C10 master cylinder plumbing - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**ga-stepside** · 03-08-2023, 04:45 PM

Which master cylinder port is the front brakes on a 1967 C10 with power disc/drum conversion? I have read that on a standard C10 the port closest to the firewall is for the front brakes, is that true. If that is true the PO plumbed this thing wrong. Also note the small size of that front line.

72SB · 03-08-2023, 05:02 PM

FWIW my CPP MC/Booster for a disc drum 72 (was a non power brake disc/drum truck) my front brakes are forward reservoir and rear drums the rear reservoir. Also the front lines are thinner than rear brake hard line....just like your set up

Not sure what donor or kit you have but suspect it would be the same.

**ga-stepside** · 03-08-2023, 05:19 PM

Quote:

Originally Posted by 72SB

FWIW my CPP MC/Booster for a disc drum 72 (was a non power brake disc/drum truck) my front brakes are forward reservoir and rear drums the rear reservoir. Also the front lines are thinner than rear brake hard line....just like your set up

Not sure what donor or kit you have but suspect it would be the same.

I have no idea where mc and pv came from. From what I have been reading the K10 and the C10 plumbing is backwards, K10 has it they way we are plumbed. Could be the CPP MC is different than the standard GM ones.

**A1971Blazer** · 03-08-2023, 05:32 PM

I have 2 K/5 Blazers and 2 C10s...the front port (bottom) is for the front brakes, the rear port is for the rear brakes on all of them. they all have disc/drum

**ga-stepside** · 03-08-2023, 05:59 PM

Quote:

Originally Posted by A1971Blazer

I have 2 K/5 Blazers and 2 C10s...the front port (bottom) is for the front brakes, the rear port is for the rear brakes on all of them. they all have disc/drum

All those posts I read about k10 and c10 being backwards came off this site. I am so confused!!!!!!!!! Makes sense since every picture I see of the PV plumbed to the MS has them plumbed that way.

HotWheelsFan · 03-08-2023, 11:37 PM

Front disc brakes use more fluid than drum brakes...

As the brake pads wear, more fluid is found in the calipers. As drum brake wheel cylinders operate, springs collapse the wheel cylinders and push the fluid back to the master cylinder. Thus you should find the larger reservoir going to the front.

Bob

**dmjlambert** · 03-08-2023, 11:52 PM

I believe it is C20's that have the front reservoir going to rear brakes, and on C10's the front reservoir goes to the front brakes. It is the C20's with the swapped plumbing that causes confusion in my opinion.

The disc brake reservoir should be larger than the drum brake reservoir. For C10's the bore size is 1-1/8 inch for manual or power brakes. Manual brake master cylinders have a deep pushrod hole, while power brake master cylinders have a shallow pushrod hole. Here is a thread with the master cylinder technical info and other good info, including some example C20 info and pictures mixed in. https://67-72chevytrucks.com/vboard/...30#post8909230
But I don't know if there is a right and wrong for the arrangement on a truck that has been converted to disc brakes. If there was a right or wrong, I think your truck is right in my opinion.

I have a C10 71-72 pre-bent tubing set from Inline Tube on my 1969 C10 that has spindles and brakes from a 1971 donor truck, and a manual brake master cylinder. Here's what it looks like, very similar to yours.
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**Ironangel** · 03-09-2023, 03:04 AM

Quote:

Originally Posted by ga-stepside

Which master cylinder port is the front brakes on a 1967 C10 with power disc/drum conversion? I have read that on a standard C10 the port closest to the firewall is for the front brakes, is that true. If that is true the PO plumbed this thing wrong. Also note the small size of that front line.

Your brakes are plumbed correctly! Only the 20 and 30 series does the front reservoir control the rear brakes and rear reservoir control the front brakes. This is copied from a 72 service manual... The smaller 3/16" line is as per the factory fittings in the MC and the Combination Valve. Your good!

**ga-stepside** · 03-09-2023, 09:33 AM

Thanks guys I feel confident mine is plumbed correctly now.

**MikeB** · 03-09-2023, 01:08 PM

My 69 has a 71-72 booster and master. Front reservoir is for front brakes. For the type of master cylinder you have, the rule of thumb is the larger reservoir is for front discs.

For whatever reason, GM used 1/4" brake lines on the rear.

03-08-2023, 04:45 PM	#1
ga-stepside Senior Member Join Date: Jan 2016 Location: Sugar Hill GA Posts: 369	C10 master cylinder plumbing Which master cylinder port is the front brakes on a 1967 C10 with power disc/drum conversion? I have read that on a standard C10 the port closest to the firewall is for the front brakes, is that true. If that is true the PO plumbed this thing wrong. Also note the small size of that front line. Attached Images __________________ 1967 C10 Step side 1970 AMX 390 1977 Datsun 280Z highly modified with '95 LT1 power

03-08-2023, 05:02 PM	#2
72SB Registered User Join Date: Apr 2022 Location: Moorpark, CA Posts: 774	Re: C10 master cylinder plumbing FWIW my CPP MC/Booster for a disc drum 72 (was a non power brake disc/drum truck) my front brakes are forward reservoir and rear drums the rear reservoir. Also the front lines are thinner than rear brake hard line....just like your set up Not sure what donor or kit you have but suspect it would be the same. Attached Images

03-08-2023, 05:32 PM	#4
A1971Blazer Senior Member Join Date: Nov 2013 Location: East Tennessee Posts: 2,198	Re: C10 master cylinder plumbing I have 2 K/5 Blazers and 2 C10s...the front port (bottom) is for the front brakes, the rear port is for the rear brakes on all of them. they all have disc/drum __________________ 1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer 1972 Chevrolet K/5 Blazer .............

03-08-2023, 11:37 PM	#6
HotWheelsFan Registered User Join Date: Mar 2010 Location: Oregon Posts: 189	Re: C10 master cylinder plumbing Front disc brakes use more fluid than drum brakes... As the brake pads wear, more fluid is found in the calipers. As drum brake wheel cylinders operate, springs collapse the wheel cylinders and push the fluid back to the master cylinder. Thus you should find the larger reservoir going to the front. Bob __________________ 1970 C20 Long Bed Fleetside - Restoration My truck videos - Youtube

03-08-2023, 11:52 PM	#7
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,859	Re: C10 master cylinder plumbing I believe it is C20's that have the front reservoir going to rear brakes, and on C10's the front reservoir goes to the front brakes. It is the C20's with the swapped plumbing that causes confusion in my opinion. The disc brake reservoir should be larger than the drum brake reservoir. For C10's the bore size is 1-1/8 inch for manual or power brakes. Manual brake master cylinders have a deep pushrod hole, while power brake master cylinders have a shallow pushrod hole. Here is a thread with the master cylinder technical info and other good info, including some example C20 info and pictures mixed in. https://67-72chevytrucks.com/vboard/...30#post8909230 But I don't know if there is a right and wrong for the arrangement on a truck that has been converted to disc brakes. If there was a right or wrong, I think your truck is right in my opinion. I have a C10 71-72 pre-bent tubing set from Inline Tube on my 1969 C10 that has spindles and brakes from a 1971 donor truck, and a manual brake master cylinder. Here's what it looks like, very similar to yours. -

03-09-2023, 09:33 AM	#9
ga-stepside Senior Member Join Date: Jan 2016 Location: Sugar Hill GA Posts: 369	Re: C10 master cylinder plumbing Thanks guys I feel confident mine is plumbed correctly now. __________________ 1967 C10 Step side 1970 AMX 390 1977 Datsun 280Z highly modified with '95 LT1 power

03-09-2023, 01:08 PM	#10
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,597	Re: C10 master cylinder plumbing My 69 has a 71-72 booster and master. Front reservoir is for front brakes. For the type of master cylinder you have, the rule of thumb is the larger reservoir is for front discs. For whatever reason, GM used 1/4" brake lines on the rear. __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!



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