So it broke again....*UPDATED* 25/09/2016 WITH PICS

My cousin and I travelled 4hrs to Miramichi Dragway for the fall brawl yesterday. I've never been there before so it was fun to try a new track. I got 5 time trials last night, only got 2 clean runs and blew the tires off the other 3...on the return road the engine didn't sound right on the last run...We pulled the valve covers and found the same stud boss that broke in May and was repaired had broken off again. Clean break, no other damage seen. Push rod looks fine and the oil pressure was fine. I wasn't really confident in the weld from the get go. I'm no welding expert by any means but I have worked in a tanker shop so I've seen a lot of aluminum tig welding and the weld didn't look all that clean to me. It's a SFT cam, the over the nose pressure is around 375lbs I believe.

My question is: should I take it back there again or send it down south to have it looked at and where???? I took it to the best engine shop there is in these parts. The owner was away racing so this was repaired by an employee. Had Alyn been there I think the weld would have been better.

I'm limited here with other places to have it repaired. One other thing on my mind is my PRW stud girdles - I hate them. They are ignorant to install and I'm wondering if they are not part of the issue here? I'm going to get a set of Jomar girdles over the winter. I have a 7000 pill in the 6AL, the last pass she bounced off it pretty hard when it hooked, spun, hooked and you know the drill as I tried to pedal it out. Here's the thread from May.

https://www.429-460.com/t24713-finally-dipped-into-the-9-s-and-then-broke

Looking at your broken boss it looks like you need more length on the lower part of the stud where it goes in the head. I'd measure how much thread there is under the boss and get as much as i could in there. At least 2 times the diameter.

If you have stud mounted rocker arms and are racing ... although any stud girdle will give some support IF they are used correctly, why aren't you using a Jomar made stud girdle in the beginning...? You probably got your money's worth.

This was my first BBF Randy, it could be one of those lesson learned deals or I may have not known about the Jomar stuff when I built this thing 5yrs ago. Up until this engine, I always ran SBF's. What little I know about BBF's I've learned here. Once I get it apart I'll post some pics. It's not as ugly as last time.

I would be tempted to go with shaft mounted rockers spread the load out

Larry Williams wrote:I would be tempted to go with shaft mounted rockers    spread the load out

This has crossed my mind.

Here's what I found. I haven't pulled the head yet. The studs have 3/4" of thread under the hex. Pushrod is dead straight.

Not nearly enough heat on that weld.IMO

A rocker stud with a longer base thread into the head does sound like it would probably help support the repaired rocker boss better.

The weld seam/joint between the broken rocker boss & head needs to have a "V" groove ground around the weld joint to help increase weld/heat penetration. This needs to be done with a carbide cutter-bit. Never use a grinding-sanding wheel/stone/drum/etc to dress an aluminum weld joint before welding. This is because aluminum-oxide grit/particles from this type grinding bit can become embedded in the parent aluminum contaminating the weld puddle.


IMO if the original rocker boss repair wasn't done dead-nuts perfectly straight the first time (and was possibly a little off center), bolting down the stud girdle probably put enough side loading on that stud/boss assembly (trying to pull the stud back straight) that could have been what broke the old repair weld.

DILLIGASDAVE wrote:..........................IMO if the original rocker boss repair wasn't done dead-nuts perfectly straight the first time (and was possibly a little off center), bolting down the stud girdle probably put enough side loading on that stud/boss assembly (trying to pull the stud back straight) that could have been what broke the old repair weld.

I was thinking the same thing. Was the girdle used to "jig" the stud/boss during the repair?

jbozzelle wrote:

DILLIGASDAVE wrote:..........................IMO if the original rocker boss repair wasn't done dead-nuts perfectly straight the first time (and was possibly a little off center), bolting down the stud girdle probably put enough side loading on that stud/boss assembly (trying to pull the stud back straight) that could have been what broke the old repair weld.

I was thinking the same thing.  Was the girdle used to "jig" the stud/boss during the repair?

No because I didn't send my girdles with the head when it was taken for repair. I wasn't happy with the weld from day one, and I'm even less than pleased with it now. I'm thinking I should send this somewhere else to be fixed this time. Shipping sucks but I might send it over the border to be repaired if you guys can recommend a place? I was hoping Dave F when see this and remind me who fixed the other 2 stud bosses for him when he got them.

The sad part is, had the shop owner been there and done it himself it would most likely have been done correctly. He was away racing at the time and I didn't know that when I sent the head down
there.

Make a trip back to that guy. He may do you right since he didn't repair it personally himself.

jbozzelle wrote:Make a trip back to that guy.  He may do you right since he didn't repair it personally himself.

That's what I was thinking but I'm going to call ahead as it's almost a 2 hour long drive from here.

Looks like a bad weld aluminum has to be super clean and like was said needed to have a v groove also. Looks like they didn't do ether one clean or groove it to much black behind the weld probley from oil in the pores of the aluminum .

dfree383 wrote:Looking at where that broke, might want to look into some studs with a longer base part?

Might be where the problem is and was on the other ones too.

I was looking at that too but when I took the other stud out to get the guide plate off it seems like the threads don't go to the bottom of the holes...It's like the stop .200-.250 from the bottom.

Can use a flatbottom tap to thread them as deep as possible.