6.9 vs 7.3 rocker arms

[Kevin 007]

Over the years I have read in many posts that fellas prefer the 7.3 style rocker arms over the 6.9 style. I respect that opinion but im uncertain why. Can someone please elabortate on the advantages. The reason I ask is because im about to build another 6.9 and I have a set of 7.3 rockers that I could use. But....all the valve train problems that I have seen with idi's like worn guides, seats and stems seems to happen with a 7.3 and I have never seen valve issues with a 6.9. I realize that the valve stems are tighter with the 7.3's is that the reason I notice more wear with them? Maybe 7.3 rockers would pair well with 6.9 seals. If its possible, thats what I will likely do.

 

[stealth13777]

I can't answer on the valve stuff, but from direct comparison of my old and new rockers, I can tell you why they changed them to 7.3 style. It's simple really: the 6.9s bolted down with an aluminum 'bracket', which then rested against moving steel parts with steel bolts holding it. The two different metals would wear until, as expected, something broke. The 7.3 style loses that aluminum piece for similar metals with a different style 'bracket'. I believe the fact that the bolts do not rest directly on the 'bracket' is another factor in the new design. Disclaimer: I have not seen a failure and this is just a visual description of the changes and why I think they were made.

My pictures aren't focused on the rockers but should illustrate the differences.

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OLD

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NEW


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[Kevin 007]

Excellent comparison. Thanks for posting pictures!

 

[IDIoit]

i still want a set of harland sharpes!!!!

 

[jaluhn83]

Not so much a 6.9 vs 7.3, but old vs new. The old style use a aluminum pivot with a 'bridge' connecting the 2 sides. The later version uses steel pivots and has a flat plate at the bottom. The problem with the old style is that the aluminum wears, causing insufficient valve lift. You can also crack the pivots if you don't tighten the bolts evenly - the newer style is less susceptible to this problem since the pivots aren't rigidly connected.

I lost a new rebuilt engine at about 800 miles due to a cracked old style rocker pivot (suspect due to tightening unevenly) holding a valve open far enough that it started tapping the piston and eventually broke off. OTH, I made ~100 miles on the freeway doing 60 at 15k GCW with a 1/2" hole in a piston and the intake valve head wedged sideways into the seat....

 

[BDCarrillo]

Yes, the tighter exhaust valve stem seals may lead to valve guide wear. They were supposedly changed on the 7.3 to reduce oil consumption.

 

[icanfixall]

I don't think we can buy the older style rockers any longer because the 7.3 rockers were a design upgrade for the better. Kind of like the non turbo head gaskets and the oil cooler bundles. All we can buy now is the upgraded turbo style parts. Thats a good thing. Not a bad thing. Roller rockers are nice but expensive. So far its not proven they benefit anything. Still nice.

 

[BDCarrillo]

Roller rockers would eliminate the valve side loading that wears away at the (relatively) unlubed 7.3 exhaust valve guides.

There is also a very slight amount of power recovered by reducing valvetrain friction. It really varies by application, but for a SBF it's about a 1-2% power improvement, if memory serves.

 

[IDIoit]

roller rockers do help throttle response also, seeing that our engines dont see very high RPM's
it would be barley noticeable. if at all
but the valve guides would be the main reason i would purchase them.
well, that and the nice orange anodized shiny's you get to smile at when you do valve cover gaskets.

less friction = less heat= the longer the metal lasts.
we could get into a huge debate about it, but ive only seen 1 person have them, and he has not ran the engine yet, that i know of.
when a hotrodder gets to building something the best he can, he goes all out!

most likely not needed, but i would love to see these mounted on a shaft assembly!

 

[FORDF250HDXLT]

you could buy a decent little beater car for cheap transportation for the set of those things though and come out way further ahead.the updated rockers are all ya need.we don't rev to 6-8k rpm. don't get me wrong,im all for engine building too (i built a super NASTY 400ci ford in my youth) but there's no point in tossing $ away either.

 

[IDIoit]

i have 5 boats, im constantly throwing money into a hull(hole) in the water lol....
you know what boat stands for? Bust Out Another Thousand!
i would be alot more satisfied with those harlands than building somthing like that 97 fireturd i lost my ass on.
its all in what you got and what you want!