621 Bellhousing on a 348 - easy question (hopefully)

[need1morecar]

I'm hoping this is really straightforward: In place of the 283/Powerglide I am installing a 348 with a TKO500. I have a '621' bellhousing (GM 3899621 to be specific) and a 168 tooth flywheel. Is there some sort of spacer or block plate that should go between the bellhousing and engine block? Or does this bellhousing just bolt directly to the block? I want to make sure I get the depth of the input shaft correct so it's engaged with the pilot bearing right. If there should be a spacer does anyone have any pictures/part numbers?

I'm asking because a lot of Fords I've worked on have a stamped steel plate/spacer between the engine block and bellhousing, as did the 283/Powerglide I pulled from my 60 Chevy and an AMC I worked on before that. I understand that the 621 bellhouing came out later on in 66/67 but I've not worked on any mid-60's Chevrolets, so I'm not sure if something was meant to be there or not.

Thanks.

 

[La Hot Rods]

It will bolt directly to the block. The tin shield will bolt to the bottom half of the bell housing from the front side.

 

[Don Jacks]

This bell bolts directly to the block,no plates used.

 

[need1morecar]

Awesome. Thanks folks!

 

[Rickys61]

Make sure your 348 is drilled for the starter bolts...

 

[1958 delivery]

Checking for starter holes, very important

 

[Jim Sullivan]

Will the 621 bell housing fit over a 168 tooth flywheel? I may be confusing this bell housing with another number, but It might be for the smaller flywheel?

 

[need1morecar]

Make sure your 348 is drilled for the starter bolts...

Checking for starter holes, very important

How do you both mean? Are there 348 blocks out there that do not use block-mounted starters? Mine has three 3/8" threaded holes. The one is hard to see with the dark photo - sorry.

Will the 621 bell housing fit over a 168 tooth flywheel? I may be confusing this bell housing with another number, but It might be for the smaller flywheel?

Everything I've read says that the 621 is 'the' OE bellhousing to use for a 168 tooth flywheel. I've mocked it up and it seems to fit fine. I believe you can use the smaller flywheel with it if you wanted. The tell-tale is the bulge in the housing for the starter.

 

[Rickys61]

How do you both mean? Are there 348 blocks out there that do not use block-mounted starters? Mine has three 3/8" threaded holes. The one is hard to see with the dark photo - sorry.
View attachment 90234


Everything I've read says that the 621 is 'the' OE bellhousing to use for a 168 tooth flywheel. I've mocked it up and it seems to fit fine. I believe you can use the smaller flywheel with it if you wanted. The tell-tale is the bulge in the housing for the starter.
View attachment 90235

The 348 has the starter mounted to the bellhousing not the block... some of the earlier blocks are not drilled...

 

[427John]

The way I understand it the earlier engines with the bellhousing mounted starter uses a tin plate between the block and bellhousing,while the 64 or 65 and later engines with a block mounted starter did not.Some GM cars switched to the block mounted starter in 64 while others continued with the bellhousing mounted starter and switched in 65.At some point before that time they started drilling the blocks to accept the block mounted starter.

 

[Don Jacks]

My 59 and 60 5011 blocks and my 63 814 block are all drilled.I think my 59 block which is now a 380 was cast in March of 59.

 

[oldskydog]

I believe the Turboglide blocks (H suffix) were drilled for starter.

 

[Don Jacks]

My 2 were power glide blocks according to the stampling.I don't know when they started drilling the blocks.I also wonder did the truck starters bolt to the bell or the block?

 

[427John]

Maybe it was an auto vs manual transmission thing,while we know the early manual bellhousing had provision for the bellhousing mounted starter,did the powerglide and turboglide?I think the adapter for the cast iron auto did, but did the aluminum case version?

 

[DonSSDD]

Ironglides all had the starter mounted to their spacer, same as manual transmissions had them mounted to the bh. Cast iron powerglides were the only Chevy transmissions with spacers. When the aluminum glide came out in 62 on a 327 and the small flywheel came out in 63, they were all block mounted. Not sure on 63 and 64 409’S , how they had their starters mounted. I think later truck starter’s had bellhousing mounts for many years.

 

[need1morecar]

That's interesting. Mine is an early 1960 5011 block that was built in the first quarter. I bought the engine after it has been removed and do not know what transmission it originally was installed with.

 

[heddrik]

Interesting. So will a 64 409 block with a 533 aluminum bell housing bolt to the block or the bell housing?

 

[DonSSDD]

All v8’s from 55 to at least the 70’s and all V8 bellhousings and all 6 bh’s from 63 on will bolt together , they have the same mounting surfaces.
There are variables in bellhousings, like 63 and later- some are only for the 153 tooth flywheel, 63’s have small input shaft holes, later trucks have larger input shaft holes, etc etc etc, but they all bolt together.

 

[DonSSDD]

You can use any cast iron open bottom 55-62 bellhousing on a 348-409.

 

[heddrik]

I have a 553 and a 64 block, so it bolts just like a 327 I am hoping, I bought a bunch of GM original starter bolts a few months ago. If I EVER get this thing started and put together. In the gathering stage now.