Cad 500 in a Jag
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500, 472, 425, 368 Discussion, Cad 500 in a Jag in Cadillac Engine Technical Discussion; In the planning stages of installing my 1975 500 in a Jag sedan. My engine came out of a 1975 ...
  1. #1
    lead sled is offline Cadillac Owners Member
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    Cad 500 in a Jag

    In the planning stages of installing my 1975 500 in a Jag sedan. My engine came out of a 1975 Sedan Calias with 61K miles, anybody heard of a Cadillac Calias?
    My goal is to build a daily driver so it must be reliable. Most of my driving is on the highway, 75-80%. Want to get good gas milage 18-20mpg on the high way, on 87 octane gas and have plenty of punch when i want it. With 500 CI I know that I will want to punch it once in a while. With the right mods, manual transmission and low rear end gearing I think that I can meet these goals. I have found sources for most of my ideas and know that I can find the right adapters to bolt this thing together.
    However I would like input on my ideas. Here are my proposed engines mods. What do you guies/gals think suggest?

    1. Regasket engine: MTS makes a freshup kit for engines like mine.
    2. Rebuild and tune the Q-jet carb.
    --From reading the posts on this forum it seem like the Q-jet is the best and most cost effective solution.
    3. Modify the factory intake to increase flow and add a 1" spacer.
    --I have come acorss some posts where they made reference to modifing the intake.
    --Does anybody have a link to the exact process of modifying the factory intake to increase flow?
    4. I have considered the Edelbrock, but with the Jag I could have some hood clearance issuses and would prefer to go to a high flow air cleaner like a RamJet dual snorkel air cleaner.
    Feel that getting more air into the carb is more benefical. I'm sure that anytime you can save wieght is a good thing but on a car that will wieghs 4000 lbs will 10-20 lbs make that much difference????
    --Also don't want to give up AC. Could be a work around here if the Edelbrock is the best choice.
    5. Install a #3 or #5 grind cam from MTS
    6. Headers with 2 1/2 " collector and a true duel exhaust with an (X) crossover pipe.
    7. Still trying to decide what to do with the heads.
    --I would prefer to leave as is and just clean up.
    --Opent to suggestions here.
    8. I'm trying to decide about the distrubritor.
    --One book that I have found seemed to indicate that the factory disb. is junk and should be replaced with a MSD unit.
    --He also indicates that the disb. would need to be recurved if modifications are performed.
    --I would think that a new MSD disb and associated coil and plug wires would be the way to go.
    --Anybody have any ideas?
    9. I'm considering on using a LT1 T56 and making the necessary mods to get the trans to handle the 450-500 plus tourque.
    --Does anybody have and suggestions on an alternative manual trans?
    --Still might go with the TH400 that I already have and install an overdrive.
    --Does anybody have any links to overdrives for this trans?

    Sorry for the length of this post. I just want to get my plan together. I have found that there is a wealth of information on this forum.

    Thanks
    Wayne

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  3. #2
    davesdeville's Avatar
    davesdeville is offline Banned
    Automobile(s): 1995 ETC, 75 Deville, Cad500 powered 73 Apollo, 94 Mark VIII
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    Re: Cad 500 in a Jag

    Quote Originally Posted by lead sled
    My engine came out of a 1975 Sedan Calias with 61K miles, anybody heard of a Cadillac Calias?

    1. Regasket engine: MTS makes a freshup kit for engines like mine.
    2. Rebuild and tune the Q-jet carb.
    --From reading the posts on this forum it seem like the Q-jet is the best and most cost effective solution.
    3. Modify the factory intake to increase flow and add a 1" spacer.
    --I have come acorss some posts where they made reference to modifing the intake.
    --Does anybody have a link to the exact process of modifying the factory intake to increase flow?
    4. I have considered the Edelbrock, but with the Jag I could have some hood clearance issuses and would prefer to go to a high flow air cleaner like a RamJet dual snorkel air cleaner.
    Feel that getting more air into the carb is more benefical. I'm sure that anytime you can save wieght is a good thing but on a car that will wieghs 4000 lbs will 10-20 lbs make that much difference????
    --Also don't want to give up AC. Could be a work around here if the Edelbrock is the best choice.
    5. Install a #3 or #5 grind cam from MTS
    6. Headers with 2 1/2 " collector and a true duel exhaust with an (X) crossover pipe.
    7. Still trying to decide what to do with the heads.
    --I would prefer to leave as is and just clean up.
    --Opent to suggestions here.
    8. I'm trying to decide about the distrubritor.
    --One book that I have found seemed to indicate that the factory disb. is junk and should be replaced with a MSD unit.
    --He also indicates that the disb. would need to be recurved if modifications are performed.
    --I would think that a new MSD disb and associated coil and plug wires would be the way to go.
    --Anybody have any ideas?
    9. I'm considering on using a LT1 T56 and making the necessary mods to get the trans to handle the 450-500 plus tourque.
    --Does anybody have and suggestions on an alternative manual trans?
    --Still might go with the TH400 that I already have and install an overdrive.
    --Does anybody have any links to overdrives for this trans?

    Sorry for the length of this post. I just want to get my plan together. I have found that there is a wealth of information on this forum.

    Thanks
    Wayne
    Calais was the entry model Cadillac until 76. It was just a Deville with fewer options.

    1. Couldn't hurt.
    2. Definately go with the QJet.
    3. Check http://www.cadillacowners.com and click manifold on the left side.
    4. If you're keeping the AC, it's easier to just not bother with the Edelbrock, especially since the modified stock seems to flow just about as well. There might be clearance issues with a non-stock air cleaner and the AC compressor.
    5&6 sound good.
    7. Ok.
    8. The stock HEI unit will do fine since you're not going to be seeing 6-7k rpm.
    9. If you want a manual a T56 is probably the way to go. For an automatic a 4L80-E is the way to go, it's basically an OD TH400, but its drawbacks are it's a bit expensive and a bit heavy.

  4. #3
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
    Automobile(s): '80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
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    Re: Cad 500 in a Jag

    If you want mileage then you either need a low numeric rear axle ratio or an overdrive. Forget the stick trans unless you want to spend a lot of money for one which will hold up to the torque. Your TH-400 has a Chevy bellhousing so an adaptor plate will be needed. Headers could be a real pain but would probably improve performance and economy. You can probably use the Cadillac compressor and adapt the high and low lines right to the Jag system.
    You may want to try the engine with the stock cam first and leave the replacement as an option. Do you know what the car weighs now?

  5. #4
    lead sled is offline Cadillac Owners Member
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    Thread Starter

    Re: Cad 500 in a Jag

    The Caddy wieghts 5000 lbs and the Jag wieghts 4000 lbs. Considering a cam change to wake up the engine and let it breath a little bit. Feel that it will also make it more efficient and get better gas milage.

  6. #5
    Stoneage_Caddy's Avatar
    Stoneage_Caddy is offline Cadillac Owners 10000+ Posts
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    Re: Cad 500 in a Jag

    what jag sedan ? we did a few swaps in mid to late 70s jag sedans tossing TPI 350s in them backed up with 700r4s

  7. #6
    lead sled is offline Cadillac Owners Member
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    Thread Starter

    Re: Cad 500 in a Jag

    Suncoast conversions makes a kit for the XJ6 sedan through 1987 and all XJS's. I would like to do a 94 XJ6/12. I also want to put in a manual trans. I have the brake/clutch pedal assembly for an XJS. Would like to come up with an pedal assembly for the XJ40.

  8. #7
    Stoneage_Caddy's Avatar
    Stoneage_Caddy is offline Cadillac Owners 10000+ Posts
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    Re: Cad 500 in a Jag

    ahh suncoast ....thats the kits we used ...good choice ...wish i could remeber in inns and outs ....

    where are you loacted , "i got a guy" ....who might be able to help you with what your looking for ....

  9. #8
    Stoneage_Caddy's Avatar
    Stoneage_Caddy is offline Cadillac Owners 10000+ Posts
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    Re: Cad 500 in a Jag

    heres a link to his site .....used to work for him , nice guy
    http://www.sparrowbritishauto.com/

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