Low RPM (vacuum?), High load bogging
 

My car runs sooo much faster now, just got a question..... When its at low rpm, or at idle, and i hit the gas and it will bog, only if i hit it too much. Because of this , as i leave from a dead stop, or accelorate out of a sharp corner i have to ease on the gas as the rpms go up, i can plant my foot at 2000rpm and it takes off!

I know that new gearing will help , but i gotta get to that later. This low vacuum high load (isnt that wat the powervalve takes care of?) is the only thing that my car will bog on. It makes it almost impossible to do a nice burnout, cause i can nail the gas right away.. plus i dont have a stall. Just wondering what u guys think, i know its not the most important thing, to be able to burn out but i like the idea of being able to do it when i want to hehee


And i changed the vacuum spring in my car already, from a medium light (which bogged at full throttle when under 2700rpm) to a medium hard (which does great all around). And im sure my vacuum secondaries arent kicking in at 1000 rpm lol.

Ive read somewhere about drilling tiny holes in the throttle plates to alow more air to compensate with that fuel at low rpms, but i figured some of you guys would have a better idea. And my powervalve is perfectly fine. Thanks.

Tom

for the record, Im green with envy right now. My car keeps messing with me. last week the throttle cable broke, now my drivers window wont go up....

I cant wait untill I can start adding cool things to my car like an intake and 4 barrel. all ive been able to do so far was an MSD 6A box and blaster 2 coil.

congrats.

a tip of the ole stetson,
Mike

Re: Low RPM (vacuum?), High load bogging
 

Your problem is with the accelerator pump. You either need to adjust it, change the pump cam, and/or install a larger squirter.

For you, I'd recommend the green pump cam (in the #2 hole) and a 27 squirter.

Take care,
~Chris

im reading in on how the accelerator pumps work. How do i adjust the one thats in there now?

It says here: http://speedfreaks.safeshopper.com/847/cat847.htm?745 that the pump cam is an easy change. But how about the squirter?

the 27 squirter would mean its .027 right? what size squirter is in the stock holley 600cfm carb?

and my car idles around 600rpm so would that mean i would wanna put it in the #1 hole instead of #2? Just trying to learn as much as i can bout it. Thanks

Tom

I'm tired, so I'm going to bed, but i'll follow up this thread tomorrow. For now:

adjust the pump with the spring-loaded screw/bolt and nut that puts pressure on the pump arm. You want zero clearance, but you don't want ti to bottom our, either. Just make sure that even if a breeze hits the accelerator shaft, fuel squirts out of the squirter. The squirter is 1 phillips screw, and the cam is 1 flathead. Put it in the second hole.

Good Night.

:)

Before I forget, what is the List # of your carb (it's stamped into the airhorn)

i need a better description of the accelerator shaft, but i think i know what it is. I dont know where those screws are that you were talkin about. So what should i do about that nut and spring part? And what accelerator pump size should i order from summit racing?

and the numbers on the air horn are "80457" and below that its "2356"

heres a picture

and another

Check back here in about 30 minutes, I'm putting together a descriptive webpage for you.

Okay, click on the link below, and when the page opens, click on the first picture, and use the controls at the bottom of the window to go through them. There are brief descriptions at the bottom of each page.

Accelerator Pump Cam Replacement

Take care,
~Chris

Thank you sooo much!!!!! now i can figure out exactly what i gotta do! And what size accelerator pump should i order? cause theyre like 9 bucks a peice at summitracing.com.... thats kinda expensive to buy a whole bunch and fiddle around... thanks alot!

oh and my pump cam is in the #2 hole right now... its a purple-red-ish color. i will try adjusting it tomorrow

You're welcome. :)

I don't have a listing for the number you gave, so I don't know what size squirter it has. I would go with a 28, but you may already have a 28. The number is stamped on the squirter. I also would highly recommend the green accelerator pump cam (has #290 on it) in hole #2.

here a page that has all the info on holley carb parts list

http://www.holley.com/HiOctn/ProdLine/CarbList.pdf


you need to have adobe acrobat reader to read it, but it will show you what your carb has and then you can figure what you need to buy. might have to zoom in to see anything.

according to this list your carb has a .031 squirter, but to be safe check out what your carb has it should be stamped on it.

Adjustability
 

To me, that's the wonderful thing about Holleys and Demons. They are infinitely tuneable and I can just buy the parts at the local parts house. A book on Holleys helps a lot.

Rev

Is there really anything i can do while the carb is on the car? Do i have to take it off and install the new pump cam? That step by step thing u made was reallly awesome, and i learned alot. But my carburator is just annoying me alot. The powervalve is fine, thats check, but every once in a while, if i put 100% throttle, and its below 1500rpm it will pop, not really loud or anything, just a small pop.

I want to be able to just plant my foot to the floor and spin the wheel(s). Instead of ANY bogging, or any popping (which happens more than bogging). There is kinda a delay when i hit the gas, but accelerating from a dead stop, as fast as i can i have to ease onto the pedal more and more till about 3000rpm then i can floor it. I need to get rid of this exhaust, it has alot to do with the problems too. it holds my rpms up at like 4500. when it was alittle loose, leakin some, it would easily get up to 5500, where i shift when it revvs well.

With all that said, im just wondering if im doin something wrong, or my carb is screwed or i have to spend another wod of cash on parts for the carburator..... i know holleys are good, but why does it have to be a pain in my ***? Had enough trouble with the last one.

Oh and i have my transmission kickdown all hooked up correctly with a spring pulling it back to normal possition.... the throttle on about 3/4 open it kits the kickdown down. Yet, when i punch it, it never downshifts into passing gear.......... My car has really good top end with all this right now... but under 40mph its slow as heck. And thats not gunna make me appreciate it any more than i did before.... I dont really enjoy doing 80-110mph really fast, its a bit dangerous. thats all my car can really do with this gearing and how the carb is runnin (well at high rpms 2500+).

Thanks for your help. I knoew i would never decide weather i liked a holley or edelbrock carb more, some people like one, some like the other, i chose to start with holley to see how i like it. Its kicking my *** right now. I wonder if an edelbrock really is easier, but im NOT about to spend the money on another ******* carb.

Im gettin alot of help on VMF right now also, if your not already a part of those forums, check em out. Tons of people in there.

Heres the thread: http://forums.vintage-mustang.com/fo...t=1&PHPSESSID=

Hey Metal, congrats on getting it up and running!! You've got to remember that 351C's are notorious for having no bottom end. They do not preform well at low RPM's. When mine was running people would leave me at the line then I'd catch them after my RPM's got over 3000. Its the large intake ports. Oh and just so you know, what feels like a bog when you go WOT (wide open throttle) is really your engine NOT getting enough fuel. All of that can be dialed in but it takes time. Be patient, change one thing at a time to see how it effects excelleration. You've gotten some good advice here already, not much I can add.
If all the tuning fails the only thing I would suggest is Port Plates. (but then you'd have to take the manifold off again) They bolck off the dead spot on the intake port. Making it smaller thus increasing the intake charge velocity, increasing low RPM performance and throttle response. Without choking the top end because they're the same size as the smallest restriction in the port anyway. Jeez did that make sense! lol Hell I confuse myself sometimes! Good luck hope everytinhg turns out ok

Johnnie

I cant nail the gas of the starting line at all. If i do, it will usually backfire through the carb. The extra shot of fuel it needs, at WOT that you were saying, supposedly comes from teh accelerator pump which im supposed to next tune.

Its really beginning to be a pain now. Im thinkin about tryin an edelbrock, which will actually help out in everyday driving anyways, and theyre pretty simple to tune. Easier than holley's anyways. And yes, i do drive my car EVERYDAY.

Changing the accelerator pump nozzle seems to be a bit trickier than going by the edelbrock tuning chart and changing the metering rods and jets. Doing the holley pump cam is simple, but i have yet to find a chart for that. Overall i will have to buy alot more accesories for hte holley than the edelbrock. And what if i put an edelbrock on, adjust the idle mixture screws, and it ran perfectly without any other tuning? Seems more simple than screwin around with a holley that flys right over my head.

Before i start messin around changning carbs and what not im gunna do my exhaust. Cause my car DESPERATELY needs a better exhaust system. Im gunna get hooker comp headers, and have the local muffler shop install 2.5 inch pipes, with 2 chamber flowmasters. How do H-pipes help? The exhaust system will cost 250 bucks alone, after i buy and put the headers on myself.

Do you know how big the cam is that you're running? The super comp hookers and 2.5 inch duels sound great. An H-pipe balances out the exhaust system gases and helps with the scavaging effect. It will help you with low end torque. You might not need the 2.5 inch pipes though, 2.25's might be better. What exhaust are you running now? The smaller pipe might increase the exhaust gas velocity more than a big pipe. Because you're running 2v heads your system probably wont flow over 6000RPM's, so the need to run a 2.5 pipe that will flow better at high RPM is not necessary. Just my 2 cents

I have no idea of the specs of my cam right now. Its a "RV midrange cam", or so im told. Watever it is its pretty weak. And 2.5 inch pipes will be good, if they dont open up anymore horses than the 2.25, well i might as well do it just for the sound :D ! hehe. Yeah im gunna get an H- pipe put in there too.

Right now i have crappy 2 inch pipes, but around the bends its about 1.75 inch diameter. And the mufflers are a "walker" brand that ive never heard of. They sound good at idle and thats about it. I already cut off the tailpipes, they were 1.75 inch diameter, but about 1.5 at the bends. Really weak.

Anyways, all the engine pics and of the swap are right here: http://www.geocities.com/spddemontc/MustangEngine.html

And some new exterior pics of my car: http://www.geocities.com/spddemontc/MustangSide2.html

I still gotta add more stuff, like route-66 2002 and what not on there.

And as far as carburetion goes, im gunna try and sell my holley for how much i paid for it, and buy an edelbrock 600cfm manual choke (part ID 1405). And buy a calibration kit for it just incase hehe. Talk to ya later.

Tom

Hey Tom, if the cam is not a radical grind, then you're probably not going to rev up over 6000RPM anyway. So everything i was going to add dosent apply. You are right for getting rid of the 2 inch exhaust though. you're choking the enigne. I still say that with a mild cam and 2v heads the 2.25 pipe is the way to go, what did the shop reccomend? But then 2.5's do sound nice! lol Thats what I'm running, but then I'm flowing alot more air than you are at this point. Listen to alot of mufflers also. There is nothing better than that low rumble when you pull up to the light. Dont be so fast to trade in that Holley. Remember 2V heads dont flow at low RPM's so changing to an Edelbrok might not help it anyway.

Well somethings up with the carb, i would before with the 2 bbl, hold the brakes lightly and hit the gas and it would push. With the holley it just dies and/or backfires through the carb. Edelbrocks are much easier to tune, already from reading their website i know how to tune em. Plus i have several friends that ABSOLUTELY LOVE THEM. Alot better for daily driving too, so it seems to be the way to go.

I havent had any suggestions from the muffler shop, but from other peoples oppinions 2.5s seem like the way to go. But we'll see. I havent heard many different mufflers, cant really find any good sound files online. I heard flowmasters quite a bit and i like em.

I would run 2.5 on the exhuast i would also recomend larger then a 600 especially if you are going to a carter/edelbrock. My first car awas a 2-V Torino stock except for i put the bigger 4-V valves in it and was running the Holley street dominator intake and I had a 750 Holley on it. It would do the classic over carbed bog it i floored it at anything under 1500 (that was with some adjustments when i first put it on it would spit back at anything under around 3000) but i was willing to live with it because of the nads it gave me up high with the stock cam I was shifting at around 7000 (valve float for me was at 7200) now I was young and stoopid at the time but realisticlly i would still carry it to 6500 if i still had it becasue it was still pulling tlike a frieght train even up that high. Also found this on a Pantera board this is how that guy took care of it. Also his is a DPP not a vacumn sec but hope it helps

> I had a very similar set of symptoms with my 750 dp - though
> probably less extreme than yours. Throttle roll in was fine but
> sudden WOT would produce a very noticable stumble. After chasing
> accel pump cams, squirters, and power valves for about 6 months, I
> finally decided that it must be the jets (doh!). I'd gotten
> fooled into thinking it wasn't the jets because my plugs were nice
> and tan after track events with lots of WOT. Eventually I decided
> my primary mixture must be too lean, so I richened up the
> primaries by 4 sizes (up to 70) and to maintain the overall
> mixture I dropped the secondaries by 2 (to 76). The stumble
> disappeared completely.
>
> But maybe the point should be that for a novice carb tuner, the
> symptoms can be very confusing. Eventually, I learned a couple of
> things from my various tuning dead-ends: 1) don't change more than
> one thing at a time, no matter how tempting it might be (the
> carb's all apart, right?), and 2) make the adjustment jump large
> enough that you will know whether you made things better or worse -
> it's not always obvious. You can always back-up by half the
> original adjustment if you need too. Eventually you'll get there.
>
> Also, most of the off-the-shelf Holley rebuild books have a table
> in the back that tells what jets etc. were in the carb when new.
> That should give you a rough starting point for setting it up.
> You just need the Holley list number off the choke horn (3779-3,
> or something like that).
>
> Just for reference, I have a pink primary pump cam and and a white
> secondary cam with 28 (p) and 32 (s) nozzles.