Hey all! I’m new to the forum and excited to get to know you guys and pick your brains. I am working on a build sheet for my 1965 Electra 225. I want to keep my original 401, but I want something a little nicer for cruising, since she is such a boat I am gearing towards fuel economy and comfort overall (she is going to be my road trip car). I currently have a 4L60E and a 10 bolt rear lying around I was thinking about using. It’s all in good shape. I was wondering how many people had tried this combo and the gearing you used. Also curious about the EFI self tuning fuel injection and if anyone has used that before? sorry for all the questions. I have never messed around with a nailhead before, but they are such fascinating engines. Thanks all!
When you say 10 bolt are you referencing a GM corporate 8.5? Your options are limited due to the factory Buick only 9 3/8” rear currently in your Electra.
That is correct. I have a complete 2003 Chevy 1500 just sitting around with a blown motor, so I already have what I need. I realize an adapter will be required but I have a full shop and access to a machine shop so fabrication of anything is no problem.
Is the width of this 10 bolt correct? Lug pattern? And will the brakes on that rear be compatable? Cant use just any ol’ rear axle assembly!
That is irrelevant to me. As I said I have full access to all machines and capabilities imaginable. I will have to narrow it slightly. Lug pattern will have to be changed but I am just going to buy some moser axels once initial build sheet is completed
Just buy the adapter it’s easier: https://www.ebay.com/itm/NEW-NAILHE...364-401-425-GM-4L60-E-overdrive-/132945125891 you will still have lots of fun fabricating the rear end, custom driveshaft length etc. Just run a 3.73 rear gear and with the 4th overdrive your nailhead will do 100 mph easy. Check the glovebox of the truck for the RPO code sticker which will tell you the gear ratio the truck has. Use a stand alone trans controller, easy peasy. You will have to move the crossmember but that’s easy. yes the Holley and other self tuning EFI are great! $700-$900 and self tuning. Stay away from Fitech in my opinion. This is my road trip car! 75 Regal with a roughly 340 HP Buick 350. I swapped the th-350 trans for a 2004R, same driveshaft worked, left the 2.56 gear. Tuned up Q jet and it runs perfect. It starts right up after 6 months of sitting and starts in -30 no problem. It gets 18 mpg so I don’t bother with EFI on mine. The reason I brought it up was the gearing. I was planning to swap the 2.56 gear out for a 3.42 but it’s so damn fun to drive at 120 mph at 2700 RPM! It’s fine off the line, the engine was built for torque using a mild cam.
Awesome! This is exactly what I was looking for! I was wondering where the best places to get engine rebuild kits and all that is? also does anybody have any experience putting turbos on these? I was wondering if putting a couple lbs on it would help. lastly I am considering machining an entire intake and using injectors from the 5.3 I have that’s blown up. Has anyone done that before?
I have a '64 with a 425 dual quad. I also wanted better fuel economy and better highway rpm's. I went with the bell housing shown in the previous post and a 4L60E. Instead of swapping out the whole diff I used a centre portion from a '64 Riviera bringing my gears from the original 3.07 to 3.23. Combine that with 255/70R15 tires and I have much better power off the line and I idle at 1750 rpm at 80 mph!
So is there any general consensus on what rear end gear work best for cruising mileage? It seems like everyone is using things all around the board. I’m tackling standard cruising at 60 mph.
No sorry. I think there are aftermarket options though if you cant find an original sway bar. Gearing and RPM cruise range depends on a few factors. I like to cruise at 80-90 MPH so my gar is geared accordingly. You'r cruise speed is 60 MPH so that effects the gearing for sure! The other main thing to think about is the engine performance range, my 350 makes great torque off idle and will pull the car around at 1600-2000 RPM in overdrive no problem. But if you had an engine that only made power over 3000 RPM (larger camshaft) you would want a higher cruise speed. My advice is to leave the trans and rear end alone until you have the engine running how you want it to. Once you have the engine performing how you want, pic your RPM range that you prefer and gear it accordingly. You may not need overdrive even. Without opening up the nailhead you could certainly add 4-5 PSI of boost and see a substantial gain! No need for an intercooler even for low boost levels. I wouldn't bother with adapting the full mutli-port 5.3 EFI onto the nail. You can fit injectors into a nail intake, custom make some fuel rails, but in the end you still need custom tuning to make it all run right. A lower cost option would be a self tuning TB EFI that can self or laptop tune with no extra costs. These work great for simplicity, and functionality. The past few years they have really came a long way! Some of the bolt on EFI are boost friendly. I would just run a small turbo on the passengers side, with a cross-over behind/under the engine to feed the drivers side exhaust to the turbo. Flowmaster makes a nice low cost 2 into 1 merge you could use. We used a 74 smogger 350 Buick on the dyno and it was bone stock, 120,000 miles and it did 160 HP to the crank. All we added was a blow through turbo carb and a $1500 turbo kit. It doubled to HP to 350 at the crank and attained 18 MPG in a 67 Buick Wagon. Then we worked on some higher end setups and saw 460 HP to the tires with still just 350 cubes. This was still a very mild build not much $ into it. It had perfect street manners and ran low 11s in the quarter with street tires. It had a 2004R 4 speed auto, 3.42 gear, and it cruised at 140 MPH easy. Attached is an article I wrote:
Does anyone know why that nailhead 4L60e adapter specifies using just a few years of truck or van transmissions? There are MANY years and models that had the bolt on bellhousing, including the early 2000s Trans Am unit I already happen to have.
