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Thanks for the many replies. Is it still possible to use the 307 motor mounts with my new 350?? I don't want to get into changing the frame towers and it seems as though it should match to a small block. Dennis
 

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1970 Chevelle Convertible & 1965 Chevelle SS Convertible
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Dennis,

I have done this swap in a 71 Chevelle and all was the same. The motor mounts for the 307 and the 350 are the same.

Rich

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70 SS - L34
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Dennis,
The motor mounts are NOT the same. The 350 motor mounts are much thicker with more "heft" built into them. The reason why I know is I've owned a 70 Chevelle since new with a 350 and my wife had a 70 Chevelle also, with a 307. Get the correct mounts or the extra torque from the 350 will rip the 307 mounts apart in short order. Plus, the 350 mounts are thicker.
 

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Dennis,
As an aside, the mount towers are the same, but you may have to loosen them and move them slightly further apart to make up for the thicker 350 mounts. After my wife's Chevelle got rear ended and totaled in 1985, I put her recently replaced 307 into my Chevelle until I could get a new 350. That's how I discovered the "mount problem"! School of hard knocks!!
 

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Dennis,

The frame mounts are different between 307s and those for 350/big blocks. Get the correct frame mounts and motor mounts.
 

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Jerry,

I never gave the thickness much thought when I did my swap. The 307 mounts bolted to the 350. Put the block in and it was ok. I didn't own the car long enough to see if they held out.

Kevin - the big block frame mounts I beleive are differnet but small block, 327, 307, 302, 350 should all be alike.

Rich
 

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Well the Chevy parts catalog shows them to be the same part number. But I also know there are some real junk aftermarket parts out there. I once purchased mounts for my 64 impala at the local part store and thought they looked to cheap, so I went a ordered GM one's and there was a very big difference in quality, not to mention the price for the GM one was twice as much.

[This message has been edited by elcamino (edited 11-12-99).]
 

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Gentlemen,
Both Year One and National Parts Depot show different part numbers for the 307 and 350 mounts, and Year One carries original GM mounts. If you have the newest Year One catalog, you can see the difference in sizes on page 244. Just going by 29 years of working on the "ole Malibu".
 

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Hey Rich,

307 mounts are unique onto themselves. 350/big block are interchangeable. Found out the hard way when swapping a 454 into a friend's 307 car. The engine just wouldn't fit correctly and interfered with the centerlink. After much research found that 880708(pass) and 880707(driver) - if memory serves me correctly - is what is required.
 

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The engine side mounts are (rubber&metal combo)different but will interchange. The 307 does not have the interlocking saftey feature, but the 350 and BB mounts does. Most companies have gone to selling the 350 version because of its inherently safer design and you only have to stock one part number. The frame mounts are the same 307 to 350.

[This message has been edited by hangten (edited 11-12-99).]
 
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