CJ 7 SBC Conversion

[Old Dog]

Still in the planning stage on this Jeep...... Looks like I'm going with a GM Crate engine.(290 HP). Anyone run shorty headers w/ 2 1/2" pipe & Flowmasters?? Would like some feedback on this...Thanks

I have the same engine with Heddman shorty headers and flowmaster hushpower mufflers. It's way to loud for me, I'll be changing the mufflers to something else one of these days.

 

[Lightnin 1]

Finally able to get back to planning on the CJ. Looking at a chevy performance crate engine delivering 290 hp. Got a Muncie 465 to go behind it. Running 3.54's. Is the gearing gonna be ok if I'm running 33's??? Not rock climbing. Mainly highway use & beach riding.

 

[Bent]

You need a 153 tooth flywheel for the 10.5" clutch. The 168 tooth and 11" clutch won't fit in the GM 4 cylinder bellhousing. You will also need the correct starter for the small flywheel. Find a late model comaro for the flywheel/starter. When you buy the motor mounts keep in mind that the drivetrain is off set 1.5 inches to the drivers side and your motor mounts need to account for this. Some do n't

 

[HackFabrication]

....By the time I get done with this project, I will probably have spent $5 to$6K.

It does add up quick. Too quick.....

.. Did have an old truck puller give me a tranny. Don't know exactly what it is but it's got a heck of a granny gear in it. Came out on a 71 Chevy k 20. He kept saying it was a Muncie, but I thought they just had car transmissions.. Hoping this could possibly be a T-18 but probably won't be that lucky.

As you've determined, it is a SM465. Un-synchronized 1st gear.

You would be luckier if it was a Muncie SM-420 (stewart/muncie). 1:7 1st really low and really strong. I have one in mine and used a advance adapter to a Dana 20 tc.

The SM stands for Saginaw Muncie (big GM Transmission plants in both Saginaw, MI and Muncie, IN back 'in the day'), IIRC. The 'newest' SM420 was put in GM/Chevy trucks in 1968 or 69. After that it was all SM465's. Although the SM420 is a nice Transmission (I had one in my 68 Chevy C20), it is getting long in the tooth.

Finally able to get back to planning on the CJ. Looking at a chevy performance crate engine delivering 290 hp. Got a Muncie 465 to go behind it. Running 3.54's. Is the gearing gonna be ok if I'm running 33's??? Not rock climbing. Mainly highway use & beach riding.

Personally, with your intended usage, I would really look into an Overdrive Transmission . Either a NV3500 in a manual (they are rated for 300 lb/ft of input torque), or a GM 700R4 in an auto. The SM465 is basically a 3 speed Transmission when driven 'on the street'. If you aren't doing a lot of trail running, it's a bit overkill, IMHO.

The 3.54's with 33's are a bit tall. You can probably get by with them with the strong crate motor. 3.73 or 4.10 would be my preference. Especially if you did opt for an Overdrive Transmission I would do the 4.10.

 

[BIGTRUCKNUT]

The SM465 is arguably the strongest light duty truck 4 speed available and a good choice to mate to a SB Chevy using a combination of stock GM parts. Considering your stated use on highway and beach riding, you will get by just fine with the 33s, 3.54 gears and the SM465. That combination will give you about 2200 rpm at 60 mph on the road while still providing a respectable 60:1 crawl ratio with the compound low gear (6.55:1) of the SM465 and the low range (2.6:1) of the Dana 300 . Also, the SM465's 3.58:1 second gear is a little lower than all of the Jeep 3 speeds' first gears and most of the other truck 4 speeds' second gears which will make take offs easier. And you always have first if you need it on steep hills or when pulling a trailer.

Would an auto or 5 speed manual Overdrive Transmission be nice - Sure, but I am confident that you will be satisfied with your Chevy SB/SM465/Dana 300 combination. Besides, you can always swap to lower gears later if you think you really need them or you decide to get a taller tire.

 

[BIGTRUCKNUT]

Jeez, just saw that you are down the road from me in NC.

 

[Lightnin 1]

Jeez, just saw that you are down the road from me in NC.

Yep!!! Bout an hour away!!!!

 

[Lightnin 1]

You need a 153 tooth flywheel for the 10.5" clutch. The 168 tooth and 11" clutch won't fit in the GM 4 cylinder bellhousing. You will also need the correct starter for the small flywheel. Find a late model comaro for the flywheel/starter. When you buy the motor mounts keep in mind that the drivetrain is off set 1.5 inches to the drivers side and your motor mounts need to account for this. Some do n't

So a GM 4cyl bell housing will bolt to a 465??