Just spit-balling here;
sorry in advance for the short book
{?} not enough Ignition timing {too retarded} could very well
be a contributing factor here too
{
it's not uncommon, especially for a lower compression engine,
especially with a big cam to want like 20* initial advance {38*+ total}
vs the normal 10*-12* initial advance {32*-34* total many say to do}
like a stock or higher compression build, it's kind of a band-aide (advancing),
usually kind of for a miss matched/wrong parts combos}
what is you timing set at ?
What is the initial & total advance in degrees ?
when is the advance all in ? & at what RPM ?
you said it has a Chyrsler EI, does it have an adjustable vacuum advance ?
if so, how much timing is added by the centrifugal &/or vacuum advance ?
what box controller are you using orange ? chrome ? or some other aftermarket box
does it have any modifications to the centrifugal weights ?
or the advance springs {lighter} to get the timing in a bit quicker/earlier ?
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just for curiosity;
how big of a camshaft does it have ? what is it ? what was it set at ?
when installed & was it degreed in ? a what deg. &/or advanced or retarded ?
if it's retarded & low compression it could be an issue
{albeit most modern cams are ground with advance for timing chain stretch like 2*-4* advance}
does it have headers & free flowing exhaust ?
what other mods were done to the engine ?
does it have adjustable rocker arms ? if so are they adjusted properly ?
{proper length pushrods}
did you do "any other or multiple changes" before trying the said carb ?
does it have a free flowing air cleaner element ? {like a K&N or is it paper}
& have you tried it without the air-cleaner ? {does it improve any}
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bear with me here, I know these are kind of
**** questions,
some of the stuff is for general knowledge,
some of it could seriously affect your type of tune...
more information we can get the better,
it will help & not have to go back & forth Q&A
does it {lean} surge when you cruising ?
or does it hold a constant rpm when you hold it at like 2500-3k rpm in neutral ?
no surging, while trying that ?
if it does any of these 2 above, it's probably too lean or a vacuum leak
or a serious ignition issue somewhere
like said before by a couple people,
too lean can cause it to bog bad too
& so will way too fat can too
not enough Hp, {
honestly not trying to be a prick} to get a bit of tire spin/wheel-speed,
dead hook can bog even a hi-hp manual combo at too low of an RPM
{
probably realistically not the issue here}
or missed mixed/matched parts, just thrown together, parts/combos
not liking each other, can cause a serious bog or tuning issues too...
IMO a Holley 750cfm DP should run like a raped ape,
it's a bit small, but should work OK {
850-950cfm could be better}
it may not be jetted correctly, bad accelerator pump charge etc.
when you look down the carb & goose it does it have a
"nice full spray/even stream, out of both the squiters" {
discharge nozzles}
also are you at any real altitude ?
or the float levels are set too low for it flowing/running condition
it should be trickling out of the fuel level bowl sight when it's idling
{
also if it's overfull or going past the needle & seat (what ever causing it) it /fuel could
come out the top vents on top, you can add a piece of rubber hose to them, to keep it/fuel
from slouching out & into the carb, that can cause a bog on hard launches too}
do you have a fuel pressure gauge ? if so what's it doing when you nail it ?
If not I'd suggest to get one & if nothing else for tuning purposes...
Does it have an electric pump ? if so which ?
does it have a mechanical pump ? if so which ?
have you tested the fuel flow/gpm ?
you can do it running into a can & see how much fuel it flowing
{probably not the issue, but lets cover all basis's...
do you have a regulator inline ? if so what's it set at ? what style ?
is it a bypass or dead head style ?
{
bypass with a return line back to the tank for unneeded fuel is always better}
either
(should be set between 5.5psi & 7psi usually/flowing pressure preferably)
have you tried a vacuum gauge, see where it's at ?
you can Google or Bing search Tuning a carburetor with a vacuum gauge
for some basics
check for a few simple things
check the clearances on the accelerator pump, make sure it's not sloppy
maybe change the acc. pump cam so it gets a better initial squirt,
more fuel right off idle
also maybe a little bigger "squiter" acc. pump nozzle go up 2 sizes
if it makes it worse,
than go the other way
you can also slightly bend {Straighten IIRC} the secondary linkage
to have the secondary's open latter
but that's just a band-aide covering up another tuning issue usually
I hope some of my short book helps directs you in the correct directions
I hope I haven't confused the **** out of you too...
I highly recommend
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