'75 Dart 4 door for a new mopar guy.

[swies]

So, This weekend I bought the following...
1975 Dart Custom 4 door.
Factory 318, AC, Power disc brakes. (Once upon a time Police Car for a local town)
Mods done,

.030 over bore.
.028 head gasket
360 Heads, 2.02 1.94 SS valves
Keith Black KB167-030 Pistions
Edlebrock Performer RPM 7176 for 318 w/ 360 heads.
Edlebrock Performer 600cfm electric choke
Comp Cams XE 268H with the lifters, springs, rockers.
Hooker headers with Flowmaster 40's at the rear axle.
904 Tranny with B&M stage 2
​

Now for the questions...
1. Brakes are really hard. Like Manual brakes. Question is, How to tell if the motor is not making enough vacuum or if the booster is bad... I don't know enough to tell.

2. Paperwork from the machine shop that did the bore / head work says they did port / polish and 'fly cut' the head and deck. It also says the 'computed compression ration is at 9.55:1'. How did they figure this?? How much is a 'Fly Cut'??

3. What rear end is in this car? I do not have enough knowledge in the MOPAR world to know. As far as I was told, rear end is LSD but is stock. I do know that rolling down the highway at 67ish mph the Tach said 2100ish...

Information is key and I only have the lock...
I bought this car as it is the best looking sleeper I could think of. I am mid 40's and have spent a long minute at the local drag track and plan on being there with this A-body.

Lastly, What would you change if you could with this car? I am looking for something in the 13-14 range in the 1/4 and still be able to run it around town just for the looks.
Will post some pics when I get some.

Thanks in advance for the help.

 

[salinasjoel]

Rear end should be 8 1/4

 

[plumkrazee70]

As for the brakes:

1. Leave engine off
2. Pump the pedal until it gets hard
3. Keep foot firm on brake pedal, and start motor.
You should feel the pedal sink a little (that is from power assist) If this doesn't happen, your boosted may be bad.

 

[Bad Sport]

So, This weekend I bought the following...
1975 Dart Custom 4 door.
Factory 318, AC, Power disc brakes. (Once upon a time Police Car for a local town)
Mods done,

.030 over bore.
.028 head gasket
360 Heads, 2.02 1.94 SS valves
Keith Black KB167-030 Pistions
Edlebrock Performer RPM 7176 for 318 w/ 360 heads.
Edlebrock Performer 600cfm electric choke
Comp Cams XE 268H with the lifters, springs, rockers.
Hooker headers with Flowmaster 40's at the rear axle.
904 Tranny with B&M stage 2
​

Now for the questions...
1. Brakes are really hard. Like Manual brakes. Question is, How to tell if the motor is not making enough vacuum or if the booster is bad... I don't know enough to tell.

Get a vacuum gauge. Power brakes need a minimum of 13 inches of vacuum to work.

3. What rear end is in this car? I do not have enough knowledge in the MOPAR world to know. As far as I was told, rear end is LSD but is stock. I do know that rolling down the highway at 67ish mph the Tach said 2100ish...

View attachment Mopar_axle.jpg

If you want to be sure about the suregrip, jack both rear wheels off the ground, spin one tire if the opposite side rotates the same direction, suregrip, if it rotates the opposite direction, open diff.

Information is key and I only have the lock...
I bought this car as it is the best looking sleeper I could think of. I am mid 40's and have spent a long minute at the local drag track and plan on being there with this A-body.

Lastly, What would you change if you could with this car? I am looking for something in the 13-14 range in the 1/4 and still be able to run it around town just for the looks.
Will post some pics when I get some.

You should be close right now, depending on rear gears. But, by what you said above about speed/RPM's, I'm guessing 2.76's or thereabouts. A 3.55 ratio is a nice medium for street/strip use.

Thanks in advance for the help.

Welcome to the site.

 

[swies]

Thanks for the help. I will get the booster and the rearend checked soonest.
And looking at your ride, sounds pretty close to my new one.

 

[swies]

So I checked the vac lines and found the booster plumbed to the large port on the base of the carb and the vac port in the manifold with a plug in it.
I moved the booster to the intake and capped the port in the carb base.
Brakes are better but get hard when the car is at idle.
Above idle, they feel like power brakes.
Does this mean I will need a vac pump? If so, how hard are they to connect?
Or is there another reason?

 

[plumkrazee70]

So I checked the vac lines and found the booster plumbed to the large port on the base of the carb and the vac port in the manifold with a plug in it.
I moved the booster to the intake and capped the port in the carb base.
Brakes are better but get hard when the car is at idle.
Above idle, they feel like power brakes.
Does this mean I will need a vac pump? If so, how hard are they to connect?
Or is there another reason?

I would check for vacuum leaks first. Take a can of carb cleaner or brake cleaner and spray the base of the carb while running. If the idle increases then there is a vacuum leak. Also try to find a vacuum gauge so you can measure how much vacuum you have.

 

[swies]

I checked the rear end and it is an 8 1/4". That is the good news. There is a build tag on it that only says "245". I hope that is not the gear ratio however I guess it does not matter as they need changed either way.
Also, having played with it some more, I noticed it shifts 1-2 and 2-3 at 3100 RPM at WOT. This seems really early. The motor is starting to pull really good and....shift. How can I adjust the shift points? I would like it to shift at about 5500. This seemed to do well when I shifted manually.

 

[KosmicKuda]

Fly Cut does not refer to how much was taken off the head and block but the type of cutter used. Many times it is done just enough to true up the surfaces. (eliminate warp and ensure good head gasket seal) Could have been as little as .005 to .060 or more. Then again, it may have been done to actually increase compression.

Calculated compression ratio to me means they used published values for the various components and did a calculation. The truer method is to actually measure volumes then do the calculation. Still "calculated" but more precise. There are real engine builders on here who may correct me. (hopefully) If you know which shop did the machining, you could just ask them.

If you have an economy rear end ratio, switching gears to something in the low to upper 3's would help out. depends a lot on how much you drive and how much you want to spend for gas.

 

[swies]

Thanks for the info Kosmic.
I don't plan to drive it much at all. It will spend most of its life at the local 1/4 mile.
Sure I want to be able to drive it to the track, maybe take it on a town run once and a while etc. But mostly want it to do 13's while still being street legal / comfortable / fun.

 

[swies]

P.S.
It does have the economy rear end.
2.45:1 to be exact.
Just doing research to see what Jeep gears I can put in it now.

 

[Kernel Sanders]

I do believe if your going to change the gear set from 2.45 to 2.76 and up you will need to also change the carrier/rotating assembly as the one for the 2.45 is different. That being said, also keep in mind the axles are 27 spline NOT 29 so DONT get a carrier from a 97 and up 8.25 as they are 29 spline.

 

[swies]

Thanks for the info. I plan on hitting the yards this weekend to see what I can find. Hoping to find something in the 3.55 - 4.11 range in a Sure Grip model. We will see.

 

[swies]

Sorted some brake issues last night.
Booster is bad. Minor leak down. Heard a vacuum / air sound after I had shut the car off. Listened under the dash and it was coming from the pass through hole that the Brake Push rod goes through.
Looks like partstrain.com has the best price at $88 plus core...
Not one here in my local parts joints.
Next to the Steering.
No noises but it is kinda like herding a bunch of 3 yr old kids down the road.
That will be for tonight. Then off to the yard this weekend to hunt a rear gear set.

 

[swies]

I was not too lucky at the wrecking yards around here.
Found an '87 Dodge Dakota with the 8.25 SureGrip with 3.73's.
Will that one interchange?
Dealer only wants $100.
Gears looked great.
If it will fit, which carrier bearings will it need?
Thanks for all the help once again.

 

[swies]

Many Thanks to 69MOPE. He has been a great help!
Loaded Booster showed up today from O'Reilly's.
$120 for the Brake Booster AND the Master Cylinder delivered to my door. Ordered it Saturday, Showed up Tuesday.
This weekend will be the Gears from the Dakota ('87). Checked them out and they are 3.90's.
That will hit my happy spot!

 

[swies]

Booster installed, Brakes Bled, 15 in vac. Brakes work perfect!
Thanks to all for the hlep