Do I have a carb issue? Help, this is frustrating

[84convertablegt]

OK, u can see my basic combo in my sig. Heres the problem. Yesterday, i was out for a little ride. I was warmed up all the way and out in the country messing around a little bit. I was under full throttle and manually shifting at like 4500 rpms, every now and then the car would just blurp and fall on its face for a second and then immediately catch itself and continue accelerating. this was only when getting on it in high rpm's. then when i got home i pulled into the garage and gave the car one last big rev and it backfired through the carb really loud, i could tell it was under the hood. besides this its running good, good idle, decent power. im wondering if its a carb issue or a ignition issue. i have a newer 4160 shiny carb and a new petronix ignitor w/ flamethrower coil with ford cap a dapt and 9mm wires, so hummmm. whats going on. it just feels like something is holding back the car when im acceleratiing a tad. timing is 10' btdc without vacuum, new fuel pump (5psi). basically new everything. its a new motor.

 

[Dark Knight]

is that 5psi at idle? electric pump?

sounds like an acc. pump prob though.. I changed to the black cam on my 84, same carb that you have, I think, and it got rid of a hesitation I had..

you might try bumping the timing up too..

 

[nds03]

you can also get bigger squiters for the accelorater pump. thats what i had to do on the demon

 

[84convertablegt]

yeah, thats 5psi at idle. mechanical pump. hummm, i love holleys until something like this. i should have got the street avenger i had one on my 84vert and that thing ran so perfectly i cant even compare them. of course i cant rule out a possible ignition miss either, but it just feels carb to me. i really dont think buying a 6a and new coil should be neccessary for my setup. i dont know. what is the black cam????

 

[Dark Knight]

acc pump cam... you can buy a pack of different ones
this will show what each cam does
http://www.carbdford.com/viewtopic.php?t=4737

might try the message board there too...

 

[grego37]

You said you initial timing is 10,
how much total advance are you getting?

 

[84convertablegt]

i dont exactly remember, but its something in the 30's i believe if i remember correctly at id guess around 3-3500 rpm

 

[grego37]

for the heck of it , you should check and see if you're getting full advance.If it checks out ok , then you can rule out the timing and focus on the carb.
Im assuming you have a timing light or can borrow one.
For safety put a wheel chauk or block in front of the front tire.
check timing at idle again to varify what your initial is.
Then bring the rpm's up slowly and watch the timing marks move on the balancer. keep bringing the rpm's up until you notice the timing marks stopped moving (approx 2500-3000 rpm) read your timing.
this will be your total timing.
example:
if you have 10 initial
and you have 34 total
that breaks down to ,
10 initial
24 advance

your total timing should be in the area of 32-36, give or take. every engine is diffrent and requires its own timing.
You just want to make sure your advance isnt getting stuck or something.

If everything checks out ok, I'd think its your carb, it may be too small?
Do you have a friend with a 650 you can throw on to see what happens?
You can also call Holley tech line, they can be helpful sometimes. You may want to bump the fuel pressure to 6psi.
Im assuming you checked the float bowl level.
good luck

 

[84convertablegt]

well, i know the advance is working, because it wasnt so i put a new vacuum unit on a month or 2 ago and it all checked out then. i will verify my timing again though just to rule it out. i have also checked the float level, it is right on according to the manual. im thinking im gonna try out that s.a.670 and see how it runs just to rule out the carb. a friend of mine owns my old 84vert with the 670 carb, so im sure he'll let me borrow it for a minute to try out this theory. the 670 on my old vert is tuned perfectly for a stock 84 302 so it should be a good test subject.

 

[65fastback2+2]

do you have the petronix ignitor II and flamethrower II?

 

[84convertablegt]

yes, why?

 

[D.Hearne]

Check for water in your fuel bowls. If it's there, it'll do just as you described

 

[2nd Mustang]

Don't know if this will help, but while driving my Stang today, I noticed that the pickup in the lower gears were significantly hampered, it just wasn't what it used to be. When I got home, I popped the hood (haven't opened the hood since the last oil change 5 months ago) and noticed the open element air filter was a dirty brown. Replaced with a new element and now am chirping tires and hauling ass in first and second gear again!

 

[65fastback2+2]

yes, why?

cuz you have to use either both I or both II, you cant mix them or they wont work properly

 

[84convertablegt]

well, its all II components and it seems to work great, so i hope thats not my problem. well, i know this is a stupid response to my problem, but i ordered a street avenger 670 yesterday and it arrived today already. ive been looking for an excuse to buy one, i should have in the first place. some may say its too much carb, but i had one on my 84vert and it worked perfectly.... besides, they look good and in my experience provide lots of power. so if that doesnt fix it, which i think it will, then time to move on to ignition and i guess ill have a spare carb laying around. nothing wrong with that. i dont really think theres anything wrong with my other brand new holley 4160 but i just like the dual bowels and center hung float bowels of the 4150 style carb. now i just have to hide the reciept from my wife. ill let u know if this fixes the problem, although i probably wont get to it until saturday

 

[2nd Mustang]

......i guess ill have a spare carb laying around. nothing wrong with that.

Don't worry, you're not alone. I have two other Holley 600's laying around. One needs a new throttle bushing and the other has the choke horn cut off.