Visit The Dirt Forum for More Information

Author Topic:   At what point are "H" beam rods 'needed'
posted October 18, 2004 02:20 PM
Am contemplating building a new engine this winter. Was going to build a 400, .030 over with lightweight flat-top pistons, 6" rods, 49cc Iron Eagles, roller rockers and a roller cam setup. I'd like to limit the rev's to 7-7200 RPM max - might go a little less revs.

I know most of the aftermarket I beam rods say they're good to 500 HP and this engine should push that (any guesses??) - but with the really lightweight pistons (450-490 grams from what I've seen) are the H-Beam rods going to be necessary??

Thanks in advance

posted October 18, 2004 02:37 PM
Different rods are rated for different HP levels both in H and I beam design. So I dont think it is merely a HP limitation. Compression will have something to do with it as well, along with what kind of car, (heavy or light and traction available), restricted intake or not etc. I think the H beams are prob better in the 400 while I beams may work jsut as well in 355-377 etc. because of the better rod angles.

posted October 18, 2004 06:22 PM
The H beam has a 7/16" rod bolt...its my choice. Better safe that sorry, unless you have a NASCAR budget!

posted October 19, 2004 03:26 PM
The NASCAR Nextel Cup guys are using a Lentz rod that is an "I" beam rod. You can buy them on Ebay, and only have one race on them. I bought a set for around $80.00, and I had the check, A-OK.

posted October 19, 2004 03:37 PM           
You can get h and I beams with either 7\16, 3\8 and now even a ultra light by howard rod I beam with 5\16..

H beams are heavy rods and are over kill in most oval track apps. My guess would be you dont need them if you have to ask.

posted October 19, 2004 05:46 PM
it really doesnt matter if its h or i beam. i have a motor i'm building that is the same combo and i'm gonna run 6" h beams (620 grams). you can get strong i beams that will work just as well but they are gonna be heavy...rods like olivers can be up to 750 grams. but on the other hand eagle makes a featherweight h-beam that weighs 545 grams. or just pony up the coin for a set of eagle titanium h-beams at 435 grams!!
seriously though..i'd get a set of good h beams that arent to heavy and you'll be ok.


posted October 20, 2004 02:24 PM
I run Ford 347 with I beam rods, cast crank with SRP pistons.......turn 7400 rpm every Fri and Sat night for last 3 yrs.

"Somedays your the dog, and somedays your the fire hydrant!!!"