i was poking around on ebay for "olds 350' parts or whatever might be on there and was amazed at the amount of engine parts listed for sale that will fit both 350 and 455. timing covers, waterpumps, oil pumps, distributers, cams, oil pans, etc. so my stupid q is: are these just a bunch of lazy a**holes listing their parts or are there actually a lot of interchangeable parts between the two motors?

lol should make for an interesting discussion even if it is a dumb question!

 

all the parts that you listed are interchangeable between the 2.
You can even put big block heads on the 350, and vice versa. It will mess with compression ratios however.

There ARE exceptions.

Small block and big block intake manifolds are different widths.
There are 3 different water pump snout lengths.
1977 and later motors use different size head bolts
Push rod lengths
lifter bank angles
Computer controlled distributors
Diesel 350's

Feel free to chime in with more differences.

 

Just to expand a little on the explanation, the big block and small block Olds motors are the same basic design. This is unlike the Ford or Chevy big and small block families. The primary difference is in the deck height; the BBO has a taller deck to accommodate the longer stroke. The big block also has larger main and rod bearings, due to the higher loads, so the crank doesn't swap (diesel motors are the exception). As noted previously, the BBO and SBO have different head castings, due to different port sizes, but the heads do physically swap. The taller deck results in about a 1 1/2" difference in intake manifold width (though some SBO intakes work on BBO motors with spacers). The distributors all interchange (including the CCC unit if you choose to run your BBO on the computer). Pushrods are obviously different lengths, but the cams interchange. Larger displacement will make a given cam act less "radical", however.

The oil pumps interchange. The oil pans interchange but are different. As noted there are three different water pump lengths, but usage is related to chassis and A/C or non-A/C, not big or small block. There are two different flywheel designs due to differences in the crank flange bolt pattern - 64-67 and 68-90. This is based on date, not engine size.

And most importantly, THE MOTOR MOUNT BOLT HOLES ARE IN THE SAME PLACE ON BOTH BIG AND SMALL BLOCKS.

 

pays to ask q's of people that know their sh*t! any chance the boltup for the th400 going behind my 455 will drop in the same as the th350 it will be replacing?

 

If your th400 has a 6 inch tail shaft, it will physically bolt right in.
I think you will have to have your drive shaft modified for a th400 yoke however.
I think the tail shaft spline count is different. 32 and 27 comes to mind.
Also, the 400 doesn't use a detent cable like the 350. It uses a kickdown switch.

 

J-(Chicago) is correct, the TH400 yoke is much beefier than the 350 or any other trans that will fit. To add some clarification, the 400 and the 425 engines also fit into the discussion of interchangability. Again, caution is advised due to different spread angles of the blocks depending on year and usage (Toro vs. others).

 

so if i come across a th400 with a tailshaft length other than the 6" that i need, can i scavenge a 6" shaft from a junkyard and swap? or do i have to hunt down the correct tranny?

thanks everybody for the continuing information help with my project!

 

Well if you have a reason to get down to Southern Oregon I just dismantled a 1971 Delta 88 with a 455 and TH400. I've got all the parts. John

 

It's not as easy as changing tail shaft housings. The output shaft is only splined enough to accommodate the yoke. If you put a 6'' housing on a 9'' trans, you would have a 3'' bald spot sticking out on the output shaft.

You can use the longer trans if you have your driveshaft shortened, and move the crossmember to the correct location if need be.

 

Newbies,

Joe's not screamng at ya, He's just answered this question about 50,000 times on 50 different boards, blogs and forums.

And tomorrow someone will most likely ask about it again.

 

Actually, I was..

 

Well once again I genuflect to Mr. P and stand corrected.

 

I have a 73 or 74 long shaft T400 that you can have for a song. Im in Port Orchard but travel north to your neck of the woods monthly.

 

TRDBRD: that would be great! I "borrow" my wireless internet signal from the neighbor and havent been successful in getting a message out to you personally so i hope youll see this one. ill keep trying though. thanks

 

Is a TH-375 out of a 73 Delta 88 gonna be a long or short tail shaft? I can get one cheap but don't know if it'll work in my 65 Cutlass and I have a nice TH-350 lined up with torque converter, kickdown cable, bracket etc out of a 67 Firebird for 100 bucks more and I know it's good, but considered picking up the TH-375 since it's a deal, but they seller doesn't know and the car is around 100 miles away.