Are the stock LT4 valve springs the same size (diameter) as the stock 87 LG4 valve springs? I actually have a set of LT4 springs (new) that I got for free and will be doing a cam swap soon and would like to know if they will fit or will I need something else. Thanks.

 

Yes. They are the same non-performance, or at best entry-level performance, diameter, 1.25". They'll work fine at lifts up to around .500", but don't believe GM's claim that they'll go to .525".... a bunch of people have experience to the contrary.

Trash the factory rotators and umbrellas, and get regular retainers and new keepers from Comp or Crane or Lunati or some other of the major cam mfrs.

 

WHOA! that was fast! Thanks alot. I will be changing the rotators and umbrellas. I just thought I would install those when I swapped the cam, not going for high performance, just a little better. The next motor is for performance

 

Ummm... You'd better be a little more specific. While I can't say for sure about the "standard" LT4 springs, the LT4 "Hot-Cam" rated springs are larger, and required me to machine to 1.550". The LT4 "Hot" springs (GM P/N 12495494) are much larger than the stock 1.260" spring seats will accomodate, and are rated to at least 0.525" lifts with 105# of seat pressure at 1.710" installed heights.

EDIT: The factory titanium alloy retainers and locks for those springs are P/N 12495492 - LT4 lightweight retainers, $15.54, and 12495503 - 10° Valve retainer key set $ 6.83. I know the LT4 lightweight retainers are a titanium alloy, since I used to maintain and repair the very National 1000 six-station coldformer that made them (and Cadillac Northstar retainers, too). You'd be surprised at how much titanium alloy GM specifies for its OEM parts. Even the old spacer/collar studs that were used on cat converters and some Delphi sensor bodies are/were titanium alloy.

 

These are the standard LT4 springs, not the Hot Cam ones. I also got the factory retainers and locks. Thanks!

 

The, as RB indicated, they'll make an excellent set of door stops. You might even be able to put them to good use in the front fork of your BMX bike, if you stack enough of them...

As long as they're out, I'd lean hard on trying to find a better set if you cam net lifts are over .460" and/or the maximum accleration rates of the valves are over 0.004"/° cam rotation.

 

I just found out that the springs are actually IRS Terminator Dual springs. Are these the same as the LT4 springs? Better?, Worse? Thanks again.