It's hard to get a perfect measurement since they taper, but I saw 1/4 to 3/8" that ran off when I mocked it up.

Here's a pic of the sachs flywheel, 11" BBC wear pattern. About 1 1/2" of the 2 1/4" contacts the flywheel.


Not sure of a T56, but I saw a spec of 6.29 on the 621 bell.

I suspect the truck bell would be fine. But remember the bearing retainer hole is larger. I've seen spacers machined (pic below), but not a common solution.

 

Gary thx for your quick reply. So if used a truck bellhousing and went with the 10 spline truck disk and pressure plate from a truck, mated to the sachs 1050 flywheel which is also from the truck i would solve the hanging splines problem and the disk mating surface issue?

Obviously i would need a spacer for correct trans placement.

Mcleod sells a flywheel they claim is 30lbs. I wonder if its lighter then the sachs 1050..

 

Keep in mind the truck bell is set up for old school pressure plates and flywheels, not sure of clearance issues.
The sachs flywheel is 26lbs.

 

i thought i would post my findings when doing this type of swap.
engine:2000 5.7 ls1
trans:borg warner super t10 from 1975 z28
(2 groove 26 spline input shaft)
flywheel: stock ls1 fbody
clutch: 11" centre force dual friction pressure plate and disk for ls1 v8.
hydraulic throw out bearing: to be determined.

measurement in mm:

engine block transmission surface to flyweel surface 28mm
engine block transmission surface to LS1 pilot bearing surface:0mm
engine block transmission surface to ls7 pilot bearing face:16mm

clutch disk tooth flange width:30mm
clutch disk flange face to pressure plate teeth:34mm
engine block trasnmission surface to pressure plate teeth:86mm

transmission side:

base of input shaft flange to pressure plate teeth:51mm or 2"
(this would be the maximum thickness of a hydraulic throwout bearing when not expanded)


with this setup, the disk sits perfectly on the input shaft splines.
you can use the ls flywheel no need to buy the thicker (.400) flywheels.

 

Good info.

 

So what if you knew a guy that could machine an adapter say .400 thick, with countersunk through holes bolt pattern of 3.11 (ls) and a threaded bolt pattern of 3.58 (gen 2/old school), machined a pilot for the ls crank and a hub for the gen 2/old school flywheel? Wouldn't that cure all issues?? run whatever came with gen 2 platform

I have yet to find one of said adapters but sure I could make some for about $50 a pop? Any thoughts??

 

Needs to be a 168 tooth flywheel in order to engage the stock LS starter.

Andrew

 

there are both 153 and 168 tooth flywheels available if I'm not mistaken?

 

I don't remember for sure, but I think 168 was BBC only...I could be wrong...

But the question is why bother doing all that when we have outlined simple, inexpensive solutions?

Andrew

 

I think I will make one and find out. Still need to dig up crank and flywheel diameters, but I will definitely make one and see how it works!! the easy part is the making...wont be able to do any testing until winter unfortunately

 

both flywheels/ flexplates interchange between BBC and SBC with the exception of the 400 and 454 having an external counterweight. I just sounds like the sachs flywheels are getting harder to find and are a bit of a pita with clutch engagement/ alignment and are cumbersome, plus the extended pilot bushing and throw out bearing. Not to mention performance parts?

Not trying to start an argument, I love repurposing/transplanting at least as much as the next guy but sometimes its not very practical is all.

 

SBC and BBC flywheels are not interchangeable, even if the engine is neutrally balanced. Also there is a difference in flywheels between the early two piece rear main seal SBC and the later one piece design.

I didn't use a Sachs flywheel and it all works well together.
Andrew

 

I am new to ls but I have built sbc and bbc for over 20 years and have been interchanging flywheels since the beginning.

yes, you are correct that the later 1 pc generation are not quite the same animal, BUT PRE ONE PIECE DO IN FACT INTERCHANGE. Again with the exception of the sbc400 and the bbc 454 which are externally balanced (they actually still interchange but are different only with the external weight/removal on the outer edge of flywheel/flexplate)
Early sbc did use a 153 tooth but a 168 could be used with only a difference in starters. Again even the 153 tooth could be used on 2pc main bbc with the correct starter.

Again ive been doing it for over 20 years

 

Wait, are you planning a 0.400 spacer to move the flywheel out?
How will the starter engage the ring gear?

 

OK....so internally balanced BBC and SBC flywheels do indeed interchange...but as Gary said, what about the starter?

Andrew

 

That was part of my initial question, ive read that the Ls flywheel is offset/ dished if you will. I don't know if and how much but I cant find the article/forum that I read this to see if a number/ dimension is given.

My spacer idea is just that, an idea. that's why I posted here to get some insight. I would have thought this would have been either invented or disproven but I cant find any evidence other than the brief finding years ago that I can no longer find??

What I can tell so far is that the ls flexplate is stamped with an offset or "bell shape" , pushing the ring gear "away" from the motor, Kinda supporting my idea, again unfortunately I have no numbers to support this

 

could I use this instead of the BBC clutch/pressure plate. Looks like this would have the correct contact patch on the 1050 flywheel. I have a 2001 lm7 that Im swapping in a 78 c10 with a 10spline saginaw transmission. I already have the 1050 flywheel and truck tranny and bell from the original truck.

 

1. You have to make sure that the clutch disk splines match your transmission input (26 or 10 spline).

2. Which truck bellhousing? You have to be careful here because as I understand it, truck bell housings have a larger bearing retainer opening than car bell housings. This is a critical point because the bearing retainer is what centers the transmission to the bell, not the bolts.

Andrew

 

Yeah it's the large bearing retainer bell and the Saginaw I have is a large retainer truck transmission. I have a 11" clutch and pressure plate but i don't like the amount off clutch not contacting the 1050 fly wheel.

 

Post pictures....I am assuming you mean the disk is not making a good contact with the flywheel?

Andrew