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| [GMCnet] P-30 MC [message #297742] |
Sun, 20 March 2016 18:48  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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We're installing disc brakes on my son's GMC. It's been 14 years since I
last did this upgrade "from scratch", so I'm rechecking all the parts
recommendations.
We need to install a larger MC. The when I did it in 2002, I installed a
Bendix 11641. Now, when I use the AC Delco parts interchange site
The recommended AC P/N is 18M1887 and a list of several hundred
applications is returned.
When I search the Cardone Master Cylinder ID Guide
<
http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Guide/index.html#1
>
I get their numbers 10-1641 and 10-1668 as having the same bore and port
sizes.
When I enter either of those Cardone numbers at the AC Delco site, it
returns the same 18M1887 number. BUT, when I go to the various (AutoZone
and OReilly's)
they list numbers similar to the Cardone -1641 and -1668, in both new and
used variants, and at different prices for -1641 and -1668.
There's obviously SOME difference between the -1641 and the -1668. From AC
Delco's offering one part for both of them it must be trivial. But is one
of them "smaller" than the other -- or "bigger"? WHAT IS THE DIFFERENCE?
Does anyone have any idea? I've got a used 11641 which we'll probably
install now, but I'd REALLY like to know what the P/N discrepancies are all
about.
Oh yeah, one reference says the 11641 is for a P-30 with 13"x2.5" DRUMS!!!
Ken H.
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] P-30 MC [message #297744 is a reply to message #297742] |
Sun, 20 March 2016 21:06  |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
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Senior Member |
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Ken,
The one that I have always used for the P-30 is the AZ# M1668 and we always swapped the ports too.
John
> On Mar 20, 2016, at 4:48 PM, Ken Henderson wrote:
>
> We're installing disc brakes on my son's GMC. It's been 14 years since I
> last did this upgrade "from scratch", so I'm rechecking all the parts
> recommendations.
>
> We need to install a larger MC. The when I did it in 2002, I installed a
> Bendix 11641. Now, when I use the AC Delco parts interchange site
>
> The recommended AC P/N is 18M1887 and a list of several hundred
> applications is returned.
>
> When I search the Cardone Master Cylinder ID Guide
> http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Guide/index.html#1
>>
> I get their numbers 10-1641 and 10-1668 as having the same bore and port
> sizes.
>
> When I enter either of those Cardone numbers at the AC Delco site, it
> returns the same 18M1887 number. BUT, when I go to the various (AutoZone
> and OReilly's)
> they list numbers similar to the Cardone -1641 and -1668, in both new and
> used variants, and at different prices for -1641 and -1668.
>
> There's obviously SOME difference between the -1641 and the -1668. From AC
> Delco's offering one part for both of them it must be trivial. But is one
> of them "smaller" than the other -- or "bigger"? WHAT IS THE DIFFERENCE?
>
> Does anyone have any idea? I've got a used 11641 which we'll probably
> install now, but I'd REALLY like to know what the P/N discrepancies are all
> about.
>
> Oh yeah, one reference says the 11641 is for a P-30 with 13"x2.5" DRUMS!!!
>
> Ken H.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] P-30 MC [message #297745 is a reply to message #297742] |
Mon, 21 March 2016 00:04 |
<rallymaster
Messages: 361
Registered: May 2014
Karma: 2
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Senior Member |
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Does the AZ# M1668 have equal size front and rear reservoirs?
RonC
On Sun, 20 Mar 2016 19:06:29 -0700 John Wright
writes:
> Ken,
> The one that I have always used for the P-30 is the AZ# M1668 and we
> always swapped the ports too.
>
> John
>
>> On Mar 20, 2016, at 4:48 PM, Ken Henderson
> wrote:
>>
>> We're installing disc brakes on my son's GMC. It's been 14 years
> since I
>> last did this upgrade "from scratch", so I'm rechecking all the
> parts
>> recommendations.
>>
>> We need to install a larger MC. The when I did it in 2002, I
> installed a
>> Bendix 11641. Now, when I use the AC Delco parts interchange
> site
>>
>> The recommended AC P/N is 18M1887 and a list of several hundred
>> applications is returned.
>>
>> When I search the Cardone Master Cylinder ID Guide
>> >
>
http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Gu
ide/index.html#1
>>>
>> I get their numbers 10-1641 and 10-1668 as having the same bore
> and port
>> sizes.
Ron & Linda Clark
North Plains, ORYGUN
78 Eleganza II
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| Re: [GMCnet] P-30 MC [message #297746 is a reply to message #297742] |
Mon, 21 March 2016 00:37 |
<rallymaster
Messages: 361
Registered: May 2014
Karma: 2
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Senior Member |
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More Info
http://www.bdub.net/branscombe/K-H%20Promo.pdf
On Sun, 20 Mar 2016 19:06:29 -0700 John Wright
writes:
> Ken,
> The one that I have always used for the P-30 is the AZ# M1668 and we
> always swapped the ports too.
>
> John
>
>> On Mar 20, 2016, at 4:48 PM, Ken Henderson
> wrote:
>>
>> We're installing disc brakes on my son's GMC. It's been 14 years
> since I
>> last did this upgrade "from scratch", so I'm rechecking all the
> parts
>> recommendations.
>>
>> We need to install a larger MC. The when I did it in 2002, I
> installed a
>> Bendix 11641. Now, when I use the AC Delco parts interchange
> site
>>
>> The recommended AC P/N is 18M1887 and a list of several hundred
>> applications is returned.
>>
>> When I search the Cardone Master Cylinder ID Guide
>> >
>
http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Gu
ide/index.html#1
>>>
>> I get their numbers 10-1641 and 10-1668 as having the same bore
> and port
>> sizes.
>>
>> When I enter either of those Cardone numbers at the AC Delco site,
> it
>> returns the same 18M1887 number. BUT, when I go to the various
> (AutoZone
>> and OReilly's)
>> they list numbers similar to the Cardone -1641 and -1668, in both
> new and
>> used variants, and at different prices for -1641 and -1668.
>>
>> There's obviously SOME difference between the -1641 and the -1668.
> From AC
>> Delco's offering one part for both of them it must be trivial.
> But is one
>> of them "smaller" than the other -- or "bigger"? WHAT IS THE
> DIFFERENCE?
>>
>> Does anyone have any idea? I've got a used 11641 which we'll
> probably
>> install now, but I'd REALLY like to know what the P/N
> discrepancies are all
>> about.
>>
>> Oh yeah, one reference says the 11641 is for a P-30 with 13"x2.5"
> DRUMS!!!
>>
>> Ken H.
Ron & Linda Clark
North Plains, ORYGUN
78 Eleganza II
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| Re: [GMCnet] P-30 MC [message #297747 is a reply to message #297745] |
Mon, 21 March 2016 06:55 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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John & Ron,
Thanks for the feedback -- even if you won't tell me the difference! :-)
Also, the 39309 is another of the "old standby's" that crosses to the AC
Delco 18M1887.
I'm beginning to think these MC numbers are like fishing lures: They've
got all those thousands of variations on the same theme just "'cause they
can" (keep us all confused).
Ken H.
On Mon, Mar 21, 2016 at 1:04 AM, wrote:
> Does the AZ# M1668 have equal size front and rear reservoirs?
>
> RonC
>
> On Sun, 20 Mar 2016 19:06:29 -0700 John Wright
> writes:
>> Ken,
>> The one that I have always used for the P-30 is the AZ# M1668 and we
>> always swapped the ports too.
>>
>> John
>>
>>> On Mar 20, 2016, at 4:48 PM, Ken Henderson
>> wrote:
>>>
>>> We're installing disc brakes on my son's GMC. It's been 14 years
>> since I
>>> last did this upgrade "from scratch", so I'm rechecking all the
>> parts
>>> recommendations.
>>>
>>> We need to install a larger MC. The when I did it in 2002, I
>> installed a
>>> Bendix 11641. Now, when I use the AC Delco parts interchange
>> site
>>>
>>> The recommended AC P/N is 18M1887 and a list of several hundred
>>> applications is returned.
>>>
>>> When I search the Cardone Master Cylinder ID Guide
>>> >>
>>
> http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Gu
> ide/index.html#1
>>>>
>>> I get their numbers 10-1641 and 10-1668 as having the same bore
>> and port
>>> sizes.
> Ron & Linda Clark
> North Plains, ORYGUN
> 78 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] P-30 MC - some possible explanation [message #297749 is a reply to message #297742] |
Mon, 21 March 2016 08:17 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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As a refugee from the aftermarket world, I bet I know what happened to the master cylinder numbers.
First a short treatise on how the aftermarket works.
They make parts to replace OE parts (Duh) and that happens one of two ways:
First - Someone had the contract to make the OE parts and then used to tooling to produce parts without the OE marking. These get sold as replacement parts only.
Second - Someone reverse engineers the OE part and tools up to make parts for aftermarket.
In the first case, the OE buyer will beat you up for a penny a part. (Just short of literally.) So the part will have as little of the cheapest material as it can be made with and still pass the corporate validation standard. The cost of a new part number is not real a big issue, but weight and warranty are. Nothing about the part can change while it is in production or new validation may be required and that also costs money.
In the second case, the part cost is an issue, but if your new part can lunch off another of your parts that is current production some of the cost of the new part can be avoided. Even better, is when you (as the aftermarket engineer -me) can redesign and existing part to meet a "cross line" application. So, you change a hole size, change a profile or something to make your part fit more applications. It may not be perfect for some, but as long as it isn't dangerous..... And, look at your aftermarket warranty => If the part fails (and I agree that it failed) I give you a free replacement and that is pretty much the limit of it. Validation will be done on most parts, but it is not the extent required by any OE.
So, lets look at a master cylinder, there are that many critical features:
The bore and depth - Well ...
The threaded bosses for lines ...
The mounting ears - the holes are important, but the ear thickness seems to be an open issue.
Those are what an installer will notice.
DOT requires that the reservoir be large enough to keep the system solid until the shoes/pads require replacement.
OE made that volume as small as they could - less metal, less fluid to fill and lighter.
Aftermarket could make it as big as they want because they care about what applications they can sell it for....
Their cost of a part number in the catalogue or on the shelf is their next big concern. And a new part number is a BIG issue.
So, for the master cylinder issue, I would go with either. We take enough care of our vehicles that needing the reservoir volume is not going to be an important issue and that would seem to be the big variable here. That and the mounting ear thickness that the aftermarket guy may just have missed, but until complaints come back though the system, he isn't going to care. And this is why I beg people to return bad aftermarket parts.
And that is the bald truth about aftermarket parts.
I am always reminded of the chandler's joke.
A buyer asks if him if his lifejackets are any good.
To which the chandler answers that nobody has ever brought one back.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] P-30 MC [message #297750 is a reply to message #297748] |
Mon, 21 March 2016 08:14 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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There's simply not enough displacement in the 1-1/4" MC to supply four 80
mm and two 63 mm calipers. The increased area of those calipers will
compensate for the reduced line pressure.
Ken H.
On Mon, Mar 21, 2016 at 8:51 AM, Larry wrote:
> What is keeping you from installing a new or rebuilt original MC. The
> bigger bore of the P30 gives you less pressure at the wheels. Just
> wondering....
> --
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] P-30 MC [message #298138 is a reply to message #297742] |
Sun, 27 March 2016 10:39 |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
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Senior Member |
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Ken,
I went to see my CarQuest buddy to see if his books or computer listings
showed the difference. He printed a poop sheet for me on each one.
Word for word and spec for spec, they were identical. The only difference
being the application. So he ordered one of each. They are sitting in
front of me at this moment. They are identical in every way, including
the casting. The only difference possible is something internal. I can't
disassemble them as they are not mine, but on my way to return them,
I will stop at the Chevy dealer and see if there is a different repair kit
for each application. Information is hard to come by.
Gary Kosier
77PB w/500Cad
Newark, Ohio
--------------------------------------------------
From: "Ken Henderson"
Sent: Sunday, March 20, 2016 7:48 PM
To: "GMC Mail List"
Subject: [GMCnet] P-30 MC
> We're installing disc brakes on my son's GMC. It's been 14 years since I
> last did this upgrade "from scratch", so I'm rechecking all the parts
> recommendations.
>
> We need to install a larger MC. The when I did it in 2002, I installed a
> Bendix 11641. Now, when I use the AC Delco parts interchange site
>
> The recommended AC P/N is 18M1887 and a list of several hundred
> applications is returned.
>
> When I search the Cardone Master Cylinder ID Guide
> http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Guide/index.html#1
>>
> I get their numbers 10-1641 and 10-1668 as having the same bore and port
> sizes.
>
> When I enter either of those Cardone numbers at the AC Delco site, it
> returns the same 18M1887 number. BUT, when I go to the various (AutoZone
> and OReilly's)
> they list numbers similar to the Cardone -1641 and -1668, in both new and
> used variants, and at different prices for -1641 and -1668.
>
> There's obviously SOME difference between the -1641 and the -1668. From
> AC
> Delco's offering one part for both of them it must be trivial. But is one
> of them "smaller" than the other -- or "bigger"? WHAT IS THE DIFFERENCE?
>
> Does anyone have any idea? I've got a used 11641 which we'll probably
> install now, but I'd REALLY like to know what the P/N discrepancies are
> all
> about.
>
> Oh yeah, one reference says the 11641 is for a P-30 with 13"x2.5" DRUMS!!!
>
> Ken H.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] P-30 MC [message #298141 is a reply to message #298138] |
Sun, 27 March 2016 11:33 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
|
Senior Member |
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Thanks, Gary. Frustrating, isn't it?
Ken H.
On Mar 27, 2016 11:40, "Gary Kosier" wrote:
> Ken,
>
> I went to see my CarQuest buddy to see if his books or computer listings
> showed the difference. He printed a poop sheet for me on each one.
> Word for word and spec for spec, they were identical. The only difference
> being the application. So he ordered one of each. They are sitting in
> front of me at this moment. They are identical in every way, including
> the casting. The only difference possible is something internal. I can't
> disassemble them as they are not mine, but on my way to return them,
> I will stop at the Chevy dealer and see if there is a different repair kit
> for each application. Information is hard to come by.
>
> Gary Kosier
> 77PB w/500Cad
> Newark, Ohio
>
> --------------------------------------------------
> From: "Ken Henderson"
> Sent: Sunday, March 20, 2016 7:48 PM
> To: "GMC Mail List"
> Subject: [GMCnet] P-30 MC
>
> We're installing disc brakes on my son's GMC. It's been 14 years since I
>> last did this upgrade "from scratch", so I'm rechecking all the parts
>> recommendations.
>>
>> We need to install a larger MC. The when I did it in 2002, I installed a
>> Bendix 11641. Now, when I use the AC Delco parts interchange site
>>
>> The recommended AC P/N is 18M1887 and a list of several hundred
>> applications is returned.
>>
>> When I search the Cardone Master Cylinder ID Guide
>> >
>> http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Guide/index.html#1
>>
>>>
>>> I get their numbers 10-1641 and 10-1668 as having the same bore and port
>> sizes.
>>
>> When I enter either of those Cardone numbers at the AC Delco site, it
>> returns the same 18M1887 number. BUT, when I go to the various (AutoZone
>> and OReilly's)
>> they list numbers similar to the Cardone -1641 and -1668, in both new and
>> used variants, and at different prices for -1641 and -1668.
>>
>> There's obviously SOME difference between the -1641 and the -1668. From
>> AC
>> Delco's offering one part for both of them it must be trivial. But is one
>> of them "smaller" than the other -- or "bigger"? WHAT IS THE DIFFERENCE?
>>
>> Does anyone have any idea? I've got a used 11641 which we'll probably
>> install now, but I'd REALLY like to know what the P/N discrepancies are
>> all
>> about.
>>
>> Oh yeah, one reference says the 11641 is for a P-30 with 13"x2.5" DRUMS!!!
>>
>> Ken H.
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
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| Re: [GMCnet] P-30 MC [message #298142 is a reply to message #298141] |
Sun, 27 March 2016 11:44 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
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If you think P-30 Master cylinders are tough, try water pumps. I have 5
different ones, all with the same part numbers. If you take the cross
indexed numbers into account, there is twice that many.
I have seen at least 4 different appearing P-30's, mostly on reservoir
design and material of construction. The state of aftermarket parts supply
is enough to confuse the best parts guys. Measure twice, cut once.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Mar 27, 2016 9:34 AM, "Ken Henderson" wrote:
> Thanks, Gary. Frustrating, isn't it?
>
> Ken H.
>
> On Mar 27, 2016 11:40, "Gary Kosier" wrote:
>
>> Ken,
>>
>> I went to see my CarQuest buddy to see if his books or computer listings
>> showed the difference. He printed a poop sheet for me on each one.
>> Word for word and spec for spec, they were identical. The only
> difference
>> being the application. So he ordered one of each. They are sitting in
>> front of me at this moment. They are identical in every way, including
>> the casting. The only difference possible is something internal. I
> can't
>> disassemble them as they are not mine, but on my way to return them,
>> I will stop at the Chevy dealer and see if there is a different repair
> kit
>> for each application. Information is hard to come by.
>>
>> Gary Kosier
>> 77PB w/500Cad
>> Newark, Ohio
>>
>> --------------------------------------------------
>> From: "Ken Henderson"
>> Sent: Sunday, March 20, 2016 7:48 PM
>> To: "GMC Mail List"
>> Subject: [GMCnet] P-30 MC
>>
>> We're installing disc brakes on my son's GMC. It's been 14 years since I
>>> last did this upgrade "from scratch", so I'm rechecking all the parts
>>> recommendations.
>>>
>>> We need to install a larger MC. The when I did it in 2002, I installed
> a
>>> Bendix 11641. Now, when I use the AC Delco parts interchange site
>>>
>>> The recommended AC P/N is 18M1887 and a list of several hundred
>>> applications is returned.
>>>
>>> When I search the Cardone Master Cylinder ID Guide
>>> >>
>>>
> http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Guide/index.html#1
>>>
>>>>
>>>> I get their numbers 10-1641 and 10-1668 as having the same bore and
> port
>>> sizes.
>>>
>>> When I enter either of those Cardone numbers at the AC Delco site, it
>>> returns the same 18M1887 number. BUT, when I go to the various
> (AutoZone
>>> and OReilly's)
>>> they list numbers similar to the Cardone -1641 and -1668, in both new
> and
>>> used variants, and at different prices for -1641 and -1668.
>>>
>>> There's obviously SOME difference between the -1641 and the -1668. From
>>> AC
>>> Delco's offering one part for both of them it must be trivial. But is
> one
>>> of them "smaller" than the other -- or "bigger"? WHAT IS THE
> DIFFERENCE?
>>>
>>> Does anyone have any idea? I've got a used 11641 which we'll probably
>>> install now, but I'd REALLY like to know what the P/N discrepancies are
>>> all
>>> about.
>>>
>>> Oh yeah, one reference says the 11641 is for a P-30 with 13"x2.5"
> DRUMS!!!
>>>
>>> Ken H.
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
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| Re: [GMCnet] P-30 MC [message #298170 is a reply to message #297742] |
Sun, 27 March 2016 15:22 |
 |
wally
Messages: 643
Registered: August 2004
Location: Omaha Nebraska
Karma: 5
|
Senior Member |
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A Dorman M39309 P30 master has a displacement ratio of 2.2 to 1 between sections, might be about right.
Ken Henderson wrote on Sun, 20 March 2016 18:48We're installing disc brakes on my son's GMC. It's been 14 years since I
last did this upgrade "from scratch", so I'm rechecking all the parts
recommendations.
We need to install a larger MC. The when I did it in 2002, I installed a
Bendix 11641. Now, when I use the AC Delco parts interchange site
The recommended AC P/N is 18M1887 and a list of several hundred
applications is returned.
When I search the Cardone Master Cylinder ID Guide
<
http://www.pageturnpro.com/CARDONE-Industries/56617-Master-Cylinder-Id-Guide/index.html#1
>
I get their numbers 10-1641 and 10-1668 as having the same bore and port
sizes.
When I enter either of those Cardone numbers at the AC Delco site, it
returns the same 18M1887 number. BUT, when I go to the various (AutoZone
and OReilly's)
they list numbers similar to the Cardone -1641 and -1668, in both new and
used variants, and at different prices for -1641 and -1668.
There's obviously SOME difference between the -1641 and the -1668. From AC
Delco's offering one part for both of them it must be trivial. But is one
of them "smaller" than the other -- or "bigger"? WHAT IS THE DIFFERENCE?
Does anyone have any idea? I've got a used 11641 which we'll probably
install now, but I'd REALLY like to know what the P/N discrepancies are all
about.
Oh yeah, one reference says the 11641 is for a P-30 with 13"x2.5" DRUMS!!!
Ken H.
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Wally Anderson
Omaha NE
75 Glenbrook
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| Re: [GMCnet] P-30 MC [message #298190 is a reply to message #298170] |
Sun, 27 March 2016 20:34 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Wally,
Where did your 2.2:1 come from, calculations or testing? The reason I ask
is that when I referred to my 2007 report on P-30 testing, I found that I
never, for some reason, had the sense to calculate that ratio. Calculating
it now (the ratio of the compression of the two pistons/springs) I find
essentially the same ratio: 2.28:1.
http://www.gmcmhphotos.com/photos/g3457-p-30-master-cylinder-testing.html
Looking at what I did then, I don't really know what I thought I was
proving with the spreadsheets and graph. That ratio is what's really
important: To me it means we need to connect the 2 front calipers to the
primary (nearest booster) and the 4 rear ones to the secondary --
obviously. And that's probably what everyone has been doing all these
years, I just don't remember that my tests verified it for me at that time.
If the spring data meant anything to me then, it doesn't right now. :-(
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc., etc.
www.gmcwipersetc.com
On Sun, Mar 27, 2016 at 4:22 PM, Wally Anderson
wrote:
> A Dorman M39309 P30 master has a displacement ratio of 2.2 to 1 between
> sections, might be about right.
>
> Ken Henderson wrote on Sun, 20 March 2016 18:48
>> We're installing disc brakes on my son's GMC. It's been 14 years since I
>> last did this upgrade "from scratch", so I'm rechecking all the parts
>> recommendations.
>
...
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] P-30 MC [message #298192 is a reply to message #298190] |
Sun, 27 March 2016 20:59 |
|
wally
Messages: 643
Registered: August 2004
Location: Omaha Nebraska
Karma: 5
|
Senior Member |
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Disassembled and measured how far the two sections moved. I've had four of the Dorman P30's and one other. The other must have been the deluxe model as it had filters over the ports in the reservoir. Been down the rabbit hole with this stuff. ha
Ken Henderson wrote on Sun, 27 March 2016 20:34Wally,
Where did your 2.2:1 come from, calculations or testing? The reason I ask
is that when I referred to my 2007 report on P-30 testing, I found that I
never, for some reason, had the sense to calculate that ratio. Calculating
it now (the ratio of the compression of the two pistons/springs) I find
essentially the same ratio: 2.28:1.
http://www.gmcmhphotos.com/photos/g3457-p-30-master-cylinder-testing.html
Looking at what I did then, I don't really know what I thought I was
proving with the spreadsheets and graph. That ratio is what's really
important: To me it means we need to connect the 2 front calipers to the
primary (nearest booster) and the 4 rear ones to the secondary --
obviously. And that's probably what everyone has been doing all these
years, I just don't remember that my tests verified it for me at that time.
If the spring data meant anything to me then, it doesn't right now. 
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc., etc.
www.gmcwipersetc.com
On Sun, Mar 27, 2016 at 4:22 PM, Wally Anderson
wrote:
> A Dorman M39309 P30 master has a displacement ratio of 2.2 to 1 between
> sections, might be about right.
>
> Ken Henderson wrote on Sun, 20 March 2016 18:48
>> We're installing disc brakes on my son's GMC. It's been 14 years since I
>> last did this upgrade "from scratch", so I'm rechecking all the parts
>> recommendations.
>
...
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Wally Anderson
Omaha NE
75 Glenbrook
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