# I have a flywheel question 70 motor swap 76



## 70droptopgoat (Apr 3, 2010)

I posted this under 2004 gto by mistake sorry, I need to get more familiar to the site. I am putting a 76 Catalina motor in my 70 gto that has a 10.5" clutch and the problem is the boss on the crank for the 76 motor is 2.5" and the flywheel hole is 2.75", looking to see what GM fw will work, also I had someone in the business suggest a spacer will work. Also, looking for the right pilot bushing, anyone run into this before? thanx for the help!!!!


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## Rukee (Feb 8, 2007)

If it were mine, if possible, I'd probably swap out the cranks with some new bearings and maybe a timing chain and oil pump if needed.


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## pontiac (Mar 6, 2011)

Crank hole sizes are:

1961-1962... 2.600"
1963-1977... 2.750"
1978-1979... 2.490"

Note:
The 1963 flywheel has the same size crank hole as the 1964-1977 flywheels but it will only accept the 1960-1963 type starter.

Technically the small register flywheel began with the '76 model year on the 400's only. Up until approximately Jan 1, 1976, clutch diameter was 10.4" at which time it switched to 11". The SAME 11" small register flywheel was used on the 400 from mid-76 through 79. The '76 455 still had the large register and 11" clutch all year.

so buy the later model flywheel for your odd 76 engine.


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## 70droptopgoat (Apr 3, 2010)

Pontiac Crankshaft Technical Information



Thanx for the info! I also found this site and if I'm reading it right I have the late 76 motor with the 2.6" boss on the crank. So would the 76-81 applications with the 2.6" hole be a match? The last 4 listed in the chart, 80-81 265, 77-81 301, and late 76-79 350 and 400. The aftermarket flywheels I'm finding range from about $50 to $500. Again, thanx for the input guys, Al.


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