In need of some numbers....
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HT4100 4.1, 4.5, 4.9 Discussion, In need of some numbers.... in Cadillac Engine Technical Discussion; Hey guys, I've had my 91' Deville for awhile (in my household, we actually have four 91-93's), and now I ...
  1. #1
    Rodya234's Avatar
    Rodya234 is offline Cadillac Owners Connoisseur
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    In need of some numbers....

    Hey guys, I've had my 91' Deville for awhile (in my household, we actually have four 91-93's), and now I have a extra working engine that I want to play around with, so I've done research on the standard mods for the engine and I want to ask a quick question. Can someone give me a ballpark estimate on what my horsepower/torque should be after these mods/upgrades?

    Heres the list:
    Custom CAI
    MSD ignition (5000 RPM rev limiter, I've helped replace enough water pumps)
    Supersonic Sparks
    Edlebrock SDT muffler/2.5" mendrel bent exhaust
    Fastchip ECM chip
    1 psi boost
    Mustang Injectors
    A good Port&Polish
    Heads shaved to 10.5:1 compression

    Well, thats it for now (I might add some stuff when I get to my home computer, this is just off the top of my heaf of want I want to put on there.)

    Thanks in advance

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    illumina's Avatar
    illumina is offline Cadillac Owners Connoisseur
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    Re: In need of some numbers....

    Quote Originally Posted by Rodya234 View Post
    Hey guys, I've had my 91' Deville for awhile (in my household, we actually have four 91-93's), and now I have a extra working engine that I want to play around with, so I've done research on the standard mods for the engine and I want to ask a quick question. Can someone give me a ballpark estimate on what my horsepower/torque should be after these mods/upgrades?

    Heres the list:
    Custom CAI
    MSD ignition (5000 RPM rev limiter, I've helped replace enough water pumps)
    Supersonic Sparks
    Edlebrock SDT muffler/2.5" mendrel bent exhaust
    Fastchip ECM chip
    1 psi boost
    Mustang Injectors
    A good Port&Polish
    Heads shaved to 10.5:1 compression

    Well, thats it for now (I might add some stuff when I get to my home computer, this is just off the top of my head of want I want to put on there.)

    Thanks in advance
    Intake will net you about 10, the exhaust will get you at least another 10, Fastchip will realistically give you 15, port and polish will net about 20, enlarging your intake valves to 1.96 will add some extra to that along with a 3-angle valve job, the shaved heads I'm not real sure about, but maybe another 10 or so. So far we have 265 hp...

    The 1 psi boost sounds like an electric supercharger; if you believe in magical flying carpets, then you'll net about 1000 hp, but realistically will not do anything for you at all. The ignition will give you maybe 5 extra ponies, but that will more or less compliment your fuel additions, so yeah, about 5 for that whole fuel/ignition combination.

    So, with all of this added, I would realistically expect between 250 - 270 ponies depending on the internal shape of your engine. Basically, you'll have something close to an LT1 FWD Cadillac...Almost

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    Rodya234's Avatar
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    Re: In need of some numbers....

    Sounds good thanks.

    I would like to have something in there to knock another 40 or so horses to reach 1hp/cube, but I'm out of options, so I'll take what i can get

  5. #4
    illumina's Avatar
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    Re: In need of some numbers....

    No problemo!

    Keep in mind that your numbers will vary according to how well off your engine is and all. You can add anything you want, but should your rings be shot or anything like that, then you will be lucky to get back to stock numbers if you understand me.

    Since you're apparently taking the heads to be done, I would rebuild the entire engine - go for new rings, bearings, gaskets, seals, and whatever else you may need. Also, you can get a set of chrome-moly rings for these engines - I installed a set on my 87 with a 4.5 liter swap.

    Also, what are you using to add 1 psi of boost??? Inquiring minds want to know!!!

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    guidematic's Avatar
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    Re: In need of some numbers....

    I wonder about shaving the heads that much, and how you will get gas to run it on that compression. The LT1's work with this compression because of the reverse flow cooling, and later engines because of superior engine management systems.

    Also, when you do this you could run into alignment problems with the intake manifold.

    I have found that advancing the base timing is a very easy way to add some real power, along with better fuel economy. But that may affect emissions, so be wary of your local laws.

    Mike

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    illumina's Avatar
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    Re: In need of some numbers....

    Quote Originally Posted by guidematic View Post
    I wonder about shaving the heads that much, and how you will get gas to run it on that compression. The LT1's work with this compression because of the reverse flow cooling, and later engines because of superior engine management systems.

    Also, when you do this you could run into alignment problems with the intake manifold.

    I have found that advancing the base timing is a very easy way to add some real power, along with better fuel economy. But that may affect emissions, so be wary of your local laws.

    Mike

    True on the manifold. I have never actually had my heads shaved, but another option is to install Northstar pistons to raise the CR to 10.3:1 or so. However, there is a little bit more involved to make those fit - there is a link I can dig up where someone has done this before.

  8. #7
    guidematic's Avatar
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    Re: In need of some numbers....

    N* pistons, eh? Now I do know that they use full floating wrist pins as opposed to the pressed in pins the 4.x engines have.

    What about the bore size? Going by displacement, it must be close to that of the 4.5/4.9.

    Mike

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    scrabblegod is offline Cadillac Owners Member
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    Re: In need of some numbers....

    On my 4.9, the heads were shaved enough to bring the CR up to 10.5-1. I will have to dig into old records to get the exact number, but it was around 50 thousandths if I remember correctly. I have had no problem with intake sealing. The heads were ported and the manifolds were gasket matched along with removing the divider in the top of the manifold under the throttle body.

    I am running a custom cam with .502 lift at the valve and 282 duration without any piston clearance problems.
    It did require new springs (late model fast burn chevy) and machining of the spring seats. It also required machining the top of the valve guide and aftermarket guide seals along with increasing the slot length on the rocker arms.

    It does have a problem in running very rich. At idle it is noticable in the smell. Under full throttle runs, the a/f ratio is about 10.1. This is killing some of the power. Until someone can tune the Caddy ecm, there does not seem to be much help. I am now looking to aftermarket FI or some other factory GM system that is tunable.

    I am running a CAI and true dual exhaust with about 4 foot of pipe on each side ending in Supertrapp mufflers.

    I enjoy the combination but it does need some refining.

    Gene

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    scrabblegod is offline Cadillac Owners Member
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    Re: In need of some numbers....

    I wanted to add, this combination did give me some hot start problems.
    I resolved them by switching to the gear reduction starter from a Caddy Allante.

    Gene

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