LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Melling M155 Affected???

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Old Apr 10, 2007 | 01:57 PM
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Default Melling M155 Affected???

Ok i just put the motor in the car and its running..but i also just found out that melling is having stress fractures in some of their pumps because of thinner castings...********....most of the stuff i have seen is on the m55...i put in a m155...is this model having the same probs as the m55....cause it has me worried sick about my new $4500 engine..can someone shed some definite light..i read one post on corvetteforums where the m155 had the thicker castings...i sure hope so
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Old Apr 10, 2007 | 03:10 PM
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noone knows
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Old Apr 10, 2007 | 09:35 PM
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Where are you seeing this 155 number? I'm looking at the catalog and I don't see that particular number for SBC/LT1's.



Originally Posted by 3pnt4maro
Ok i just put the motor in the car and its running..but i also just found out that melling is having stress fractures in some of their pumps because of thinner castings...********....most of the stuff i have seen is on the m55...i put in a m155...is this model having the same probs as the m55....cause it has me worried sick about my new $4500 engine..can someone shed some definite light..i read one post on corvetteforums where the m155 had the thicker castings...i sure hope so
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Old Apr 10, 2007 | 11:46 PM
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Originally Posted by 3pnt4maro
Ok i just put the motor in the car and its running..but i also just found out that melling is having stress fractures in some of their pumps because of thinner castings...********....most of the stuff i have seen is on the m55...i put in a m155...is this model having the same probs as the m55....cause it has me worried sick about my new $4500 engine..can someone shed some definite light..i read one post on corvetteforums where the m155 had the thicker castings...i sure hope so
Measure the thickness of the casting with a dial or digital caliper. The new ones are .80", the good ones are 1.25". If yours measures out to 1.25" or greater then you're good to go.
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Old Apr 11, 2007 | 01:17 PM
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What year did they thin it down? I'm not gonna take my pan off and check it. I've had my M55HV since 2002.
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Old Apr 11, 2007 | 01:37 PM
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the box says m155...there site lists it..i cant exactly measure it cause its in the motor and in the car...i have seen several sites list the m55 m155 and m55hv...let me find the link
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Old Apr 11, 2007 | 02:11 PM
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http://www.chevelles.com/forums/show...hlight=melling

here is the link that had the most info...there are several on the net
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Old Apr 11, 2007 | 02:28 PM
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Originally Posted by dhdenney
What year did they thin it down? I'm not gonna take my pan off and check it. I've had my M55HV since 2002.
Nevermind, someone said it was Jan 2004 in another thread.
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Old Apr 11, 2007 | 11:18 PM
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Originally Posted by 3pnt4maro
the box says m155...there site lists it..i cant exactly measure it cause its in the motor and in the car...i have seen several sites list the m55 m155 and m55hv...let me find the link
Stock the lt1's have a 3/4" dia pickup tube (Melling M155), but your older SBC's had a 5/8" dia pick up tube (Melling M55). You have the correct replacement oil pump with the M155. I will measure the thickness of a couple of the M155's that I have on the shelf for you tomarrow.
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Old Apr 11, 2007 | 11:22 PM
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Originally Posted by 1997bird
Stock the lt1's have a 3/4" dia pickup tube (Melling M155), but your older SBC's had a 5/8" dia pick up tube (Melling M55). You have the correct replacement oil pump with the M155. I will measure the thickness of a couple of the M155's that I have on the shelf for you tomarrow.

thank you please do..im getting mixed words from several people and cant decide what the deal is..just seen that some folks were running the m55 and it was cracking and they were having problems with them..cant get a definite on the m155..does the years affect it..i just bought mine in february and it had the infamous "warning note" in it..i have factory motor mounts and it only see the strip maybe twice a year..and no circle track stuff.
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Old Apr 12, 2007 | 07:50 AM
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The sites mention other qualifying issues besides just solid motor mounts. Whether the bolt head was lubricated, whether a washer was used under the bolt, whether a stud with washer was used, the insert being a different metal and the expansion rates of the two metals caused a crack. I went ahead and ordered/received the Melling "M" select pump #10555 and bolt on pickup 12557. As soon as it quits snowing here (Upstate NY-Global Warming my a**, Al Gore) I'll pull the pan and install it. I'll be able to examine the current M55HV and see what, if anything has occurred. I've spun the motor to 7,000 a few times and plan on racing it quite a bit this Spring/Summer/Fall. I don't want some evil surprise in the oil pump to kill this brand new motor.

Originally Posted by 3pnt4maro
thank you please do..im getting mixed words from several people and cant decide what the deal is..just seen that some folks were running the m55 and it was cracking and they were having problems with them..cant get a definite on the m155..does the years affect it..i just bought mine in february and it had the infamous "warning note" in it..i have factory motor mounts and it only see the strip maybe twice a year..and no circle track stuff.
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Old Apr 12, 2007 | 02:16 PM
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Originally Posted by mightyquickz28
The sites mention other qualifying issues besides just solid motor mounts. Whether the bolt head was lubricated, whether a washer was used under the bolt, whether a stud with washer was used, the insert being a different metal and the expansion rates of the two metals caused a crack. I went ahead and ordered/received the Melling "M" select pump #10555 and bolt on pickup 12557. As soon as it quits snowing here (Upstate NY-Global Warming my a**, Al Gore) I'll pull the pan and install it. I'll be able to examine the current M55HV and see what, if anything has occurred. I've spun the motor to 7,000 a few times and plan on racing it quite a bit this Spring/Summer/Fall. I don't want some evil surprise in the oil pump to kill this brand new motor.

yes but from the testimonials i have read the people with the problems are the ones who are heaily modded cars with solid mounts and who do alot of racing
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Old Apr 12, 2007 | 03:13 PM
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I got you the measurement on the two M155 pumps that I have on the shelf. From the machined surface to the oil pump mounting bolt face they bolth measure 1.321". However they do come with the solid motor mount advisory to go to the Melling select series oil pump.
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Old Apr 12, 2007 | 03:33 PM
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Originally Posted by 1997bird
I got you the measurement on the two M155 pumps that I have on the shelf. From the machined surface to the oil pump mounting bolt face they bolth measure 1.321". However they do come with the solid motor mount advisory to go to the Melling select series oil pump.
awesome...but when were they produced..are they the old one or is it a new one like mine
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Old Apr 12, 2007 | 03:48 PM
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I just bought these oil pumps a week ago from my supplier. They didn't have any on the shelf there and ordered them straight from Melling.
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Old Apr 12, 2007 | 03:50 PM
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Originally Posted by 1997bird
I just bought these oil pumps a week ago from my supplier. They didn't have any on the shelf there and ordered them straight from Melling.
wow thats a big relief..im not gonna worry about it so much now..especially since you measured them and everything..i sure do appreciate you taking the time to do this,..that was the extra step i needed to see what the deal really was
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Old Apr 12, 2007 | 03:52 PM
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Glad I was able to help out!!
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Old Apr 13, 2007 | 09:37 PM
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Just an FYI.....I just got my Summit oil pump today. It is stamped on the side with M55HV. The thickness with the pump (SUM-121155) is a little over 1.25". So that makes it the good M55HV right? For $20.00, if it is the good one, I'll be pretty happy. Thanks.
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Old Apr 14, 2007 | 08:10 AM
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Oddly enough, it seems like no one has found a pump with this thin casting.......
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