[fonzoayala88]

so on my 351c i have a 670 cfm holley vacuum sec SA. hand me down from my 302 i used to have. ive been tuning it because i have a off idle hesitation/stumble, only when i mash the pedal, if im gentle and accelerate slowly there isnt a problem ( but then wtf is the point of a 351c if ima slowly accelerate??) so i bought a bigger discharge nozzle # 35 used to be # 31 to get a lil more juice in it, and i bought a set of quik fuel pump cams via summit. so my problem is i went through all the cams except this ridiculously big one, and none of them seem to fix the problem. my question is, do i really just need to jump to a higher size nozzle like #40, and upgrade to a 50 cc pump? or is there a different route i can go???

any one have had the same problem and went that route to fix it?

i have a weiand xcelerator intake on 2v heads, stock cam, hooker super comp headers. and full msd ignition.

as always all help and input is greatly appreciated.

[cindys_sn95]

unless the adjustment is way off the larger squirter should have done it. have you tried pulling the timing up a little?

[The Greek]

The problem may be in how the accelerator pump linkage is adjusted. You need to follow Holley's method with the throttle held completely open. Then you will need to fine tune it at closed throttle so that the pump starts actuating at the moment the throttle starts opening. If you have slack in this linkage, no matter how slight, it will delay the pump's delivery and still cause you to have the flat spot. The pump's actuating arm should slide across the diaphram's contact point, but without diaphram depression. If you adjust the arm and it is depressing the diaphram, the pump's nozzles will dribble fuel. You have to find that "Sweet spot" between having slack and depressing the pump"s diaphram.

Holley's web site has all of the instructions and info that you will need. Good luck.

[fonzoayala88]

i have the box wrench dvd on holley carbs. ive watch the tuning part several times, every time i put a new cam i would readjust. but then it says also on the dvd that a large plenum intake would effect the way the carb works, and the xcelerator intake is pretty big, and its a single plane. i havent got a chance to mess with it today, busy setting up bs for my girls bday party tomorrow. ima try advancing the timing like cindy said. once i put the bigger nozzle the first time it did help a bit, but i probably should get back in and check that slack issue and use the .015 feeler gauge like the dvd says too. the msd ignition gives alot of spark up to 3k rpm. then its just a stronger spark so. it should burn up all the gas regaurdless, dont really think the timing is the issue, cuz its only off idle when it acts that way, and when it reaches up to about 15 to 1700 rpm it hesitates a very very slight bit then picks up, not a problem at all, but the intakes rpm operating range is said to be from 15-1700 up so it would make sense for it to do that at that point.

[The Greek]

I didn't realize that you have a single plane intake. These don't work too well at the low RPM range required in street driving. The large plenum area is diluting the velocity of the intake charge. You may never get the hesitation to completely go away with this type of intake. If you can find a high rise dual plane intake you will still be able to retain most of the higher end performance of single plane, but with its smaller plenum area, you will be able to establish better intake charge velocity and better response from the carb.

[fonzoayala88]

hmm, i thought so, but id imagein its worth the try to get the bigger nozzle and the bigger cc pump. im sure that fuel is the major issue, so maybe if i can get enough it will work out well. cuz like i said if i eaze it open slowly it doesnt have any hesitation what so ever, its only when the throttle opens fast, then is hesitates and picks up again. so maybe if i through in more fuel right away as it opens it will cancel the hesitation. what u think greek?

[cindys_sn95]

where is your timing set at?

[The Greek]

Going to the larger 50cc pump is what I'd do before investing in another intake. This pump has a taller housing which may require you to install a spacer on the carb base. Holley recommends a 5/16" thick heat insulative spacer between their carbs and manifolds, regardless. Having this in place should give you the needed space. The spacer, being insulative, prevents fuel bowl perculation from heat soak and the resulting hard starting. I won't mount a carb without one.

Here's Holley's part numbers for the pump kit and the insulative spacer.
P/N 20-11, 50cc Accelerator Pump Conversion Kit. This kit includes everything required for installation, including Nylon pump cams.
P/N 108-12, Heat Insulator w/Studs,Nuts 5/16" Thick w/Phenolic Eyelets.

You just might get enough fuel down the throat of that intake to have success. Let us have an update when you have a chance. Holley has their catalog on line, FYI. Cindy's question on timing is valid. You may need to advance or retard a couple of degrees.

[fonzoayala88]

all right, ill be sure to adjust the timing if needed. then go with the 50cc chamber, either way eventually i will need it. i dont really want to buy another intake, i mean it is functional its just a really anoying. i also found a 50cc pump kit from quik fuel thats a little less expensive threw summit. ill be sure to post up on my progress and on any issues if they come up, hopefully will get to work on a friends 01 stang, he needs a new clutch install told him id do it all for 50 dollars. that way i can order the necessary stuff.