'79 Cutlass; SBC 305 --> Olds 425

[DRIVEN]

For a long time, I had been planning on doing a 403 swap but now I've decided on a 425 instead for several reasons -- those reasons aren't really the point of this post. I've been trading emails with a guy about 3 hours away who has a '67 longblock with C heads, an intake (not Toro), oil pan, and filter adapter. I'm concerned with the best options to make it look like a factory install in a car that originally came with a 305.
-Would it be in my best interest to looks for an Olds powered donor car for all the supporting pieces? I know I'll need to get a driver's side battery, Olds motor mounts, accessories and brackets for an Olds, Olds spec AC compressor and hoses, wiring harness. Anything else?
-Would Olds W and Z exhaust manifolds fit without clearance problems?
-Will a Performer intake with a Qjet and stock air cleaner fit under the hood? Any other intakes that would be better on a stock 425?
-If I can't come up with the "correct" Quadrajet for an Olds 425, are there any other applications that seem to run good on the Olds? I have a Cadillac 425 carb but suspect it's probably calibrated pretty lean.

The engine I'm considering was supposed to be a runner when it was pulled so I'm not planning much more than a cleanup and reseal with rings, bearings, timing set, and head refresh. I'll likely reuse the cam if it looks fair. This car is 99% cruiser and won't be seeing strip duty. I plan to have my 200-4R upgraded to handle the added torque but will likely cross my fingers on the 7.5" and probably pick up some spares.

I welcome any input and suggestions. Thanks in advance.

 

[Bar50]

I put a 455 from a Toro in an 84 Cutlass. I used the Toro manifold on the right and a typical 455 manifold on the left. I used Olds 307 frame mounts/stands. When I built the car around 15 years ago there were no W Z manifolds to be had for less than a small fortune. Mine has the Toro pan, intake and Q-jet. I added a one in nitrous plate and it fit under the hood.

Mine has a TH350 and a 3.73 posi from a Monte, I still have it, but the motor is done. The Teflon lined timing set let go and clogged the oil pick up. I have an Olds 403 to swap in...a tree fell on the car in an ice storm....kinda stopped progress on it since.

 

[DRIVEN]

Thanks for the intake height info. Did you use the 307 accessories and brackets too? I know there is a deck height difference from small to big block.

 

[Bar50]

I used the 307 stuff, it just took longer belts, I know I kept the G-body power steering pump.

 

[L92 OLDS]

For a long time, I had been planning on doing a 403 swap but now I've decided on a 425 instead for several reasons -- those reasons aren't really the point of this post. I've been trading emails with a guy about 3 hours away who has a '67 longblock with C heads, an intake (not Toro), oil pan, and filter adapter. I'm concerned with the best options to make it look like a factory install in a car that originally came with a 305.
-Would it be in my best interest to looks for an Olds powered donor car for all the supporting pieces? I know I'll need to get a driver's side battery, Olds motor mounts, accessories and brackets for an Olds, Olds spec AC compressor and hoses, wiring harness. Anything else?
-Would Olds W and Z exhaust manifolds fit without clearance problems?
-Will a Performer intake with a Qjet and stock air cleaner fit under the hood? Any other intakes that would be better on a stock 425?
-If I can't come up with the "correct" Quadrajet for an Olds 425, are there any other applications that seem to run good on the Olds? I have a Cadillac 425 carb but suspect it's probably calibrated pretty lean.
.

Q: Will a Performer intake with a Qjet and stock air cleaner fit under the hood? Any other intakes that would be better on a stock 425?
A: A performer RPM intake will not fit but a performer should with the right drop base air cleaner.
Check out the RPM pic below....not what you want unless you have a hood scoop. I came across a real W30 intake that I was planning to use but was offered stupid money for it and sold it for a handsome profit.

Q: Would it be in my best interest to looks for an Olds powered donor car for all the supporting pieces?
A: Yes, look for a complete set of accessories from a late model 307 powered Oldsmobile. IIRC, some minor mods to head mounts on AC side is required due to taller deck on BBO.

Q: Would Olds W and Z exhaust manifolds fit without clearance problems?
A: Yes. I have a factory set and mocked it up on a 455.

Q: If I can't come up with the "correct" Quadrajet for an Olds 425, are there any other applications that seem to run good on the Olds?
A: Look for a late model 800 cfm Q jet. You can change primary jets and secondary metering rods for your application. These came on a variety of Olds motors and all 403's. You can find them on e bay and the forums.

 

[olds307 and 403]

That 425 Cadillac carb should be 800 cfm and passable, a reasonable starting point. The R4 compressor never came on BBO cars, you actually have to add about an inch onto the brackets due to the taller deck. You need a 2" filter and a drop base to clear under the hood.

 

[DRIVEN]

Good info, guys. Looks like I'll probably be farther ahead to just keep an eye out for a complete 260/307 donor car. I've been doing quite a bit of cross-referencing part numbers on Rockauto but that only gets me so far.
-The radiators are the same part number. Are the Chevy and Olds fan shrouds the same?
-Would I likely notice any performance difference by using the lower profile Toro intake?

 

[MrSony]

Good info, guys. Looks like I'll probably be farther ahead to just keep an eye out for a complete 260/307 donor car. I've been doing quite a bit of cross-referencing part numbers on Rockauto but that only gets me so far.
-The radiators are the same part number. Are the Chevy and Olds fan shrouds the same?
-Would I likely notice any performance difference by using the lower profile Toro intake?

everything I've seen in junkyards and on the net, g body olds shrouds are shallow and angular, like half octagon shape, and everything else is round. The mounting holes are the same though. Generally low profile intakes create more torque than horsepower. Taller, longer runners = higher peak hp.

 

[Texas82GP]

Chevrolet condenser has outlets on the driver's side. Olds. condenser has outlets on the passenger side.

 

[Texas82GP]

Also, if you want to use a stock style air breather, you will want one off of a 307 car. It will have provisions for the crankcase breather on the driver's side (Chevy is on passenger) and the 'arm' or 'panhandle' points to the driver's side, which you will need since the A/C compressor and hoses will be in the way of the air intake duct on the passenger side.