lighten rod weight

[bits&pieces]

whats the lowest weight for a 5250 top guided rod I can go too?

[half fast]

Dewayne ,You can go to 0 grams but you won't have anything left. hf... You mean safely go to ??? I do not know. later d

[W. Tripp]

What are you planning to do with this engine? How will it be used? Is this a race only engine? What kind of rpm will it see? How long will it see high rpm runs? How often will it be lugging a large pitch prop at low to mid rpm? Who is doing the rod lightening? Are the flywheel, pistons and crank already lightened? What hull will this engine be run on? What is the complete rigged weight of this boat? DO the rods you are starting with show any sign of the caps fretting? Have they been inspected for cracks?

Lightening rods will reduce the reciprocating mass and help the engine rev, but other parts should be lightened first. Where the weight is taken from on each rod is a big part of lightening a rod. For ultralight reciprocating assy work, take it to someone who has learned through experience just how light will be possible for your use. If you are after the lightest rod you can reliably run, do not expect it to last as long as a slightly lightened and ballance matched rod/pin/piston combination on a high performance lake boat.

For my lake engines, I only polish the rod beams and ballance the rod ends. The piston and pins are matched to each rod. For the not so average high performance enthusiast, an ultra light assy will not even be noticed unless you are racing.

[Rickracer]

As mentioned above, further lightening should be done by someone with the experience to know what you need, and what your combo will tolerate. Just MHO. :cool:

[bits&pieces]

Mr. Tripp :eek: thanks for going into detail.whew my boat is a '90 pro comp stv 1.200lbs with me in it,no lighting of crank hi perf flhweel, light wrist pins balanced top pinned t20's. 34cc heads I'm going to turn up to 9.200 rpm when needed, port work on exh only by robborie. mostly for lake racing but not below 7.8000 rpm's .My rods have been checked and were anywhere from 495 grms to 475 so it matched balanced them all to 450 with a lap wheel going with the rod beam. thanks again snf damn now everybody knows still got 1 more supprise rolleyes: hey HF how's the jsre monsta' comin, what boat you got?

[Jay Smith]

We lower the weight on the 50 series rod 100 grams to 390 grams ........ With no problems !

[ken medendorp]

Please explane rod cap fretting and how to check for it .Thanks Ken

[W. Tripp]

Put the rod in a vise and torque the rod bolts to spec.

Then look for any signs of a lip forming on the bearing suface by dragging a finger nail along the areas where the cap meets the rod.

This lip is caused by the cap hammering against the rod at high rpm, and is a sign if the stress the rod has been put under. Some will hone this lip out with a brake hone. I personally, feel that the rod has seen too much stress if this lip is present, and is due to be replaced. But then again, I replace my rods on a regular basis anyway.

ALSO, I do not like to torque SPS rod bolts more than 4 times - TOTAL. Replacing them is (fairly) cheap insurance against a rod taking out a very expensive block, crank, etc.

Just my .02, but I hope this helps,

[ken medendorp]

Thanks Wayne for the info

[bits&pieces]

Jay/Wayne , thanks for the pro advice :D