Well guys I am new to the Classic Chevy scene and I am looking for some advice. I just bought a 63 C-20 with a 292 L6 that runs pretty good (smokes a little needs new valve seets) but is not much faster on the top end than the speed of smell. Keep in mind that my last build was a 76 Scout II that I put a 400 small block in and had way to much power. The top speed is about 50 mph in the truck and I know that it has the Eaton rear end and a granny gear 4 speed (not sure yet as to which model). My question is if I am wanting to do say 60-65 without turning 4500 rpm would I need to swap out the rear end or the tranny. I am also considering converting the susp. over to a 1/2 ton set up. Any help for the noob would be appreciated.
Hi, welcome. you have a few options and it all boils down to gearing. all older transmissions will typically have their highest gear in a 1:1 ratio. in the 80's chevrolet introduced the overdrive tranny with a .8:1 (not positive on the exact numbers) typically 5 speed standard or 4 speed overdrive (700R4). this is an excellent swap to get more speed & better mileage and can be done by the average mechanically inclined individual over a weekend. (spend a night & read previous posts for more information on parts, installation etc.) Rear end: as your truck is a 3/4 ton (20 series) the rear end is probably very low for hauling loads, probably in the mid 400 ratios. Unless you plan on staying original or using your truck for a tow truck (or drag racer) you will want to swap these gears (or rear end) out for a more user friendly gearset... I would aim for a 3:42 or 3:73 gearing (typical C10 set up). This will give you more speed & lower cruising RPM. Depending on your transmission you may opt to change both tranny & gears! On a side note, the 292 is a cool, rare motor that made GOBS of torque but not much horsepower. check out this website, it will make you want to rebuild that 292! my truck was an original C10- 292 truck, I swapped in a 350, 700R4 tranny with the original 3:73 rear end but I kept my 292 in hopes of one day rebuilding it... I cruise on the hwy at around 2000 rpm. I hope this helps.
Which axle do you have? Is it the 12 bolt? On the twelve bolt axle to go lower numerically than a 3:73 you will have to change the carrier. A five speed or 700R4 is a good option.
Starting Point Well after pulling the head off and finding some pretty nasty scarring in the pistons. I have decided to put a 350 small block in it. Keep in mind that the head needed redone, intake had hole in the heat exchanger, and the exhaust manifold was leaking. Taking into account the cost of rebuilding it I opted for the SBC. I think that this may help my top end a little bit. Well now I have the problem of mounting my my small block between the framerails. I had the original 292 and the mount on the driver's side looks like it will fit, but the passenger side is too far foward. I have seen some mount kits online by cpp, but I wanted some advice on these before I shelled out the cash. Also I plan to keep the 4 speed granny trans for a while at least. Any advice would help out this noob. Also what headers are you guys running that have done this? Thanks.
Also the axle is I believe an Eaton, looks like a 9 inch on steroids. Not sure of the gear but I am sure it is pretty low. Also is the 292 a rare or desirable motor, just want to know before it goes in the scrap heap.
If better cruising speed is the goal ?? Ditch the Granny 4 speed !! The rear is "probably" a 4:11, ( or 3:70 ). If it's a 3:70 you can leave it if you decide to go with an over drive trans , like the 700 r4. The left motor mount will work, but the right needs to be replaced with a V8 mount. The aftermarket mounts should work fine. http://www.persh.org/pickup/perches.htm I would Craig's List the motor to see if anyone bites. The 292 is a favorite among the inliners... dv
What rear end would be the best to replace the eaton with? I found some paperwork from the PO which said it has a 4.57 gear in it. I would eventually like to swap it over to 1/2 ton running gear. I can fabricate the needed hardware such as the trac-bar and spring perches so that is not too big of deal. Also I am planning to run air suspension so the springs will also be swapped out. Thanks for all the help.
If your are looking for good gas milege or highway speed then you'll have to ditch the 4.57. It probably goes like hell til you hit 60 mph. I would go with 3:73 gearing. You can keep the carrier, you can tow and will help with the RPM's. Look at also doing a 700R4 or 5 Speed swap to help the rest of the way. Personally I would reccomend the 700R4 swap. It was the best money I spent on my truck. Also the is a huge car show and swap meet a Daytona Speedway this weekend.
