OK, I'm going to put a 401 into my 66 Skylark. I understand that I need some special parts for this swap. I was told I'll need special motor mounts, oil pan and exhaust manifolds. Anybody have any pictures of what I need, so I know what I'm looking for? Or a good description? Thanks, Dan :3gears:
401 swap Hi, guy, I did this swap a loooong time ago. You will need a rear sump oil pan and the pick up tube to the oil pump. The pick up is kind of hard to find but I understand carmen faso has them and TA perf. You will need the adapter plates the factory made to make the motor mounts work . In a pinch You can make these out of 1/2" hot rolled steel . You will need the 401 motor mounts. Dont throw your old 401 mounts away because You may need to get them rebuilt. You will need a transmission, Personally I went withe the switch pitch th 400 from a 66 big car. [ use the short tail shaft type] [easier swap&handles torque well] You will have to change the front drive shaft yolk , and get a custom drive shaft built because of the lengthis different and the factory two piece,rubber jointed shaft that you have now wont handle the power of a 401/425. You will need to change starters . [ use the short nose starter for a 66, the old long nose will hit the bell housing before it will bolt up. You will need at least a 3 row or better yet a 4 row radiator or you will have heat problems.Also a 7 blade fan and shroud. [a 401 puts out a lot of heat] you need the special GS exaust manifolds and the heat shield that goes with them for the starter side. The starter cables will be different. [longer] The colom shift will work. You will need to change the rear cross member for the trans or modify the one you have and move it back about 6 '' or fabricate one. The 401/425 weighs 640 lb so you really need to change the front springs for G S front springs. also put air bags inside the rear springs or you will have severe wheel hop.[air lift] IF you havent bought the engine yet and you can find one go ahead and get a 425. Use heavy duty shocks. use heavy duty u joints. use metallic brake linings. If you put a big truck battery in the trunk over the rt rear wheel, it will balance out the car. you WILL NEED a posi. Dont let this list scare you off, when you look at it there are a lot of things that you can do ahead of time to prepare for the swap. When you know what is coming up ,then you dont have near the hassel that you have like I did by just doing it cold turkey ,with no one to advise on these things. When the car is finished it WILL be a beast that will have corvettes for breakfast. good luck and enjoy the ride.The results are well worth the effort.
66 Slylark GS parts Dan to bad you live so far away. This spring I will be parting a 66 GS with most of the parts you will need. I do have a complete set of under hood wiring for a 66GS that I had on the board a while back. I was asking $40.00 plus shipping. This was from another 66 I am parting. Here is a picture. By the way Doc did a very nice job of listing the things needed to do this swap. Thanks Bill Sangster.
Bill, Hi - remember me! I still haven't used those mounts yet! But did track down a set of GS manifolds. I may be interested in that wiring. Do I really need it all or can I adapt the 225ci wiring? I was thinking of getting a full new rewire for the car so I can hide all the wiring from the bulkhead and make the install look very pretty indeed. What do you think? regards Nick
Nick, nice to here from you. Not sure if you need all the wiring. I have never put a 401 in a Skylark but the battery and starter are on the other side on a 401 and if you are buying a new set of wiring better get it for a GS. Thanks Bill.
I have a rebuilt ST-300 trans left over from my GS, I installed a used trans and had the one originally in the car rebuilt. I'm into it for around $250 in parts, so that's all I'm asking. No torque converter, but Buick535 on this board has some good converters and good prices. I bought the drum assembly from him after seeing mine was grooved up badly.
I haven't seen anyone say anything about using a ST300 with the 401. My transmission man says the ST 300 is stouter than a powerglide, and if you race at all, you know what they do with those, with mods I understand. I'm going to try it. I do love the switch pitch idea. Russ has all the parts for this swap, so he says. Thanks for guys like him.
Hi, DId the same conversion a few years ago on my 65 lark, along with converting to a stick which was worth the cost of the parts to do so, Believe Doc covered most items, also if have to remake the adaptor plates you can also use a Chevy motor mounts (3-bolt) if you do not have the stock motor mounts and I have also hear of someone having mounts made by using big car plates that mounted to the engine and custom making the u-plate to fit the frame mounts. as for wiring harness I reused my 300 harness, had to lengthen a few wires and shorten the ones for the coil, either way not that hard, note 65 GS wiring harness has a large box that the positive battery cable goes to look at the factory manual may be different on 66 but just a word of caution but a good place to save a few hunderd bucks unless you have a donor Also note if you plan on running a 4 row radiator you will need a GS upper support or modify a 3 row one (ther is a dimple by the rubber that you can flatten out and it will work) Have you considered doing the manual trans route as it makes it real fun and now seems to be a little more affordable with the newer aftermarket bellhousings and linkages Good luck with the project you mak also want to check out 65gs.com for more info,
well the are other options also. for a trans eelco makes a adapter to run a chevy trans. my car has a gn 200-4r od with nailhead. ta makes a aftermarket set of headers i found a set used for 70 bucks. radiators you can use a aluminum unit from ebay or jegs there under 200 dollars. just depends on if your wanting a real stock looking car or just a nailhead engine and all modern stuff. i have about the same in my parts as you would all the stock parts. but od headers and aluminum radiator cant hurt performance or driveability.
I have raced the 2 speed and the disadvantage with it is when you come out of low gear it goes to straight 1 to 1 ratio....and the car loses punch half way down the track....whereas with the th400 when you come out of low, it goes to a intermediate gear and is still gaining punch at the half way point ..... If you gear the rear end low enough that the car pulls strong on the high end the low gear is a bear but does not last very long..... The best set up is a switch pitch th400 well built , and a 3.55 or 3.73 gear out back.... or for drag racing 4.11 gears.......
sorry to disagree with you but my 2-speed keeps on pulling from low to drive,dosnt miss a beat.takes 25 less hp power to run than a 3-speed,and is about 40 lbs lighter. plus a 3-speed just will add to more will spin off the line. hard to hook it as it is.
You have a point about the less power to turn and lighter weight.... but both transmissions have a low of around 2.48 to 1 and high is 1to 1.... but the intermediate gear spreads the power range out so the car has more oomph 3/4 way down the track....at least mine did....I am talking the same car, same diff gearing,,,, same tires....and when you throw a switch pitch into the mix the gear ratio changes dramaticly , making the car a real bear off the line and in second gear.....high is still 1to 1 in either case, but the switch pitch still makes the ''straight line'' ratio in high gear a lot lower in each gear.......
i agree on the switch pitch, with out it on a 2-speed would be a lot slower off the line. i leave mine on high stall till i go into drive. if in low stall when going into drive you can feel the load on the engine.
It may help if you go into low stall in low gear at about 3500-3800RPm's. Then back to high stall when going into high & back to low stall when you again get up to about 3500-3800RPM's. Not as much slippage & the MPH will almost definitely increase with less slippage.
thanks Tom i will do that. read some were it takes longer for the converter to go from low stall to high stall than from high stall to low stall.
