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HT4100 4.1, 4.5, 4.9 Discussion, 4.1,4.5,4.9..Which You Prefer? in Cadillac Engine Technical Discussion; I dont know why they chose to make them out of magnesium.... Post a pic of the mystery bracket....
  1. #46
    Sevillian273's Avatar
    Sevillian273 is offline Cadillac Owners Connoisseur
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    Re: 4.1,4.5,4.9..Which You Prefer?

    I dont know why they chose to make them out of magnesium.... Post a pic of the mystery bracket.

  2. #47
    the recluse is offline Cadillac Owners Connoisseur
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    Re: 4.1,4.5,4.9..Which You Prefer?

    Out of habit I tape all the corresponding screws to the appropriate holes so I don't lose them. For the life of me I cannot remember where this thing goes...

    Sorry for the crappy saturation, low light levels on a cell phone camera
    Attached Images

  3. #48
    the recluse is offline Cadillac Owners Connoisseur
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    Re: 4.1,4.5,4.9..Which You Prefer?

    Found the bracket location, it's the water pump/power steering pump support bracket located over number one cylinder plug.

    Pretty much ready to drop in the hole...
    Attached Images

  4. #49
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    Re: 4.1,4.5,4.9..Which You Prefer?

    haha thats my intake! Looks way better on that motor! I never thought to paint the center area. I used duplicolor 500 degree red. Damn good paint - the engine heat cures it hard.

  5. #50
    sprocket is offline Cadillac Owners Member
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    Re: 4.1,4.5,4.9..Which You Prefer?

    I took the 4.5L out of my '88 Eldo and installed a 4.9L. I used the 4.5 intake and distributor. Yes, it is possible to do this. The car has great power but idles kind of rough. I have not yet determined whether the rough idle may be due to the fuel volume requirements of the 4.9L. This must be one of the only 4.9L with throttle body injection around.

  6. #51
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    Re: 4.1,4.5,4.9..Which You Prefer?

    sprocket you should put chevy 305 injectors in the TBI to get the flow rate closer to a level that is appropriate for the displacement

  7. #52
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    Re: 4.1,4.5,4.9..Which You Prefer?

    I would absolutely be willing to try the 305 injectors. Thanks for the tip. Can you give me a vehicle and year that those would be used on so that I can look them up?

  8. #53
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    Re: 4.1,4.5,4.9..Which You Prefer?

    Any GM 305 TBI but these are the hot rod years usually listed on ebay

    chevrolet camaro (1988 - 1989)
    chevrolet camaro rs (1990 - 1992)
    chevrolet caprice (1989 - 1992)
    chevrolet caprice classic (1989 - 1993)
    chevrolet caprice classic brougham (1989 - 1990)
    chevrolet caprice classic ls 1993
    chevrolet caprice classic ltz (1991 - 1992)
    pontiac firebird (1988 - 1992)
    pontiac firebird formula (1989 - 1992)
    pontiac firebird trans am (1988 - 1989)

  9. #54
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    Cool Re: 4.1,4.5,4.9..Which You Prefer?

    Thanks,
    I've been cross referencing on Rock Auto and then looking to see what vehicles might be available at the local U-pull place. I might try used before I fork out for new.

    It looks like the 305 TBI was used on many Chevy pick-ups and vans and those are fairly easy to find at U-Pull. Even the '91 Cadillac Brougham used the 305 with TBI and there is one of those at the yard. But in many cases the 350 was also an option, so I'll have to get lucky to find a 305 with the injectors still on it. I love searching for good used parts; it's like a treasure hunt to me.

    I could always send them to Witch Hunter for cleaning.

  10. #55
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    Re: 4.1,4.5,4.9..Which You Prefer?

    Completely blanked at U-pull. I went 0 for 13 on vehicles that potentially had the 305. All of them had the 350 and the injectors appear to be one of the first things people take. I might just buy new. There are some refurbished ones on Ebay.

    I wonder if the throttle body itself is different on the 305 vs the 4.5L? I looked at a picture and they appear identical.

  11. #56
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    Re: 4.1,4.5,4.9..Which You Prefer?

    The bolt pattern is the same but other things can vary, like vacuum ports, ISC setups, cruise control, tranny TV cable, etc. Best to keep the one you've got for simplicity's sake.

    If you look at my 4.1 to 4.9 thread there are some other comments in there

  12. #57
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    Re: 4.1,4.5,4.9..Which You Prefer?

    Quote Originally Posted by ehall View Post
    The bolt pattern is the same but other things can vary, like vacuum ports, ISC setups, cruise control, tranny TV cable, etc. Best to keep the one you've got for simplicity's sake.

    If you look at my 4.1 to 4.9 thread there are some other comments in there
    The 4.9 is in the car. It is what it is. I'm not going back to the 4.5, so I just consider this a fun experiment. "Easy" is not what I am after. Fun, challenging, unique, those are the things I care about. It is totally drivable now. I have other vehicles. If this never pans out the way I would like it to, it's not that big of a deal. It's a hobby; that's all.

    From my research the 4.9 has a bore of 3.62" and a stroke of 3.62". The 4.5 has a bore of 3.62" and a stroke of 3.31". They both use the same pistons. The connecting rods are different. This gives the 4.9 a longer stroke and therefore a larger displacement. Externally they appear to be identical. Internally they must be either identical or nearly so. I can't see why there would need to be much internal difference just to install different connecting rods.

    Of course the intake is different, but I am using the throttle body intake from the 4.5. Also the 4.5 distributor. I installed the intake gasket set and all the openings lined up perfect. The exhaust is also from the 4.5.

    The displacement is 9.4% larger on the 4.9 than the 4.5. The 4.5 injectors are therefore not optimal. HOWEVER a 5.0 Chevy is only 2.4% larger than the 4.9. The 5.0 injectors should be a much closer match.

    And you can tell that this engine currently tends to run lean. I can watch the O2 readings in the diagnostics and see that the tendency is to run lean and then the fuel/air mixture is compensated and the swing is to the rich side, but there are more lean readings than rich. The cross counts tend to be low, but they would be with more lean readings. I am going to install a new O2 sensor though, just to be sure the sensor isn't sluggish.

    One last thing. I DID find used 5.0 injectors quite cheap and I am picking them up tomorrow morning. Hopefully they are in good shape.

  13. #58
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    Re: 4.1,4.5,4.9..Which You Prefer?

    If you want to have some fun playing around you can try to install a big block throttle body. It will give you more airflow and let you burn more fuel for bigger combustion. You'll need a throttle body spacer since the butterfly valves are too big for the intake and will jam up. The 8-6-4 Cadillac 368ci engine was BB TBI according to other posts here, and it should be more or less setup the same. You could also look at the ISC interchange and cross ref for the 454 engine injectors to find a BB TBI with a similar setup.

    Another thing is that your computer might not work right with the 4.9 or a larger TBI at wide open throttle. You may need to play with an adjustable MAP to get the higher flow tables worked out. A wideband AFR will help with this. That's the only thing I plan to add, for just that purpose.

  14. #59
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    Re: 4.1,4.5,4.9..Which You Prefer?

    OK, I put in the injectors from a Chevy 5.0 and...

    It wouldn't start.

    BUT, I changed the whole top which included the fuel pressure regulator. I had a new FPR in the other top so I swapped them out and...

    It started and runs much smoother!

    According to the reading from the O2 sensor it was running quite rich at first but the computer was able to compensate. It tends to run rich when you slow down to idle, but I think it's getting better all the time. The O2 sensor seems sluggish sometimes. Sometimes the cross counts are low (even zero) and then they pick up and even go above 20. I have a new O2 sensor but the weather just sucked today so I will get it in tomorrow. Assuming I can get the old one out.

    The, what do you call it? The pollution stuff, the air pump, or whatever it is called, is all either removed or not hooked up. The holes in the manifolds are plugged. The holes in the air cleaner are left open for more air flow. The thermac valve is disconnected and the vacuum line plugged so the air cleaner only gets outside air.

    I think I can now consider this a success story. The car has balls. The power is there across the board. At 55mph the instant economy shows 28-30 mpg.

    It can be done. You can have a throttle body 4.9. I did it. With tips I found here. Thanks, to those who helped.

  15. #60
    sprocket is offline Cadillac Owners Member
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    Re: 4.1,4.5,4.9..Which You Prefer?

    Today I also installed a new O2 sensor and an OEM idle speed control. Believe it or not the the average MPG at 55mph is showing up as 28-31. I thought maybe the readout wasn't accurate when the gas tank was low, so I filled it. Same thing, 28-31. Of course driving around town takes a real toll on MPG but even still, I never saw much more than 21-22 on the highway before.

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