Honda F4 connecting rod markings

[Charlie]

Not sure if anyone can help me with this, but I am in a situation where I need to use a connecting rod from one F4 into another. The rods in this 1999 F4 are all marked B1 or B2. The number is the size of the big end bore. But I don't know what the letter means. The manual is no help, and Honda only sells one replacement connecting rod part number.

All my other connecting rods are marked A1 or A2. So it would really set my mind at ease to know what the letter means. I will start doing a lot of measuring but if anyone knows what it means it will save me a headache.

Thanks

[Charlie]

Not sure if anyone can help me with this, but I am in a situation where I need to use a connecting rod from one F4 into another. The rods in this 1999 F4 are all marked B1 or B2. The number is the size of the big end bore. But I don't know what the letter means. The manual is no help, and Honda only sells one replacement connecting rod part number.

All my other connecting rods are marked A1 or A2. So it would really set my mind at ease to know what the letter means. I will start doing a lot of measuring but if anyone knows what it means it will save me a headache.

Thanks

[B Lewis @ PE Engine Management]

Hey Charlie,

I can't be any help here, but if you find an answer offline please post your findings. Thanks.

[Mark100]

Don't know about the F4, but most engines have rod revision numbers. Either a letter or a number is used to denote the rod revision. The higher the letter or number, the latter the revision. Whether or not it's a letter or number, you'll have to decide. Sometimes it's just a material change, but sometimes a rod can be longer or shorter.

[Charlie]

I'm worried about height. I can swap all 4 rods if necessary, but we had negative deck height with this engine, and I want to keep it. I just tore down a 2001 F4i of ours to put in a new trans, and it has all 'A' rods as well.

[Mark100]

Well, you should be able to measure the center to center distance then. CMM would be the easiest, most accurate, but if you can't do that or need it fast otherwise it shouldn't be too hard to compare the measurements of the two different rods. Especially with a lot of each.

[Kevin Hall]

Charlie

Make sure that you weight the rods before swapping. It shouldn't be too tough to digitize it and get the length, but that's a pain. I think a small change in mass would be the biggest problem a revision could cause........but to be on the safe side, measure and make sure you wont be mashing valves with pistons.......

[Charlie]

Thanks for bringing up the balancing point. It may be best to swap as a set for that reason.

I will definitely check valve clearances, as I have learned the hard way in the past. I also learned with this engine, to check dome height to cylinder head clearance. http://fsae.com/groupee_common/emoticons/icon_redface.gif Rod bearings don't take kindly to even mild bashing of the piston into the head.

[Charlie]

Our good sponsor Willies Cycle hooked us up with a used 99 F4 crank & rod assy that has the 'B' rods. Not sure what the B means just yet but I'll be using these rods along with the crank so balancing should not be an issue.

If I go to the trouble of investigating the letters, I'll post the results.