what is the difference between a light rod and a, well, heavy one. I am sending away a set for exchange, and want to make sure I send the correct ones

Heavy rods are much fatter along the beam,and heavier.

Thanks Jack. Ill check to see if I have two different sizes in my parts stash. Do they have a different part number, just in case I have all heavy ones? What years were they produced, etc?

If you have the Macs 2010-11 catalog the have a picture on pg 31. The light (acceptable) rod is 5/8" wide on the piston end & 3/4" on the other. The heavy (unacceptable) is 3/4" & 1".

I tired to find it on their website, but didn't have any luck.

What is acceptable or not acceptable about the 'rods?

Kep, it's about what's acceptable to send in exchange as a core to the rebabbitters. If you have an early engine and want it really authentic, I guess it's possible to get the heavy ones rebabbitted too, from other sources (but probably at a higher price)

Almost noone wants to use the heavy rods though, since the lighter ones are plentiful & strong enough for the job - and they give less of a strain on the bearings and the crank shaft.

The vendors will not accept the heavy rods as cores when you buy rebabitted rods from them. That shouldn't be any problem for you in New Zealand if you buy from a vendor in the US because the shipping cost to return the cores to get your $10 for each rod would probably be prohibitive.

Kep,

The light ones are the most desireable and what you are getting from a vendor who sells rebuilt rods exchange. The heavy rods are not desireable because of more rotating mass in the engine. Therefore light acceptable and heavy not acceptable.

LOL! I suppose if you really wanted your early engine authentic, you'd also use cast iron pistons, and if so, the heavy rods certainly aren't going to add much more weight.

Did anyone see what the final eBay bid price was on the star rods a while back?

At what point did Ford stop using the heavy rods?

According to the MTFCA Encyclopedia, under "E" (engines) the new lightweight rod with 1/16" thick babbitt was introduced in the 1920 model year.

So if that coincides with about unit #4,000,000 and they made 15 million cars, they made some 44 million light connecting rods for production. Even more if you add service parts.

Richard, was it the 1927 X-rods with tin pistons you were thinking of? http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=110576940765
They went for $420.. Rare stuff. I wonder for how long these parts were used in spare engine production after '27?

http://www.mtfca.com/encyclo/E.htm#eng2
All heavy rods isn't the same - Ford made the connecting rods lighter for the 1915 model year too, but the're still considered heavy rods. Rare early 1909 heavy rods with integrated oil dipper would probably fetch high prices just like the X/star rods.

When I took apart the 22, I found 3 different type rods in it! It will run with a combination, but it is not properly balanced that way. It now has all light weight rods.
Norm

Sounds like Tom Joad from the Grapes of Wrath worked on your car Norman. They blew a rod on the way to Californ-i-a and he goes to a junkyard,finds a rod the looks OK, fits it and their on the road again. Off to further disasters. Then again I'm not sure if it was a T.

I have pulled apart a couple of engines with a mix of light and heavy rods. The most recent was one reworked by a fellow who had a business working on model Ts and was claimed to be a professional. He said he had used this engine in his T for awhile when rebuilding the original one. I refitted a light rod from my stock in its place. I wonder how many old engines are out there with a mix of light and heavy rods.
Drive safely, W2

i might end up with a mixture of light and heavy 'rods as i cannot find a matching set. i weighed them and there is something like 140 grams difference but the 2 "matching" 'rods have alot of difference too

But nowhere near any 140 grams - that's over 1/3 of a pound!

I think Tom Joad drove a Hudson. Sure it had babbitt rods, my 47 Hudson has them. My 21 engine had 2 front main caps instead of a center main cap.