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Drive train angle

1K views 29 replies 9 participants last post by  Stumpfarming 
#1 ·
I am installing a GM small block in my '74 CJ, adapted to a T18 and Dana 20, with 1" body lift. I will be running a Quadrajet carb. I have been trying to keep things high and tight between the frame rails and I have good clearances; however, my drive train angle has come out a bit steeper than the recommended 3-5 degrees. Angle on the tranny is almost 7 degrees, and the angle on top of the intake where carb sits is 4 degrees. Will this case me any problems in tuning the carb, or exacerbate potential fuel issue when running on steep ground? Do I need to drop the drive train angle down so that the carburetor will sit closer to level?
 

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#2 ·
I can't answer your drive line angle question. As for tuning your carb do you always tune on a perfectly level surface? I'd be curious to see what a bubble level looks like on the manifold.

Expressed differently driving with a four degree angle at the manifold would equate to a driving up a 1.1 percent grade--4/360.

Nice work! Wish I had the patience to keep my arse out of the seat and do it right like you are doing. Nice looking home too.
 
#3 ·
bob4703 said:
I can't answer your drive line angle question. As for tuning your carb do you always tune on a perfectly level surface? I'd be curious to see what a bubble level looks like on the manifold. Expressed differently driving with a four degree angle at the manifold would equate to a driving up a 1.1 percent grade--4/360. Nice work! Wish I had the patience to keep my arse out of the seat and do it right like you are doing. Nice looking home too.
Here's a couple pics with the bubble level (leveled up the chassis first). Thanks for the compliment. Both are a work in progress (house and jeep :) ). My advantage is that I have never actually driven my jeep, so my only way of getting my "arse" into the seat is to get it done. The figurative carrot in front of my nose..... Rolled it off the trailer and started tearing it down.
 

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#4 ·
That is quite an angle.

The Qadrajet is rare in having a float bowl that is not linked to the venturis, sloshing fuel does not end up in them. You should be OK but if not you can lower the float a little. The only place you are going to see this is on the trail, on the highway it should not make any difference.

You cannot lower the engine mounts a little or raise the transmission mount?

A CJ5 rear shaft is very short and you will probably need a CV shaft. IF your pinion and transfer case output are parallel and the angles at each U joint looks like it will be at or more than 10 degrees, you should think about a CV. They are not very expensive and will work much better in such a case. If your angles are 14 degrees or higher, they will likely lock and CV is the only option.
 
#6 ·
BagusJeep said:
You cannot lower the engine mounts a little or raise the transmission mount? .
I cannot raise the tranny any more, it's already squeezed up tight, even with the 1" body lift. I already tried to drop the engine block to the lower set of holes on the Novak mounts; however, this will require me to shift the tranny mount rearward as the engine drops. (Tried it already and it bound up). I am asking the question here before hacking things up unnecessarily. My simplest solution is to elongate the mounting holes for the crossmember, allowing the tranny to move rearward a bit so the engine block can drop down. Do the mounting holes need to be solid, or can they be oblong forward and back without causing a potential problem?
 

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#8 ·
I see a CV shaft in your future anyway, those CJ5 rear shafts are awfully short.

Slotting the transmission crossmember is no big deal, it is there to take the weight of the transmission and control roll, if you have the torque arm fitted. Both the engine mounts and transmission mount allow some back and forward movement as they are elastomer but the slip joint in the driveshaft prevents anything but minimal longitudinal force being exerted on the transmission. The bolts holding up the crossmember are not subject to shear so there is no concern about slipping, just use some washers under the bolt heads so it gets a good bearing on either side of the slot.

You may need to mod the transmission tunnel to get that transmission in clean but that is no big deal in a CJ, the upper bulkhead and rear step are plenty strong enough to carry the load whilst it is opened up and worked on.
 
#9 ·
Thanks for the feedback Bagus. That confirms my understanding of the torque and sheer forces. I think that tells me what I think I need to know to go forward and be dangerous. :). In my case, I think the best I can do is run the recommended drivetrain angle and "do it right." Should be a simple fix...... :) (famous last word)
 
#10 ·
I would leave it as is until your finish assembling the rest of the Jeep. By the time you add the front sheet metal, fill the radiator and bolt on the winch, you may be level or nose down. Otherwise I think you are fine. Most sit at that angle or more once they have added a drop block to the trans/tcase crossmember or have gone to a 1" motor mount lift to help driveline angles.
 
#13 ·
This was my original line of thinking as well. However, I started to question this as I realized how "un-level" the top of the intake manifold looked to me. Truth be told, I made a novice mistake mocking up the drivetrain my first time by measuring my angle on top of the intake (note that it is perfectly between 3-5 degrees :grin2:), when in fact I later realized that the intake is angled such that it should sit more or less level when the drivetrain is at the recommended 3-5 degree angle. (Have I mentioned I am learning A LOT on this project? :brickwall ) At first I thought I would have to rebuild the crossmember to some extent. If it really is as simple as elongating the crossmember mounting holes and dropping the block down to the lower set of holes, then I think I will go ahead and do that now. I can always raise the engine to the upper set of holes later if it turns out to be better that way once the front end is fully loaded. If I was already further along, I likely keep it as you suggest. Thanks for the input. Much appreciated.
 
#12 ·
You may want of to mock up your radiator/grill installation. That way you can assure the fan is parallel with the radiator, and there are no clearance issues.

Matt
This right here, with the 1" body lift on my CJ-6 and a low motor mounting location, i had to run an electric fan as the water pump is well below the center line of the radiator. To get the motor level, i had to cut out a chunk of hat channel to fit the t-case and also cut out a chunk of the trans tunnel to fit the shift tower.
 
#15 ·
The T-18 will definitely be worth the effort. No problems with dropping the motor mounts down a set of holes, just make sure that you don't interfere with the steering or the front driveshaft. I wouldn't know from experience about polishing the high steer draglink with the crank pulley:surprise:, but my motor sits a bit farther forward than yours does.
 
#16 ·
I've been looking at the front driveshaft and I should be find. Likewise, I think the steering shaft will work based on how things looked when I had the tub on last. If either fail, then I guess that makes the decision for me regarding which set of engine mount holes to use. :grin2:
 
#17 ·
I dropped it to the lower set of holes on the engine mounts. That puts me at 5 degrees on the drivetrain and 2 degrees on top of the intake. I think I'll run with that. It makes a huge difference visually. My only concern looking at things now is that my harmonic balancer is only 4" from the top of the front differential. Is this of concern? I'm running 2.5" lift springs.
 

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#19 ·
Huh! I went out and looked at my CJ-5. It has 258 with a 2" Skyjacker lift on it. The harmonic balancer is way up there. Maybe 7 or 8" above the front diff. Maybe you were better off where you were. I guess when you do an engine/trans conversion there will be compromises. I used to own a 64 CJ-6 and we stuck a SBC in it. I don't recall harmonic balancer to front diff clearance being a problem but we were worried about overheating so we raised the engine so as to get sufficient fan to radiator coverage. Ended up chopping up the firewall and floor pan which is the same as yours I think. this was in the 70's and no body ever thought about electric fans. As it turned out, the engine ran too cold. Had to run a 180 thermostat and hotter plugs.
 
#20 ·
80cj said:
Looking at the head on pic, you appear to have sufficient clearance. In the last pic, you're measuring at an angle may be a little deceiving.
Here's a couple shots from head-on.
 

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#22 ·
I'll look and see if I can find some good pictures, but that should be very similar to what mine was. I tried to get the crank centerline at the center of the frame, and I didn't really have any more lift (maybe less) than you. I've compressed my front shocks quite a bit :laugh2: and never had an issue.
 
#23 ·
AFRd_CJ5 said:
I'll look and see if I can find some good pictures, but that should be very similar to what mine was. I tried to get the crank centerline at the center of the frame, and I didn't really have any more lift (maybe less) than you. I've compressed my front shocks quite a bit :laugh2: and never had an issue.
Thanks AFRd_CJ5! That will be be very helpful. It at least let's me know I am on the right track.
 
#24 ·
Stumpfarming,
I had a little issue with one of my Cj5's with driveline issues, like yours. What I did is put a Tom Woods drive shaft in the rear with a double cardan driveshaft plus I installed a Throttle Down Kustom 1 1/2" drop skid plate/transmission mount. I have a AMC 360 in that with a t18 dana 20 and it worked out well with no binding with a SOA.

By the way will you post or send me a pic of your side bars/nerf bars. I love how they are done and are looking for new idea's how to make new ones for my fenderwell header exhaust. I cut an old side bar and welded a big pipe that would allow the muffler inlet to pass thru on the last one, but not to fond of it. Also NICE house!!!:grin2:
 
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#25 ·
I have always planned to use a double cardan. With this drivetrain install I was still trying to minimize that need though, and ended up with things runnning a bit too steep "up hill." I think I have it now. I'm not completely satisfied with my current cross-member that I built, so that might be a modification down the road that I use to dial in my drive-line angle a bit more if need be. Thanks for the suggestions.

The frame mounted rock sliders I am building (in progress) are re-purposed from the original roll bar that came with my CJ, as well as from another old roll bar I picked up on Craigslist. There are more pics of them on my build thread starting towards the bottom of page 14, and then the install is shown more recently (page 30?).

http://www.jeepforum.com/forum/f22/stumpfarming-s-73-cj5-build-1935041/index14.html

I am bumbling along with some help from a few key folks here on the forum. The sliders are my own version of other ideas I have seen here, but no gurantees I put them together right! :grin2: I was given a 5 minute lesson on welding about 20 years ago, and just picked it up again last year as part of this project, so please don't use my work as a model. :laugh:
 

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#26 ·
Not sure if the helps much, but hopefully. Mine might not be quite as low. The motor plates sit at the top of the frame, which is about where the crank centerline is. You can kind of see it in the pictures. The alternator is about even with the crank centerline, so the second picture kind of gives an idea where it sits. The last picture was the result of having to let off the gas, and having a slight bottom out problem. I broke 1 shock that day, and that's not the first time I've broken a shock from the same thing. Never hit the pan though.

[/URL]https://www.flickr.com/photos/93907388@N06/[/IMG]

https://www.flickr.com/photos/93907388@N06/

https://www.flickr.com/photos/93907388@N06/
 
#27 ·
Thanks for the pics. I'll put a straight edge across mine tonight. It does look like my placement is similar to yours. At this point, I think it is what it is, until I find some reason to change things. If I rebuild my tranny crossmember, I might take a bit more of the angle out out of the drive train (3-4 degrees instead of the 5 degrees I am at now); however that will only make the driveline angle less favorable. I know I can't raise the engine any higher without some serious sheet metal work (which I don't think is necessary) if I want to maintain the angle I have now. It's time to move forward..... :cheers2:
 
#28 ·
I know my intake wasn't straight, or close to it. I can put an angle finder on the SBC we have in dads this weekend to see where that sits. Pretty sure that's not level either.
 
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