I'd like to know if swapping the original 6 cylinder motor in my 1948 model 66 for a 1948 straight eight motor is an easy thing to do. Will the motor mounts match-up and will there be trouble with the radiator clearance and tranny hook-up? I'm trying to keep this car as vintage as possible but I'd like to install the 8. I've never done a job like this before but I'm pretty good with a wrench. Thanks for any advice.

 

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If you've never done an engine swap it can be daunting. It is most easily done by removing the grille and everything behind it to and including the radiator to get at the engines. Some would even suggest removing the front outer and inner fenders. Of course an engine hoist of some kind is required but they can be rented. Just be sure to get a heavy duty unit. Hand tools can be used but air or electric make the job easier. Expect some rust, possible rounded bolt heads or broken off bolts.

But don't buy and engine or turn a bolt until you do your homework. Ideally you would have access to a 1948 model 68 to do measurements to compare to your model 66. If you don't read on:

Virtually all of the parts that would affect a swap from a 6 to a straight 8 in your car have the same part number including frame, frame cross members, radiator, radiator core support, driveshaft, transmission, clutch housing (with a std. trans.) and front and rear motor mounts.

After looking all that up, I'm left wondering how Oldsmobile accommodated the different engine lengths within the same wheelbase, same motor mounts, same transmission and driveshaft, same core support and radiator and even the same fan shroud.

That is something for you to solve by getting engine length measurements from an 8 cylinder engine and comparing them to your six cylinder engine length. I looked on the Internet but could not find any data relating to engine block length.

Other important comparative data points would be distance from radiator to front engine mount and from front engine mount to rear engine mount/transmission mount for both 6 and 8 cyl. what that would show is if Olds put those cross members that support the mounts the same distance apart on both 6 and 8 cyl. cars. ( even though these parts have the same number doesn't mean Olds put them in the same location along the length of the frame).
Good luck if you decide to undertake the swap.

Finally, if you haven't found it subscribe to the thread under this forum titled 46-48 How Many Have Them. People with information on these years hang out here and you might find some good information and helpful people.
Jerry

 

I own a '37 L-37 with an Eight. On the '37s, the frame and wheel base is longer, and the fenders are further forward to accomodate the extra length of the 8 engine. The engine is substantially longer. Other than the fenders, no front sheet metal interchanges between the 6 & 8 on the '37s.
The other thing I can tell you is that engine parts for the straight eight seem infinately tougher to find than parts for the flat six.
If it were me, I'd leave it as built, but then I am also a purist.
Jerry

 

Thanks guys for the replies. I'm going to re-post this to the "who owns" thread. Someone must have done this already, I'm thinking.
As it is, the six was supposed to have been rebuilt but it sat for years and is stuck. I tried to free it by all the conventional means but it is really tight. This, plus it is missing ancillary parts. By the time I pull it from the car and spend time and money on parts and who knows what else; it could be a can of worms anyway. I can do this if I just get some advice on the match-up.
I have all the tools: Hand, air, mig welder, etc. Ive even got a chain-fall in my garage. But the beams might not take the weight.

 

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Hi Jerry, By 1948 the wheelbase was the same (119 in.) on both 66 and 68 models. I neglected to mention that in my reply. I think I listed the other parts that were shared between 66 and 68. That is what makes it somewhat puzzling as I'm sure you are correct in the 8 being a longer engine than the 6. I am left thinking Olds must have designed the chassis for the 8 and made some changes to the 6 to get the proper relationship of fan and radiator for effective cooling.

I appreciate those who restore just as much as those who modify. To me either direction is a valid personal choice.
Jerry

 

In my 47 66 the radiator support to move it up is already there just have to remove the second part of sheet metal to the radiator top support pan

 

I guess I'm confused. Do these last replies indicate that the engine swap would work?
I've almost considered dropping in a V8, but I am not experienced in this either.
what am I to do?

 

It will definitely work the 66 & 68 model r identical the only difference is 66 has the six straight & 68 has the 8 straight. If u choose to go with a v8 please contact me I will be interested on buying some eight straight parts from u