IRS?

[3-0-II]

here's a question for all you hardcore modders and anyone else mechanically inclined (im still learning) out there. First you need to know i just had a 302/AOD combp dropped into my '76 cobra II (previously a 2.8L and RAD4). they're still working on my header issue (drivers side hedman header wont fit... i have to get a custom header made now )

now my mechanic tells me this motor is going to make too much power for my stock V6 8" axle. first of all... how much power have you all run through your 8"s. I'd especially like to hear from anyone running a V6 axle. that is.... if they are different internally. are they?

second, if i do have to ditch it... where should i go? old school with a 9"? a little more modern with an 8.8"? i was discussing this with some friends yesterday and the idea of an ultra radical 8.8" IRS swap came up in discussion. i've been seeing these all over ebay and craigslist for not that much $$. any idea how much fabrication would be needed to get it all in there? i think it would be really cool to have something as modern as cobra IRS in my old cobra II. as much as i love the straight line, driving through the twisties is alot of fun. plus i've always been a fan of unique cars (hence my mustang II ) so this would be like a dream come true for me lol

thanks a bunch!!!

 

[G.A. Heath]

the 8" is a tough rear end, unless your drag racing it the 8" should be ok. An IRS will require you to build a subframe for the rear of the car and will most likely require refabricating the rear floor pan. Essentially you would be back halving the car as many drag racers do to install a ladder bar or four link suspension. If it were me in your situation I would go with a 9", if for some reason that was not an option I would build up an 8.8" and fit it to the car. remember than an 8.8 will need C-clip eliminators to be as safe (with a powerful motor) as an 8" or a 9". On the upside with a non Mustang II 8" or an 8.8 or even better a 9" you can run many disc brake solutions and you have a large aftermarket of parts. The only odd thing about the Mustang II 8 inch is the wheel bearing/axle tube ends which are unique to the cars.

 

[3-0-II]

sounds good. I'll run with the 8" until i start making some more serious power, and then upgrade to an 9"

im also planning a 5lug conversion in the relativley near future. so based on what you're saying theres no way to do 5 lug discs on a MII rear? my other option i suppose is to get my axle drilled and new studs put in at a machine shop or something. i've seen that somewhere before... is that a good idea? im drooling over some bigger 15" 5lug 5slot mags and a set of magnum 500s(cant decide yet) but i need to know what to do before i go buy parts and such.

 

[LILCBRA]

The 8" should be plenty strong, especially if your 302 is basically stock right now. I still have an 8" in my Cobra, and I swapped in a 3:55 gear set from a V6 car. I can't tell you how well it is holding up right now, as I haven't gotten it running yet. Financial strains amnit: But since they are basically the same unit as a 9", there shouldn't be any reason to switch, unless you are running a high torque engine, say above 400 ft/lb or so. Don't take my word as gospel on the numbers, but it is a plenty strong unit. About the only downfall to an 8" is there is not as much out there for accessories-i.e. brake kits, gears, locker units- as there are for the 9", although there is stuff available. Good luck on your install and keep us informed with the 8".

 

[G.A. Heath]

The 8" is plenty strong, and the typical 8" bearing end is the same as the small 9" bearing end (its just that we II owners have a special bearing end). I have a 302 that snapped stock 8.8" axles(when it lived in my old 88 fox) like they were twigs but it hasn't had any problems with a Mustang II 8" (I had the motor and rear from my 76 in a 66 for a season). Now the motor is getting castrated down to 350 or so horses (hopefully) ideally I would like to get it down to 300 or so (purely a street motor when it and the rear go back into the 76). I will probably take the rear and have the bearing ends cut off and regular 8" ends welded on so I can run disc brakes. alternatively I may have an 8.8 cut down to fit, weld spring perches on it, and put a set of strange axles w/ c-clip eliminators to finish it off. The only reason I am considering an 8.8 is because of the weight savings.

 

[3-0-II]

so now that i know my axle is strong enough, onto my secondary goal:

what can i do to make her handle better? i know for the front im looking at som 450lb springs in the front (although only the 425s seem to still be around on ebay). also... i see all these street rod tubular A-Arms and such.. are those worth using on a II? i know they should fit, technically, but are there other issues that come up by installing these parts?

and ive looked into getting some of stumpy's subframe connectors, and traction bars. i hear those are pretty good.

i also have seen some leaf springs from JCwhitney with an extra leaf for the back to increase traction and raise the rear end a little bit (for tires) anyone use those? if so, opinion?

and lastly.. will the 8" stand up to a blown 302.... i have this old roots style blower designed for a 2.9L V6 (Bronco II/Ranger motor) and planned to install it, along with all the EFI peices on my II when i still had the 2.8L V6 in it. since i dumped the 6 (the EFI bronco II parts i got were crap, and i already had the 302, so i just dumped the V6 altogeher) i thought i had no need for it. lookig back thoiugh... i can probably fab up some adaptor plates to hook the blower up to a 302 intake. id ont know the psi that this blower pumps out, but i do know that it was in a bronco II that kept up with a modded n/a fox 5.0 coupe. thats saying something for a truck. im not really sure what im asking... i guess if my axle and trans can hold up to that kind of abuse. i'll dyno it when im done with the swap and if the hp/tq levels are radical (400+) i'll look into a new axle.

 

[G.A. Heath]

I would think the AOD will die before the rear, but neither will like 400+ HP without being beefed up. another note is that you will need to put a cage the car to stiffen it up with those kind of #'s. As for the handling there are a few auto-Xers on here that can help you out more than I. For all of my handing questions I get ahold of thinkkker (he lives about 80 miles south of me now).

 

[3-0-II]

Good point on the tranny. I'll keep researching (as I cant exactly afford much more right now, being a high school student and all) until I find what I need. Thanks for all the help!

 

[78CobraII]

... they're still working on my header issue (drivers side hedman header wont fit... i have to get a custom header made now ) ...

What are you using for the engine stands and mounts? The stock parts pushed the 302 to the passenger side about an inch, so none of the MII/302 headers would likely fit without the stock mounts.

Drilling the axles will work fine (along with early Ranger drums), but your easiest 5-lug conversion is probably a Maverick or early Granada 8" or 9" rear. Their perch spacing is within 1/4" of the MII rear.

Good looking car!

 

[3-0-II]

im using stock motor mounts. bought em off ebay over a year ago. i guess that explains the situation...

ahh well. at least i'll be getting it back sometime next week.

and thanks for the compliment i pride myself in driving a II (well.. when it was actually around to drive lol). saved up for four years to be able to buy it (yep i was 12 when i started)

its alot harder to find parts and stuff for this car, but heck.. thats half the fun right?

and i'll keep an eye out for a maverick/granada rear. although ive only ever seen two mavericks and one granada in my life out here in the bay area. and theres hardly ever any on craigslist. if nothing else, i may go to RCmotorsports.net and get one of their disc conversions for the 8". i should probably check the local junkyards as well