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Thread: Crazy '88 Ram 50 build: Twincharged-Twinturbo SOHC 6G72

  1. #26

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    Ill have to take a look at it tonight.

    Sorry to hear about the crappy install. All it takes is as little as 1/8" dent to cause it to starve. Any dent is a restriction, especially when taking in account your maxing out the revs on our motor.

  2. #27

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    Got a video of the noise a minute ago. My phone's mic is too cheap to record it from the engine bay without it being drowned out by other noises, so I had to record it from the cab. At least this way you get to see rpms and oil pressure. The trans was in neutral, clutch out, and the truck was started for the first time that morning about 30s before I started recording. I also checked thoroughly for any oil pan dents and found it unscathed. After researching why​ dents cause issues it became apparent that the issue is when the low part gets rammed up into the pickup screen causing it to collapse and restrict. Mine is fine, and I should add that in order for that to happen you'd have to annihilate your steering in the process, as it runs right below the pickup's location.



    Note the subtler knock on acceleration as well as the rattley clicking that is somewhat constant above 1700 rpms (extra obvious on decel).

  3. #28

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    Your valvetrain noise 'should' back off after running it for a while (needs to get some blood pumping through it by warming it up). The knock sounds like a second order noise from somewhere else - your gearbox mounts and cross member are good? You might need a friend to jump in the cab and rev the engine while you get under there and investigate. Unfortunately these kinds of noises are hard to hunt down unless it is something glaringly obvious.

  4. #29

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    Yeah that's pretty much where we're at . The valvetrain (for lack of a definitive source) noise is persistent and gets worse as it warms up to the point that it is present straight off the idle (about 500-750 rpms). It does have your typical lifter click for maybe a second and a half after a cold start, but that will cease and give way to the noise in the video from then on. You can barely see in the vid that my oil gauge was reading about 40psi, and it does indeed work correctly

    That deeper noise has (seemingly) migrated to to the driver's side bank (err, by that I mean the right one, usdm and all) in the week since the truck started last. I will replace the motor mounts before I tear it down to see if I'm getting a slight oil pan contact with the front axle, although as the video shows it is present even when the truck is stopped. My next step from there is the old screwdriver test for bad rod bearings and/or wrist pins.

    As for the tranny mount, it's solid and was inspected after the noise occurred. The rubber isolator is quite flexible, but clearly not ripped. Even so I will try your suggestion when I have a second person available for it. I'll also unbolt the crossmember with the trans supported to ensure that the mount is good.

    There is an exhaust leak from the right bank manifold to the y-pipe (old gasket), and it makes an audible noise that will also be remedied before the teardown.

    Thank you for all of you time and thoughts on this, this forum is one of the best vehicle specific websites that I've encountered, and folks like you and the others who chime in are what make it so .

  5. #30



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    I herd lifters and an exhaust clunking around I think.
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  6. #31

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    Ok, I've done some more diagnosis on the engine and found the source for both noises within a good margin of confidence. The light tapping/clicking noise is due to a crack which has re-formed in the driver-side exhaust manifold. It had previously been brazed over as a temporary fix before the turbo manifolds were fabbed and installed. So that's the good news I suppose. Here are a few pictures of other potential sources of exhaust leakage, with the first two and last being known sources of leaks: driver's side manifold, the driver's side joint to the Y pipe (makes a dull muffled pulse, but not one that is easily ignored even from in the cab), and the joint from the y-pipe to the rest of the exhaust (lets out some of the motor's growl).
    Click image for larger version. 

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    The exhaust is not a strong point for this build ATM. It is a known temporary component and has not received much attention due to the redundancy of perfecting it. Don't worry, it's all going in favor of dual 2 1/2" stainless piping all the way back (with an x-pipe for the O2 sensor just below the passenger foot-well).

    The other noise is more than likely a spun rod bearing on the #4 rod. This was determined by removing the spark wires systematically until the noise ceased. When I got to #4, the knocking under load went away, but the clicking persisted (makes sense). The test for the clicking was to unbolt the valve cover for the driver's side bank to see if the noise grew in volume when it was slightly lifted, while performing that test, I noticed the crack. The noise did not grow while the cover was lifted. Due to the shape of the intake I was unable to remove the valve cover entirely for inspection without a much more in-depth disassembly.

    As for the cause of these problems, I still need to wait until I have the funds and time to actually fix the motor entirely to pull it apart for a more thorough investigation. Thanks as always guys for all the help on this project. It isn't dead, just on the back burner. More will come in the future, but I'll need to fix it first.

  7. #32

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    OK, I'm going to be cracking into the engine within the next two or three days, depending on weather. My suspicion is either a loose oil pickup that let air into the system (unlikely given my fairly good oil pressure, but it is a possibility) or a crank bearing that was installed backwards. Since #4 went rather than #6 (the most common source of failure based on my research), I'm betting (and hoping) that I simply made a mistake on the rebuild. The oil is already out, and despite it being the engine's 2nd batch of oil and only ~700 miles old, it has a lot of fine, powder sized, shavings which to me seems very excessive even for a newly rebuilt motor. Whatever I find will be reported here for future owners to avoid and or be cautious with.

    Once again, with the motor coming out I will be happy to provide any hard to access measurements or potential hazards that anyone wishes to know. I can already tell you that the rubber brake line that goes from the master the the frame is dangerously close to the driver's side manifold. Once my motor mounts sheared, the small (~1/2") change in proximity caused the line to melt and burst on the trip to the shop. I'm going to try to retrofit the '90 MM brake lines into mine to fix the leak and avoid any future issues.

    With regard to the turbos, the manifolds will still need to be welded up, and I will need to get it running off of an aftermarket ECU before they can be installed. The stock VR4 turbos need to be reclocked to be properly installed up high where they will fit, and I'm going to be running the stock V5MT1 until it fails. Wherever that point is will be recorded here as a stress test for future builders. Hopefully there will be nothing to report...

    Does anyone here know what a good stock N/A fuel and timing table might look like for these motors? I've read about a few who have already switched theirs over to a megasquirt II, but so far I have been unable to find any tables for a base safe tune.

  8. #33



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    Do you have a flopping piston on a wrist pin in that engine? Like maybe a wrist pin fractured possibly. I had an engine sound just like that and it was worse when the compression wasn't putting pressure on the piston and it allowed it to literally flop around in the cylinder from the worn out pin.
    If your going turbo, your going to put a major stress on engine parts. If you don't go through the engine and replace/rebuild things, you may find out rather quickly which parts were the weakest, lol.

    Great build also...keep it going.
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  9. #34

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    Quote Originally Posted by BradMph View Post
    Do you have a flopping piston on a wrist pin in that engine? Like maybe a wrist pin fractured possibly. I had an engine sound just like that and it was worse when the compression wasn't putting pressure on the piston and it allowed it to literally flop around in the cylinder from the worn out pin.
    If your going turbo, your going to put a major stress on engine parts. If you don't go through the engine and replace/rebuild things, you may find out rather quickly which parts were the weakest, lol.

    Great build also...keep it going.
    Not sure how much of the thread you've read, but the entire engine was rebuilt before being put in the truck, just 1500 miles ago. So far it seems like I'm already finding out what the weak parts are in these motors (and transmissions...) lol. It was late in the day when I pulled the pistons out, so I didn't check each one to see if the wrist pins were holding up, but I'd be willing to bet that they aren't in too hot of shape due to metal shavings in the oil... I'll check 'em first thing tomorrow morning.

    Anyway that brings me to the findings... Spun rod bearings on #2, #4, and #5. The lower oiler retainer ring on #1 folded over, gouged out the cylinder wall, cracked in several places, and smashed the oil ring land on the piston. Even the rods that still had good bearings seemed scored, and all of the unspun bearings were elliptical rather than hemicircular when removed... As far as I can see the block is shot until it can be bored out, and the crank and rods are probably in need of repair and/or replacement.

    Here is a picture of the ring damage on the #1 piston. Apologies for the quality, I had to use my phone.
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    And here is a spun bearing, with maybe 30 miles on it. All of the spun bearing rods, plus the rod for #1, were more difficult to remove. To me that suggests that they may have become slightly egged out, thus moving the main studs closer together and binding up the rod cap.
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    The oil I drained out of it was free of large debris, but the crankcase had lots of big coppery colored shavings throughout. The pickup tube was completely undamaged, but did have some shavings stuck in the screen. It's gasquet looked fine too. Many of the machined surfaces felt gritty to the touch. Looks like the bearings took it out on the rest of the motor after they spun.

    A junkyard kinda sorta near me has a good shortblock for $100. I will probably just buy that rather than try to fix mine. I'll probably post again tomorrow with any other findings...

  10. #35



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    Oh wow, it looks like you have a lot going on in there.
    When I had my engine rebuilt the shop must of left some debris in an oiler or installed too tight of rod bearings and clogged up. It took out the first bearing to not receive oil, #1. Bearing lost its coating onto the crank. Good thing I had a doner engine with a perfect crank. I did the measuring for the repair and replaced with racing rod bearings with a closer matched set so it got a better lubrication. If you want it done right, you got to do it yourself. I questioned their work because the bearing locked onto the crank at 25mph, so it definitely was something left in an oiler or missed measuring specifications and clogged. It's ran perfect ever since I fixed their work, lol.
    *BUILT & OWN*
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    '89 Toyota MR2 GT -(Purchased '08)
    '74 Toyota Celica GT -(Purchased '76-Sold '12)
    "Ford Thunderbirds"
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  11. #36

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    Well I have the junkyard short block it currently at the machine shop being bored. I had taken the heads off of it to put on the original motor when I first built it, and the southern Oregon weather had not been kind to the cylinder walls... Still, it was in need of less boring than the original block, and hadn't endured the grit blasting from three spun bearings, so it made more sense to use than the original.

    I will be rebuilding it and dropping it in over the next few weeks.

    I figured I'd give you guys the final prognoses on the other block.

    When piston #1 was being installed on the rebuild, the lowest oiler ring must have slipped past the ring compressor and folded in the bore. Over the course of its 1500 mile journey, the cylinder wall was being turned into grit by the dragging ring, which then cycled throughout the motor. That grit (which was visible in the oil and pan as a grey sludge) ate the bearings, pump, and every other bearing surface until the tolerances were so bad that they finally spun. The motor had simply reached its limit while out in the woods. The straw that broke the camel's back if you will.

    Thankfully it appears as if the motor had a good reason to fail. We'll see how this next one holds up, but by every account that I've read they are very reliable. Hopefully it will survive the turbos.

  12. #37

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    Not good news. Sorry to see all that work destroyed in such a short period of time. Hopefully the bargain $100 shortblock will be solid.

  13. #38

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    Are you still pursuing this?


    Thanks for putting up you're knowledge and experiences guys.


    I've recently started buying parts to make a similar setup, when i did some research i found this thread.


    My goal is 260 - 300 hp, on the 6G72 with twin turbo's, but i'm getting mixed opinions off the internet as to what these engines can handle, and what gives in etc... And local knowledge is all but non existent...


    Does anyone know how similar the bottom end is to the twin turbo version? If they are pretty much the same, then we shouldn't have any trouble pushing decent numbers....


    With that in mind, i am about to do a complete proper rebuild on a spare 6G i have here, and would like to know if i should be considering forged pistons or conrods, and are there any other upgrades or tricks i should be aware of while i have it all apart?


    I'm in the process of stripping the engine down now. I'm hoping my 4D56T currently in my Triton lasts long enough to get this engine built. :D

  14. #39

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    Quote Originally Posted by Brady93 View Post
    Are you still pursuing this?


    Thanks for putting up you're knowledge and experiences guys.


    I've recently started buying parts to make a similar setup, when i did some research i found this thread.


    My goal is 260 - 300 hp, on the 6G72 with twin turbo's, but i'm getting mixed opinions off the internet as to what these engines can handle, and what gives in etc... And local knowledge is all but non existent...


    Does anyone know how similar the bottom end is to the twin turbo version? If they are pretty much the same, then we shouldn't have any trouble pushing decent numbers....


    With that in mind, i am about to do a complete proper rebuild on a spare 6G i have here, and would like to know if i should be considering forged pistons or conrods, and are there any other upgrades or tricks i should be aware of while i have it all apart?


    I'm in the process of stripping the engine down now. I'm hoping my 4D56T currently in my Triton lasts long enough to get this engine built. :D
    Yeah, It's still going together, but a few months ago I got a job as an actual mechanic, so getting motivation to work on my own engine over the weekend is proving to be more difficult. I've got it long blocked now with the intake in place, and I'm going over to install the ridiculous $300 OEM oil pump today.

    As for your power question, the SOHC 6G will hold that no problem, but the manual trans is probably approaching it's limits at those power levels. Unfortunately, no one has been able to provide any info on what the stock V5MT1 trannys can hold, so I'm probably going to be the guinea pig on that particular test (up to around 500hp that is). The auto trans is supposed to be quite strong however, so if already have one or you're willing to swap, you might find more reliability there. I know a guy who claims to have built a twin turbo SOHC up to about 310hp, with stock everything (in a Dodge Raider), and apparently he got 60,000 miles out of it without any issues. That was with stock wastegate actuators and the V5MT1 manual 4X4 trans too.

    The bottom end is supposed to be the same for the SOHC and early DOHC 6G72s, and the rods are the same for the whole run of 6Gs. Truck pistons are among the most desirable for boost as far as OEM pistons go, so you should be fine there. The later DOHC 6G72s had a 4 bolt main and forged crank, but unfortunately there is no way to use that block or crank with our SOHC motors.

    I hope that covers everything.
    Feel free to ask if you run into any other issues along the way .

  15. #40

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    Thanks Speednsnake!

    I'm unsure what i should do about an ECU, i have no ECU at the moment. With plans for boost, it would make sense to buy a standalone and fit that from the get go. Did i read you are going to use megasquirt?

    Cheers
    Brady

  16. #41

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    Has anyone tried running a 6G72TT ECU on these engines or know if it would work? Both engines seem very similar.... Minus turbo's..

  17. #42

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    great work, I love the dash man! and I feel ya on the working as a mechanic deal its hard to get on my own projects as well.

  18. #43

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    Quote Originally Posted by Brady93 View Post
    Has anyone tried running a 6G72TT ECU on these engines or know if it would work? Both engines seem very similar.... Minus turbo's..
    Unfortunately my experience with the DOHC motors is near nonexistent, so the nuances of it's ignition and fuel control systems is beyond what I can tell you. A few things immediately jump out at me though. First, the odds of it being able to be plugged right in is... pretty slim. Furthermore, making it try to figure out the distributor would be a pretty big hurdle, as the DOHC motors use coil packs.

    If you passed that hurdle, you would still find yourself having to re-tune it anyway, as our heads breathe differently, and our stock O2 setup is incompatible with what it will expect, meaning that it would throw a whole mess of codes if you got it to run at all. Not necessarily impossible, but probably more trouble than it's worth.

    You did read correctly that I will be using a Megasquirt, and since it uses it's own harness that will deal with whatever you give it, I found that to be the simplest solution (then again, I haven't gotten that far yet.). As a bonus, I've read that it works quite well with our distributor's single rpm output. The only issue with the Megasquirt is that I will need to find or make a stable ignition and fuel table to get the engine past it's first startup after moving over to it. Once I have those tables (and subsequent power tunes of those tables), I would be happy to provide them here for any future builders.


    Quote Originally Posted by rida4christ View Post
    great work, I love the dash man! and I feel ya on the working as a mechanic deal its hard to get on my own projects as well.
    Thank you . I hope that I adequately explained the process of how to retrofit it into our trucks should you or anyone else try it for themselves in the future. As it stands, I believe that I am the only one to ever do it, but I welcome others to try it for themselves.

    Yeah working on other cars sure gets you burned out on working on your own. I hope to drop my recently completed (N/A rebuilt) motor back in this weekend, but you know how it is. Between moving, doing the brakes on my parents' suburban, and actually enjoying my weekend, it's sounding less and less appealing lol.

  19. #44

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    First, I will say nice build. I have the same truck well mitsu. I know I'm off topic a little from everyone but I was wondering, have you installed the bouncy seats? If so how have they worked out and how hard was the install? Thanks

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