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Olds increased the deck height of the 371 and 394 to accommodate the long stroke after the 303 and 324, so obviously the 371/394 is somewhat wider than their earlier first-gen counterparts. There were a slew of other differences between various years, but in terms of actual fitment, how interchangeable are the 371 and 394 in cars that came with 303s or 324s? They all use the front cradle mount and ear mounts on the crossmember, but in terms of width, exhaust manifolds, etc., has anyone put a 371/394 in a car where a 303/324 once resided and what issues if any arose?
Years ago this was a very popular swap .
A 300 plus HP 371 or 394 in a relatively light '49 thru '56 two door made for a very potent "sleeper " .
The biggest problems are probably in the exhaust . 62 thru 64 exhaust manifolds may have trouble working in early chassis .
Early Hydra -Matics will bolt to 371/394's . But the crank must be drilled for a pilot bushing and the flywheel must be offset balanced .
Years ago this was a very popular swap .
A 300 plus HP 371 or 394 in a relatively light '49 thru '56 two door made for a very potent "sleeper " .
The biggest problems are probably in the exhaust . 62 thru 64 exhaust manifolds may have trouble working in early chassis .
Early Hydra -Matics will bolt to 371/394's . But the crank must be drilled for a pilot bushing and the flywheel must be offset balanced .
Charlie, thanks for that great insight. My thought was the biggest issue would be the left exhaust manifold, which is definitely different than the earlier manifold. Since the right exhaust manifold from the earlier style has the "pass through" blocked off for the duals, the 394 manifold has the same setup. I wasn't sure if the extra width of the 371/394 posed a major fitment issue in the 49-56 body
thanks for the information.I'm fitting a 1961 394 into my 54 Super 88 with the original 1954 hydra-matic . It looks like the driver's side of the engine has no room for a custom exhaust application to the 394 due to the brake booster and steering shaft and box taking up the area.
My search for a driver's side manifold continues.....
Last edited by 394 Guy; October 28th, 2020 at 08:30 PM.
One other note ;
Use your '54 lower bellhousing and starter . The '61 flywheel was smaller and the starter was in a slightly different place .
You will have to add a large weight to one side of the '54 flywheel to make it match the " imbalance " of the '61 flywheel .
You will need to get the whole rotating assembly balanced .
I've been looking for some where in my pile of papers a list of what it takes for that swap, more than you would think as I remember. I have helped in a swap in a 55- 394 a long time ago and it was very doable but it evolved more than we thought at the time. If I find it I will post it here.....Tedd
I've been looking for some where in my pile of papers a list of what it takes for that swap, more than you would think as I remember. I have helped in a swap in a 55- 394 a long time ago and it was very doable but it evolved more than we thought at the time. If I find it I will post it here.....Tedd
Hi Ted, I was wondering if you found that list yet. My 324 needs an overhaul after 67 years. I was offered a refurbished 394. Just doubt whether I will start it, price is the same as the complete revision set at Kanter (including shipping and VAT).
Hi Ted, I was wondering if you found that list yet. My 324 needs an overhaul after 67 years. I was offered a refurbished 394. Just doubt whether I will start it, price is the same as the complete revision set at Kanter (including shipping and VAT).
Keep in mind that if you do go with the 394, even though it is a fresh engine, it will still have to be torn down completely.
Because the crankshaft needs to be drilled for a pilot bearing. and to re-balance the engine after weight is added to one side of the flywheel.
You may be better off re-building your 324.
I think overhauling the 324, adding a newer aftermarket camshaft, Oversized pistons would be much easier. Parts needed to transplant the 394 would be much harder to find in Netherlands.
I put some pictures in a earlier post https://classicoldsmobile.com/forums/vintage-oldsmobiles-63/swap-engine-169715/#post1479899
It would be a temporary fix for me. To take my time (I'm not a car mechanic and most parts are hard to find here or for a much too high price, but if you really need it, no price is too high) to overhaul the 324 and put it back. But I understand that adjustments have to be made, which have to be undone in order to put the 324 back.
If anyone is interested, this engine is still for sale near Gouda, the Netherlands
August 24th, 2020, 01:01 PM
