I'm installing ported heads that have been milled at least twice and Impala head gaskets and 1.7RR on the stock cam. With the guideplates off to clear the adjusting nut on the adjustable pushrod I measured for the correct length pushrod and got 7.100 as the best and centered valve pattern. I also have ARP 7/16 studs. when installing the rockers yesterday I noticed that some of the rockers, only once 1/2 turn preload was applied, would be firmly against the corners of the hex on the studs. Anyone else have this problem?

How should I correct this, just grind a little more clearance where needed on the rockers? It doesn't look like much would need to be grinded to clear.

 

Can you post a photo?

 

At work now, so can't, but basically the bottom of the rocker is just hitting the stud, and seems to do so only after 1/4 turn preload, so by the time I get to 1/2 turn preload, it sits against the stud a little tight. It doesn't do it on all the valves, depends on how the hex head is oriented on the stud on if the rocker hits. I am thinking of just doing a slight clearancing on the rockers that rub, just enough to clear. Would that be my best bet?

I know that I checked pushrod length correctly, using an adjustable pushrod, dial caliper to verify length, and a stock lifter that I made into a solid.

 

I'm almost positive that you have to measure the pushrod length with the guideplates on. Without the guideplates you moved the stud down ~1/8" and had the clearence for the 7.1 pushrods, but now that the stud is in the correct place you bottom out the rocker. I had the same problem when I ordered my pushrods, you may need some 7.15s or 7.195s to clear the stud.

Just remember that when they mill the heads its usually only .010 that they take off, so if yours have been done twice they are probably ~.025 or so thinner than when they were stock, so take that from the stock 7.2 and you should probably be able to get away with a ~7.175. But don't quote me on that, I'm just trying to give you some ideas.

 

I don't see why it would matter if the guideplate is on while measuring the pushrod length, since the rocker is not supposed to contact the bottom of the stud anyway and the guideplate does not affect geometry. Measuring pushrod length is done with a stock lifter made solid to keep the lifter at zero lash while measuring. I do have clearance at zero lash with these pushrods, the contact only happens after the preload is applied, and only on a few rockers. BTW when I measured using 7.150 length, it put the pattern a little too much toward the exhaust side of the valve, wasn't perfectly centered.

 

You may have to go with lash caps and longer push rods to raise the rocker up.

 

Yeah you need to have the guideplates in there buddy. IT DOES EFFECT THE GEOMETRY WITHOUT A GUIDEPLATE THE ROCKER GOES WHERE EVER IT WANTS.

What rockers are you running those Scorpion things? If so you get what you pay for.

Bret

 

Shouldn't he also factor in the amount of preload; add that amount (.030-.040"@ 1/2 turn from zero) to the measured length then round up to the next longest rod that's available. That is unless he's going with custom made rods.

Jake

 

What don't you like about Scorpions?

Thanks,

Jake

 

That's why I made one of my old lifters (both old and new are GM stock lifters) a solid lifter, so that the measured length was the length at zero lash. If a hydraulic is used, then it bleeds down at 1/2 turn preload and will measure a longer rod than it actually needs because of that preload.


I just remeasured using the guideplates on one of the rockers that cleared the studs, just had to take the guideplates off every time to insert/remove the adjustable pushrod, and got the same measurements as before: 7.150 was too long, towards the exhuast side of center, 7.100 was perfect centered, and 7.050 was just slightly above center. The mark left on the rockers is less than a millimeter, so I test ground one by just a hair, put it on the stud that seemed to have the most problem and it fits perfectly, even after rotating the crank. So I guess I'll just grind/file the tiny amount I need to clear. Shouldn't have any problems with that, right?

No I've got Angus Racing Rockers, haven't heard much about them.

I know that, I'm smart enough to know not to attempt to run it without guideplates, the first time I turned the crank by hand while someone watched the rockers to make sure they stayed straight, which they did. I was just saying that the thickness of the guideplate itself shouldn't affect the length of the pushrod needed, since the angle of the stud stays the same whether it has a guideplate under it or not.

 

they are junk, break in half

Get the isky guede plates and probly new rockers....several others ahve had the same problem including me. do a search there are pics posted

 

I saw the thread with your rockers touching the studs, and although mine touch in the same place, it seems as if yours touched a lot more than mine do. There literally is just a *tiny* mark about the size of ' that the 6 or 7 rockers that touch is left with. I'm just running the stock cam and don't plan on revving above 6100, plus is 95% daily (when no rain) use and 5% autocross, with only 1 or 2 times at the local 1/8th mile track per year. I'll try to clearance just what is needed and use that I guess. I know its not the "best" thing to do, but with the tiny amount of filing needed, I don't think I'll have a problem. If I do, then I guess I'll get the Isky plates and different rockers, but only if needed. I just wanted to see if anyone else has tried to do any clearancing on some rockers.

 

^^ if you don't have guide plates that should give you a little room.



If there is plenty of meat there then you could clearance them a small bit