PontiacBonnevilleClub.com

Not enough. That's why they broke. 45 ft-lbs

They are 5/16 bolts, not 3/8.

Re-drill and tap for 3/8" and you'll be good for 150#

They ave to fit through the rockers.

Could re-drill those too.
That's what you have to do sometimes when you go above and beyond stock.

Uh, I dont think weakening the rocker trunion and body would be a good comprimise to put a bigger bolt in.


I put some thought into a girtle system for those rockers before shelving them and eventually selling them to matt. It can be done but fitting under the valve cover might be hard.

Then he should back down to the 130# that have been proven to work on the fastest INTENSE Bonneville.....albeit it wasn't a turbo but it had a wipple charger. He ran a 10.7 @ 125 or 8-Ball with a Gen V at 12.2 @ 112

Being conservative, a turbo system has a 2:1 back-pressure ratio, 3:1 is not unheard of. And I have every intention to run 20 psi on the turbo. Which means the exhaust side is running 40psi+. I don't know what the Whipple or the Gen V are running in either setup, but it's not anywhere near 40psi. And I will be pushing this setup to 6800RPM, the ST5 cam makes good power there. I know this sounds crazy, even with what I've managed to do, but I'm shooting for an 11.5 quarter mile.

I'm not convinced that an over-torque is not the root cause of this failure. I need to find a good metallurgist who can read these bolts, I'm seeing two distinctly different fracture patterns on the set of bolts that broke. For reference, the pre-load on these bolts was in the 5000lbs+ range. Even if both springs were compressed at the same time each bolt wouldn't see more than 900lbs load (I think I calculated that correctly based on a 500lbs compressed/spring). The only way they could have failed is if only one bolt was holding both rockers down being subjected to both torsion and tension forces.

This could be validated by the comp cams bolts NOT failing, another 170,000psi bolt.

Got a better video with a Gopro. We really need some daylight for this though.

https://www.youtube.com/watch?v=L0I-tpd ... e=youtu.be

That video is so much clearer. If I had time to take off, I would love to go back up to Michigan to see that car!

What turbo was he running? I've only ever seen the videos of that burnout, hadn't seen any build thread.

T4/62-1 according to the 2nd page of the GMForum thread. (not sure if linkable on here)

I read he was only running 6 psi in his wastegate, but it compounded to ~16 psi. Seems like that size turbo was overkill for such a small amount of boost.

They were the guys that built my limited slip diff.

bs009 wrote:I read he was only running 6 psi in his wastegate, but it compounded to ~16 psi. Seems like that size turbo was overkill for such a small amount of boost.

Yes. Yes it is. Any twincharged setup that isn't running in parallel is overkill with any turbo that isn't physically larger than the supercharger. I'm also interested in what cam he was using. Looks like he had a series 2 L67 as well.

Is he still around? I want to pick his brain.

I haven't noticed him post in years. You can try here, maybe you can peak his interest with your build.

http://www.engineered.net/eplsd.htm

Brake bias is definitely too much in the rear. The correct way to fix this is to use a properly sized rear caliper piston, but for the cost I might just try an aftermarket proportioning valve. If I'm reading correctly they are a constant linear decrease in line pressure, not at all like the OEM proportioning valve for the rear drum system which doesn't take effect until a set pressure is reached.

So I filled up today. 8.7mpg. I can't say the driving I've done has been indicative of my normal DD commute. But I have to say I might be able to give the new Hellcat a run for it's money on who can drain their fuel tank faster...

Pulled the trigger on a 2.8" pulley and MPS hub, the 3.25 and hub I'm currently using will go on the '97 LeSabre I'm working on.