Modifications on the 352's C6AE-R heads...

[blykins]

After the last dyno session on the 352, I sent the heads to Joe Craine to have them ported.  Joe was able to pick them up over 40 cfm, which should net some nice gains the next time we make some pulls on it. 

On disassembly, I saw where we were getting some fretting from the rocker stands moving around on the 1-piece stand shims. 



I was running 280 lbs seat pressure and about 670 lbs open, which starts to tax the factory 4-stud mounting system.  Obviously, things were moving around at rpm.  Fortunately, I was able to prove the function and reliability of my non-adjustable roller rockers as they held up perfectly. 

I knew that Joe was going to dress up the valve job and the valves would probably sink a hair.  It was an exercise in patience to nail the lash on all 16  valves with non-adjustable rockers.  I also knew that I'd likely have to order another set of pushrods and since there was no reason to test my non-adjustable rockers again, I bit the bullet and ordered a set of T&D street rockers. 

So the task at hand was to address the fretting with the T&D's, since their street rockers use the factory mounting system. 

I had found a weak thread in the factory heads while assembling the engine the first time and had to helicoil a hole.  This time, I just went ahead and put in some thick inserts in all 8 holes. 



In my mind, that eliminates any weak issues with the factory bolt/stud holes.

The next task was to keep the stands from squirming around.  I thought about pinning them then thought it would be easier to tighten up the fit in the stand hole.  As they sit, the hole is pretty sloppy around the stud:



The way that I addressed this is to counterbore the bottoms of the T&D stands, then press a bushing in.  The bushing had to be reamed to size, so it would have just enough clearance to slide on the stud:



There's a shadow around the stud in the picture.  It's a pretty snug fit but allows the stud to slide in and out. 

After that, I reassembled the T&D assemblies and since the kit was for a MR head, I re-arranged the rocker spacing.   

I feel that this will tighten everything up considerably, but I'll know for sure after the next dyno session.  Between the bushing locating the stand on the stud and the clamping force from the washer/nut at the top, it should add a lot of rigidity. 

I would have already had the heads back on the short block this morning, but I'm out of 5/16" valve stem seals and had to order some.  They'll be back on before the week's over.

[turbohunter]

Nice idea.

[BigBlueIron]

Forgive me if this a rookie question, but what keeps one from increasing the size of the fastener?

Seems it would be much stronger in all aspects and well easier. What am I missing?

Ive never had anything badass enough to have to face this issue head on so excuse my ignorance.

[blykins]

Forgive me if this a rookie question, but what keeps one from increasing the size of the fastener?

Seems it would be much stronger in all aspects and well easier. What am I missing?

Ive never had anything badass enough to have to face this issue head on so excuse my ignorance.

The holes in the shafts would be the limiting factor. 

[BigBlueIron]

Yep, duh. Just dawned on me.

[cjshaker]

I wonder how hard they'll be to put back on as a unit? The looser fit allows the stands to self align with the shafts. I'd assume that the stud holes aren't perfectly aligned, so it may be a bit of a booger to get them all to slide on. I know what assumptions can do, but so few things are machined perfectly from the factory. Not at all saying it's a bad idea, just that it might cause a different issue for you.

[428 GALAXIE]

I shouldnt be messing with this but why not pin the stand to the head?
Wouldnt that really keep things in place.
I have been taught that fastener (bolt)clamps things together and the friction of the surfaces should keep things together not the bolts sides.
 
Iwe done machining jigs same way that the bolt alings things but rocker fretting seems wrong place for that.

Im not saying that dosent work just ive been taught to think difrent way.

[My427stang]

To the guys questioning the utility of locating this way, you have 16 rod bolts and 4 head bolts that use the same theory, it is particularly applicable to the rod caps, which are located either by this method or by the shank of a bolt

In fact, many main caps are "pinned" this way as well, although factory FEs generally do not do it, it is a proven and simple way to locate something

Personally, I think it's very clever, and when adding the thread inserts, its also a logical time to correct the location of the holes if they measure wrong but my gut tells me there is a little more play in the fore and aft dimensions, it would be the left and right (toward intake or exhaust) that would be tougher to manage and require correction to stay on shaft centerline.

[blykins]

I wonder how hard they'll be to put back on as a unit? The looser fit allows the stands to self align with the shafts. I'd assume that the stud holes aren't perfectly aligned, so it may be a bit of a booger to get them all to slide on. I know what assumptions can do, but so few things are machined perfectly from the factory. Not at all saying it's a bad idea, just that it might cause a different issue for you.

Not bad at all.  They don’t fall on but I haven’t had to get the 3 lb hammer out either. 

[Gregwill16]

Would there be enough thread in the head to machine a recess at the top portion and have a longer bushing that would register in the recess of the head and the stand?

[frnkeore]

The springs are pretty hefty, for the rpm level, that your at now, with those valves. I assume your going to raise that, at some point?

Do you have the same issue on your higher rpm builds or just this one?

Personally, I think this issue is caused from a bending moment, if so, I don't think it will help, in the long run. The soft bushing will also fret.

As Greg is suggesting, a harden steel bushing (.500x.375x.625 Lg) might be worth a try, pressed into the head, at least 1/4" and slip fit in the stand.

7/16 bolts/studs would also help, you'd only have to enlarge the shaft holes accurately and open the stand holes.

[DubyaTF]

Which brand of shaft stands are those? The set I have from Survival has a small countersink on the top side for the washer and nut to index onto. I can't tell if there's one on these photos.

[blykins]

Which brand of shaft stands are those? The set I have from Survival has a small countersink on the top side for the washer and nut to index onto. I can't tell if there's one on these photos.

They're T&D. 

[blykins]

The springs are pretty hefty, for the rpm level, that your at now, with those valves. I assume your going to raise that, at some point?

Do you have the same issue on your higher rpm builds or just this one?

Personally, I think this issue is caused from a bending moment, if so, I don't think it will help, in the long run. The soft bushing will also fret.

As Greg is suggesting, a harden steel bushing (.500x.375x.625 Lg) might be worth a try, pressed into the head, at least 1/4" and slip fit in the stand.

7/16 bolts/studs would also help, you'd only have to enlarge the shaft holes accurately and open the stand holes.

There's a lot more to spring pressure than the rpm and valve sizes.  The cam has the most bearing on that.  An aggressive lobe needs a lot more spring pressure than a lazy one. 

I don't have this problem on higher rpm builds because I usually use T&D race rockers, which use the head bolts to fasten everything down.  On this engine, I wanted to give my non-adjustable rockers a beating, so I used Harland Sharp shafts and POP stands/end stands.  It's certainly not a bending moment, the stands are just moving, the same as a main cap will move and fret. 

The only other engine I've seen it on was a solid roller tunnel port, which had T&D street rockers.  It fretted the stands as well.  However, you can't easily convert the tunnel port heads to T&D race rockers, so it was either a good street rocker, or change to a flat tappet with less spring pressure. 

I think this will work just fine.  More than one way to skin a cat, but this one makes sense to me and we'll know after the dyno. 

The dowel in the head isn't a bad idea, unless there would be an issue with the hole where the oil comes up.

[cjshaker]

I wonder how hard they'll be to put back on as a unit? The looser fit allows the stands to self align with the shafts. I'd assume that the stud holes aren't perfectly aligned, so it may be a bit of a booger to get them all to slide on. I know what assumptions can do, but so few things are machined perfectly from the factory. Not at all saying it's a bad idea, just that it might cause a different issue for you.

Not bad at all.  They don’t fall on but I haven’t had to get the 3 lb hammer out either.

Good deal. It'll be interesting to see how well it works, although at that level people are probably better off with the T&D setup.

7/16 bolts/studs would also help, you'd only have to enlarge the shaft holes accurately and open the stand holes.

Opening up the shaft holes would be a really bad idea. The shafts are already significantly weakened by the existing holes. Enlarging them is inviting failure.