1966 Frame

Discussion in '1965 - 1973 Classic Mustangs -General/Talk-' started by rjpkrp, Nov 23, 2013.


  1. rjpkrp

    rjpkrp Member

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    Quick question....I've searched but haven't come across any information (maybe my queries were wrong, but who knows).

    I'd like to know how much hp/tq a stock '66 frame can handle without welding in sub-frame connectors and torque boxes. I'm on the fence about what I want to do with my car. I do not want to alter (by welding, etc) the frame. My car is a factory 66 GT, so any changes I make need to be easily reversed (with the original, or original style equipment) with little work. My car is a driver not a show car.

    So, I was looking at just rebuilding the block back to OE specs, etc (225hp gross, etc). Or, I've thought about changing out the intake, carb, heads and cam and pulling 275-300hp out of the engine. I'm just not sure what the frame can handle without altering it. Does anyone know?
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  2. rjpkrp

    rjpkrp Member

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    whoops, didn't see the subforums. Maybe a moderator could move this over to the classic mustang tech subforum
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  3. rbohm

    rbohm Founding Member

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    the shelbys made a rated 306hp without those things in 1966. it really depends on how you drive though. if you only get on it once in a while, and dont push it through the corners hard, it can handle up to 400hp easily. but understand that it will be rather flexible and there may be areas of the body that will deform and crack.
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  4. rjpkrp

    rjpkrp Member

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    You are correct, it is only the convertibles in 1966 that had the torque boxes, so I would think I would be safe rebuilding the bottom end and warming the top-end up to somewhere between 275-300 net hp (~220-250 rwhp). This car isn't about being a "sportscar" or a "track monster". I have a NSX that is for fun, handling, track, sportscar driving. The mustang will be my cruiser vehicle. With 275-300hp will I get on it some? Sure I will, but I'm not a street racer......those days are over 20 years behind me at this point. However, I would like the car to be a little more fun to drive than my 262hp/248tq 4000lb Flex station wagon (which with its gearing, etc, does a 0-60 time in a surprising just over 8 seconds)! That is all I'm really going for.
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  5. rbohm

    rbohm Founding Member

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    300hp will make for a nice performing street car. that is about the power level my mustang will have when i get to putting it together. remember that is going to be about a 10:1 weight to horsepower ratio, which is common among the faster cars of the 60s and 70s. with the right gearing, and some good driving, your stang should be capable of running in the high 13s in the 1/4 mile, which is quick in anyones book.
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  6. rjpkrp

    rjpkrp Member

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    I think I might end up going with a CME (Carolina Machine Engine) 289F000P5. It is a "performance upgrade" 289 rated at 9.5:1 compression, 280hp and a lopey cam (next upgrade is a 300hp choppy cam, but not interested in choppy). I think 280hp at the flywheel will be just fine in this car and make it a fun driver. Then I can just plastic wrap my OE engine and have it available to drop back in or include with the sale of the car down the road.



    I'm presuming 8" rear end should be fine with 280hp, and with..what? 310lb/ft or torque or so (is what I'm estimating) the C4, I'm thinking, should be fine with a standard rebuild (although I'm sure I might do a mild performance rebuild on it).


    EDIT: unless an AOD would be a direct bolt in, then I might plastic wrap the engine and transmission. However, if there are modifications that need to be made for an AOD, then I'll stick with my C4. Besides, 3 speed works well for engine braking with manual brakes!
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  7. rbohm

    rbohm Founding Member

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    an 8" will work just fine, my 289 should make about 325hp and i am keeping my 8". an AOD is and isnt a direct bolt in swap. you will have to shorten the drive shaft, change the trans cross member, change the flexplate to one with 164 teeth and the proper balance factor, and add a properly adjusted TV cable. not that hard to do, but must be done otherwise you can burn up a good AOD in short order.
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  8. rjpkrp

    rjpkrp Member

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    Alright,

    I decided to go with the ATK 302 for the engine swap. It is supposed to make 300hp/336tq. So, if it is close to those numbers I should be alright. I'm going to use a Weiand Stealth 8020 intake, Holley 4160 1850-2 600CFM carb, HEI distributor and tri-y 1-5/8 headers. Should be alright and I'm sure will be close to the published crank numbers. At any rate, I'll rebuild my C4 and make it a bit more stout and the car should be a lot of fun to drive (in a straight line anyway).

    I will end up pulling and wrapping the original 289, intake, autolite 4100 (480cfm), distributor and exhaust manifold and keep them for rebuilding back to 100% stock and to put the car back to original in the future....since it is a factory GT car.
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  9. rbohm

    rbohm Founding Member

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    sounds like a plan to me.
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  10. rjpkrp

    rjpkrp Member

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    [​IMG]

    Getting it ready for the swap. Just not sure about welding in subframe connectors. Once they're in...can't go back to being original. However, it is a '66 GT (factory GT) so while it is desirable it isn't that "rare" a car. I'm not sure that subframe connectors will devalue the car any more than the 3-point restraint system (seat belts) I will install. Both are safety modifications and shouldn't devalue a vehicle (unless the next buyer is looking for concours, but then my car has had a repaint in it's nearly 50 year life).
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  11. candphall

    candphall Member

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    You can spend a lot of money and time trying to get your 66 to perform and handle like your NSX. For my money I would bypass all that and build myself a nice 300hp pump gas cruiser. And as far as that year not being a rare model remember you only have one. I look forward to following your project, it looks like it will be a good one.
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  12. rjpkrp

    rjpkrp Member

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    Oh heck no. It will never handle like the NSX....I'm just a little concerned about possible chassis...or better yet....unibody flex (and body waves), as I'm sure I will occasionally get on it (no matter how infrequently). Like I said before....this car is a driver. Not only a driver, it is my daily driver for Spring/Summer months. However, three-point harnesses are a must, so they will be done no matter (I have three children who will also be riding in this car). I consider the subframe connectors to also be a safety modification....not necessarily a performance modification (although they will help the car handle and ride a little better).

    As far as tracking the car....I can honestly say I doubt that will ever happen. I hardly track the NSX (twice in 5 years of ownership) (and never the Porsche, or the Vette). That's just not my thing......I had my fill of "tracking" when I raced stockcars on Friday and Saturday nights for fun back in the day.


    EDIT: probably concerned about nothing. Maybe I should put my efforts into deciding if I want to change the carb out for a more reliable EFI unit. If I go that route, I'd go TBI so I can maintain an "old school" look yet get the reliability and maintenance of fuel injection. I only consider this since the car is a daily driver.
    Last edited: Dec 22, 2013
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  13. rjpkrp

    rjpkrp Member

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    Whoops, I forgot the description of the engine when I posted the pic. It is an ATK Engines HP79 Ford 302 @ 300HP/336TQ. It's been painted Ford Blue, has a Weiand Stealth intake and Hedman 1-5/8 longtube headers. I'm putting a Holley 4160 1850-2 600cfm carb on it and Pertronix Ignitor II distributor conversion. (the original 289, instake, Autolite 4100 and distributor will be cradled and bagged until it is needed in the future (whether returned to the car or sold with the car if/when the car is sold).
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  14. rjpkrp

    rjpkrp Member

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    Came across something cool. While prepping the engine compartment for the new engine, noticed some stenciling under the paint on the radiator support. Just a hint. So we spend a little bit of time with a razor blade carefully stripping the paint and found the stenciling for the original dealership when they prepped the car almost 50 years ago.

    [​IMG]

    So, we finished painting the engine compartment but left this section. Going to shoot a little clearcoat over it though to further protect it. Just a cool little piece of history.
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  15. horse sence

    horse sence Please don't call me Mom SN Certified Technician

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    I restored a 65 coupe for my cousin with a vinyl top. He decided he didn't want the top so i striped it off and under the vinyl we found a big dent with some kind of rubberized putty troweled into it. beside the dent it said return to closest dealership for repairs . i think it was damaged on the transporter and repaired at a dealership and the vinyl top was added to cover it up.
    I like to see that writing and take pics of it when i find it ,some times the builders even wrote names in the quarters and left little notes .
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  16. horse sence

    horse sence Please don't call me Mom SN Certified Technician

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    this car may have been a dealer reps . car . is the DSO on the door tag longer than two numbers ?
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  17. rjpkrp

    rjpkrp Member

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    Nah, the DSO is 71 (Los Angeles). From what I can tell, Coberly Ford was a Los Angeles dealer from the early 1900s until the mid to late 80s. It does, though, help to authenticate it being a California car (along with the Assembly Plant, DSO, and CA Black plates that came with the car).
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