max spring pressure with aluminum heads

[Jim Comet]

Hey guys, what's the max spring pressure you would run with T&D street rocker set up in aluminum Edelbrock heads. I am set up for 650lbs over the nose. Should I consider putting in time-serts while the heads are off? T&D said it would be no problem, but I worry about pulling a stud out of the head. That's the problem with machining taking too long, it gives a guy time to worry about stuff instead of slapping it together and just running it!!!! Jim

[jayb]

I would put in some inserts, there's really no downside to doing it and you'll get some peace of mind that way - Jay

[blykins]

I’ve pulled the studs out at 600 lbs of spring load.  When I do aluminum head solid rollers now, I use a different insert or a T&D race rocker.

[Jim Comet]

Just went and checked and the holes have full length heli-coils in them. Would you take them out and do time-certs? If so, is there a better brand of insert I should use or just something off the local shelf. Jim

[Barry_R]

Same deal here.  My heads have inserts for a reason.  I've pulled threads in aluminum at 610-620.

[TJ]

For soft metals like aluminum, might consider key locking inserts.  Time serts sometimes back out with the bolt.

[jayb]

I use EZ Loks, same inserts I use in my cylinder heads.  I would pull out the helicoils and drill and tap for EZ Loks.  I've had poor luck with Timeserts, have had them crack and come out.  On my tunnel port heads I use EZ Loks with a 9/16-12 outside thread and the 3/8-16 inner thread.  Jim if you want to stop by sometime I will show you what they are like.

[Barry_R]

I've had decent luck with the Heli-coils.  I've had time-serts break off at the "hat" - so I do not use them.

[Jim Comet]

Thanks everyone. I do have some EZloks. I think I will do like you said on an old post and use an old shaft and pedestals to make jig to accurately drill the new larger holes. I found some 3/4 inch long inserts so they will have thread engagement the whole length of the hole in the head. Thanks, Jim

[Tunnelwedge]

When I was drilling holes in some Edelbrocks I drilled the oil drains and cut a bigger oil drain slot.
I pulled the coils out and put in my home made thread inserts.
I also drilled the bolt hole for the oil feed to the rocker. It is a tad smaller than a stock Cobra Jet head.
I was using a 625 lbs spring.

[galaxiex]

Here's a fun test of thread repair inserts...

https://www.youtube.com/watch?v=jknMrFOGMOQ&ab_channel=ProjectFarm


Go to approx 10 minute mark to see the pull tests.

[Jim Comet]

I watched that. Good info.

[Stangman]

So I guess either one of the inserts are good for 650 lb spring pressure.

[1968galaxie]

One must always remember that the spring pressure is not directly below the attaching rocker shaft bolts.
There is that rocker arm which multiplies the 650 lbs (example) of the spring. The rocker arm is a lever, multiplying
the force as seen by the rocker shaft/attaching hardware.

With a 1.76 ratio:
600lbs of force at long end of rocker/lever.
600 lbs X 1.76 = 1056 lbs of force at the short side of the rocker/lever.
The pivot point (shaft centerline) sees 600 + 1056 lbs of force.

No wonder T&D race rockers do not rely on the 4 mounting bolts.