Hello Everyone, I'm a new member and was hoping to get some help with my 1951 chevy project. Let me start by saying I got my truck partially assembled and so there are some areas I'm not fully certain I have all the parts needed to complete the project. I have the assembly manual for 1947-1954 but have a 235 engine with a sm420 manual transmission with the emergency brake on it from a 1956.
I'm also planning on putting a 2012 mustang rear-end in with 273 gearing to get lower rpm's while driving on the highway, plus disk brakes and limited slip.
My main questions are about the installation of the 235 engine and transmission.
1. What is needed to mount the engine in the front and rear. Can I drill alignment holes in the lower front flange on the 235 to mount to the standard flat two hole mount location. Engine originally had side mount brackets. I could also fabricate a block that would be contoured to the flange and flat on the bottom to bolt to original mount. In the rear should I make a cross member to support under the transmission or is there something already out there that works.
2. Do I need any addition parts to tie in the original clutch pedal to the sm420. Where would I find a part schematic and any parts I might need.
3. Should I take off the brake setup on the transmission or leave it in place. I have already pulled the braking mechanism, just have the round drums which appear pressed on to a snap on the rear plate. There are 4 studs which I assume are to mount a yoke. Do I need to do anything special as far as the speed cable, gages, etc. because of the transmission and rear-end I'm using.
4. Is there any other things I need to know when working on this project.
I'm also planning on upgrading to a 12volt system and I have a restoration manual that speaks to the necessary changes.
Thank you all for the help and I look forward to learning more about these beautiful early American trucks.
Update to question three. I was able to remove the brake drums for the emergency brake. So now I just have the 4 studs for bolting on the yoke for the drive shaft.
I still have the question regarding the speed cable.
Beginning 1954 the rear engine mount design changed. Crossmember and bell housing affected. You have a 1951 truck so you will need a pre-54 bell housing.
Last edited by buoymaker; 03/04/20229:21 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
I found that in a search but I wasn't home to verify that the front flange has that flat spot.
I assume you can come off the harmonic balancer for engine centerline.
I was wondering what your thoughts are on fabricating a custom rear mount rather than looking for an older bell housing. Does the older housing match up to the sm420 transmission.
I have access to welding and a local machine shop. So making something custom is not very difficult.
My main question regarding that approach would be a height reference for the correct position of the transmission maybe relative to the top or bottom of the frame rails.
Click on "Click here" to expand the drawing. The centerline is shown for the engine and the crossmember.
Your 51 crossmember (rear engine mounts) will be riveted to the frame. My thought is not to remove or cut the crossmember but it's your truck to do want you want.
I match the bell housing to the year frame so I can use stock mount parts. Picture top is 54-62, bottom 48-53. Find a junk yard or post in parts wanted.
Beginning 1963, the next generation (194, 230, 250 etc.) engines have bell housings that do not bolt up to the older engines.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
A 48-53 truck bellhousing for the 216 or 235 is a bolt-up swap to both the engine and the SM 420 transmission. There is no need to fabricate any sort of Rube Goldberg adapter. You will learn to hate the 2.73 rear end gear- - - -a 235 doesn't have enough torque to handle that ratio. You'll be "rowing it with the shift lever" between 3rd. and 4th gear on any road that's not as flat as a pool table. Something in the 3.30 to 3.50 range will be a lot more flexible, and a 3.70-something gear would be my first choice with any kind of normal-looking tires. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I have the bellhousing from the top photo , so 54-62 which make sense seeing the engine, transmission and bellhousing were from a 1956 truck.
So based on that I have two options, I can find a bellhousing from a 48-53 or I can make a bracket that ties into the cross member that uses the rubber mount off the shelf.
As far as the 2.73 gearing, I was mainly basing it on the mathematical calculation to have the engine run at 2500 rpm at 70mph with the original tire diameter.
I probably should have reached out to this forum first but if the only down side is shifting more often, that's no big deal to me.
My main goal was being able to drive it occasionally on the highway without the engine screaming but yet keep it as stock as possible with the engine and transmission.
My other reason for choosing this rear-end is it is only 1/2 narrower than the original rear-end and I get disk brakes and limited slip.
Can anyone tell me where I can find the yoke that bolts to the four bolt pattern on the back of the sm420.
