What rpm to run 7.3

Binder man · Aug 14, 2013

I wouldn't think about spinning them to hard with added power on stock pushrods. Besides Smith Bros. pushrods are only like $120 if I remember right.

JD3020 · Aug 14, 2013

littleredstroker said:
Is this doable on stock pushrods?

910s were shimmed to 1.750 +-.005 , is that enough ?

I had asked a couple times in 3 different threads about correct shim height and nobody really responded...

sent while staring at a windowed block

I've said it a million times that i've got it written down, but i still haven't found my shim specs. LOL But IIRC my valves were sunk in the head .005" over factory specs(valve seat wear). And then i added .060" shims. I wanna say it came in somewhere around 1.735 or 1.745" installed height, or somewhere around 135-140lbs of seat pressure.

Still running stock pushrods, but i need to get some extra rockers and find a decent deal on pushrods for when i decide to start spinning her past 4k.

strokin'_tatsch · Aug 14, 2013

1.750" is what I set up the 910's at, but I'm not sure how far in the RPMs to take them to. Don't think I've ever twisted one past about 4100 RPM.. Comp 910s at 1.750" is about 135lbs seat pressure.

Magnum PD · Aug 14, 2013

I got a few complete rockers if you need them JD3020.

littleredstroker · Aug 14, 2013

It would only be when pulling, so 5-6 times a year, I have buckets of spare pushrods... I guess I am hesitant to go stronger rods, because I like my weak link to be something cheap and easy to replace.

How many rpm is 1.750 good for ? With say 40psi

sent while staring at a windowed block

JD3020 · Aug 14, 2013

If 1.75 gives us 135lbs of pressure, they should be good up to 84psi(going off a valve size of 1.6 i saw in a post by Swamps). Now as to RPM's, IDK. I'm sure theres calculations for that.

Binder man · Aug 14, 2013

your rocker arms will just be your next weakest link. Don't worry the pushrods are well worth the investment. Rocker arms have to be taken off to change a bent pushrod anyway, so you ought as well throw them in and break a rocker instead of a pushrod. But it is fairly "odd" to break a rocker. Normally they break when the springs aren't shimmed right and the valve kisses the piston.

PSDEng · Aug 15, 2013

Binder man said:
your rocker arms will just be your next weakest link. Don't worry the pushrods are well worth the investment. Rocker arms have to be taken off to change a bent pushrod anyway, so you ought as well throw them in and break a rocker instead of a pushrod. But it is fairly "odd" to break a rocker. Normally they break when the springs aren't shimmed right and the valve kisses the piston.

:whs: I've put about 30 hooks on 910s and Carson's pushrods with stock rockers and haven't had a problem. I too think you're better off to put in some good pushrods and run the risk of replacing a rocker.

Chvyrkr · Aug 15, 2013

What bends pushrods?

Serious question, with a point.

JD3020 · Aug 15, 2013

Chvyrkr said:
What bends pushrods?

Serious question, with a point.

From my understand the high pressures of the springs will cause the stock pushrods to deflect, when opening the valves, and they'll eventually bend.

Cody · Aug 15, 2013

Chvyrkr said:
What bends pushrods?

Serious question, with a point.

I tore apart my relatively stock 180k mile motor and had bent push rods..

vanderchevy18 · Aug 15, 2013

Binder man said:
Don't be afraid to run them to 4K plus if needed and you have springs/pushrods. Your not making as much power up there but your keeping wheel speed up until the sled pulls you down into your sweet spot for RPM's.

Exactly. Who cares if your power drops off a bit? You're looking for speed until the weight drops.

Chvyrkr · Aug 16, 2013

JD3020 said:
From my understand the high pressures of the springs will cause the stock pushrods to deflect, when opening the valves, and they'll eventually bend.

I've actually never heard that before. I'd expect any deflection in the pushrods to be permanent. As in, first time there's deflection, it stays that way (bent).

I think as long as you keep the valves off the piston, the pushrods will stay strait.

Cody said:
I tore apart my relatively stock 180k mile motor and had bent push rods..

I believe that.

Cody · Aug 16, 2013

Chvyrkr said:
I've actually never heard that before. I'd expect any deflection in the pushrods to be permanent. As in, first time there's deflection, it stays that way (bent).

I think as long as you keep the valves off the piston, the pushrods will stay strait.

I believe that.

I didn't have any valve contact at least that I could notice.. Yet had 7 or 8 that were bent..

littleredstroker · Aug 16, 2013

My old motor had lots of valve slap, but never bent a pr

sent while staring at a windowed block

JD3020 · Aug 16, 2013

littleredstroker said:
My old motor had lots of valve slap, but never bent a pr

sent while staring at a windowed block

I honestly find that hard to believe.

One of these days i'm gonna tear my old engine down, it had 205k miles when i yanked it. AD's went in at 185k and i ran the piss out of it, and blew up a transmission. Hell i didn't even have gauges, and it never left the race tune. Then at 193k 175/100%'s went in, and again i ran the piss out of it. I'm sure i'll have a few custom pistons in there somewhere.

Is the stock balancer sufficient for a few high RPM runs, or is an ATI needed?

littleredstroker · Aug 17, 2013

JD3020 said:
I honestly find that hard to believe.

One of these days i'm gonna tear my old engine down, it had 205k miles when i yanked it. AD's went in at 185k and i ran the piss out of it, and blew up a transmission. Hell i didn't even have gauges, and it never left the race tune. Then at 193k 175/100%'s went in, and again i ran the piss out of it. I'm sure i'll have a few custom pistons in there somewhere.

Is the stock balancer sufficient for a few high RPM runs, or is an ATI needed?

Would u like to see pics of the pistons??? Stock push rods that are actually in my motor I'm running now

sent while staring at a windowed block