I have the stock 2 bbl on my 425 and I was thinking of putting a 4 bbl up there. any suggestions for good options and also things to stay away from would be great. What do you guys think of holley?

 

good carb . I have used the edelbrock 750 man choke and very easy to work on and tune jmo

 

I would go with electric choke for whatever carburetor you get. The cheapest swap would be to go with a stock cast iron intake and Q-jet. Of course a Q-jet would probably have to be rebuilt.

You might check out the new Summit carburetor. There was a recent post by Joe Padavano that talked about that carb.

http://www.summitracing.com/parts/SUM-M08750VS/

 

I think a stock intake with a Q-Jet would give you more power, but if you are starting from scratch you need to decide if you want more power or MORE POWER.

Q-Jets are touchy to adjust; it always struck me as more of an art than a science. Like anything else they run well when they are set-up right, but they don't seem to stay that way for long.

If you go for the MORE POWER route then consider increasing your braking power. I never had any problem with getting my 67' 98 up and running, but trying to quickly stop 4500 pounds with four drum brakes was always interesting.

If you don't have front discs then please factor a swap in that area into your final costs. Someday you will need them.

 

I'd have to wonder just how much more power you will get from that motor simply by changing the intake and carb. I'd have to think that exhaust (likely single?), compression (high or low comp 425?) and cam profiles would be limiting factors regardless of carburetion, and that simply adding more CFM wouldn't necessarily make much difference.

Maybe you'd get more of a "punch" when the secondaries kick in, but little else?

 

high compression. single exhaust stock everything. I'm sure there are many who have done this. If you have what are your thoughts? was it a successful operation or should I keep the two barrel for a while longer?

 

I have done the 4bbl swap from a 2bbl and also put duals on a 66 Delta, HC 425. The biggest seat of the pants increase came by adding dual exhaust. The 4bbl carb in my opinion did little till after 40-50 MPH.

 

My first car (daily driver) was a 66 Delta conv with drum brakes and single reservoir master cyl. I knew nothing of disc brakes or dual master cylinders. The car stopped just fine and I never crashed nor know of a rash of crashes due to a failed master cylinder on the 60's GM cars. I drove this car for 10 years and did "hot rod" it as kids will do. While disc brakes would probably be an improvement it, I dont feel they are necessary for a weekend cruiser classic car.

 

when you did the dual exhaust did you use the stock manifolds or upgrade to headers? also I know there is a clearance issue with the driver side header due to the rear power steering pump. Can that be relocated to the front of the engine (would have to make custom brackets) and driven off the serpentine belt?

 

Mine has a "newer" dual reservoir master cyl. and drum brakes. I'm not planning on doing anything extreme with the car or brakes so I think they'll work for now.

 

The left side manifold or S manifold is reproed and that is what I used. There are no headers off the shelf that I am aware of for these cars. The problem with headers is the frame mounted steering box not the pump.

 

Do you have an underbody picture of where you routed the pipes? I'm assuming that the 67 and 66 are similar underbody. let me know if i'm wrong.

 

With the S manifold and the RT side crossover port plugged as the factory did the stock dual exhaust piping can be used. I do not have a picture but the factory shop manual will show all. The only thing is that the column shift automatic linkage on factory dual exhaust cars is slightly different so as to clear the left header pipe. A diagram of this used to be posted on the 442.com site, how to modify or create this part. A muffler shop can make the pipe so the original linkage can be used.

 

thanks for all the info. Once I get around to this I'll post some pics.

 

Thornton makes reproduction dual exhaust manifolds for the B and C body. Here is a link:

http://thorntonmusclecars.com/produc...aust-manifolds

 

thanks. that will help a lot. Luckily I have a welder friend with a head full of fabrication knowledge to help with the pipes. hopefully he'll take sub sandwiches and pizza as payment.

 

I just added the duel exhaust to my 69 - 98 convertible and bought both manifolds from Thornton's. With the crossover pipe you will either need a new passenger manifold or simply put on a block off plate. One more thing to check is the linkage from the column shift to tranny. It needs to be the curved one and not straight as the exhaust pipe will run right past it.

 

I suggest having a good welder plug the crossover hole in the passenger's side exhaust manifold. If you use a block off plate with a gasket it might leak eventually.

 

What years and engines can I take the drivers side manifold off of for my 67 delta 88 w/425? I have the salvage yard guy looking to see what he has but he doesn't seem to know exactly what I need.

 

Well if you dont know what you need how should the junkyard guy know? The drivers side manifold for duals or the S manifold is very rare as few (optional) dual exhaust systems came on factory 65 to 70 BB B bodies. Majority of S manifolds came on the 66 and 65 Starfires as they were dual exhaust cars. The cances of finding this manifold is slim in a junkyard.

 

I said I needed a drivers side manifold from a late 60's oldsmobile big block with dual exhaust and he said he'd go get one and have it in the shop in two days. If it doesn't fit I can take it back but I'd rather know before I try.

 

Ok but you should have said you needed a fullsize Olds left side dual exhaust manifold from a 65 to 70 with factory dual exhaust and a big block. Then the yard man should have said wow,I doubt I have or can find one but I would look anyway and if one cannot be found you can get a repro from Thornton.

 

haha. Perfect. Thanks. When/If he calls to say the part is ready or can't find one(this is most likely) I'll let him know. thanks.

 

Moved thread because of all the posts and interest in the subject.