4100 secondary mods

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4100 secondary mods

Postby 289kford » Tue Sep 10, 2013 12:18 pm

Since I changed out my 4.11's for a 3.50 gear set, I'm wondering if I can get the secondaries to open a bit sooner. I know it's based on load and RPM, but with the faster RPM increase of the 4.11's, they popped open pretty quick before, and combined with that 4.11 gear.....
So now, it's like, 'wait a minute, almost, ahh here we go..' type of thing.
In the past, if I remember correctly, I read that Holley springs could be used (would be preferred method). I also know that there was a conversion kit made by Cal Corp. and that somebody on this site repros that. I think I have even seen a cable link added that would help start the secondaries. I don't want to make any changes that can't be reversed. This is not a must do project and probably something I shouldn't even mess with.
Just wondering if any one has made either change and opinion of such.
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Re: 4100 secondary mods

Postby 66kcoupe » Sat Sep 21, 2013 9:37 am

Mine has a kit to make secondarys mechanical, has been on the kar since new. Somebody repops them, easy install, no permanent mods, really nice to kick them in exactly when you want them.....NOW!
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Re: 4100 secondary mods

Postby rockhouse66 » Sun Sep 22, 2013 5:48 am

There is a check ball and a spring in the secondary vacuum circuit/diaphragm. I put a lighter (Holley) spring in mine, and removed the check ball completely, with great results. You can play with spring tensions and run with or without the ball to dial in the response change you want.
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