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HT4100 4.1, 4.5, 4.9 Discussion, I'm going to try the 4.1->4.9 conversion in Cadillac Engine Technical Discussion; I reinstalled my Accel 8.8 wires to see if it made a difference on anything, and the engine smoothed right ...
  1. #136
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    Re: I'm going to try the 4.1->4.9 conversion

    I reinstalled my Accel 8.8 wires to see if it made a difference on anything, and the engine smoothed right out, and also killed some engine noise. These replaced a brand new set of Belden wires (admittedly one of them had a nick in the insulation), and this is the second time I've had this result. I've used those Beldens on other cars with good results but they don't seem to work very well on the Cadillac.

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    Re: I'm going to try the 4.1->4.9 conversion

    Maybe Belkin should stick to making outrageously expensive USB cables.

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    Re: I'm going to try the 4.1->4.9 conversion

    Huh? USB cables don't work?

  4. #139
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: I'm going to try the 4.1->4.9 conversion

    You might want to try a MAP sensor. When mine was acting up the tranny shifted pretty weird.

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    ehall's Avatar
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    Re: I'm going to try the 4.1->4.9 conversion

    I've tried two different replacement kickdown/detent cables (the Dorman one is nice), and two different vacuum modulators, and still having problems with long slow shifts and lots of slipping in 3rd. At this point I gotta take it to a tranny shop to make anymore progress. I will have to wait a while on that until work picks up again, since it's not a high priority item.

    I have also done a little more work on the engine bay while messing with that stuff. The EGR did not have a vacuum leak, it's just stumbling at tip-in like my old one did until it broke in, so hopefully that will go away after break-in too. The cruise control vacuum lines were swapped, and it works fine with no vacuum leak once that was figured out and fixed.

    I have one last problem which is that the throttle isn't returning to fully-closed position anymore. Basically, once the engine warms up a bit and I press the gas pedal, the engine falls back to idling at ~1500 RPM, like a vacuum leak. I was looking for a leak, and noticed that if I press the ISC plunger with my finger, then the ISC fully seats and the idle settles down to a happy 600-800 RPMs. Then I rev it again and the same thing happens. I have replaced the ISC with one of my spares and it's still doing the same thing. It's not a vacuum leak--the gauge shows 17-18 hg when idling correctly. Maybe the throttle return springs are stretched... I have more springs from the junkyard, and I suppose I could probably find a high performance spring online. Very weird. Anybody seen this before?

    Other than that the engine runs wonderfully, and the car is very responsive with plenty of power reserve. I love driving it around the neighborhood in 1st and 2nd ...

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    Re: I'm going to try the 4.1->4.9 conversion

    Nevermind on the throttle return! I'd adjusted the cruise control actuator to the snug position, and when the engine air got warm the air volume shrank, producing a mild vacuum, tugging on the arm. Moving the actuator to the next position fixed it.

    The EGR stumble is also gone now... stupid vacuum systems

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    Re: I'm going to try the 4.1->4.9 conversion

    I tweaked with the TV cable and vacuum modulator some more and everything seems pretty much dialed in best I can get it. Shifts aren't bad anymore, and 3rd gear is the only problem now. A little bit of gurgle at cold start, and there is still the water pump pulley angle to resolve, but everything is operational and I am able to get around in 1-2-4 alright. It has a good feel to it.

    [youtube]HznRskp1reQ[/youtube]

    At this point I am going to call it a successful project and consider the transmission a separate problem.

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    jzchen is offline Cadillac Owners Fanatic
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    Re: I'm going to try the 4.1->4.9 conversion

    Wow, congratulations! I guess I'm the only one left with an '85 and the original 4.1...

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    Re: I'm going to try the 4.1->4.9 conversion

    Congratulations on the conversion. You've got the best of both worlds, a 4.9 engine and a short bodied Cadillac. Regarding the tranny, go find yourself a 440-T4 that's 87 and newer. There were significant improvements made and I believe you'll be much better off rebuilding one of those than what's in your car. Make sure that when the transmission is rebuilt, you have a Transgo shift improvement kit installed. It'll help the transmission handle the extra torque of the 4.9 and the transmission will be just a lot more refined unit when finished. When the transmission is rebuilt, MAKE SURE A NEW SPRAG GEAR is installed since it has a limited lifespan. I would also highly recommend a new chain and new lock up solenoid. All the tolerances should be measured and shims added to bring the tolerances back to spec.

    Also, there is no reason why you can't rebuild a 440-T4 yourself. It'll save you a bundle of money and you'll know exactly what went into the transmission. There are too many shyster transmission rebuilders out there who make their money on just getting the transmission so it'll go past the 10k mile warranty. Also, the markup is quite tremendous. I rebuilt my last 440-T4 for under $150 and that included some hard parts.

  10. #145
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    Re: I'm going to try the 4.1->4.9 conversion

    It's been a month so wanted to do another follow-up.

    The power well is deep and easy to tap. I love having it available.

    I haven't found any fluid leaks. Yay me

    The 4.5 vacuum setup is working fine, and once I got my earlier leaks sorted out there hasn't been any vacuum shortage. I am very close to just forgetting about the 4.1 vacuum pump. The principle benefit from the pump was that it made the interior accessories work consistently, but they are working just fine with the reservoir setup. It's also nice to not hear the constant buzzing noise from the pump--damn thing makes a racket. They were changed from 85 to 86 so the 85 is especially hard to find, which means replacing it would be difficult. I am going for super-stock with this car not factory restoration, so I am not really hung up on the pump. I think I will just forget about it.

    The transmission is still slipping in 3rd a bit. Specifically, if I am getting on the gas from a standstill and it goes 1-2-3 then it will slip very bad as soon as it gets to 3rd. If I coast along slowly 1-2-3 it doesn't slip right away, but it will slip whenever I try to accelerate. If I start in 2 and then manually move the selector to D at around 45 MPH, it seems to shift straight into 3rd with converter lockup and that works alright. If I am cruising along and downshift to 3rd for passing gear it also works alright. So basically 3rd without lockup is where it slips, which tells me the clutch plate is probably bad. However it also seems affected by load, and it doesn't slip when the modulator is disconnected, so I think the clutch plate is just kind of marginal and if I could get vacuum pressure in the right place I could probably make it work. I have the adjustable modulator dialed all the way down and it feels good; if that would go a little more it would be great I am sure. I have tried a couple of ways to reduce vacuum from the throttle body to the modulator but they don't seem to make any difference. I also put in some Trans-X to try and clean the valve body and seals hoping that would do something but it didn't make any significant improvement in this problem. Maybe if I opened the transmission and diddled with the internal hydraulics I could tweak something, but since that requires pulling everything out I'm going to just put something better back into the car if it gets that far. Right now I am favoring the 4T65-E with standalone controller option, seems like it would be a good fit with the 4.9 upgrade, and would get me another 20+ years of duty with lots of options. So that is my plan, pull the 440-T4 and replace it with a 4T65-E, and in the meanwhile keep trying to get the vacuum right.

    The only real "problem" I have with the injector setup is that the engine runs rough at cold startup. It stumbles and burps until it's warmed up. Since the Chevy 305 injectors are about 1.7% larger than needed for the 4.9 engine displacement, the default start is causing the engine to run on the rich side. Once everything warms up and the ECM switches to closed loop mode, then it is like glass and no problems with anything. If I drive a couple of miles then park and restart a couple of minutes later there's no rough start condition (everything is already warmed up). This isn't a big problem, but it is a mild irritant. 1st gear is rough when the car is belching. Once it warms up everything is perfectly fine. Irritating that I can't fix it.

    Fuel economy took a hit in the nuts. 20% larger displacement means 20% more fuel is required for the same RPMs and duty. It's another mild irritant and something you may want to consider. I haven't confirmed yet, but my Jeep Cherokee may actually be more efficient now.

    Overall everything is fine except for the transmission and the minor annoyances. OTOH the car has more power, the engine is much more reliable, and everything is simpler without the smog pump and vacuum pump. I'm very happy with it and would recommend the swap to anybody looking for long-term usability

  11. #146
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    Re: I'm going to try the 4.1->4.9 conversion

    I wonder if manually activating the lockup solenoid @ 3rd gear would compensate for the slippage? The computer simply grounds the solenoid when it sees fit. You could use a switch to do the same on your own.

  12. #147
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    Re: I'm going to try the 4.1->4.9 conversion

    Something doesn't make sense. If a physical problem 2-3 clutch pack was creating the slippage, it would slip whether the converter was locked or not. The fact that it only does it under certain conditions and it disappears when you play with the modular points more towards a valve body, pump, or even fluid type issue if it was a transmission problem, but I'm leaning more towards incorrect vacuum to the modulator since this coincidentally began as soon as the swap was finished. However, running it as it is could eventually create clutch problems that you don't currently have.

    I don't remember what you have and haven't done, but do you know if the vacuum with your current setup is even close to factory specs or have you just been running it as-is because you notice it runs accessories just fine? Have you tried an adjustable modulator?

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    Re: I'm going to try the 4.1->4.9 conversion

    Specs are 13-16 hg inches at the vacuum supply to the modulator. It's the same for the 4.1 with 440T4 and 4.5 with 4T60-E (I thought they might be different but research says they are the same). The last time I checked, I was at the top of that range, right around 16 hg at idle. It was probably on the low side when I was having post-swap vacuum leaks (cruise control and EGR). This is why I have been trying to get the vacuum pressure down again, but without success.

    I have two of the adjustable modulators. They have both been dialed all the way down to the firmest setting. All of the adjustable modulators seem to be the same, just sold in different boxes.

  14. #149
    aeronca36606 is offline Cadillac Owners Enthusiast
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    Re: I'm going to try the 4.1->4.9 conversion

    I am relatively sure that the idle vacuum would be the same between the 4.1 and your 4.9 conversion. What i am not sure is whether the vacuum pressure roll off curve is the same. At part throttle the 4.9 conversion may have more vacuum then the 4.1. This has to do with having to work the 4.1 harder to get the same acceleration that the 4.9 probably does easily. I do not know if the transmission's valve body is calibrated to your present vacuum curve. (I don't know if this even possible or matters)

    I think your idea to use a 4T60-E with a controller will give you all of the adjustment you will need. I am sure that it will make for a smooth shifting transmission.

    I was also thinking of your roughness when cold. If you can tune the injector flow with either a different flow injector or adjustable fuel pressure regulator and get the open loop mode running smooth, I think the closed loop mode will learn the flow tables necessary for smooth operation.

    I believe that if you disconnect the engine temperature sender the car will remain in open loop mode. (Watch to be sure the radiator fans still work. They can be made to run all the time by disconnecting the control connector next to the battery. It is a 2 conductor plug with the smaller gauge wires that go to the fan control module behind the left headlight).

    Thanks for the parts!

  15. #150
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    Re: I'm going to try the 4.1->4.9 conversion

    The transmission is slowly fixing itself. I have changed behavior a little bit to help it shift better (such as holding and releasing gas pedal to help it shift from 2-3 faster), but there is also a definite improvement in the trans operation. I don't have to manually shift from 2-D from a red light anymore. However if I drive around for more than 30 min then 3rd will start acting up again, slipping in downshifts etc, so maybe it is still acting up when fluid gets hot (may point to a seal). Maybe the modulator is shifting position, or maybe the seal conditioner is kicking in, or maybe there is some clutch material getting worked out of the valve body, or maybe I am losing engine vacuum ... who knows. Hopefully the trend continues and it will fix itself entirely. I will do a fluid swap at some point but want to let it keep going for a while more

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