The Stovebolt Site Forums The Shop Area The HiPo Shop Rear engine mount for 235 w/SM420 transmission

I guess I’m a bit bumfuzzled as to why this thread ended up in the HiPo Shop. Modifying a transmission mount to install a stock (maybe not to your truck) but nevertheless stock is not, in my opinion, a High Performance modification. Instead of bumping this thread all over the board we can certainly leave it right here for further discussion if needed. It sounds like you have made a plan and are capable of reaching your goal. Good luck on your project and don’t hesitate to ask future questions, we are here to help.

Edit: I see that you are changing the rear end to a Ferd, therefore the move to HiPo is appropriate.

Hi Justhorsenround,

I guess I don't really have a concern getting the engine and tranny to fit and have various options but I am wondering is there anything I should be concerned about relative to engine angle and alignment to rear-end as it pertains to tieing everything together.

For argument sake if I make a custom crossmember and drop the back of the bellhousing 2- 3 inches to clear my floor will that cause any unforseen problems.

Thanks
Scott

In the real world probably not. Since you are changing out the rear end to open driveshaft you can set the pinion angle before welding on spring perches. As long as there is not a unusual driveline angle all should be ok.

The rear end change to a Ferd is cause for the thread to be moved to the HiPo Forum.

I did some more research on the alignment of pinion angle for rear end, transmission and engine.

Bottom line it looks like you want to maintain a 2-3 degree downward angle from front of engine to back of transmission.

If that is what I need to maintain then how I get there really becomes a mute point. I will have to do whatever is necessary at the rear support/crossmember to achieve this angle.

Maybe that is most easily achieved with going back to the original bellhousing and just cutting the floor as needed or I may need a custom crossmember and support for the current housing.

Either way I will be able to determine my options once I get the engine back in and mounted to the front crossmember.

Since the rear-end is from the mustang, I will need to weld on perches to the axle and can set the angle during that install.

Thanks Justhorsenround for indirectly pointing me in the right direction.

I think I finally am clear on what I have to have when all is said and done, now I just need to go and execute now.

Scott

Since the topic has been moved to HiPo I decided to add more food for thought.

The 1957 235 engine has FRONT-side mounts (car and truck). The original 1950 216 engine mounted in the FRONT-center at the support below the timing gear cover. To use the side mounts you have to make or buy a bracket on each side going to the frame (weld-in or bolt-on). If you do the front center mount, you only have to drill new holes (investigate yourself). Whatever you decide to alter on the bell housing support/crossmember will most likely negatively affect the alignment of the front mounts.

At one time I owned a 1950 with a 1957 235 engine. The old style bell housing was used and the front support was drilled for center mount. It had a 3-speed Saginaw transmission (column shift) and rear axle that came from a 1968 Camaro. At the time this was the logical way to do it (old school). Less labor to put it together. Parts could easily be found in the wreck yard. This was once the combination to have that gave all the speed you needed for sensible driving (not negotiating 75 mph expressway traffic).

Today the popular manual transmission that best fits the nature of a 235 (reported by several Stovebolt members) is the T5 (with the preferred gear ratios). This has to be coordinated with the gear ratio of your rear axle. The 235 is designed as a high torque low RPM engine so the gearing of the T5 has it's benefits for highway driving.

The SM420 is an excellent heavy duty truck transmission with a granny 1st gear (7.05) for hauling on steep mountain dirt roads or working in farm field.

Glad your back Buoymaker,

My plan was to use the front mount and drill the two holes to secure the engine. I guess to minimize any stress at that location it would be best to have the rear in its final position to achieve the 2-3 degree angle and then drill the holes.

As far as the rear-end, I selected the Ford mustang because it was only 1/2 inch different on width and had all the brake setup I wanted plus I could get it with 273 gearing. Which when I calculated the gear ratio base on my tire size, put me at around 2000 RPM's at 70mph. Now someone in the forum back when I first joined mentioned that I would be shifting a lot with the combination I have but no one mentioned any significant problems.

Hopefully this combination will meet my intent which is to mostly drive around town and occasionally go on the highway just to travel to a local car show.

Thanks again
Scott

With that 2.73 rear end gear, your granny 1st gear may actually become useful for more than just rock climbing. I'm curious to see how the truck responds once you shift into 2nd gear.

You can create an RPM/MPH graph for each gear. Identify the power band (example 1800 to 2200) then identify the best shift points.
Ideally you want the engine RPM and mph to stay "up" between gear changes for highway driving.
Not the wind-up and slow down shifting of a gravel hauling truck, for an exaggerated example.

Your second gear is your first gear. 3.57 X 2.73 = 9.75 is a decent combined ratio for getting the truck moving.
There will be a big gap between second and fourth gear that the third gear has to cover (need to downshift/upshift).
This is where the extra gear of the T5 comes in handy.
Fourth gear is 1:1 so your rear axle ratio is the final combined ratio (1 X 2.73 = 2.73).
First (7.05 X 2.723 = 19.25) and reverse (6.78 X 2.72 = 18.44) will "jack rabbit" so go easy on the gas pedal.

For what its worth although my truck is a one ton weighing in at around 6,000 lbs. I found 2000 rpm to low at highway speeds . I found at that rpm. every grade or cross wind would have me searching for a lower gear . I eventually switched the rear end gearing to run around 65 mph . at 2,500 rpm .
Both seat of the pants observations and the vacuum gage back up this move .

John

Thanks guys for the comments. At least I feel now that I'm not installing a combination that right out of the shoot won't work.

May have a few idiosyncrasies that I will need to get used to but nothing that can't be overcome.

I'm getting totally pumped up now after 100's of hours of work that I'm finally at the stage of reassembly and seeing it all come together.

Thanks Again and Have a Great Holiday

Scott

I think the 2.73 will be OK if you are using smaller diameter tires. Since you are planning to use a Ford rear end, I expect you will have issues if you want the same rims at all four corners (+spare).

I have 205/75 R15 tires. Rear end has highway gears; 2.41. Fourth gear is used like an overdrive - 65 MPH at 2,000 RPM. I don't win any races, but I don't try as I'm mature.

BTW, the 6 cyl Camaro with standard transmission used a 2.73 axle. (Don't know if anybody bought a Camaro with a 250)

Hi Gord & Fran,

I'm trying to stick with the stock rims and white wall tires. I will need to see because obviously the bolt patterns don't match.

I'm going to need to buy or fabricate a spacer to make the conversion. I will probably need to solve this in a couple weeks because I'm going to have to have the truck on all fours to setup the rear axel.

Stay well.
Scott

I would think you need the engine and transmission to load the front leaf springs to get the proper rear axle angle and determine driveshaft length.
Hopefully someone with more experience than myself will pipe-in here.

Getting the drivetrain set up and installed is the "meat and potatoes".
Wheels and how they look are "icing on the cake".
Normally the cake eating comes last in a meal (project).
My wife says I need to learn how to "multitask"....so...

Currently 6 X 5.5 front and 5 X 4.5 rear

For consideration:
Adding wheel adapters is a touchy subject here (safety).
Convert front to disc brakes and use "FERD" bolt circle pattern discs.
To get around disc clearance issues, seek out Wheelsmith.
Smoothie or Vintage rims and center caps that say "Chevrolet".
Coker original look tires for "eye candy" but radials, hands down, perform better.
If down the road you want IFS, you can reuse the discs and wheels.

Thanks Buoymaker,

I'll be honest I never thought about clearance to the brake caliper with the current rims. I may end up having to change them out.

I agree I guess you don't need the wheels installed but need to have the load on the suspension system when setting the rear end angle.

My approach to this project is try to be proactive and stay ahead of my next steps but in some cases it's figure it out when you get there kind of approach.

The good thing is I have plenty of work to keep me busy while I wait or work to solve other issues.

Thanks for your continued help.

I will keep everyone posted on my progress, maybe some of the things I do will help others with their projects.

Happy Holidays
Scott

Since we are miles away from talking about rear engine mounts, perhaps you would like to start a project journal?

I know that this is the "Hi Po" shop and anything goes, but back in the other forum we were trying to keep you from building a "FrankenTruck" that nobody will want but you. Furthermore you are increasing your issues/risks beyond a point anyone here can keep up with. Floor issues with trans issues and diff issues with mismatched wheel lug issues with brake issues with crossmember fab..........
This is your fourteenth warning. As they always say here, it's your truck, your business. What I'm giving is side track advice because you are engaging members about your project. My comment is from a fellow aerospace mechanical design engineer and old truck refresherist.

As John M said, we are here to solve issues and I will dispense from the negative vibe. Just think on it as you go.
Merry Christmas Scott. Very nice looking truck.

This thread has outlived its usefulness. Scott, please contact me by Private Message if you have additional pertinent content and I will unlock it.