80 Mirada 318 tweaks

[MiradaCMX80]

Hi,
New member..... I just brought home my 1980 Mirada CMX 318 2 barrel. I'm already planning and tinkering. First thing I want to do when it's registered and insured is get it to my local exhaust shop for 2 1/4 H-pipe dual exhaust. The Y-pipe is leaking and the pipe right behind the cat is full of pin holes, so might as well.

After that, I'm looking for a reliable 4 barrel setup. I'm already getting confused as I scour the internet for info. Use this manifold...use that one...use a Holley 600....no, use a ThermoQuad (Really??) Some articles even said upgrade the 2 barrel (!)

The car is all stock, 83k miles. Stock 904, 2.7 axle, blah blah. Looking for reliability, and decent mileage. I removed the A/C lines and condenser as it is inop, and after I find the correct pulley the compressor will go too. Also deleted the smog air pump. I just want to liven it up a bit to enjoy weekend cruising. In the distant future, I *may* do a swirl port head swap with a 340 cam, but for now, stock tiny heads and stock tiny cam.

So what do you experienced folks recommend as a good 4 barrel and intake setup? I'd like an easy swap, don't want to monkey too much with custom throttle and kickdown brackets and stuff. Fire away.

 

[MiradaMegacab]

Welcome aboard! You can run a shorter belt from the crank to the alternator when doing an AC delete.

 

[Duke5A]

• Edelbrock Performer intake, not the RPM version. The regular Performer has the 318 port size and is a better match for what you have. Idle to 5500 is it's advertised range. The RPM intake is 1500 to 6500.
• Factory linkages can be made to work with modification, but the easiest setup is Lokar cable kits for both kick down and throttle. If you want to stay factory you'll need to source a longer 4bbl throttle cable and a 4bbl kick down arm. Both these pieces can be found on the AHB cop cars, but are getting hard to find. Even finding them people want what you can get the Lokar stuff for.
• Holley 600 CFM, single pumper, vacuum secondary or maybe an Edelbrock 1406. I like the Holley carbs and jet changes are stupid easy.
• Take it Doug's Muffler in Mount Clemens for your exhaust for a budget friendly setup, or take it to PF&E in Chesterfield Township for a pro setup.
• You didn't mention if you already did away with the Lean Burn computer. If not, you'll need a distributor and electronic ignition box. I might have this stuff up in the attic to be honest.
• Finally, the trick @MiradaMegacab mentioned works great. If the car has a replacement water pump already you may not need to make any modifications. I've seen pumps that didn't have those ribs cast into them.

 

[johnnyspeed]

Hi,
New member..... I just brought home my 1980 Mirada CMX 318 2 barrel. I'm already planning and tinkering. First thing I want to do when it's registered and insured is get it to my local exhaust shop for 2 1/4 H-pipe dual exhaust. The Y-pipe is leaking and the pipe right behind the cat is full of pin holes, so might as well.

After that, I'm looking for a reliable 4 barrel setup. I'm already getting confused as I scour the internet for info. Use this manifold...use that one...use a Holley 600....no, use a ThermoQuad (Really??) Some articles even said upgrade the 2 barrel (!)

The car is all stock, 83k miles. Stock 904, 2.7 axle, blah blah. Looking for reliability, and decent mileage. I removed the A/C lines and condenser as it is inop, and after I find the correct pulley the compressor will go too. Also deleted the smog air pump. I just want to liven it up a bit to enjoy weekend cruising. In the distant future, I *may* do a swirl port head swap with a 340 cam, but for now, stock tiny heads and stock tiny cam.

So what do you experienced folks recommend as a good 4 barrel and intake setup? I'd like an easy swap, don't want to monkey too much with custom throttle and kickdown brackets and stuff. Fire away.

 

[johnnyspeed]

I have a pulley and bearing to eliminate the air conditioning compressor. Also have a bracket. Just contact me and pay shipping and it's yours.

 

[MiradaMegacab]

So the OP has a 1980 T Top Mirada, nice car BTW.

How many 1980 T Top Miradas were made?
Rumor has it only 8 were made.

 

[AJ/FormS]

The car is all stock, 83k miles. Stock 904, 2.7 axle, blah blah. Looking for reliability, and decent mileage.

IMO, you need to start with gears and a TC.
Are you sure it has 2.7s? And I'll bet the tires are 205/75-15s at 27 tall, and; I doubt the 318 can spin the tires; so;
with the tires locked to the road and a power peak of 130@ 3600rpm what are you expecting from a 4bbl?
I can tell you that the 2bbl is good to 3600 at 80%VE all by itself. So its good for about nothing until after 3600.
With 2.7 gears, and 27" tires, this would be about 42mph, where the 4bbl finally starts to count for something. Well it would if it could breath.
Ok so lets level the playing field;
130hp @3600 is a NET number. At the flywheel this might be 155, so lets talk flywheel from now on.

Wiki says your car weighs 3380 before you climb into it.
By your enthusiasm I suspect you are a young guy and say 160 pounds , making your Mirada 3540 ready to race. 3540/155=22.8 pounds per hp. This is a huge huge problem, especially for 2.7 gears.
Wiki also says that your 318 makes 230peak ftlbs at 1600, leading me to believe yur car will have a very very low stall TC.
To have even a modicum of fun with that car, you will need to get the power to weight ratio down to under 15/1 . At 3540 this means yur 318 needs to get pumped to 236hp. That's after you install a 2400TC and at least 3.23s. That is an increase of 81hp or 52%; that's a lot.
Even if the 4bbl added 10 hp at the powerpeak of 3600/ 42 mph, it does nothing except roar, until the 2bbl runs out.
At yur current output the dual exhaust will add nothing until the rinky-dink carb starts running low, say 3000rpm or 35mph.
So, I say again, IMO, you need to start with gears and a TC. And a serious weight-loss program. The car,lol,Not you.

Or you could just transplant a 5.2Magnum. They are born at 230NET hp, possible 270 crank. If you get the Mirada down to 3400race weight, this would be 3400/270=12.9 pounds per hp. There is your reliability and mileage, wrapped up in a performance package. This engine still needs a decent TC and more gear won't hurt it a bit.

 

[Mikes5thAve]

For 4bbl go with a performer intake. I'd use an edelbrock carb over a Holley. I don't mind thermoquad either but with little to no support they can be harder to find the right one and setup properly.
Youd be better off with aftermarket kickdown setup because the factory parts are designed around either thermoquad or quadrajet and sometimes need a bit of tweaking for something different. The original throttle cable should be usable if you either use the proper 4bbl throttle bracket or an aftermarket one.
If you still have the computer you'd also want to change to the vacuum distributor and ecu at the same time.
You can use all these parts with swirl port heads if you do that change later.

Spend some time browsing around the forum and other ones. This is all basic stuff that's been covered thousands of times and hasn't changed much over the years and you'll probably find some ideas you didn't think about.

 

[MiradaCMX80]

View attachment 40329 Welcome aboard! You can run a shorter belt from the crank to the alternator when doing an AC delete.

I saw that on some A-Bodies and thats the route Im going to go.

 

[MiradaCMX80]

• Edelbrock Performer intake, not the RPM version. The regular Performer has the 318 port size and is a better match for what you have. Idle to 5500 is it's advertised range. The RPM intake is 1500 to 6500.
• Factory linkages can be made to work with modification, but the easiest setup is Lokar cable kits for both kick down and throttle. If you want to stay factory you'll need to source a longer 4bbl throttle cable and a 4bbl kick down arm. Both these pieces can be found on the AHB cop cars, but are getting hard to find. Even finding them people want what you can get the Lokar stuff for.
• Holley 600 CFM, single pumper, vacuum secondary or maybe an Edelbrock 1406. I like the Holley carbs and jet changes are stupid easy.
• Take it Doug's Muffler in Mount Clemens for your exhaust for a budget friendly setup, or take it to PF&E in Chesterfield Township for a pro setup.
• You didn't mention if you already did away with the Lean Burn computer. If not, you'll need a distributor and electronic ignition box. I might have this stuff up in the attic to be honest.
• Finally, the trick @MiradaMegacab mentioned works great. If the car has a replacement water pump already you may not need to make any modifications. I've seen pumps that didn't have those ribs cast into them.

It does have an aftermarket water pump. In fact, the alternator bracket bolt is stripped out in it already Doug's Muffler is where I plan to go I know Doug....I worked there for a couple months after my divorce. Great place!

Do the Lokar kits fit the 904 trans? I always see them for 727's. I dont mind a Lokar set because I know they plain WORK.

My car didn't have lean burn. It has electronic ignition with a replacement blue box. The previous owner did a full tune up...plugs, wires, cap, rotor, blue box, ballast resistor, but left the original coil. ??? Weird.

I have heard Edel is slipping in quality....is the Performer Non-EGR still worthy against say a Weiand Stealth? Which, a lot of folks seem to favor over the Edel.

 

[MiradaCMX80]

IMO, you need to start with gears and a TC.
Are you sure it has 2.7s? And I'll bet the tires are 205/75-15s at 27 tall, and; I doubt the 318 can spin the tires; so;
with the tires locked to the road and a power peak of 130@ 3600rpm what are you expecting from a 4bbl?
I can tell you that the 2bbl is good to 3600 at 80%VE all by itself. So its good for about nothing until after 3600.
With 2.7 gears, and 27" tires, this would be about 42mph, where the 4bbl finally starts to count for something. Well it would if it could breath.
Ok so lets level the playing field;
130hp @3600 is a NET number. At the flywheel this might be 155, so lets talk flywheel from now on.

Wiki says your car weighs 3380 before you climb into it.
By your enthusiasm I suspect you are a young guy and say 160 pounds , making your Mirada 3540 ready to race. 3540/155=22.8 pounds per hp. This is a huge huge problem, especially for 2.7 gears.
Wiki also says that your 318 makes 230peak ftlbs at 1600, leading me to believe yur car will have a very very low stall TC.
To have even a modicum of fun with that car, you will need to get the power to weight ratio down to under 15/1 . At 3540 this means yur 318 needs to get pumped to 236hp. That's after you install a 2400TC and at least 3.23s. That is an increase of 81hp or 52%; that's a lot.
Even if the 4bbl added 10 hp at the powerpeak of 3600/ 42 mph, it does nothing except roar, until the 2bbl runs out.
At yur current output the dual exhaust will add nothing until the rinky-dink carb starts running low, say 3000rpm or 35mph.
So, I say again, IMO, you need to start with gears and a TC. And a serious weight-loss program. The car,lol,Not you.

Or you could just transplant a 5.2Magnum. They are born at 230NET hp, possible 270 crank. If you get the Mirada down to 3400race weight, this would be 3400/270=12.9 pounds per hp. There is your reliability and mileage, wrapped up in a performance package. This engine still needs a decent TC and more gear won't hurt it a bit.

I enjoy your comments. I AM a young(ish) guy (35, thank you...) and 150 pounds. I LOST weight during isolation I have no idea what the car weighs, I can only tell you the options it came with (very few) and what I removed already.

I'm not positive of the 2.7 axle, it could be a 2.9 since the car has A/C.... just going by the brochures. But I should have mentioned that I do want a 3.23 axle as well. The car currently has 215/70x15 Radial T/A's on all 4.

Yup....it has a turd convertor in it as well, which I would also address during the install of the other parts.

You're suggesting a 4 barrel would be overall useless with this combination? I wanted a 4 barrel because I know them, and Im not a fan of the Carter BBD. Though I will say mine is new, and seems to run just fine all things considered. It wont kill me to keep it.

A Magnum swap was also considered, as well as an E58 style 360. For the time being, I would like to enjoy the 318 as long as possible. I have no problems with a 318, just want a LITTLE more oomph out of it. I do not plan on it being a tire melting race car...just something fun and reliable that me and the kid can cruise on the weekend, and actually get on to the freeway without too much embarassment.

The exhaust will be done first, no matter what. The flanges are leaking at the manis, and the cats are rattling and theres holes all over the Y-pipe. Today I spent a lot of time deleting all of the unnecessary vacuum lines/amplifier that it doesn't need to run. The A/C was inop and junky, so I removed all of that, minus the compressor. Unhooked the EGR valve. Readjusted carb. Vehicle runs a lot better now. Still slow, but happier. I appreciate everyones advice, and yes...I have been reading much

I have a friend that can swap my gears and refresh the axle...he does super quality work at a great price. After the exhaust, perhaps I'll start there. If I do this and keep the 2 barrel for a bit, what is your recommendation for a TC?

 

[MiradaCMX80]

So the OP has a 1980 T Top Mirada, nice car BTW.

How many 1980 T Top Miradas were made?
Rumor has it only 8 were made.

Thank you....its far from perfect but I dig it. I dont know how many T-Top cars were made for '80....just 5000 some CMX's for '80. I also heard 72 or 73 were built with the 360, but they didn't pass the sniffer test and it quietly vanished from the options list.

 

[MiradaCMX80]

View attachment 40329 Welcome aboard! You can run a shorter belt from the crank to the alternator when doing an AC delete.

MiradaMegacab, any idea what belt length is needed? I'm sure i can find the V dimensions online. Our parts store punks in my area aren't too bright........

 

[Duke5A]

Don't worry about a torque converter until you're ready to swap the cam. Right now it's factory matched for the torque curve of the motor that is in the car.

Look on the axle cover bolts for a tag with numbers stamped into it. That is the gear ratio. If it isn't there I would pop the cover off and give it a look over. To my knowledge those cars never left the factory with 8.25" axles, so someone must have swapped it in at some point. Good opportunity to change the gear oil too since the entire car is somewhat of an unknown. You may get lucky and it has a 8.25" pulled out of a Diplomat cop car. Most of those were 2.94 SG axles.

Parts Galore has had AHB (cop Diplomats) in the yard before. You might be able to find all of the goodies if you go looking.

 

[MiradaMegacab]

MiradaMegacab, any idea what belt length is needed? I'm sure i can find the V dimensions online. Our parts store punks in my area aren't too bright........

I believe it’s the same length as the PS belt.

 

[MiradaCMX80]

I crawled under the car last night and confirmed it is an 8 1/4. The car is said to be "all original" so.... Either way...oval cover, 10 bolts. Time for 3.23 gears and maintenance.

Reading reading reading....I was unaware that my 904 is a lockup converter. How disappointing. That will make things a little harder when it's time to swap cam/converter. Looks like the stock cam will stay for a bit and I'll hope the dual exhaust and gear change help it enough for the time being. Not to gloat, but my friends friend is a Mopar trans whiz and can assist with the trans/TC when the time comes.

I have to take all the belts off and redo the brackets so I will confirm if the P/S belt length is correct to go to my alternator. Is there any way to tell which alt is in it? Parts guy asked me if it was 100 amp. I have no clue.

 

[Mikes5thAve]

I've heard of quite a few of those that have 8 1/4. But I don't know how many really have it or if people are only looking at the consistent axle tube diameters.
If your alternator is the old style rounded off looking one it's the smaller one. If it's big and squared off it's the higher amperage heavy duty one. check Rock auto there are pictures of both on there. I think that's another thing that for some reason a fair number of miradas and cordobas have the bigger one.

 

[80mirada]

80 Mirada with a v8 is most often and 8.25, mid 81 and later are more likely to have a 7.25

 

[80mirada]

lockup torque converters are not to hard to get, even in higher stall speeds

 

[MiradaCMX80]

lockup torque converters are not to hard to get, even in higher stall speeds

Maybe I'm looking in the wrong spot then...I couldn't find much.