Firewall Clearance

I recently pulled the carpet out of my 72 CJ5 to twin stick the transfer case and discovered oil coming through a crack in the firewall, opposite the back of the valve cover. I always knew I had an oil leak at the back of the valve cover but now see that the rear of the block/valve cover is against the firewall. How much clearance is usually there with a 258? The previous owners put a 4” lift on it and dropped the drivetrain lower at the rear. There is a 1” spacer between frame and trans xmember. I didn’t think that was enough to rock the engine back that far. Is it possible this 258 did not come with this CJ and the motor mounts are positioned for a shorter engine? V-8? V-6? 4 banger? I plan to fab a deeper removable firewall pocket so I can get the valve cover off. What are your thots? Am I missing something?

 

the v8 and the i6 share mounting locations not sure about the four, on my 74 when it had the 6 the valve cover just missed the firewall but it was a glass tub. the 76 had an i6 and same story not much clearance. the motor mounts could be soft letting them settle some check the trans mount too. but I would guess its the drop at the trans mount causing this.

 

Post or decipher your VIN which will tell you what came from the factory.

 

That jeep did not come with 1" lowering spacers. The engine may be angled back far enough from this to cause the valve cover to contact the firewall.
That is a poor mans way of correcting the driveshaft angle when lifting a jeep with a D20. Note the extra bracing on the xmember added by AMC.

 

The rear diff had been re directed toward the Tcase, so that’s a good thing. I have 3 options. Get a double cardan, ditch the 4” lift and the 1” xmember drop or re configure my firewall so I can reach that bolt at the back of the valve cover. The cheapest option is the firewall alteration.

How much clearance is normal between the firewall and an I6? 1/2 inch, 1 inch?

 

Make sure, that even with your rear axle rotation, that the centerline of the pinion is parallel with the transfer case main shaft.
I'm guessing you still need a CV joint at the rear of the transfer case.
This diagram illustrates right and wrong.

 

And to add to that. If you run a Double Cardan at the transfercase, the pinion needs to be pointed at the transfercase for no vibration. This is because the Double Cardan is a constant velocity joint:

 

Thank you for the two graphics . Those will be very helpful in the future.

For those of you who have I6 258 engine in your post 72 CJs, can you tell me what the distance is between the rear of the engine and the firewall in you’re rigs?

 

I squished my fingers in and measured my fingers with a caliper. I got 1.3". My engine is tilted down 6 degrees in the back. This is also an MD Juan tub that I positioned and drilled all the body mount holes, so I'm not sure how close everything is to stock. Hope this helps.

 

I have a 4 Wheel Drive Hardware fiberglass body with a v8. The PO installed a 1-1/2 transfer case drop . There is less than a 1/2" clearance between the left valve cover and firewall. My jeep is a project, ditching the spacers and getting with Tom Woods is on my to do list.