1970 Coronet brake questions

oldrustycars · 07-11-2007, 09:55 PM

Hi everyone, new guy here. I'm trying to straighten out a brake problem on a 1970 Coronet 9 passenger wagon for a friend. He had someone install a disc brake kit, they finally gave up. The trouble is an extremely hard pedal, very poor braking. What I've determined so far...they didnt bother to install a combination valve, just plumbed from the master directly into the lines. I've obtained the correct valve. Secondly, I see the kit to install the power booster has very different linkage for a factory manual brake car, versus a factory power brake car, leading me to believe I may have a pedal ratio problem. I feel a car like this...a 70 Coronet, 9 passenger wagon, with a 383, power steering, and A/C, would have surely come with power brakes, even though they were drum. The owner insists it had no booster when he got the car, and stopped terrible, even though the brakes were in good shape, and the previous owner "thought" the booster went bad and they just ripped it out. So....my question to you experts, is there any way to tell if this car had factory power brakes? The brake pedal pad has been replaced with a fancy one, so no "power brake" imprint, and the intake was changed to an Edelbrock at some point so no trace of the vacuum port. A vacuum pump was installed by the guy who was fiddling with this, supplying 20 inches of vacuum, so that is not the source of the hard pedal. Thanks for reading this long post.

oldrustycars · 07-11-2007, 10:15 PM

The kit is from Master Power Brake, they seem like they know what they're doing. The owner purchased the kit for factory manual brakes. Also, this car is made into a Super Bee wagon, obviously a "one of none" clone. Sublime Green, woodgrain, and a wild green and white interior...I'll post pics if anyone would like them.

ucfierocharger · 07-13-2007, 07:05 AM

Actually, you may be suprised.....I saw a sublime superbee wagon at a local car show about 2 months ago. I have some pictures of it, Ill see if i can find them and post them. I donno if they are the same car or not, I didnt think this one is a 383, but I couldnt remember and I wouldnt imagine too many people doing this. So post them up lol

oldrustycars · 07-13-2007, 07:19 PM

Pics in my crowded garage dont do it justice. Has Challenger T/A style Flowmaster mufflers, Rally wheels, Super Bee hood, and the Super Bee emblems.

ucfierocharger · 07-13-2007, 09:06 PM

Here is the one that I saw.

unclemike · 07-18-2007, 11:31 PM

I bought a 1968 Plymouth Sport Satellite wagon off a family friend to do the same. Sadly it's too rusty to restore.
Are you running any kind of big cam in that motor? If so did you check your vacuum levels? I can't really see where you have the power booster's vacuum hose hooked up either.

oldrustycars · 07-19-2007, 08:05 AM

Unclemike, it DOES have a bumpy cam, and only makes 13 inches at idle, so it has a vacuum pump, set to 20". I also determined that the brand new booster was bad, and it has the wrong master cylinder. I have the new parts, and i'm fiddling with it today.

unclemike · 07-20-2007, 10:25 PM

Hi, rusty. Wrong mastercylinder? My son bought a MPB kit for his 1966 Ply. Satellite, since then they released a kit that uses a four bolt mastercylinder instead of the two bolt set up. Is that what you mean? When I asked him if he was dissapointed he said not as he could use the later Mopar two bolt unit in place of the MPB mastercylinder.

440roadrunner · 11-09-2007, 08:39 PM

I'm always suspicious of EVERYTHING

Could be bad booster

Wrong master--the drum masters had a little valve in the end of the "kit" that keeps residual pressure, that disk units don't have

Checked the link rod between the master and booster? Too long, to short?

Any chance of some restriction(s) in the lines/hoses?

So far as pedal ration, I'd think that a manual system pedel should have MORE leverage on your booster, not less.

When this stuff was made, people did some funny things with options. I once saw a hemi convertible with A/C, but no radio

07-11-2007, 09:55 PM	#1 (permalink)
oldrustycars Junior Member Join Date: Jul 2007 Posts: 4	1970 Coronet brake questions Hi everyone, new guy here. I'm trying to straighten out a brake problem on a 1970 Coronet 9 passenger wagon for a friend. He had someone install a disc brake kit, they finally gave up. The trouble is an extremely hard pedal, very poor braking. What I've determined so far...they didnt bother to install a combination valve, just plumbed from the master directly into the lines. I've obtained the correct valve. Secondly, I see the kit to install the power booster has very different linkage for a factory manual brake car, versus a factory power brake car, leading me to believe I may have a pedal ratio problem. I feel a car like this...a 70 Coronet, 9 passenger wagon, with a 383, power steering, and A/C, would have surely come with power brakes, even though they were drum. The owner insists it had no booster when he got the car, and stopped terrible, even though the brakes were in good shape, and the previous owner "thought" the booster went bad and they just ripped it out. So....my question to you experts, is there any way to tell if this car had factory power brakes? The brake pedal pad has been replaced with a fancy one, so no "power brake" imprint, and the intake was changed to an Edelbrock at some point so no trace of the vacuum port. A vacuum pump was installed by the guy who was fiddling with this, supplying 20 inches of vacuum, so that is not the source of the hard pedal. Thanks for reading this long post.

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07-11-2007, 10:15 PM	#2 (permalink)
oldrustycars Junior Member Join Date: Jul 2007 Posts: 4	The kit is from Master Power Brake, they seem like they know what they're doing. The owner purchased the kit for factory manual brakes. Also, this car is made into a Super Bee wagon, obviously a "one of none" clone. Sublime Green, woodgrain, and a wild green and white interior...I'll post pics if anyone would like them.

07-13-2007, 07:05 AM	#3 (permalink)
ucfierocharger USB car drive man Join Date: Jun 2007 Location: Cincinnati OH Posts: 142	Actually, you may be suprised.....I saw a sublime superbee wagon at a local car show about 2 months ago. I have some pictures of it, Ill see if i can find them and post them. I donno if they are the same car or not, I didnt think this one is a 383, but I couldnt remember and I wouldnt imagine too many people doing this. So post them up lol

07-13-2007, 07:19 PM	#4 (permalink)
oldrustycars Junior Member Join Date: Jul 2007 Posts: 4	Pics in my crowded garage dont do it justice. Has Challenger T/A style Flowmaster mufflers, Rally wheels, Super Bee hood, and the Super Bee emblems.

07-13-2007, 09:06 PM	#5 (permalink)
ucfierocharger USB car drive man Join Date: Jun 2007 Location: Cincinnati OH Posts: 142	Here is the one that I saw.

07-18-2007, 11:31 PM	#6 (permalink)
unclemike Junior Member Join Date: Jul 2007 Posts: 8	I bought a 1968 Plymouth Sport Satellite wagon off a family friend to do the same. Sadly it's too rusty to restore. Are you running any kind of big cam in that motor? If so did you check your vacuum levels? I can't really see where you have the power booster's vacuum hose hooked up either.

07-19-2007, 08:05 AM	#7 (permalink)
oldrustycars Junior Member Join Date: Jul 2007 Posts: 4	Unclemike, it DOES have a bumpy cam, and only makes 13 inches at idle, so it has a vacuum pump, set to 20". I also determined that the brand new booster was bad, and it has the wrong master cylinder. I have the new parts, and i'm fiddling with it today.

07-20-2007, 10:25 PM	#8 (permalink)
unclemike Junior Member Join Date: Jul 2007 Posts: 8	Hi, rusty. Wrong mastercylinder? My son bought a MPB kit for his 1966 Ply. Satellite, since then they released a kit that uses a four bolt mastercylinder instead of the two bolt set up. Is that what you mean? When I asked him if he was dissapointed he said not as he could use the later Mopar two bolt unit in place of the MPB mastercylinder.

11-09-2007, 08:39 PM	#9 (permalink)
440roadrunner Senior Member Join Date: Nov 2007 Posts: 272	I'm always suspicious of EVERYTHING Could be bad booster Wrong master--the drum masters had a little valve in the end of the "kit" that keeps residual pressure, that disk units don't have Checked the link rod between the master and booster? Too long, to short? Any chance of some restriction(s) in the lines/hoses? So far as pedal ration, I'd think that a manual system pedel should have MORE leverage on your booster, not less. When this stuff was made, people did some funny things with options. I once saw a hemi convertible with A/C, but no radio