Today’s Carnage…!!! It’s Broken Pretty Good

[oneg360]

Pulling away from a light about 4k Rpm herd a noise pulled valve cover and found this.

 

[BEATAV8]

ouch!

 

[GNVYUS 1]

Sorry to see that damn.

Curious what the others will comment on GN1 Rockers vs TA (T&D), metal quality etc?

 

[pacecarta]

it wasnt the rockers it was the champion aluminum pedestil that gave up , fixed a few over the years
if you ask me whats the cause its sand mixed with the alum during the pour making them weak

tap whats left in head for helicoil , chamfer the edges of the broken part and drill out any threads , thoroughly clean both parts, bolt it back down with a straight rocker shaft and longer bolt that reaches deep into the helicoil .. then weld it

alternative is what i did years ago for my GN1 8bolt heads is have champion mill them for 14bolt , this will allow you to step up to scorpion individual shaft rockers or better i went with the jesel rocker setup$$$

 

[BEATAV8]

I have a set of the same style heads, still new never run. I’ll be installing rocker shaft studs that go as deep as possible….

 

[oneg360]

it wasnt the rockers it was the champion aluminum pedestil that gave up , fixed a few over the years
if you ask me whats the cause its sand mixed with the alum during the pour making them weak

tap whats left in head for helicoil , chamfer the edges of the broken part and drill out any threads , thoroughly clean both parts, bolt it back down with a straight rocker shaft and longer bolt that reaches deep into the helicoil .. then weld it

alternative is a little more expensive and thats to pull heads and have champion mill them for 14bolt , this will allow you to step up to scorpion individual shaft rockers or better the jesel rocker setup$$$

it wasnt the rockers it was the champion aluminum pedestil that gave up , fixed a few over the years
if you ask me whats the cause its sand mixed with the alum during the pour making them weak

tap whats left in head for helicoil , chamfer the edges of the broken part and drill out any threads , thoroughly clean both parts, bolt it back down with a straight rocker shaft and longer bolt that reaches deep into the helicoil .. then weld it

alternative is what i did years ago for my GN1 8bolt heads is have champion mill them for 14bolt , this will allow you to step up to scorpion individual shaft rockers or better i went with the jesel rocker setup$$$

Thanks. I will explore all options. How much do you think it will run to send them in a get them upgraded?

 

[BEATAV8]

Thanks. I will explore all options. How much do you think it will run to send them in a get them upgraded?

After it has broken like that I think I would prefer converting the head to the 14 bolt style where all that material would be machined away. Not sure what champion would charge but it can’t be too awful as they do that type of work all the time.

The t&d rockers will cost about $1700 though. Or the cheaper option is scorpion stud mount rockers.

 

[pacecarta]

and you should be able to source the new shaft and anything else needed to repair the rocker shafts from T+D

 

[oneg360]

After it has broken like that I think I would prefer converting the head to the 14 bolt style where all that material would be machined away. Not sure what champion would charge but it can’t be too awful as they do that type of work all the time.

The t&d rockers will cost about $1700 though. Or the cheaper option is scorpion stud mount rockers.

Thanks I will pull the heads next week and contact champion. I will update this post and let you guys know.

 

[pacecarta]

i looked up the cam specs for the cam in your signature
was the cam spring combo checked for coil bind ?? or bottoming on the guides
unless those 8bolt heads have taller valves or modified spring pockets there is no way the cam you have should be run on those heads with a 165 rocker ..and you may need new springs too

from ft website
Camshaft Specs: 218 intake 224 exhaust. .545/.543 with 1.55 rocker, .563/.560 with 1.6 rocker .581/.578 with 1.65 rocker

generally anything over .500 lift at valve on the 8bolt usually needs additional work to make it fly
with a 1.80 spring height (most 8 bolts are 1.75) and 1.25 coil bind (behive may be at 1.15 bind) thats only .550-560 lift max and max is not the target you should run at generally i shoot for .030 from bind
with that cam and those heads i would have run no bigger than 1.55 rockers

i had champion put tall valves in mine allowing dual springs and upto .600 cam

on murphsters 8 bolt heads he was stuck at 133mph just couldnt pull any more rpm
i found clearance issues with the guides and poor spring choice for his 224/224 cam (even with 1.55 t+d) , sent heads to bison for machining of the spring pocket for more spring height and lower the guides and the result was over 10mph and over a full second gain in the 1/4

 

[oneg360]

i looked up the cam specs for the cam in your signature
was the cam spring combo checked for coil bind ?? or bottoming on the guides
unless those 8bolt heads have taller valves or modified spring pockets there is no way the cam you have should be run on those heads with a 165 rocker

from ft website and you may need new springs too
Camshaft Specs: 218 intake 224 exhaust. .545/.543 with 1.55 rocker, .563/.560 with 1.6 rocker .581/.578 with 1.65 rocker

generally anything over .500 lift at valve on the 8bolt usually needs additional work to make it fly
with a 1.80 spring height (most 8 bolts are 1.75) and 1.25 coil bind thats only .550 lift max and max is not the target you should run at generally i shoot for .030 from bind
with that cam and those heads i would have run no bigger than 1.55 rockers

i had champion put tall valves in mine allowing dual springs and upto .600 cam

Had Valve work done and measured for this cams install height.

 

[BEATAV8]

I noted in the photo that the broken pedestal had a helicoil in it. I think that probably contributed significantly to the pedestal failure as it concentrated all of the load in the upper 1/2” (or less) of the pedestal threads and therefore all of the load in just the top 1/2” of the pedestal itself. I measured the depth of the threaded hole and found it’s an inch deep. Ideally the entire length of the thread would have a bolt or stud engaged in it to distribute the load as deep as possible.

This stud kit from TA probably would’ve prevented the carnage.

I will find out this summer as I have 2 sets of these heads I’m messing with right now. One new set going on the wagon is set up with 26056 beehives @ 1.72” & .553” lift. 195lb seat & 410 open. The other set is on Rich’s 82 GN and well seasoned, been running soft (26918?) beehives that float @ 5500 and being reconfigured with pac 1222x @ 1.735” & .519 lift for 208 seat and ~425 open.

 

[Turbo6inKY]

it wasnt the rockers it was the champion aluminum pedestil that gave up , fixed a few over the years
if you ask me whats the cause its sand mixed with the alum during the pour making them weak

Yup, you can tell from the texture across the break. It's really coarse. Each one of those depressions was probably some kind of contamination. The fact it failed so uniformly is a tad scary. I'm surprised that head isn't porous and leaking water through the casting wall.