Hello,
Ive been reading some great advice. I need some input. I have a 68 Cutlass Supreme with the orig 350. I have a line on a rebuilt 455 and want to know what to expect if I swap the olds 350 for the olds 455. I also was wondering if there will be a header clearance problem. I heard the supreme engine mounts are offset and headers are not available. Any help would be greatly appreciated since I have defected from Chevy. The 350 doesn't have the hp/torque im used to from my BB chevelles.
Thanks,

 

Welcome, there are a great many wives tales pertaining to engine offsets and what headers will work on a Cutlass S. They are all BS and there are a great many threads relating to it. So, the normal header problems as far as fit apply to Olds just as Chevy, they are always an adventure.

Going from a SBO - BBO is a fairly easy swap.

Ok, with that said post some pic's when you get a chance.

 

It is a very easy swap. Use all from the 350 and you will be good.Be sure to use mounts meant for the 350. You need to upgrade the radiator. Also a T-400 would be the way to go. The 2 speed trans will be just OK. Also the rear end will keep you back, 2.56 or 2.78 will get you down the freeway just fine. 3.08 or 3.23 will make the world of difference.
Post pic's and let us know how you progress.

Gene

 

Welcome to CO!

What Eric said about headers. If Joe P finds this thread I'm sure he'll list the various other threads that put this myth to bed.

I agree with Gene on the trans and gear swap too if you're planning to drop in a torque monster. That will likely mean a new driveshaft too. Do you know what the gear ratio code is for your car? It will be stamped onto the Passenger side axle tube below the vent tube. Should be something like R8, RA, RC if an open diff, R9, RB, RD if posi.

If your car has it's original engine it's a 10.25CR 350 4bbl. What transmission do you have now? A 68 350 HC should put out a lot of snap. Might just need a good build to turn it into an asphalt melting monster again.

 

Thanks for the tips.
I will post some pics later. I already had the 350 trans rebuilt to handle 450hp+ so that is done. I was going to build but the parts availability for the olds 350 is pushing me to the 455. I want at least an honest 400+ hp/torque. I need to check on the diff but after the swap I will be adding the posi and changing the gear anyway in the 12 bolt (any suggestions). Just staying on the street but may hit the strip a couple times a year for fun. If anyone has a 68 Cutlass with a 455 it would be great to have the part number for some headers that I know will work. Im not a numbers matching guy but I would like to keep it olds and not go small block chevy.
Thanks

 

If you're changing to posi, you might have to go away from 12 bolt, not sure. IIRC it's getting much harder to find carriers for that.

2 CO members who deal exclusively with driveline and are EXCELLENT with their advice and offerings:
(monzaz)
Jim Mitschke
J D Race & Restoration
Muscle Car Differential Specialists
Richfield, Oh
1 330 990 8155
1 330 659 7117

(507OLDS)- the only contact info I have on him is:
Brian Trick
thetrickfamily@yahoo.com
Erie, Pennsylvania

 

Actually, despite what many motor mount and Olds restoration catalogs may say, for 1968, the 350, 400, and 455 all used exactly the same motor and frame mounts. Get Anchor P/N 2261 mounts if you need new ones - always a good idea when the motor is out.

Since others have already covered it, I don't need to add anything about the offset motors myth.

Just get headers for a 1968 442 with the 400 motor and they will work just fine.

 

Hey guys, thanks for the help. Please check out the info on the motor and give input. I'm not sure about the head numbers. How do these GA heads compare to the C heads? Do you guys know of any good olds crate engines out there that are reasonable? I'm in the process of selling my olds 350 to help out on the 455. Unfortunately is was rebuilt 3 years ago and was built pretty much stock but the hi lift cam installed and carb were huge. While it sounds lopey the thing has absolutely no punch off the line and you can smell the gas from running way too rich. To top it off it had a huge stall convertor I'm guessing 3000rpm. I cant even drive it like this. I have learned more from you guys in two days than I have searching for info over the net for the last year. Most people only know chevy!
Description



1972 Block I.D 396021F & "GA" Cylinder HeadsNew Speed Pro/SilverLite Performance Pistons 9.7:1 Compression and Moly Rings. Premium 92 Octane or higher fuel required.
New Melling Performance High Torque Camshaft & Hydraulic Lifters.
New Melling High Volume Oil Pump.
New Clevite/Michigan77 Mains & Rod Bearings.
New Edelbrock or Reman OEM Intake Manifold Included depending on intended application.
New Comp Cams Double Roller Timing Chain with Sprockets.
New Victor Gaskets.
New Rocker Arms.
New Exhaust Valves and Seats.
Three Angle Valve Job.

 

396021 F is the proper 455 block code for your engine. The GA heads are the proper ones too.

9.7:1 is quite a bit higher CR than OEM which was 8.1:1

 

He is changing to silvalite/KB pistons, or has already been done.

Gene

 

Very nicely done, Allan.

 

Hey guys,
I have a question. I took out the ac but when I take out the 350 and drop in the 455 what brackets can I use. Can I use the alternator brackets, power steering brackets, and pulleys from 350. Also been reading on engine info. Thanks Joe P. Also thanks for all other input.

 

Far as I know you can transplant the brackets and pulleys straight across to the 455. I would put in new motor mounts though.

 

You can use all the brkts. from the 350. The pulleys also, if the water pumps are the same length. If you go with a new water pump, make sure it is the same length as the pump on the 350. New mounts is a great idea. If you are going with headers, get them for a BBO.
The BBO will improve your performance, be sure to check your rear end ratio, for a gear change from say 2.56/2.78 to a 3.08 or 3.23 will be even a bigger improvement.

Gene