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HT4100 4.1, 4.5, 4.9 Discussion, 4.9 performance in Cadillac Engine Technical Discussion; excuse me... i meant to say the "motor" DOES NOT determine how it revs....
  1. #61
    LacSeville's Avatar
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    Re: 4.9 performance

    excuse me... i meant to say the "motor" DOES NOT determine how it revs.

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    Re: 4.9 performance

    Quote Originally Posted by LacSeville
    excuse me... i meant to say the "motor" DOES NOT determine how it revs.
    To some degree you were closer the first time, a long stroke motor like the 4.9 is NOT a high revver, the 4.5 by virtue of it's shorter stroke will rev higher so to some degree the "motor" does determine how it revs, of course any motor is the total sum of it's parts. From what I've learned about these motors so far you have to do a LOT of work to the valvetrain to keep them together at high RPM the weakest link being the rocker arm stands. If that is NOT correct somebody tell me now because that's what is holding me back from doing more mods.............

  3. #63
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    Re: 4.9 performance

    I see what you are saying about the stroke, i don't know why i didn't think about that when i replied. what's the redline on the 4-5? 5250 for the 4-9 right?

  4. #64
    kcnewell is offline Cadillac Owners Connoisseur
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    Re: 4.9 performance

    The thing that you are likely to have trouble with is the aluminum rocker arm support bars breaking with the bigger cams and higher RPM. in any case the bars will deflect and cause you all sorts of grief in the valve train department if you don't do something to them. I have seen several installations that heliarced small aluminum tabs to the intake manifold so that the rocker arm support bars could be bolted to the tabs to stiffen and brace them from bending. This is a "custom fit" sort of deal that has to be fabbed up on the specific engine but it is effective.

    The other thing to do is to root thru the parts catalogue - the 89-92 Allante 4.5 engines and the export 4.5/4.9 PFI engines had forged STEEL rocker arm support bars that are much stiffer than the die cast aluminum bars. If I was to do any work on a 4.5/4.9 I would chase down a set of the forged steel bars first thing.

  5. #65
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    Re: 4.9 performance

    Quote Originally Posted by kcnewell
    The thing that you are likely to have trouble with is the aluminum rocker arm support bars breaking with the bigger cams and higher RPM. in any case the bars will deflect and cause you all sorts of grief in the valve train department if you don't do something to them. I have seen several installations that heliarced small aluminum tabs to the intake manifold so that the rocker arm support bars could be bolted to the tabs to stiffen and brace them from bending. This is a "custom fit" sort of deal that has to be fabbed up on the specific engine but it is effective.

    The other thing to do is to root thru the parts catalogue - the 89-92 Allante 4.5 engines and the export 4.5/4.9 PFI engines had forged STEEL rocker arm support bars that are much stiffer than the die cast aluminum bars. If I was to do any work on a 4.5/4.9 I would chase down a set of the forged steel bars first thing.
    Been lookin' for a used set ever since you told me about them last year over at the now defunct GM Forums, may have to break down and try the local Cad dealer but buying new takes all the fun out of it... ANYBODY can do it that way...........

  6. #66
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    Re: 4.9 performance

    then what do you do about valve springs if one had a camshaft ground?

  7. #67
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    Re: 4.9 performance

    are larger valves a good option? i read somewhere something about ford 300 valves are slightly larger, but need some kind of machining? this probably isn't worth the extra money (assuming you already had the heads off)

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    Re: 4.9 performance

    Got the soulution to that problem right here... LOL Just found this, looks like a good idea to me. Guy's never e-mailed me back though....

    http://www.fieroaddiction.com/caddy49h.html


    D.

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    Re: 4.9 performance

    Quote Originally Posted by HippieD9
    Got the soulution to that problem right here... LOL Just found this, looks like a good idea to me. Guy's never e-mailed me back though....

    http://www.fieroaddiction.com/caddy49h.html


    D.
    I had e-mailed him last year when I first started thinking about my 4.9 swap. Never heard back from him either.

  10. #70
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    Re: 4.9 performance

    Quote Originally Posted by LacSeville
    then what do you do about valve springs if one had a camshaft ground?
    You must buy new ones. Ones that will accomidate a higher lift. I'm sure you can find some for the 4.9. If not then the lift on the cam will have to be less agressive. Plus if you can't do headers, intake, and heads an agressive cam won't work well anyways, so a less agressive cam would be the way to go. Not sure the specs but I'm sure the cam is really mild on a stock 4.9 so if you could actaully swap that out and put headers, intake, and port/polish your heads, you would gain a lot of HP/TQ.

    Later,
    Dave

  11. #71
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    Re: 4.9 performance

    anyone know how much lift stock 4-9 springs can handle... safely and reliably??

  12. #72
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    Re: 4.9 performance

    what about specs on stock cam? assuming it's new and the lobes aren't worn!! hehehe

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    Re: 4.9 performance

    Quote Originally Posted by LacSeville
    what about specs on stock cam? assuming it's new and the lobes aren't worn!! hehehe
    Like HippieD9 (no relation ) posted above, you will find this and the answer to questions you haven't even asked yet and may never ask at ......... fieroaddiction.com
    Check out the Performance Mods section, it goes a little deeper than just valve springs. Don't try to run a high rpm cam in a full size Caddy like the Fiero guys, they have a "slight" 3/4 ton weight advantage. 220 degrees duration @ .050" valve lift is a fairly lumpy cam in a small motor and will take away some of the low end torque you need to get a heavy car rolling. The wrong cam can completely ruin an otherwise great car, believe me I learned the hard way. I really wouldn't mess with the cam unless you're swapping your motor into a lighter car. Concentrate on maximizing torque in the low and mid range and utilizing it as efficiently as possible.

    You'll get more from a gear change in the transaxle than you will from a cam change. I had a '92 S-10 with the 4.3, 700R4 and a 3.08 open diff, a coworker had the EXACT same truck except for a 2.56 differential. We got identical fuel economy but mine could blow his doors off and I mean BAD. The only difference was the final drive ratio. The stock Cad 4T60E has a final drive ratio of 2.84 to 1, changing gears requires removing and disassembling the trans BUT it will give you a very noticeable performance improvement albeit at the loss of some top end speed and fuel economy but it will get you to the next stoplight a lot quicker. Simply swapping the 35/35 drive sprockets from the Cad trans for the 33/37 sprockets from a 4T60E out of a 3.4 DOHC car will change your FDR to a 3.18 to 1 without changing the ring and pinion. Use the DOHC's 3.06 R & P as well and you get a 3.43, that's a difference you will definitely feel on the old "butt dyno". Or you can swap in the 3.33's from a 3.1 powered car as is or combine them with the 33/37 sprockets for a FDR of 3.73. If your doing a trans overhaul anyway it's the perfect time. Take a look at a torque converter out of a 3.8 full size car while you're at it to bump the stall speed up a couple hundred RPM but don't go crazy, the 4.9 will make it stall a couple hundred higher than what it was rated for behind the 3.8. The stock Cad conveter is a 1500 stall, a 3.8 converter rated for 1600 will probably be enough as the higher torque of the 4.9 is probably going to make it stall closer to 1800. Don't get carried away here, too loose of a converter will make your car MISERABLE to drive and generates a ton of heat which in turn will cook your trans.

    The 4.9 can be made to run a lot better but as far as being "fast" I have to agree with 99Zee28, it will never be "fast" by musclecar standards. BUT.... it can be made to surprise the unwary who just see Grandpa's car sitting next to them and that's half the fun isn't it. :coolgleam

  14. #74
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    Re: 4.9 performance

    now this is a LOOOOONG SHOT but.... would it be possible to convert say.. my 93 Seville 4.9 to a 5speed manual??? im not even sure if there is a FWD manual trans that would be able to mate up to the 4.9, I mean ive seen a 4.9 in an ISUZU TROOPER 5spd 4wd I kid you not!!! but i think the seville would be a hell of a better performance car if it could take a manual trans. if it can be done i would do it in a heartbeat if i hadnt just dumped $1600 on a new 4T60E.
    Click this link to see that Isuzu
    http://myweb.cableone.net/bcanderson...c/cadillac.htm

  15. #75
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    Re: 4.9 performance

    Quote Originally Posted by caddypimp93
    now this is a LOOOOONG SHOT but.... would it be possible to convert say.. my 93 Seville 4.9 to a 5speed manual???
    absolutely... as long as you have the $$...

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