes into full retard, which is around 25 degrees. When driving a Trailblazer/Envoy you can definitely feel the difference when it goes into full retard. It's almost like the secondaries on a 4 barrel opening up.
As far as locking the phasers out, somewhere in the middle would be my best guess. On the other hand, why would you want to? I've never heard of any 4200's having problems. These engines have a good torque curve from 1500 all the way to 4000 RPM
I know the 3V Ford engines have had cam phaser lock outs and limiters for years. It has mostly to do with the reliability of the design.
The intake ports on the 4200 flow over 300 CFM, I'm guessing the 2V Jag falls short in that regard.
Marc, AKA, EFI-DIY, has done a bunch of playing around with the VVT setup on these engines, I know he had custom cams made and locked his out at one time. He still pops in every once in awhile at the Inliners forum.
Wait im confused. Why were you asking to “lock” the cam?? I was under the impression you wanted to disable the VVT. I wouldn’t do it personally but I thought thats what you were going for??
I was planning to make an adjustable timing gear so the cam timing could be set at a specific point during dyno runs. It appears that the cam is spring-loaded in the advance position, and a solenoid-operated oil pressure valve controlled by the computer moves it toward the retard position. I'm also looking at the possibility of adapting a HEI distributor with vacuum advance from a Toyota Supra driven off the end of one of the camshafts and a side draft Weber DCOE 2 barrel carburetor to the original intake manifold to make it a completely "dumb" engine. Once dyno numbers are available for comparison, a permanent exhaust cam timing position can be selected. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Glad you jumped in Jerry. Really would prefer a "dumb" Atlas but would probably go with the FiTech 39001 2bbl tbi. It's good for 400hp, self contained and self tuning which alleviates a lot of worry from the carb guys. It will be a good while before engine work happens as first I will design and fab a firewall recess that gives uncrowded room for the Atlas (I don't think they make wheelbarrows that skinny) and second, to try and keep the lube system factory, a front suspension that allows a front sump pan to fit. We used to use Volare/Aspen cross torsion bar ifs but no need to go with something scarce now. Some of the modern GM rides have torsion bars but track width is too wide I'm sure. If the monsoon season ever ends I can start looking under and measuring both American and foreign set ups. About 1500 vehicles (not mine) down in the yard right now waiting for the crusher so have a big selection to choose from. Not me, but some have used the Ford Crown Vic ifs and since Ford has used front sump engines for years something might measure out right there. As some of you have guessed I'm not the brightest bulb on vvt but that's why I'm pulling your chain. 83 with an iffy ticker and diabetes makes me one they won't even waste a hospital bed on so may be a pest till the scare is over. Last, I have an option on a half dozen 4200 Atlas engines with one that's supposed to be good so if anyone else wants one to brainstorm with, let me know. The supposed to be good one has my name on it.
Why would you go with a FiTech system, when the OE Fuel injection is already tuned/made for the motor?
Anyhow, if one were to install some sidedrafts or ITB's that would cool. The achilles heel would be the ignition. There's a ton of belt drive ignitions out there for anything V8, just haven't seen anything for a 6. I just saw one for a newer 5.0 Coyote, which got my wheels spinning. If one were to get rid of the 4200 AC pump, build a bracket and mount a CCW ignition, like a Willy's 226, with the cap facing the firewall. Well, a belt drive ignition may be possible for the 4200... Drive cogs and belts are fairly cheap, it's the machine work that'll be the big issue.
Whitedog said "Why would you go with a FiTech system, when the OE Fuel injection is already tuned/made for the motor?"
FiTech is a totally standalone unit. You install a wideband CO2 sensor, supply and return fuel line and that's about it beyond the throttle body injection unit and a simple wiring harness. No adapting the factory wiring harness or computer. The FiTech unit is self-contained with a internal computer to run the show. It looks pretty much like a carburetor and is tunable with a remote unit in the vehicle. You do install a 50ish psi fuel pump. The internal cpu can control fans and even ignition (depending on what you're running).
I could have gone with factory fuel injection on the vehicle I'm running a FiTech on, but wanted more of a old school (read 60's very early 70's underhood look) clean engine compartment uncluttered by wires and hoses. FiTech filled that slot. Clean looks with all the advantages of EFI.
Adapting the FiTech unit to a 4200 engine would be a Herculean task to begin with. A custom intake would need to be fabricated. Also, the timing issue, which we've already touched on. The 4200 is designed as a package unit. The factory ECM is bolted right to the intake. The Under hood fuse box is 6 inches away. You have a quick connect firewall harness, and couple other plugs, and hoses, then the whole engine is ready to come out. I'm sure it was designed that way for simplicity on the assembly line.
I won't deny that adding a Fitech unit and adapting some sort of ignition system, would definitely clean things up under the hood. On the other hand, it would open a can of worms elsewhere.
I 've often wondered what difference changing the timing on these engines would make. They have a 58 tooth cam sprocket. So if you do the math, moving the chain 1 tooth, would be around a 6 degree difference. The purpose of the VVT has to more with emissions than it has to do with performance. They have zero overlap at idle, because there's no EGR. So, if one were to retard the exhaust an extra 6 degrees, giving us some overlap at idle, allowing some timing advance without pre detonating. Would it give us some more mid range, because of the timing events happening earlier. The end result would be a total of 31 degrees retard, which may be too much. On another note, some of the 2002 and 2003 engines had there cam phasers limited at 20 degrees. I don't know if it was done mechanically or electronically, so I don't see the extra 6 degrees harming them at all.
Anyhow, the only way to know for sure is to put a degree wheel on the engine and figure out when things happen. If course someone smarter than me would need to do the programming since the cam sensor and crank sensor would be out of sync.
Whitedog, Thank you for the input but as was originally stated the object is to make a "dumb" engine---no computer, no wrist sized wiring harness, etc. Kind of a throwback to what the old 302 GMC guys of yesteryear did. We have access to very extensive machining and fabrication capabilities so intake or anything else is not a problem. Also a flow bench and dyno to see how much we lose/gain over the factory specs. After a test mule is put through its paces then one can shift to "easier to make, faster, and cheaper". Good possibility that the whole project might tank but when your 83, stuck at home, and bored as he!! one can lay around and die or get off ones butt and do something; even if it's a dead end. Besides, when gathering in groups is allowed again there is a good chance I'll win the biggest fish story contest. Pics are of a big success project and a big failure---learned from both. Big shop and fancy machines are gone now but my friend of 60 years has them so I'm sure he will let me turn big pieces into chips and tailings for the Atlas project.
Don't know if you ever saw the Ron Bohn Vortec 4200. It is more high tech than anyone could imagine. I think the only factory part left on it is the block and heads, which were all massaged quite well.
Here's one I just came across, A 4 BBL manifold and Dizzy on a 4200. The Dizzy takes the place of the PS pump.
GM wiring is super simple. To “adapt” it to anything or make the complete stock harness “standalone” should be pretty simple. Find the factory pinout and chop chop and add power, ground, fuses and relays. Use HPtuners software or EFILive and flash it to do whatever you want. It will run like its still in the trailblazer or whatever it was in. Makes everything else pretty simple.
Hey coilover...... read down to post #6 here. This is your complete pinout for the atlas. Looks a lot like a factory LS harness to me. All the same GM stuff. Orange wires are constant, pinks are all key on 12v+ and the injector stuff and O2 stuff all looks familiar to the harness that im used to building. You should be able to build a small fusebox with like 3 relays (main, fuel pump, fan) and a few fuses for the ECU, MAF/HO2’s, coils, injectors and you should be up and running. Will probably need someone with HPtuners to flash the ecu and turn off the factory VATS so it will start. Should be pretty straightforward. Atlas Pinout
Just a side note. GM used 4 different ECM's on the Trailblazer during it's run. The 02-03 is different from the 04-05. The 06-07 are again different, but I believe the harness ends are the same, GM just added Mass Air Flow to the engine. The 08-09 are again different do to the fact that they have a 58 tooth reluctor on the crank vs. The earlier engines having a 7 tooth.
I've seen the pinout for the 04 before, I also have the pinout for the 08-09. I've compared them to the LS, and yes I would say they are about 90% identical. The Trailblazer ECM has the TCM (Trans. Control Module) integrated into it, with the exception being the 08-09 models. They also have the TAC (Throttle Actuated Controls) module built in also.
Just a side question, would you be able to adapt a T5 bell housing to the block. I have some experience with the Atlas and have owned 2 Trailblazers, good lock with both. I have inside information on a 63' C10 with a blown motor, this would be a great candidate for a swap.
~ Craig 1958 Viking 4400 "The Book of Thor" Read the story in the DITY 1960 Chevrolet C10 "A Family Heirloom" Follow the story in the DITY Gallery '59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane
I think they have their own proprietary pattern but you can get them with a 4l60 or a nv3500 behind them so you have ok options either way. Im surprised nobody makes a adapter housing yet.
Besides these guys. That was some major work but they made it happen and i like that. Atlas bellhousing adapted
I figured the flywheel would be the hard part. The bell housing could probably be done using a modified 4.3 L.
~ Craig 1958 Viking 4400 "The Book of Thor" Read the story in the DITY 1960 Chevrolet C10 "A Family Heirloom" Follow the story in the DITY Gallery '59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane
The bell housing is proprietary to the Atlas engines. The Chevy Colorado/GMC Canyon or the same era share the same bell housing pattern, that's it. I have a, AR5 trans from a Colorado bolted to my mock up block right now, but I think I'm going to stick with the automatic. There are a couple places making adapters for the standard V8 pattern. As far as the flywheel goes, a custom machined one is it. Other than that you're stuck with the 4L60e/4L65e.
Manual transmission vehicles also need to have acetylene gas headlights and a hand crank for starting. It's virtually impossible to get an automatic transmission in the "wrong" gear. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
