All,

I was breaking down an FE engine this weekend, and got down to pulling the crankshaft. I was sure the engine was a 352/360, but I figured I'd check the connecting rods and crankshaft, anyway. I think the connecting rods are the shorter rods, but I'm still checking them out. The crankshaft has "C1AE-A" cast into one counterweight (which means a 390, right?), but the next counterweight has a "3." I've seen postings about a "3U," but nothing with just a "3," and I can't find anything on Google. I expect it's a 390 crank, but I'd really like to find out about the "3" before declaring anything. Does anyone have any pointers?

Thanks,

Joseph

 

C1AE-A should be a 390 crank, easiest think to do is set the crank back in the block and measure the stroke.
352-360 stroke is 3.50", 390 stroke is 3.78", with there being over a 1/4" difference you can do a rough measurement with a ruler and figure it out.

 

If you want to know if it is a 390 or a 360 ,,, remember a 360 rod is 6.54 long and a 390 is 6.488 or as others have said, check the stroke of the crank. 3.78 vs 3.50
Also, if you had a 360 rod, it is much more wimpy than a 390 rod.
Another way is to take your rod and compare it with a 390 rod at a auto parts store. Or post a picture of your rod and we can tell you if it is a 360 or a 390.
Now for those that like to argue, it is possible to use a 360 rod with a 390 crank, and a modified piston, but not practicable, nor likely.

 

I wouldn't want to use those puny 352-360 rods in any type of performance or stroker build I was paying for.

 

I agree, plus I would not use a stock 390 nor a 427 rod for a performance build. The 390 is to weak and the 427 to heavy. After market rods such as the Eagle, are a better choice for engines putting out more than 700 hp.

 

Ummm, I guess I did post in the Performance section, but I think I'll keep things closer to stock for now. ;-)

I'll probably do a partial reassembly this weekend, and measure the stroke on one cylinder. That will give me the no-kidding answer. I was just hoping someone would be able to provide some insight into the "3" vs "3U" on the counterweight. I noticed last night that there is a "4" cast into the same counterweight, on the other side of the shaft, and a bunch of drilling marks in the counterweights to balance out the shaft. Oh, and the rear has both the half-moon cutout and the square notch. In short, nothing special.

Joseph

 

All you need to do is set the shaft back in the block on a couple of bearings, turn it till a rod journal is near the oil pan rail and measure the distance from the pan rail to the journal, then turn the crank so that the same journal is at it's farthest from the same location and measure that distance, subtract the short measurement from the long one and the difference is the stroke.

 

Even though my 406 is just going to be a street cruiser, and I'm only hoping it will make at least the same 405 hp as the factory engines, I have a set a Eagle H beams in it.

 

Hey, that's a great idea! I was thinking I would have to attach a piston to a connecting rod, hook that up to the crank, and so forth. But I'm only measuring the difference, so who cares what the offset is. That makes it a LOT easier!

Thanks,

Joseph

 

You don't need to do anything more than post the engineering numbers of the rods to know what they are.

 

I'll check those tonight, when I check the crankshaft.

Joseph

 

Good luck with that. I doubt he'll find a 390 rod at any parts store now-a-days.

 

C1AE-A crankshaft is a 1st generation 3.78" stroke crankshaft. The "3" on the adjacent counterweight is just the specific mold core number used to cast it. The "3U" casting ID mark is for the last generation of 3.78" stroke cast FE crankshafts used from '68-'76.

 

Okay, seven of the connecting rods are C3EA-C. The eighth is C6EA-C. The one site I found so far said that the C3EA-C are the short rods for a 427, but it doesn't list anything for the C6EA-C. So, I'm still looking.

I didn't have too much time to check the crankshaft. I had to do a quick check with a couple of wood blocks on the work bench, but the difference measured out to 3-3/4", or thereabouts. Definitely over 3.5", though. I'll get a more precise measurement this weekend.

Joseph

 

It's a 390. With two different rod numbers, it's been rebuilt at least once. More'n likely a factory reman engine with different rod numbers. Check the bore diameters before going further, it might be at the limits already for that. Ditto for the crank journals. The undersizes will be stamped on the back of the bearing shells. Piston overbore will be stamped in the tops.