Which starter for a 621 Bellhousing with a small flywheel - Chevelle Tech
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  #1  
Old Jul 12th, 09, 11:19 AM
richls richls is offline
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Default Which starter for a 621 Bellhousing with a small flywheel

I decided to replace a scattershield with a stock style bellhousing on my '68 Camaro Z28 (302 small block/Muncie 4-speed) when I had the engine out for rebuilding. This car has the small flywheel with the 153 tooth ring gear and 10.4" clutch. I mistakenly installed a 621 style bellhousing which I've since learned is typically used with an 11" clutch. Everything bolted up fine and I reinstalled the engine/transmission in the car with no problems. The problem came up when I tried to install my old starter motor. It doesn't fit. I don't want to pull everything out again right now to install the correct bellhousing. I'll do that at some point in the future. In the meantime, what starter can I use with the 621 bellhousing and the 153 tooth ring gear flywheel? b.t.w, the starter bolts must be straight across...not staggered. Do I go with an afternmarket high torque mini-starter (which one?) or is there a stock Chevrolet starter motor that will work with this situation? Thanks for your help.
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  #2  
Old Jul 12th, 09, 12:10 PM
pdq67 pdq67 is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

I think you need the big snout straight bolt starter.

Not the staggered bolt small c/i snout one.

pdq67
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  #3  
Old Jul 12th, 09, 2:32 PM
oman oman is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

Quote:
Originally Posted by richls View Post
I decided to replace a scattershield with a stock style bellhousing on my '68 Camaro Z28 (302 small block/Muncie 4-speed) when I had the engine out for rebuilding. This car has the small flywheel with the 153 tooth ring gear and 10.4" clutch. I mistakenly installed a 621 style bellhousing which I've since learned is typically used with an 11" clutch. Everything bolted up fine and I reinstalled the engine/transmission in the car with no problems. The problem came up when I tried to install my old starter motor. It doesn't fit. I don't want to pull everything out again right now to install the correct bellhousing. I'll do that at some point in the future. In the meantime, what starter can I use with the 621 bellhousing and the 153 tooth ring gear flywheel? b.t.w, the starter bolts must be straight across...not staggered. Do I go with an afternmarket high torque mini-starter (which one?) or is there a stock Chevrolet starter motor that will work with this situation? Thanks for your help.

If I recall correctly you need to use the flywheel and starter and bellhousing as a set. The 621 bell is for the 11 inch clutches. The 621 compatible starter is for the 11 inch flywheel. Once you get the starter right you are gonna likely find that the correct starter for the 621 bell will not work correctly with the 153 tooth flywheel.

Somebody will certainly correct me if i am wrong but I fear you are looking at an R&R of the bell housing. To my knowledge there is no starter that will work with you incorrect combo. Everything bolted up SO FAR but you are now at the point where the mismatch is gonna become painfully obvious.
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Old Jul 12th, 09, 3:54 PM
dyno jonn dyno jonn is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

The 621 bellhousing will work with the 153 tooth flywheel or the 168 tooth flywheel. The sheet metal shield that is normally used with the 621 bell has the wrong hole for starter clearance so it can not be used if you are going to use the small flywheel. Simply get a starter made for a small flywheel or flexplate, take off the tin shield, and you should be good to go. That will be a starter that takes one short bolt and one long bolt, and has both bolts lined up at one end of the housing.
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  #5  
Old Jul 12th, 09, 5:50 PM
richls richls is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

The problem with installing my old starter is that the starter nose will not clear the 621 bellhousing because the starter is designed for the original '68 bellhousing which fits the original 12-3/4", (10.4" clutch) 153 tooth flywheel....not the 14", (11" clutch) 168 tooth flywheel which the 621 bellhousing is designed for. (The tin flywheel cover plate is not important.) Although the 621 bellhousing is unnecessarily large for my application everything except the starter motor fits fine and bolts up. Because it is already installed in the car I want to find a starter motor that will work with this application for now. The starter motor bolts are straight across not staggered. I'm assuming that several of the small high torque aftermarket starters would work because they are designed to fit Chevy engines with either 153 or 168 tooth flywheels, but I'd like to have that confirmed before buying one (See the Summit Racing catalogue page 101). But I'm also wondering if there is a factory starter motor that will work. (A cover plate designed for the 621 bellhousing looks like it would work fine but I'm not too concerned about that because if I have to I can run without a flywheel cover plate.) Again, thanks.
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Old Jul 12th, 09, 7:12 PM
oman oman is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

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Originally Posted by richls View Post
The problem with installing my old starter is that the starter nose will not clear the 621 bellhousing because the starter is designed for the original '68 bellhousing which fits the original 12-3/4", (10.4" clutch) 153 tooth flywheel....not the 14", (11" clutch) 168 tooth flywheel which the 621 bellhousing is designed for. (The tin flywheel cover plate is not important.) Although the 621 bellhousing is unnecessarily large for my application everything except the starter motor fits fine and bolts up. Because it is already installed in the car I want to find a starter motor that will work with this application for now. The starter motor bolts are straight across not staggered. I'm assuming that several of the small high torque aftermarket starters would work because they are designed to fit Chevy engines with either 153 or 168 tooth flywheels, but I'd like to have that confirmed before buying one (See the Summit Racing catalogue page 101). But I'm also wondering if there is a factory starter motor that will work. (A cover plate designed for the 621 bellhousing looks like it would work fine but I'm not too concerned about that because if I have to I can run without a flywheel cover plate.) Again, thanks.
You don't need a new starter. Even though I was apparently wrong on the flywheels I know that the following is true.

There are different noses for the starters. One nose is for the 621 bellhousing and others are available for other applications. You need to get the correct nose for use with the 621. Perhaps (just PERHAPS) the same starter nose is used on TH400 automatics and on the 621 bell equipped stick cars. Can't be sure. The nose for the 621 will bolt right onto your existing starter. I am currently running a starter that was originally on a 350 CI TH 350 equipped car on a 454 CI engine with a 621 bellhousing. All I did was swap the starter ends.
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  #7  
Old Jul 16th, 09, 11:54 AM
richls richls is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

Here is the solution in case you ever run into the situation I did: First, after much research I've learned that no stock GM starter will fit because the 621 bellhousing is designed for a starter that engages a 168 tooth ring gear on a 14" flywheel. My 12.75" flywheel is smaller and has the 153 tooth ring gear. So, the correct starter for the flywheel won't fit the 621 bellhousing and the starter that fits the 621 bellhousing won't work because it's designed for the larger 168 tooth flywheel. Switching the nose on the starter is also not a solution because you end up with the same issues. The solution I found was to use an aftermarket mini-starter. I purchased one with no nose (most come that way), just the starter pinion gear sticking out. It's designed to be used with either the 153 or 168 tooth ring gear and works on both Chevy small and big block V8 engines. (It has four mounting holes and you pick the two you need for your application.) Because there is no nose on the starter it went right in and looks to mate up correctly with the ring gear. I haven't tried starting the motor with it yet but there are shims in case I need to move it slightly. I hope you don't run across this problem but if you do a mini-starter is your solution.
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Old Jul 16th, 09, 12:09 PM
oman oman is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

Quote:
Originally Posted by richls View Post
Here is the solution in case you ever run into the situation I did: First, after much research I've learned that no stock GM starter will fit because the 621 bellhousing is designed for a starter that engages a 168 tooth ring gear on a 14" flywheel. My 12.75" flywheel is smaller and has the 153 tooth ring gear. So, the correct starter for the flywheel won't fit the 621 bellhousing and the starter that fits the 621 bellhousing won't work because it's designed for the larger 168 tooth flywheel. Switching the nose on the starter is also not a solution because you end up with the same issues. The solution I found was to use an aftermarket mini-starter. I purchased one with no nose (most come that way), just the starter pinion gear sticking out. It's designed to be used with either the 153 or 168 tooth ring gear and works on both Chevy small and big block V8 engines. (It has four mounting holes and you pick the two you need for your application.) Because there is no nose on the starter it went right in and looks to mate up correctly with the ring gear. I haven't tried starting the motor with it yet but there are shims in case I need to move it slightly. I hope you don't run across this problem but if you do a mini-starter is your solution.
I said this a few days ago.

Some "expert" in this post said that the 621 will work with the smaller flywheel. The rubber meets the road when you try to put a starter in there when you have the 621 bell and the 154 tooth flywheel bolted on your engine. The cover plate is irrelevant to the situation. Removal of the cover plate is a bandaid fix at best but it is not gonna work anyway. Anyone who ever tried this would have see that the "leave off the cover' solution is a non starter. Pun intended!!! The starter that works with the small flywheel wont work with the 621. The starter that works with the 621 won't work with the small wheel.

I should have stood my ground and challenged this misleading poster who said you could somehow make the 621 work with the small flywheel. Live and learn for both you and I. It has been a long time since I fooled with this problem and I was almost sure that what you eventualy found out was right. You can switch the starter noses ad use what was a non 621 starter on a 621 Bellhousing Or you can switch the noses and use a 621 starter on a non 621 housing. What you cannot do is make a small 153 tooth flywheel work with a 621 bellhousing! No matter what you do to the starter nose it is not gonna work.

This is what I said earlier this week.....

"If I recall correctly you need to use the flywheel and starter and bellhousing as a set. The 621 bell is for the 11 inch clutches. The 621 compatible starter is for the 11 inch flywheel. Once you get the starter right you are gonna likely find that the correct starter for the 621 bell will not work correctly with the 153 tooth flywheel.

Somebody will certainly correct me if i am wrong but I fear you are looking at an R&R of the bell housing. To my knowledge there is no starter that will work with you incorrect combo. Everything bolted up SO FAR but you are now at the point where the mismatch is gonna become painfully obvious. "


THis is the erroneous post.

"The 621 bellhousing will work with the 153 tooth flywheel or the 168 tooth flywheel. The sheet metal shield that is normally used with the 621 bell has the wrong hole for starter clearance so it can not be used if you are going to use the small flywheel. Simply get a starter made for a small flywheel or flexplate, take off the tin shield, and you should be good to go. That will be a starter that takes one short bolt and one long bolt, and has both bolts lined up at one end of the housing. "

Last edited by oman; Jul 16th, 09 at 7:21 PM.
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  #9  
Old Jul 16th, 09, 7:51 PM
DZAUTO DZAUTO is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

GOOD GRIEF!!!!!!!!!!!!!!!!!!!!!!
THERE IS NO SUCH THING AS AN 11in FLYWHEEL!!!!!!!!!!!!!!!! NONE, ZERO, NADA, ZIP FOR A CHEVY V8!!!!

FLYWHEELS ARE EITHER 14in, 168 TEETH, OR, 13in(actually about 12/34in), 153 TEETH!!!!
The 153 teeth flywheel will ONLY use a 10 1/2in clutch and the 168 teeth flywheel will use EITHER a 10 1/2in or 11in clutch (depending on how it is drilled)!

AGAIN, THERE IS NO SUCH THING AS AN 11in FLYWHEEL!!!!

Here are the two sizes of flywheels for a Chevy V8-----------NEITHER is 11in!
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Old Jul 16th, 09, 8:01 PM
oman oman is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

Quote:
Originally Posted by DZAUTO View Post
GOOD GRIEF!!!!!!!!!!!!!!!!!!!!!!
THERE IS NO SUCH THING AS AN 11in FLYWHEEL!!!!!!!!!!!!!!!! NONE, ZERO, NADA, ZIP FOR A CHEVY V8!!!!

FLYWHEELS ARE EITHER 14in, 168 TEETH, OR, 13in(actually about 12/34in), 153 TEETH!!!!
The 153 teeth flywheel will ONLY use a 10 1/2in clutch and the 168 teeth flywheel will use EITHER a 10 1/2in or 11in clutch (depending on how it is drilled)!

AGAIN, THERE IS NO SUCH THING AS AN 11in FLYWHEEL!!!!

Here are the two sizes of flywheels for a Chevy V8-----------NEITHER is 11in!
My appology ...a thousand pardons. I should have been more specific. ..."the 14 INCH flywheel that is used with the 11 inch clutches" should have been my statement!

A thousand pardons

Your picture shows WHY the starter fix (when implement by leaving of the cover plate) will not work1

Last edited by oman; Jul 16th, 09 at 9:05 PM.
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  #11  
Old Jul 16th, 09, 8:17 PM
DZAUTO DZAUTO is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

OK now, the starter (we're talking STOCK, GM Delco) for the 153 teeth flywheel, when used in CONJUNCTION with a 621 style bell housing, as already pointed out, won't work because the starter nose interferes with the bell housing starter nose bulge. You COULD trim the 621 housing to accomodate the 153 teeth style starter--------------but that would be a gross sacrilege!!!!!!!!!!!!!!!!!
Certainly an aftermarket, universal fit type mini starter may solve the whole problem. If that is a satisfactory solution, go with it.
If the car was mine, AND IT IS NOT, I would pull the tranny and install the correct type 403 type bell housing.
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Old Jul 16th, 09, 10:29 PM
pdq67 pdq67 is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

Tom,

Just asking b/c when I had to replace my staggered-bolt 350SS/396/427/ h-d GM starter, the Counter Person brought out one w/ a big snout on it and after I told him that I needed the smaller snout, he fixed me right up.

What's the deal w/ the big snout GM starter?? I'm thinking it was aluminum, BUT it's been since '86???

pdq67
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Old Jul 17th, 09, 3:58 PM
DZAUTO DZAUTO is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

Paul,
Several months ago, I did a major coverage, with pictures, of flywheels and bell housings and another on starters. The one about starters was SPECIFICALLY about factory, GM Delco type starters. Any aftermarket/mini starters may present a completely different situation.
You can probably find both by doing a search, or maybe someone will throw up a link.
But, for now, here is the answer to your specific question, as I understand the question.
FOR ANY 14in DIAMETER, 168 TEETH FLYWHEEL/FLEXPLATE:
You need a starter nose that has the STAGGERED bolt pattern (remember, this is for stock GM Delco type starters).
There ar TWO versions of the staggered bolt pattern starter---alum nose and CAST IRON nose.
When using a manual tranny (such as a Muncie), 168 teeth flywheel and 621 style bell housing, you MUST use a starter with the cast iron nose.
A starter with a cast iron nose will work with EITHER an auto tranny/168 teeth flexplate. But a starter with the alum nose will ONLY work with an auto tranny/168 teeth flexplate.
So, to get a starter with the correct cast iron, staggered bolt pattern, ask for a starter for something such as a 68-72 Chevelle with a BB and 4sp.
Then, when the parts guy hands you the box with the starter in it, open the box to confirm that it has the iron nose.

Why is the end of an iron starter nose smaller than an alum nose? I have ZERO clue! That's just how they made them.
Most of the rebuilt starters that I've seen for GM engines which are sold by reputable parts stores (NAPA, O'Reillys, etc) are GOOD, dependable starters. I just checked at my local O'Reilly store a couple of weeks ago on a BB/4sp starter-------------the parts guy brought out the right one with the iron nose-----------------my cost, $40!!!

By the way, while we're on the subject, I have never seen a straight across bolt pattern starter nose that was cast iron--------------they were all alum.
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  #14  
Old Jul 25th, 09, 1:46 AM
richls richls is offline
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Default Re: Which starter for a 621 Bellhousing with a small flywheel

Since there seems to be lot's of opinions and some mis-information I figured I should let you know my outcome just in case you run into the same situation I did. In short, a mini-starter is your solution. It works. No stock GM starter will fit because the 621 bellhousing is designed for a starter that engages a 168 tooth ring gear on a 14" flywheel. A 12.75" flywheel fits fine inside a 621 bellhousing but it has the smaller 153 tooth ring gear so the correct starter for the flywheel won't fit the 621 bellhousing and the starter that fits the 621 bellhousing won't work because it's designed for the larger 168 tooth flywheel. The solution I found was to use an aftermarket mini-starter. I purchased one with no nose (most come that way), just the starter pinion gear sticking out. It's designed to be used with either the 153 or 168 tooth ring gear. Because there is no nose on the starter it went right in and mates up correctly with the ring gear. I've now used it and it works great. If you use the correct bellhousing for the 12.75" flywheel you won't have this problem and you can use the factory starter...so if you are still in the building stage then do it this way. But if like me...you end up with a 621 bellhousing on an engine with a 153 tooth flywheel and decide you don't want to pull everything out again (at least for now) then the mini starter is your solution.
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