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Question on starter motors

3K views 22 replies 10 participants last post by  Jimbo17 
#1 ·
I have been having problems keeping a starter motor in a 1977 Chevrolet 350 engine.

After changing five starter motor along with the flex plate, new battery and all new cables and grounds I noticed that when cranking the engine over the starter motor was moving which is what I believe is the problem.

The starter motor came from NAPA.

My question is are all new and rebuild starter motor being made with the universal holes larger so they can be used with either 3/8 SAE of Metric bolts?

The problem appears with the starter torqued down to 45 foot pounds because there is so much play between the hole sizes in the starter motor and the 3/8 bolt size once you crank the motor over it's moving the starter motor up and down and in turn breaking the shafts and teeth.

The bolts are brand new and from NAPA and I also purchased another set of bolts from a Chevrolet dealership.

I have rechecked the starter motor and it is tight!!!

I noticed the high torque units with the billet front section the the 3/8 bolts fit is much tighter with very little play in them.

The hole size in the NAPA starter motor is 3.94 and the 3/8 shaft on the SAE bolts is 3.74 and the shank part is about 3.86 and there is just to much play in the bolt.

I also found out that this problem has been going on for years.

Any good idea's on the best way to fix the problem?

Thanks Jim
 
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#6 ·
Poncho

Because the current NAPA starter motor is a rebuilt unit I needed two shims to get the correct clearance of about 1/8"

On most rebuilt starters you will have to use the shims because every time they rebuilt a starter motor they a cut off the top to make sure it flat.

I have no idea how many times they rebuild each starter motor common sense would say if they did five times you would need shims and I found that this one needed two of them.

Thanks Jim
 
#7 ·
PMGR starter

When you give up on that starter motor, try a permanent magnet gear reduction starter motor. Chevy started using them in about '96 and you can get them anywhere at a reasonable price. It weighs about half of what you have and you won't need that extra bracket. Be sure you get one with the staggered bolt pattern. I don't know the part number but if you look up a starter for a 97 98 99 454, you should be able to find one. Car Craft did a junk yard finder story and you can probably find it in their web site. In fact, you will learn more about them if you do. I have been using one for about 10 years now. Good luck.
 
#8 ·
PMGR starter motors

I have thought about using one of these PMGR mini starter motors because of the billet front on them they the size of the holes being a much better fit for a 3/8 SAE bolt.

I stopped over at a friends shop and he has a 502 engine in his 83 Chevrolet tuck and he had five broken mini starter motors sitting on the floor that he wanted me to see before I purchase one.

I do not like using a starter motor that has holes for bolts that are 20 thousands bigger the the shaft of a 3/8 SAE bolt.

Every mini starter I measured with a caliper had a much tighter fit with the bolt. I like that because I believe the reason many of us are having starter motor problems is the fit between the starter motor and the bolts.

I can watch my starter motor moving up and down with brand new SAE bolts that are torqued to 45 foot lbs.

Jim
 
#9 ·
I have thought about using one of these PMGR mini starter motors because of the billet front on them they the size of the holes being a much better fit for a 3/8 SAE bolt.

I stopped over at a friends shop and he has a 502 engine in his 83 Chevrolet tuck and he had five broken mini starter motors sitting on the floor that he wanted me to see before I purchase one.

I do not like using a starter motor that has holes for bolts that are 20 thousands bigger the the shaft of a 3/8 SAE bolt.

Every mini starter I measured with a caliper had a much tighter fit with the bolt. I like that because I believe the reason many of us are having starter motor problems is the fit between the starter motor and the bolts.

I can watch my starter motor moving up and down with brand new SAE bolts that are torqued to 45 foot lbs.

Jim
Reading this, I have to ask.....You are using the proper knurled bolt on the starter, right?.....By reading above, you are using a regular bolt.

 
#11 ·
Poncho

The picture you showed is exactly how it is suppose to look.

The starter motor I purchased from NAPA is what they call a universal starter motor which means you can use either SAE bolts or Metric bolts and that why the hole size is 3.95 in the the starter motor and the shaft on the 3/8 bolt is only 3.74

When I put the SAE bolt in the starter motor on my work bench the knurled end slides right through the hole of the starter motor and you can put a paper clip end between the bolt and the starter motor hole.

This is why each time I checked to make sure the bolts were tight they were. It's just the starter motor that is moving on the shafts of the bolts.

For anyone having similar problems have someone simply crack the engine over while you watch the starter motor to see if yours is moving because that is what was breaking each starter motor.

I learned a good lesson don't purchase a universal starter motor.

Jim
 
#13 ·
Latech

That is a very good point and yes sometimes the bolts are to long and a very simple test is to use some type of washer under the head of the bolt to see if that corrects the problem.

I do not mean you use leave the washer on the bolt it is simply a test to see if that corrects the problem which in my case it did not do.

Using any type of washer on starter motor bolts is not a good thing to have to do.

Thanks for your help. Jim
 
#14 ·
Don't know if you got your problem fixed, but you might want to consider adding a press fit bushing to your starter if you have access to a drill press(mill preferably) with a rigid vise. Probably a last resort as you will need some other tools as well. If you have to ask what kind you probably shouldn't attempt it. FWIW(not much)
ssmonty
 

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#15 ·
ssmonty

The bushing is something I was thinking about doing.

The way I see to fix the problem is either install a bushing or on Monday I am heading over to the local Chevrolet dealer to take a look at a OEM starter motor because I want to see if the holes are the same as what NAPA is selling or if the bolt holes are much tighter with less clearance.

If they have something where the bolts fit much better I will buy it.

The weird part is now I realize why some of the starter motors I put in the truck would last from a few days to a week or two before the starter motor started to move around and then simply either take the teeth off the Bendix or snap a shaft off.

At first I thought the problem was the wrong bolts but I now thing manufactures that build and re-manufacture starter motor are simply building them with universal size holes so they can use the exact same starter motor that can except either SAE 3/8 or Metric 10 mm bolts for a number of different year engines saving them money but creating a major problem for anyone who buys one.

When the knurled end of the bolt simply pushes all the way through the hole what the hell good is it.

Sorry to rant on but this is a problem many people who purchase these starter motors are going to have.

Jim
 
#16 ·
A photo always helps

Take a look at the three photo's of the starter motor.

The paper clip is 30 thousands and the paper clip on the right side could easily slid right along side the brand new 3/8 bolts and the paper clip on the left side also went easy but just not as far.

Each time I installed a New starter motor after the last one breaking the shaft off or taking the teeth off I would torque the starter motor bolts down to 45 foot pounds with brand new bolts and sometimes it would hold for a few days or a week and other times the very next morning it would start grinding all over again.

Don't purchase a universal starter motor that has these larger size holes so that it can be used in many different engines using either 3/8 SAE bolts or Metric 10 mm bolts which have a larger diameter shaft size then a 3/8 SAE bolt.

I would warn everyone who is having starter motor problems to have someone crack the motor over while you are looking at the starter motor to make sure yours is moving which you can easily see by just looking at it.

If I cannot find an OEM Chevrolet starter motor with the holes made to fit a 3/8 SAE bolt I will look at purchasing a high torque starter motor with a billet front with the correct size holes.

Thanks for all of your help and advice Jim
 

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#18 ·
Where to purchase OEM Chevrolet 1977 350 starter motor

Guys I am trying to purchase a brand new OEM Chevrolet starter motor for a 1977 350.

Many of the online places tell me they have the right starter motor but when I read the fine print they are all rebuilt starter motors.

I am trying to find an original OEM starter motor that has the correct sized homes drilled in it for a SAE 3/8 bolt starter motor bolt with the knurled and threaded end.

All the re-manufactured units are being made with the universal style homes which can be used with either a SAE 3/8 starter motor bolt or a 10 mm size starter motor bolt.

There starter motors will work great if you are using the 10 mm starter motor bolt because it has a larger diameter then the SAE 3/8 starter motor bolt which is about 3.74 in diameter and the hole size in the re-manufactured starter motors is 3 94

This 20 difference is the reason when you torque the starter motors down to 45 foot pounds they will work for a while before the starter motor starts moving because of the 20 clearance in both bolt holes.
The bolts to not appear to be coming loose its the the torque of cranking the engine that is making the starter motor move.

Jim
 
#19 ·
Look up PG260 starter. That is the mid 90's style PMGR starter all the OEM's started to use in the 90s. This is not a latest trick aftermarket starter. It's a better your lighter weight design. PG 260 is the type of starter the actual part number is something you'll have to look up. Look up a starter for a 97 Chevy pick up with a 454 and you will find it. It will work on small blocks too.
 
#21 ·
I thing I found a solution to the problem!!

The way I fixed the problem with my starter motor was the following,

After looking at the holes in the starter motor from NAPA and at first wondering why the holes were so big that the SAE 3/8 brand new starter bolts went right through the holes and had 30 thousands of clearance on the bottom holes and 20 thousands clearance on the top holes a friend on mind who stopped over to help me said not wrap the bolts with air conditioning tape with the aluminum exterior.

I check the tape and it was 5 thousands so I cut 1" strips and wrapped it tight around each bolt below the Knurled end and it worked like a charm.

The bolts now fit snug in the holes and I reinstalled the starter motor.

The motor started right up without the grinding noise that I have heard for the past 8 months.

Now I want use the truck and see if anything changes but I believe it is fixed.

For anyone purchasing a new or rebuilt starter motor understand that they are now using universal holes so that the same starter motor can be used in many different models of cars and trucks.

If you are using 10mm Metric bolts you may not run into the same problem I had because the shaft on the 10 mm bolt is larger then the shaft on a SAE 3/8 bolt.

One last bit of advice if you are having starter motor problems with grinding have someone crank the engine over while you watch the starter motor to see if it is moving up and down. If it is the chances are it is not the bolts but the clearance between the bolts and the holes in the starter motor
Thanks to everyone who offered advice on how to fix the problem.

Thanks Jim
 
#22 ·
What you're describing doen't add up. You've had many repeat problems with with multiple flywheels/flexplates? You mentioned measuring for shims - I'm not familiar with that - how and what are you measuring?

My experience has been if the starter is noisy after installation, then add .005" or shim stock and recheck. If the noise is still present, then double it and recheck. I've never ended up with more than .015". Also, I've never encountered the bolt hole slop issue that you described. Maybe I've been lucky, but that isn't how things usually go for me. My method has been fool proof for more than 20 years for me. I'm very curious how you've been this unlucky. FWIW, Napa starters aren't anything to write home about. The only starters I've ever had to warranty on light engines have been Napa.
 
#23 ·
Small hair lines cracks

After changing about six or seven starter motors with each one lasting from a few months to only lasting a few day's I found the real problem with the starter motors.

The outside bolt hole had two hair lines cracks on the very bottom of the hole.

It was strange that the outside bolt was tight and not lose or moving until you turned the engine over and then the starter motor would move up and down.

I consider braze welding the block but each welder said they would only do it if I removed the engine from the truck first.

A drag racing friend of mine told me about a two part epoxy that Summit Racing sells and he told me they have had a good luck using it on race engines.

I grind-ed down the block and then used a rotary tool to cut a V groove into the hair lines cracks and then washed the entire area down with alcohol a few times. I applied to two part epoxy over the whole area and then let it sit for a three weeks without touching it. I also installed the starter motor bolt in the hole first and made sure it was tight before installing the epoxy. At this point I did not install the starter motor just the outside bolt.

The reason I waited so long with the epoxy was because I was busy with other projects.

I put the starter motor back in and it has now been about two weeks and the truck starts perfectly every time.

The epoxy can be drilled and tapped if need be.

I was not sure this would work buy so far everything is fine.

Thanks to everyone who offered idea's on how to fix the problem.

Jim
 
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