I can say for sure 67 68 B body big block towers are lower, can't say the same about 69 70 though. I can dig up photos of both sets side by side if need be.
ABC123 said
March 5th
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.
There are subtle differences between the small and big block frame mounts. In my Nova the big block was positioned slightly to the passenger side, slightly forward and slightly lower. These differences allow more clearance from the steering linkage, the master cylinder, the firewall and the hood.
The change showed itself at the transmission mount.
-- Edited by Mike Ward MB on Tuesday 5th of March 2024 10:26:21 AM
koolconvertible said
March 6th
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.
4SPEED427 said
March 6th
3955186 RH and 3977235 LH is the correct part number for 1969 Impala 350. I don't have a Pontiac parts book handy at the moment but I assume it will be the same as Impala.
1967 - 1969 Impalas use the same part numbers for 427 according to the Chevy parts book.
Mike Ward MB said
March 6th
koolconvertible wrote:
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.
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
seventy2plus2 said
March 6th
I've put big blocks into a small block 69 & 70 Canadian Pontiac chassis.
I'm sure on the 70 I put the exhaust manifolds on with the engine in the car without a problem, but on the 69 I couldn't get the drivers side manifold in without lifting that side of the engine about an inch. (The 69 chassis is under my 70 Parisienne)
DonSSDD said
March 7th
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.
4SPEED427 said
March 7th
DonSSDD wrote:
Carl, did you use the 283 mounts with your 427 in the 66?
Yes, it was as simple as bolting 283 engine side mounts onto the 427 and dropping it onto the frame mounts. (with the correct B body oil pan of course)
ABC123 said
March 7th
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 ?
DonSSDD said
March 7th
The taller frame mounts in the xframes were for the 6 cylinder, at least for the 235, not sure if the later 230-250 used taller mounts.
seventy2plus2 said
March 7th
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 said
March 7th
seventy2plus2 wrote:
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.
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.
seventy2plus2 said
March 8th
Prefectca wrote:
seventy2plus2 wrote:
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.
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.
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.
seventy2plus2 said
March 8th
It looks like that cleaned up perch doesn't have the tube through it for support.
-- Edited by seventy2plus2 on Friday 8th of March 2024 04:51:23 PM
ABC123 said
March 10th
seventy2plus2 wrote:
It looks like that cleaned up perch doesn't have the tube through it for support.
-- Edited by seventy2plus2 on Friday 8th of March 2024 04:51:23 PM
I was cleaning up the original engine to frame mounting blocks and of course, more high torque damage.
I know where I can get a set of a 1969 350 car but are they the same ?
I can say for sure 67 68 B body big block towers are lower, can't say the same about 69 70 though. I can dig up photos of both sets side by side if need be.
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.
https://www.chevelledepot.ca/chevelle-malibu-big-block-engine-conversion-kit-1964-1967
Had to do the same changes to my 72 Nova for a big block conversion.
https://www.chevelledepot.ca/engine/engine-mounts/engine-frame-mounts-brackets/chevelle-engine-frame-mounts-small-block-1964-1967-401949
https://www.chevelledepot.ca/engine/engine-mounts/engine-frame-mounts-brackets/chevelle-engine-frame-mounts-big-block-1966-1967
There are subtle differences between the small and big block frame mounts. In my Nova the big block was positioned slightly to the passenger side, slightly forward and slightly lower. These differences allow more clearance from the steering linkage, the master cylinder, the firewall and the hood.
The change showed itself at the transmission mount.
-- Edited by Mike Ward MB on Tuesday 5th of March 2024 10:26:21 AM
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.
3955186 RH and 3977235 LH is the correct part number for 1969 Impala 350. I don't have a Pontiac parts book handy at the moment but I assume it will be the same as Impala.
1967 - 1969 Impalas use the same part numbers for 427 according to the Chevy parts book.
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
I'm sure on the 70 I put the exhaust manifolds on with the engine in the car without a problem, but on the 69 I couldn't get the drivers side manifold in without lifting that side of the engine about an inch. (The 69 chassis is under my 70 Parisienne)
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.
They sit on an angle, would the distance across from hole to hole not be different ?
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.
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.
It looks like that cleaned up perch doesn't have the tube through it for support.
-- Edited by seventy2plus2 on Friday 8th of March 2024 04:51:23 PM
Optical illusion
If you look in pic #1 you can see it.