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.
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
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72 Nova SS, 66 Beaumont Sport Deluxe, 09 Pontiac Solstice GXP Coupe
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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cutting a roof off a four door is NOT a convertible.....
65 Parisienne convertible.one of 49 built for RHD export market,402BBC, T400, 2500 stally, posi rear, upgraded brakes with front discs, FUEL FAST efi custom built by me.
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.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
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
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72 Nova SS, 66 Beaumont Sport Deluxe, 09 Pontiac Solstice GXP Coupe
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)
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.
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63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC. 1963- Pontiac top selling car in Canada
Mahone Bay, NS Still not old enough to need an automatic
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)
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
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.
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63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC. 1963- Pontiac top selling car in Canada
Mahone Bay, NS Still not old enough to need an automatic
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 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.
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.
