I'm trying to decide if it's worth the extra $$$ or not to buy new ones. how much seat pressure can they take before the locks start pushing through?

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JSP Motorsports
ICON Motorsports

 

there isn't any far as i know. only time i change is when i use bigger springs or differant angle locks

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ICON Motorsports

1st & 3rd

 

It's worth it.

Ever drop a valve?

It'll really be worth it after you do. They're real cheap compared to cleaning up that mess.

Don't know the spec, if there even is one. I have seen them get hammered through by coil bind though. I replace the whole group of stuff whenever I put on new springs. I figure if the springs are inadequate or worn out, the retainers probably are too. I change the keepers practically every time I take them off.

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"So many Mustangs, so little time..."

 

now that i ithnk about it a little more i change them too when i use afretmarket springs. usually i have had to to get the correct installed height. the stock set up isn't very good and it adds weight to the valve train.

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ICON Motorsports

1st & 3rd

 

RB83 got it right when he mentioned about them getting shoved through on coil bind. Usually they don't fail unless you goofed up something in the valvetrain.

I've used stock STEEL retainers and 7* FACTORY locks with as much as 135 PSI seat pressure. That's a wicked-strong spring when you consider it was only a stock 1.25" diameter valve spring!

Realistically, if you're running more than about 120 on the seat, though, you're probably already going to be moving up to larger diameter springs, which require larger diameter retainers, at which point you basically have to move up to stronger pieces (and maybe 10* locks) anyway.