I have a set of Eagle H beam rods. Its going into an all motor set up. I am taking the pistons down to the machine shop to deepen the valve pockets for sufficient piston to valve clearence. And I was wondering how much do these rods would stretch under 9500rpm. Should I add in some more clearence or just go with what the piston maker recommends? Any recommendations? Thanks.

 

Anyone?

 

The rods arent gonna stretch your gonna wanna go with what the piston maker reccomends.

You probably arent gonna need 9,500 rpms anyways.

But i can tell you that i have the eagle rods in an ls/vtec that ive took to 9,500 (though not necessary, but just to see if it would hold) and its just fine. They even have the small bolts i think.

The bolts would stretch before the rod, and if they are new eagles they should have the fatty bolts and u are good to go.

 

yeah you should be good to go. i had some too in my ls_V it was cooo.

 

Yeah, I was wondering if the rod stretches due to lots of HP or just high RPM. Since you all say its fine, I assume it doesnt have much to do with RPM. Thanks guys.

 

Rods stretch because of rpm, not horsepower. The higher the rpm, the more they try to stretch. However, with steel rods, you might build a factor of .001-.002" just for the heck of it but the steel just won't stretch until it breaks. If you were using aluminum rods, you might experience .020"-.030" stretch with that rod at high rpm.

 

hey earl, does the stretch of the aluminum rod at high rpm reduce its life at all?
sounds like that much stretch would fatigue the rod quite quickly...

 

Aluminum rod motors are most commonly setup with a negative deck height of .010" to compensate for rod stretch. The rods don't stretch (and then shrink back) when the engine is running, they simply stretch out over time due to load and heat. Once an aluminum rod has stretched .010" it is time to be resised or in most cases, replaced. To answer the question. Yes, rod stretch does effect their strength qutie a bit which is why most engine builders opt to replace the rods after they have stretched .010" Titanium rods in high HP applications supposedly also have stretching issues as well but their life expectancy is something like 10x greather than that of an aluminum rod.

 

Wow I always thought ALum rod Grew from thermal expansion

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MAX_CFM &raquo;</TD></TR><TR><TD CLASS="quote">Wow I always thought ALum rod Grew from thermal expansion </TD></TR></TABLE>

Brad, why do you go and post something like that when there is already so much good info in this thread?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SMSP &raquo;</TD></TR><TR><TD CLASS="quote">Brad, why do you go and post something like that when there is already so much good info in this thread? </TD></TR></TABLE>

 

Do you mean Al grows more than steel when it gets hot? like pistons do. Who'd a thunk it.

 

Kind of .. Lets do the math ....

Thermal exspansion rate per deg ... Alum 0.0000122

Oil temp cold 80 deg.. Race oil temp 200 to 240 so lets say 130 deg diff


6 inch rod times 0.0000122 times 130 degrees =


6.0 x 0.0000122 x 130 = .0095

So the rod will grow about 9 and half thou in lenght


now you can do with also .935 with ...

Thats only about .0015 ....

Well anyways if you biuld the engine to be run cold like prostock ...

you wont need much piston to head.. if you run it hot .. Look out ....


there is my 3 cents ....

 

Well, if you are going to give it up, how much does the piston crown grow @ 1200 degrees, how much of the bearing cl. and pin clearance is used up at 9500 RPM, plus the actual stretch of the rod, elongation of the big end, above the thermal expansion? Just stuff, kinda like, does the valve adjustment get loser or tighter on a Honda when the engine is hot? Leave that one alone, many experts will answer it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">Well, if you are going to give it up, how much does the piston crown grow @ 1200 degrees, how much of the bearing cl. and pin clearance is used up at 9500 RPM, plus the actual stretch of the rod, elongation of the big end, above the thermal expansion? Just stuff, kinda like, does the valve adjustment get loser or tighter on a Honda when the engine is hot? Leave that one alone, many experts will answer it. </TD></TR></TABLE>


Don I hope your Kidding ? I hope talking about peak temp on power stroke

A piston Crown Does not see average 1200 deg temps

What does 2618 alum melt @ LOL ...


Thermal Properties 2618 alum
Melting Point 549 - 638 °C 1020 - 1180 °F
Solidus 549 °C 1020 °F AA; Typical
Liquidus 638 °C 1180 °

Doesnt the intake charge cool the the piston?
I think the rings soak some heat also .. Thats the experts tell me

The average piston temp is alot lower...

What i was trying to say

Alum rod motors are effected from thermal expansion more then rod stretch

I think maybe someone should toss a alum rod in a oven @ 300 @ remeasure

Center to center

~BRAD

 

Sorry had EGT in my brain, 1200-1300, piston temp.is lower unless detonating. Does the crown grow? Actually I do not need to be here, rods do not stretch, pistons do not grow, bearings always run at the set clearance, and valves follow the cams perfectally. If you have valve to piston clearance you are fine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">Sorry had EGT in my brain, 1200-1300, piston temp.is lower unless detonating. Does the crown grow? Actually I do not need to be here, rods do not stretch, pistons do not grow, bearings always run at the set clearance, and valves follow the cams perfectally. If you have valve to piston clearance you are fine. </TD></TR></TABLE>


haha Im just busting yur ***** ...


....

 

Because of the accident, it would be ball. LOL

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnzm &raquo;</TD></TR><TR><TD CLASS="quote">hey earl, does the stretch of the aluminum rod at high rpm reduce its life at all?
sounds like that much stretch would fatigue the rod quite quickly...</TD></TR></TABLE>
Good for about 30 passes, I've heard. I won't run aluminum personally.

 

Yeah the original poster asked about eagle h-beams anyway.

 

The topic was about rod stretch, not thermal expansion. Big difference.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Phase Change Racing &raquo;</TD></TR><TR><TD CLASS="quote">The topic was about rod stretch, not thermal expansion. Big difference. </TD></TR></TABLE>

Yup .. So tell me how much does a eagle rod stretch then?

 

Uhhh lemme get out my calculator here....... none.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Phase Change Racing &raquo;</TD></TR><TR><TD CLASS="quote">The topic was about rod stretch, not thermal expansion. Big difference. </TD></TR></TABLE>

Well the question was about rod stretch but it was in regard to clearance, and thermal expansion on a piston doesnt just happend on the skirts, the dome and cr height actually increases as the piston heats up, at the same rate as your skirt clearance lessens(is that a word?..lol) so your technically losing clearance there.

I remember a buddy who yhad a Guide head that was milled so much that when it overheated you could hear the pistons tapping the head. Whe he pulled it apart because it eneded up killing his rod bearaings the head had the little markings that were stamped into the piston flat, stamped into the head.. He never blew a head gasket or did anymore damage then that..it was crazy

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">
Good for about 30 passes, I've heard. I won't run aluminum personally.</TD></TR></TABLE>

2200hp Pro-Mods get 75-100 passes per set...so why would our little hondas only get 30?