CRG Discussion Forum

Camaro Research Group Discussion => General Discussion => Topic started by: WaltZ on November 13, 2020, 07:38:49 PM

Title: Jet & Power valve thoughts for 69 stock rebuilt 302
Post by: WaltZ on November 13, 2020, 07:38:49 PM

1: rebuilt to stock 69Z 302, Holley 780 correct carb: running primary jets 70 with 4.5 power valve. Had a 6.5 pv and replaced it, this did away with the mid range stumble.
Now just a a stumble or stall from a dead stop, once it gets going it's smooth and snappy after about 1200rpms.

2: Secondaries: what jets and pv would be recommended for secondaries and what about a secondary plug vs. a pv

Thanks in advance
W

Title: Re: Jet & Power valve thoughts for 69 stock rebuilt 302
Post by: crossboss on November 14, 2020, 07:35:27 PM

Sounds like an off idle lean stumble to me. Check your carb adjustments! Especially, your accel pump cam is correctly set. If all else fails, try installing a one/two step up squirter size.

Title: Re: Jet & Power valve thoughts for 69 stock rebuilt 302
Post by: Stingr69 on November 16, 2020, 08:10:42 PM

I agree with crossboss.  You might have slack in the accelerator pump arm at the linkage.

Set floats first before any other carb adjustment.

If you change anything in the accelerator pump system, you need to re-check the accelerator pump linkage for ANY slack.  The proper adjustment is frequently misunderstood.  The arm needs to be able to travel FURTHER when the carb is at wide open throttle so it does not bottom out.   If the pump linkage bottoms out, you will bend the linkage and add slack which will cause the lean pop or bog at a minimum.  No slack allowed at rest.

Also need to make sure the transition slot is not too far exposed.  If you turn the carb over upside down and look at the transition slot, the butterflies should only expose enough of the slot that you see a "square".  If it looks like a "rectangle" the butterflies are too far open and you can get a stumble at tip-in.  Probably a rich idle mixture along with that.  Once you close the butterflies down so you have the square, do not adjust the idle speed screw.  Sounds crazy but this is how to do it.  You may need to adjust the secondary butterfly stop screw if you need more air at idle.  Might help if you re-curved the distributor advance mechanism to add more initial advance.

Readjust the idle mixture screws last.

Title: Re: Jet & Power valve thoughts for 69 stock rebuilt 302
Post by: WaltZ on March 29, 2021, 02:42:07 PM

thanks,
bumped up the squitter from 25 to a 28 and made a noticeable difference,
Thanks again!