Poli-Locks

[cecil misner]

Will someone tell me why I keep breaking poli-locks on my 468 BBC?

[Indycars]

Will someone tell me why I keep breaking poli-locks on my 468 BBC?

Can you give us some more info.....Is this a new build or did it just start breaking them?
Camshaft specifications, mainly lift and duration? etc etc.

How about some pics, that would be very helpful?

[cecil misner]

The engine is a 468 BBC with Edelbrock heads. Cam is a .570 intake lift and a .635 exhaust lift, it was made for this engine by a grinder here in Oregon. Engine dynos at 485 HP and 510 ft lbs torque. Running a Wieand tunnel ram and 2 Edelbrock 500's. Engine is fresh. Heads have adjustable guide plates and uses 3/8th pushrods, hyd roller lifters and roller tip rockers. To date, I have broken 2 poli-locks.

[Indycars]

I'm not sure I understand how the polylock is breaking, does it strip the threads or split in half or .......

Any pictures?

[Indycars]

Bottom line, you must have a valve train clearance problem.....something is binding and overly stressing the polylock. Did you check valve train clearance and geometry? Even if you have an engine builder assemble the engine, you don't know for sure until you check. Even the best builders make mistakes occasionally.

http://garage.grumpysperformance.com/in ... post-66870
http://www.enginelabs.com/engine-tech/c ... -it-right/
http://www.hotrod.com/articles/ctrp-061 ... -geometry/

ValveTipW_7.45_Pushrod_1530&1536.jpg (63.64 KiB) Viewed 297 times

ValveOnBaseCircle1559.jpg (52.27 KiB) Viewed 297 times

ValveAtHalfLift_0.235_1563.jpg (52.87 KiB) Viewed 297 times

ValveAtMaxLift_0.470_1561.jpg (52.42 KiB) Viewed 297 times

RetainerToSealClearance1559.jpg (57.65 KiB) Viewed 297 times

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[cecil misner]

The engine builder and I decided to go with a stud girdle and while we are in there we will check for spring bind and any other problem. The polylocks are breaking at the set screw and the top of the lock. The wrench surface and set screw will be laying in the head.

[Indycars]

Ok, so if I understand you correctly, then you are in the process of checking
now.....right? One can never go wrong with checking/verifying any clearances.
The only other possible failure point would be the polylocks themselves, I agree
that's kinda far out there, but I suppose it could happen. Maybe bad materials
or faulty hardening process.

If you get any pics, sure would be interesting to see.....definitely is a strange
failure for sure!

[cecil misner]

I will keep you up to date on what we find. Thank You for the outstanding tech information.