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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; No, not on the PFI engines....
  1. #76
    drewsdeville is offline Cadillac Owners Master
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    Re: I'm going to try the 4.1->4.9 conversion

    No, not on the PFI engines.

  2. #77
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    Re: I'm going to try the 4.1->4.9 conversion

    Thanks

  3. #78
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    Re: I'm going to try the 4.1->4.9 conversion

    Looks like we will do the swap next week. I have been doing some more research and making some junkyard runs during the downtime and everything is pretty much figured out at this point. My 85 has the studs on the firewall in the same place for the 4.5 vacuum canister so vacuum is going to be easy with that canister. The outlet sizes on the exhaust manifolds appear to be the same size on the 4.1 and the 4.9 so I think my crossover and intermediate pipes will also bolt right on with no modifications, which means I will be able to keep my intake with the thermac working. 4.1 valve covers bolt right up to the 4.5 intake, so my accessory mounting should be alright. The only thing that doesn't work easily is that the 4.9 spark wire loom won't directly mount to the 4.1 valve covers--I may use some sheetmetal screws with some spacers to get the 4.9 loom on there as a secret handshake to other enthusiasts.

  4. #79
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    Re: I'm going to try the 4.1->4.9 conversion

    Got wheeled into the shop this afternoon and immediately ran into a problem--some of the bosses are different on the 4.1 and 4.5 intake manifolds. Specifically the alternator mounting bosses are different and one of them is even missing. In one of my trips to the junkyard, however, I grabbed a 4.9 accessory bracket for future reference (this was when I was thinking to use the PFI intake) and test fitting showed that it has the same bolt pattern as the 4.5 TBI intake but as was already discussed in this thread the mounts on the alternator are different between the 4.1 and 4.9. A quick trip to autozone and I see that the 4.5 alternator is the same physical layout as the 4.1 (third bolt in same place). So... in theory a 4.5 TBI accessory bracket will bolt to the 4.5 TBI intake (duh) and have the same bolt pattern as the 4.1 alternator so I should be golden. The ECU connector on the 4.5 and 4.9 alternator is a a little different but worst case scenario I should be able to hack the wiring, at which point I would be able to run 4.9 alternators going forward.

    Sorry I forgot my camera

  5. #80
    aeronca36606 is offline Cadillac Owners Enthusiast
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    Re: I'm going to try the 4.1->4.9 conversion

    I was looking at the same problem. I am trying to decide weather to use 4.1 or 4.5 heads and intake manifold on my Allante 4.1 build up. I also had some concern with the throttle cable mounting bracket. (Thought that i could use the 4.5 cables in the 85 if necessary) I am planning to use the 4.1 throttle body. I like the idea of a duel plane manifold. I also like the change in the intake manifold water passages on the 4.5. I do not want to change the Volumetric Efficiency to much. Fuel mileage and reliability are my main concern. Anything else you find that may be a problem, Please give me a heads up. You are about 2 to 3 weeks ahead of me.

  6. #81
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    Re: I'm going to try the 4.1->4.9 conversion

    This morning very early I went to a junkyard about 40 min up the road where they had a 4.5 TBI and a 4.5 PFI still in the cars. Both of them use the 4.9 style alternator and bracket, with the 3rd bolt hole in the center. I don't know what I was looking at in autozone last night. Anyways I grabbed a 4.5 bracket just in case and the alternator too so I could figure out how to modify wiring, and the yard monkey let me out for $20 when I told him what I was doing.

    I got back to the shop and started moving parts off the engine. Everything went pretty smoothly using a mix of older and newer parts based on what works better. When I got to the alternator I decided to try mounting just the two ears (leaving the 3rd bolt in the back empty), and it seems perfectly stable to me. IIRC the CS-style alternators have always just used two anyway and while the 3rd certainly provides some stability I doubt it's absolutely necessary for moderate load. So for now I'm using the 4.1 with just the two ear bolts, and later on will convert to the 4.9 alternator wiring and upgrade then.

    Here's a couple of pics of the transformation so far. The big open spot in the left rear corner is where the cruise servo assembly goes.





    Vacuum integration is more complicated than I thought--I might pull the pump entirely until I can get it rewired, then stick it back in when I figure out what to do. I have not started working on the coolant or power steering lines yet. The crossover exhaust on the 4.1 is off a hair on the 4.9 manifolds, we may cut the pipe and weld it back, or I think we can just bend each ear by half an inch and get it there. Tomorrow we will do all of that and replace the transmission mounts too.

    Here's some pics of the old 4.1. Gonna junk it because of low compression on #2 cylinder and issues with some of the components.







    Power steering fluid leak and dust from belt wear (pulley wobble) made a nice black goop over everything

  7. #82
    aeronca36606 is offline Cadillac Owners Enthusiast
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    Re: I'm going to try the 4.1->4.9 conversion

    Let me know before you junk it. May need some parts and would be willing to buy.

  8. #83
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    Re: I'm going to try the 4.1->4.9 conversion

    Alright did some research that I should have done before. The 4.1 uses a 17SI alternator, while the 4.5 and 4.9 use a CS-144. The mounting is correct for the classes. The third bolt is for stability and two bolts are alright as long as you aren't hot-rodding all the time. The SI and CS series are different (internal vs external regulators) and you need an adapter with an inline resistor but they are at least available and well understood. There is an alternator shop up the road here and I will ask them about it when I come back to this.

    aeronca, np on the parts but I don't know how long they will let me keep it at the garage

  9. #84
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    Re: I'm going to try the 4.1->4.9 conversion

    FWIW, I've replaced 2 alternator brackets on other 4.X's due to cracking where the ear bolts go through. What did the two instances have in common? You guessed it - missing 3rd bolt (is it really that common for people to leave them out?). I highly recommend you find the right configuration rather than running it with the 2.

  10. #85
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    Re: I'm going to try the 4.1->4.9 conversion

    We got almost all the checkmark items done today. Everything has pretty much gone as expected although a couple of deviations. I decided to delete the vacuum pump and will go natural for that, so I pulled the pump and harness and will closet them until I figure out how to reintegrate. Cruise control got installed after drilling out the throttle linkage to fit over the single throttle shaft on the 4.5 throttle body, as expected. The high-pressure steering line will be installed after the engine is swapped; the low pressure return has the right quick-connect flare already (hidden under the small little 90-degree elbow) so we are keeping that; I have replaced most of the soft line portions on the return line with new hoses and will finish that in the morning. Heater lines are installed on the engine using the 4.9 heater setup, but have to wait until the engine is installed to hookup the heater core. All of the motor and tranny mounts have been replaced except for one, where I don't get the right part (don't know if it was my fault or rockauto), and the tranny input seal was also replaced (torque converter looks good). I also degunked most of the engine bay so that it will be easier to spot new leaks, and did some more cleanup.

    The most interesting part of the day was figuring up exhaust. The first problem was that the 4.9 manifolds have a slightly different angle and the 4.1 crossover pipe doesn't mate up correctly, and it was risky to go with the 4.5 crossover due to the changes in the intake filter style and placement, relocated cruise control, etc. I just didn't want to go there. The other problem was that the rear outlet on the 4.9 manifold into the intermediate pipe before the cat converter is larger than the rear outlet on the 4.1 manifold, so I would need to buy an intermediate pipe from a 4.5 from somewhere and nobody is selling them. We pulled the old manifolds off the 4.1 to get a better handle on things and noticed that the exhaust port sizes are identical, so we decided to install the passenger/rear 4.1 manifold on the 4.9 after pulling the AIR inlet tube. This solved both problems in that it let us use the existing 4.1 crossover and intermediate pipes with no additional changes.

    I also did some more research on the alternator conversion and have a solid line on an adapter cable. The usual adapters are two-wire for the most popular SI designs, but on the 4.1 there is a third pin that provides a tach signal for the computer. The CS models also have a pin for this signal, but you need a 3-wire adapter to make it work, and they are not very common. I have found somebody that says they can get it, and I will install the CS-144 from the junkyard 4.5 (with all three bolts) once I get it.

    Here's two more pics





    Here's a pic of the 4.1 intake manifold after everything has been stripped down. It is the single-plane style, and look how small those runners are



    Tomorrow we will install the engine, the vacuum lines, the heater core hoses, the power steering hoses, and then setup the TPS and ISC and all that jazz, then see if it starts.

  11. #86
    ehall's Avatar
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    Re: I'm going to try the 4.1->4.9 conversion

    The guy that I was teamed with called in sick and I didn't want to move his hardware, so we did some small stuff and will finish up on Monday instead

  12. #87
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    Re: I'm going to try the 4.1->4.9 conversion

    Engine is installed, and the power steering, coolant and vacuum lines are configured. Unfortunately I'm not able to set the ISC or TPS or anything else since the BCM is blowing fuses as soon as they are installed. Pretty sure we need another one.

    Here's a pic.



    Probably won't be anything more happening until I can get another BCM.

  13. #88
    ehall's Avatar
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    Re: I'm going to try the 4.1->4.9 conversion

    Current status is that the car is still down. The battery was wired up backwards and the car blew a *bunch* of fuses. Once I got the battery wires correct and drained the capacitors, the BCM stopped blowing fuses. However, neither of the service engine lights are coming on, and the fuel pump doesn't seem to be working (no pressure at test port).

    The BCM shows F32 which is ECM cannot be found. All the fuses to the ECM are good and the power and ground wires to it test good too, so either the BCM is fried on the ECM link circuit, or the ECM is fried. Since the BCM seems to be operating correctly we are betting on the ECM, and besides it also has that burnt electronics smell. I found a nearby junkyard via car-part.com that listed my ECM for $40 after shipping so I bought one blind, but unfortunately the one they sent is for the RWD 4.1 Deville and Fleetwood models, which is wrong for my car. I found an unopened new-in-box reman ECM on ebay for $45 after shipping and am waiting for it to show up. Once we get the check engine lights to come on we will chase down any fuel delivery problems, and then try again on the TPS, ISC, and timing setup.

  14. #89
    drewsdeville is offline Cadillac Owners Master
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    Re: I'm going to try the 4.1->4.9 conversion

    I've got 3 of them sitting in the basement that will probably get tossed at one point. I would have sent one to you at no cost if you paid the shipping.

    Oh well.

  15. #90
    aeronca36606 is offline Cadillac Owners Enthusiast
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    Re: I'm going to try the 4.1->4.9 conversion

    Do the other numbers other than the part number match? If so, You should be able to change the prom from your 85 fwd to the replacement ECM. I do not know this for sure, but many times the computer boards are the same just a different prom. Of course if the boards are different, Then all bets are off!

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