easy way to tell 727 big from small??

Posted By: toplescuda

easy way to tell 727 big from small?? - 07/18/05 06:46 PM

i got a 727 in a deal with a car the 727 was inside the car has no converter what is the most easy way to tell if it for a small block or big block?
thanks ralph

Posted By: Leadfoot

Re: easy way to tell 727 big from small?? - 07/18/05 06:52 PM

The small block has a bolt hole in the top center of the bell housinr and the big block doesn't

Posted By: toplescuda

Re: easy way to tell 727 big from small?? - 07/18/05 07:09 PM

cool deal thanks for the info now i got to go look lol
ralph

Posted By: John_Kunkel

Re: easy way to tell 727 big from small?? - 07/18/05 07:30 PM

Neither bellhousing has a bolt at the top center.

The easiest way to tell them apart is the bottom row of 4 bolt holes in the bellhousing, the big block has 4 small holes while the small block has two small and two large holes.

Posted By: Leadfoot

Re: easy way to tell 727 big from small?? - 07/18/05 09:49 PM

My mistake! But now I'm confused.I went and checked a block and there is a hole in the top center. I checked my trans and there is no hole. What gives?

Posted By: amxautox

Re: easy way to tell 727 big from small?? - 07/18/05 10:00 PM

Quote:

My mistake! But now I'm confused.I went and checked a block and there is a hole in the top center. I checked my trans and there is no hole. What gives?

My 4-spd bell housing has the top center hole. No I can't take a picture, it's in the car and can't get a camera back down there. Maybe if you beg enough I could pull the car out and try.

Posted By: Blown_Hemi

Re: easy way to tell 727 big from small?? - 07/18/05 10:18 PM

Quote:

Quote:

My mistake! But now I'm confused.I went and checked a block and there is a hole in the top center. I checked my trans and there is no hole. What gives?

My 4-spd bell housing has the top center hole. No I can't take a picture, it's in the car and can't get a camera back down there. Maybe if you beg enough I could pull the car out and try.

My cast iron small block truck bell has a hole at the top also. John is correct about the 727 housings. That is how I usually tell the difference.

Posted By: Anonymous

Re: easy way to tell 727 big from small?? - 07/18/05 10:20 PM

another easy way to tell- small block starters are below the crank center line , big blocks are inline with the crank centerline. horizontally of course...

Posted By: Leadfoot

Re: easy way to tell 727 big from small?? - 07/19/05 12:14 AM

Quote:

Quote:

Quote:

My mistake! But now I'm confused.I went and checked a block and there is a hole in the top center. I checked my trans and there is no hole. What gives?

My 4-spd bell housing has the top center hole. No I can't take a picture, it's in the car and can't get a camera back down there. Maybe if you beg enough I could pull the car out and try.

My cast iron small block truck bell has a hole at the top also. John is correct about the 727 housings. That is how I usually tell the difference.

I guess I just put a bolt wherever there was a hole and never paid much attention.

Posted By: Anonymous

Re: easy way to tell 727 big from small?? - 07/19/05 12:50 AM

I also use starter position to tell the difference. Use the kickdown linkage boss as a refrence point. If I remember right, its above the top starter bolt on the SB and below the top starter bolt on a BB. Its hard to explain but its an easy way to tell them apart.

Posted By: toplescuda

Re: easy way to tell 727 big from small?? - 07/19/05 01:15 AM

wellm mine dont have a hole in the top so here is what i did i measures the center between the 2 top bolts on a my big block (in car) it is 8 inches(or close enuff) from center of bolt hole to center of bolt hole and the small block is 6 3/4 some tranny have a inch and a half or so on top but those are for motor homes and vans to check the timing through
ralph

Posted By: Mopar-Al

Re: easy way to tell 727 big from small?? - 07/19/05 02:06 AM

Quote:

Neither bellhousing has a bolt at the top center.

The easiest way to tell them apart is the bottom row of 4 bolt holes in the bellhousing, the big block has 4 small holes while the small block has two small and two large holes.

see the tranny on the left? look just under the starter. See the curve? That's the easiest way for me to tell it's a small block. By the curve. And the 2 brace mounts for the block at the bottom of the dust cover helps too.

Posted By: AZ_A12_BEE

Re: easy way to tell 727 big from small?? - 07/19/05 02:40 AM

Quote:

another easy way to tell- small block starters are below the crank center line , big blocks are inline with the crank centerline. horizontally of course...

I use this method

Posted By: Rhinodart

Re: easy way to tell 727 big from small?? - 07/19/05 03:21 AM

I always used the square hole in the top for reference. The small block has about 2" seperating the bolt hole and the square hole while the big block has it about an inch.

Posted By: amxautox

Re: easy way to tell 727 big from small?? - 07/19/05 03:25 AM

What square hole?

edit; that one sorta next to the bolt hole? [looking at the picture posted above] Never seen or at least paid attention to it before.

Posted By: Reggie

Re: easy way to tell 727 big from small?? - 07/19/05 03:59 AM

Quote:

Quote:

another easy way to tell- small block starters are below the crank center line , big blocks are inline with the crank centerline. horizontally of course...

I use this method

Ditto here. Quick and dirty.

Use the input shaft centerline as a reference and imagine looking at a clock...

BB starter location will be dead on at 3:00 and the SB starter location will be closer to 4:00.

Posted By: Anonymous

Re: easy way to tell 727 big from small?? - 07/19/05 03:09 PM

Quote:

I always used the square hole in the top for reference. The small block has about 2" seperating the bolt hole and the square hole while the big block has it about an inch.

Easy way for me is if i can fit one finger between the square and round hole it's a big block, two fingers and it's a small block

Posted By: Rhinodart

Re: easy way to tell 727 big from small?? - 07/19/05 04:35 PM

Quote:

Quote:

I always used the square hole in the top for reference. The small block has about 2" seperating the bolt hole and the square hole while the big block has it about an inch.

Easy way for me is if i can fit one finger between the square and round hole it's a big block, two fingers and it's a small block

Ahh, Two Fingers Tequila, I think I remember it.....

Posted By: 70dart360

Re: easy way to tell 727 big from small?? - 07/19/05 04:36 PM

What the heck is the square hole there for? I've always wondered about it.

Tim

Posted By: amxautox

Re: easy way to tell 727 big from small?? - 07/19/05 05:41 PM

Ok, the square hole is only on the INSIDE of the bell, it can't be seen from the outside, it doesn't go all the way thru. Somebody might have mentioned that. I just went out to find these elusive holes. As I said earlier I've never even seen a square hole.

Whenever I've had a tranny off I've only looked at the seals, ect. Never figured why I'd need to look at the holes. Now I have a reason to look at the holes too.

Posted By: John_Kunkel

Re: easy way to tell 727 big from small?? - 07/19/05 09:39 PM

Quote:

What the heck is the square hole there for? I've always wondered about it.

I've always wondered too, I suspect it's a tooling hole used to locate the case for machining.

Posted By: 70dart360

Re: easy way to tell 727 big from small?? - 07/19/05 10:20 PM

That makes sense John, never thought about it that way.
Tim