289 Connecting Rod Length Questions

[66P51GT]

I believe the standard connecting rod length for a 289 is 5.115". A friend of mine has a set of forged connecting rods with 3/8" ARPs that are 5.090" that I'm interested in but not sure on a couple of things...

1. Assuming the Rod Journal and Pin Sizes are the same, can these rods be used?
2. Will I need to deck the block to retain the compression ratio? Or will it be negligable?
3. Also, Does zero deck height mean the piston at TDC is level with the head mounting surface?
4. Are there any drawbacks to not having a zero deck height?

Also, I'm also installing a set of 58cc Windsor Jr. heads.

Thanks,
-Chuck

 

[D.Hearne]

You've got the length wrong----- it's 5.155. You will need pistons with a 1.55" comp height to use them with a 302 crank. Zero deck is just what you posted. Anything less than zero, just detracts from performance and resistence to detonation

 

[SuperDave]

Even with zero deck, the wrong rods will cause problems. I once had a customer who had an "el cheapo" rebuild that made strange noises because it had the wrong rods. Different rods = end of problem.

 

[D.Hearne]

The pin and journal dimensions are the same between the two, but to interchange them between a 289 or 302 crank requires the correct pin height to acheive as close to a zero deck height as possible. You really don't want your pistons to be .060" or farther down the hole at TDC. The comp ratio will suck and the motor if it will run will be a dog. You could run a supercharger or turbo it, but the detonation from the lack of quench will drive you nuts and ruin your pistons.

 

[66P51GT]

What's wrong with your 289 rods? Are you planning to build something in excess of 400 HP and 6500 rpm? If no, then 289 rods with ARP bolts and shotpeening (optional) is fine.

Nothing is wrong with the rods. My current build will be around 325HP - 350HP. I just have a chance to pick them up for less than $50. I thought it would be an easy swap while I had the motor disassembled. At a minimum, I will install the ARP bolts in the stock rods. Since I will probably never see 6500 RPM, I'll probably be OK.

One last question, is the stock connecting rod bolt size 5/16ths?

Thanks for the replies!

 

[D.Hearne]

Yes they're 5/16ths unless you lucked out and got a set of the Hi-po rods, they had 3/8ths bolts. You stock rods are good forgings and with quality bolts are good to 7500 rpms.