Ok thanks !

I remember now,

The mounting blocks are different.

It's the 350 engine mounts that are the same as big block motors that year.

327s have different engine mounts.

Interesting question. the original engine in my 65 parisiene was the 4 barrel 327. Now putting in a big block. Do I need to change the engine mounting blocks. Have been running the originals. Might as well do it while the engine is out If I need to.

koolconvertible wrote:

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Interesting question. the original engine in my 65 parisiene was the 4 barrel 327. Now putting in a big block. Do I need to change the engine mounting blocks. Have been running the originals. Might as well do it while the engine is out If I need to.

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 Not everyone changes them or are even aware there is a difference. Some will tell you that they had no trouble leaving small block mounts under their big block but those who dont sometimes wonder why they had such a battle getting their upgrade engine to line up and wind up denting their firewall to clear the HEI.

That being said, the fact that there is a difference in frame mounts and there is a correct part for your application, I would suggest changing them.

-- Edited by Mike Ward MB on Wednesday 6th of March 2024 08:43:24 PM

HEI fitting in older than HEI GMs has been a firewall issue in all GMs, all xframes had same chassis mounts for all V8s. I dropped the 409 in place of the 283 in the 59 without issue. I doubt the engine mount changes the orientation forward and backward or you would then have an issue with transmission mounts.

On the 409, the engine mounts on the block are in the same place as on any V8, everything from there back is dimensionally the same for mountings bellhousings, transmissions, shift linkage, and zbar. The size difference between the 409 and sbc is forward of the frame engine mounts and wider at the valve covers/exhaust manifolds, that length at the front is about 2.5 inches and means you have a shorter front to back fan shroud.

Carl, did you use the 283 mounts with your 427 in the 66?

There was an issue with the driver side mount breaking in some 60s V8s, they was a cable added to keep the block from torquing up too far, the solution was a stronger mount. I can see that being done for a big block, adding strength to the mount, but GM would likely not have 2 different parts for bb and sbc? Better to have one?

My comments relate to B bodies, Acadian/A bodies frames and mounts are a whole other subject.

The part number check should answer this question on which engine frame mount is correct for each car.

So the small block ones I sourced are taller than the originals.
They sit on an angle, would the distance across from hole to hole not be different ?

I seem to remember looking this up in my parts book when I had trouble putting the drivers side manifold in. I think there were 2 different part #'s, but I also remember measuring the perches in the 454 Laurentian and they were the same as on that 69 chassis with the small block perches.

Prefectca wrote:

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seventy2plus2 wrote:

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I seem to remember looking this up in my parts book when I had trouble putting the drivers side manifold in. I think there were 2 different part #'s, but I also remember measuring the perches in the 454 Laurentian and they were the same as on that 69 chassis with the small block perches.

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 I know that the 1967 to 72 pickup trucks had different frame mounts for the big blocks. The big block frame brackets were a different shape to clear the exhaust manifolds. Perhaps some car manifolds are slightly different from year to year for clearance. 

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 68-70 B body big block exhaust manifolds are the same.  Passenger side manifold is same for A, B, F & X body cars, driver side is unique to B body to clear the power steering pump.