'74 vs '77 Front Carrier

[Mark Olson]

I have a front carriers from both a '74 and a '77. The '74 has a significantly thinner trailing arm to the tie rod end. I understand from the MWB site that the '74 is case hardened and the '77 is not. There is a 2# difference in weight, not much of an issue for a street car.

Question - should I have a preference for which one I use? Going on a K20 conversion and Eurosport body kit so not concerned with originality.

 

[dragonsgate]

With the K20 and the lighter body go with the smaller set as the front wheels will be off the ground most of the time anyway.

 

[DanielForest]

I think the bearings are the same. The lighter one make sense, but Fiat tend to make some amelioration from time to time, so I guess the heavy one was stronger because there was a problem with the previous one...

 

[lookforjoe]

Interesting - my '87 has a lighter weight carrier also - the tie rod arm and the hub have less material than the one on my '81 parts car

is the front side tapered like mine also?

 

[johnph]

Or, if this is a hot rod, you could go with the 79 or later which experts here say have beefier bearings.

 

[Mark Olson]

....is the front side tapered like mine also?

Yes, they have a similar taper. I cleaned one of the heavier ones up so you could see the differences between them:

You can notice the tabs all have a much larger radius where they join the hub, and the arm on the right has an angle built in as opposed to a curved corner.

In this shot above you can see a rectangular protrusion off the side of the hub on the heavier one.

Thanks to Hussein for making me look at these differences, as a difference showed up that made my decision for me! The tie rod arm on one of the lighter carriers is bent.

Here are all 4 of them lined up, 3 are virtually identical and the front one is ....oops!

Another shot of them from a different angle:

I am wondering now if I bent this myself. I had a VERY difficult time getting the bearing retainer out. I know I tried using a 3' snipe on my breaker bar and it would not budge (I eventually chiselled it out and used a thread file to clean up the threads). Did I have the tie rod arm in the vice at the time? I don't recall but if I did...........my bad!

 

[lookforjoe]

Ouch! Perhaps that could be heated and reshaped back to align? I don't know what the impact of heating & reshaping cast iron means to the structural integrity of the casting. Maybe Heat, shape & dunk in water immediately - that's how steel is hardened, I think.... trying to remember high school metalworks class....

The early ones look so much better. I wouldn't expect the load on that arm to be so high that it would bend unless involved in an accident (or in the press).

Based on the visual difference in the outer bearing hub ID/OD taper & landing, comparing my pic to Marks, I wonder if the later cars like mine with the larger bearings, Fiat used the same casting & bored it out more? I don't see why they wouldn't, honestly.

 

[Mark Olson]

The early ones look so much better. I wouldn't expect the load on that arm to be so high that it would bend unless involved in an accident (or in the press).

Yeah, this is off the car that I have scrapped due to rust and a bent unibody. It did get hit hard in the front.

 

[Dr.Jeff]

If it wasn't bent I'd tend to prefer the lighter weight ones. Unsprung mass is a big deal in terms of performance; something that wouldn't matter on a stock X, but might be worth the difference on your hotrod. But maybe that's why they went to a heavier design, perhaps bending wasn't so uncommon? By the way, my guess would be that was from accident damage, not your doing on the press.

 

[Rupunzell]

Once bent, the material is never the same. Trying to put the bent arm where it was originally will be difficult to not worth the effort due to the easy availability of spares. There is also a significant risk of crack-stress fracture development or have developed within the part that is not visible causing a part failure that can ruin more than your whole day.

Suggest using the later 1500cc/5sp front uprights as they have larger wheel bearings that are typically more durable. As for weight -vs- heat treated uprights. Never looked into the material these are made of. If cast steel, then Fiat could have done a weight reduction with not much trade off in strength of the part. It does make the part more $ to produce in various ways.


Bernice