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Discussion Starter · #1 ·
Has anyone figured out the best main jet for stock 70 ls5 Ihave 78 now stock seems slugish and how much timing adv, at idle with vac adv temporarally disconected,ps engine is fresh and broke in but still have low rpm ping if I retard timing it kills low end I even put hei out of my zz502 it didnt help ???any ideas thanks Shawn.

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Shawn Wills
# matching LS5 70 convertible black cherry
2001 tahoe LT sunset gold
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Shawn what rods are they? And how do the plugs look ( assuming you've been driving and not just idling ).

[This message has been edited by Gene Chas (edited 12-18-2001).]
 

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U can go to your local speed shop, and ask the counterman for Edelbrock Quadrajet parts.

Edelbrock now stocks replacement jets and rods, and while you're at it, get yourself a vacuum gauge to tune your carb.

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Shawn, when you time an engine for "best tune" you really are concetrating on total timing, not initial. With your vacuum disconnected like now, rev the motor to 3500-4000 ( bring it up and down slow so as not to put undue stress on the rods). You will want to see a total of somewhere between 35-40, with 38 as a nominal. Once you get that , then see where your initial is. Then you can say, e.g., 38 is 15 inital so if we go to 12 we'll have 35, and if we go to 17 we'll have 40 etc. Plus this will make you check to see if your advance curve is functioning properly. You can plug the vacuum back when you;re done ( you'll see like 25 initial, dont fret!).

Of course, to do this you'll need either a timing tape on the balancer or a dial back timing light.

Shawn, I would reset the valves in a motor that has just been run in as well. Check a few and see where they are.

[This message has been edited by Gene Chas (edited 12-18-2001).]
 

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Discussion Starter · #8 ·
Gene thanks I am at 12 and 35 , valve lash is set 1/4 turn my ls5 coup I had did the same thing , could be the quiet exhaust as I hear even the slightest detonation I just went to 80 main and going for a ride thanks shawn
 

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that sounds like a lot of jet to me, i run a BB buick 462" motor with a 800 q-jet(runs high 12's)...073 jet with a 48 rod, mine runs rich with a .075
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by redbuick:
that sounds like a lot of jet to me
<HR></BLOCKQUOTE>


I second that.

It wasn't that long ago that I ran a Q-Jet with my combo and the richest main jet I ever ran was .075 with a .045 main rod and I'm making far more power than you.

78 jets are way too big no mind 80's.

Rejet that carb with 71 main jets, .041 main rods, AX secondary rods with a G hanger and your good to go.



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Discussion Starter · #11 ·
Thanks for the advice ,with the 80 s plugs are still tan but I will go back down in size and try that Shawn
 
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