1982TA

iTrader: (1)

I was talking to a guy at work that used to be a mechanic and was telling him about my car and engine. I told him I was thinking about going the FI route because I'm sick of my carb. Anyway, we were talking and asked what kind of carb. I told him it's a Holley 750 (3310) It has dual fuel feeds. He then goes to tell me that the carb is too big for my engine. He says I'll be running rich. Now I know you can adjust the jets and all but is it really too much carb for my engine? It's a SBC 400. He said I should go with like a 650cfm. I've always thought my car was running rich but I just don't have time to tune it, and don't have much knowledge about tuning them. I'm not even driving it right now, but I'm always afraid to mess with it because I might not get the car to start after

It has vaccum secondaries, but I don't even know if they are opening and it bogs down on the express way when I'm going about 70-80 when I try to accelerate. Basically just want to know if I should get a smaller carb and IF I go the FI route what would a the flow of a TPI be compared to a carb? I want to keep my low end torque and I'm not looking for a high revving engine.

spartyon

why are you trying to accelerate past 80? ? besides the speeding factor, what have to done to the 400? any upgrades at all? i dont think its too much carb, personally i would get a book on tuning holleys and try to tune it the best that you can.

Keith_Indy

750 isn't to big for a SBC 400

If you have time to change carbs, you have enough time to tune the one you have.

Some Holley tuning tips...

http://www.mortec.com/carbtip1.htm

1982TA

iTrader: (1)

Well, living just south of Detroit in Toledo, OH Im about 10 minutes from the Michigan border. On I75 the limit is 70 but if you go that everyone is passing you. The closer you get to Detroit you have to be going 80 or else you will be causing accidents by going too slow. The cops don't even really bother with pulling people over unless they have to meet their quota, or out of state like me

Anyway, I could be going 60 and it still bogs down before it downshifts. The only mods I have are headers, heads, intake, upgraded ignition, and cam. I don't know the specs on the cam but it's got a lope to it. This probably doesn't help you any and I'm starting to think I should just start over so I know what I have.

1982TA

iTrader: (1)

The link doesn't seem to be working.

swimster

The fact that this guy USED to be a mechanic should tell ya something.. if he thinks a 750 is too big for a 400ci engine, he's an idiot and is OBVIOUSLY not destined to be a mechanic. now.. a 750 on a 305 is on the large side.. just ask me how i know.. lol.. Had one on my 305 85 Monte SS.. went from 27 mpg highway with the q-jet to 12 highway with the 750.. lol.. Even though the q-jet was also a 750, the design and tuning let it give the engine only what it needed. But anyways.. a 750 holley should work out GREAT for your 400. I just bought another 750 (3310) the other day.. out of the box new, it is set for a 396 big block. They say iut's a good all around average program for the carb for out of the box use.. it'll get you up and running basicly. you just gotta tune it from there.

Apeiron

Even if it was too big, at least it has vacuum secondaries.

RB83L69

That carb was stock - as in from the factory - on some 396s. IIRC, it even came on some 327s, and 302s. It's not too big.

"Big" doesn't make a carb run rich.

"Bogging" on throttle opening is usually a sign it's too lean.

Try increasing the primary jets 4 sizes from whatever they are, and rasing the power valve 2 numbers (from a 6.5 probably to a 8.5); and see what happens.

swimster

you should get a vaccum guage too.... very very helpful in carb tuning.

88IROC350TPI

I love the old-school thought that a bigger carb will run richer... WRONG! A carb that is too big for an engine will run LEANER than a properly sized one. Why? because if you have a 750cfm carb and your motor is only pulling 400cfm through it, the booster signal will be weak, thus the carb will not draw enough fuel.

My 750 Speed Demon runs pretty lean out of the box on my weeny 350. We put this carb on my friends 400 that makes a bit more power and it ran optimal.

CaptPicardsZ28

I agree with what everyone else said. I am running a holley 750 double on my 406 and it is fine. Don't let that guy ever work on your car.

novass

iTrader: (1)

Related, from those with experience would you say 850 cfm dp for a 454 with .6 lift 450 duration(rumpty idle)? Street use? According to the standard calculations it comes out to 780 cmf.....

Or would 750-800 range be better

Keith_Indy

working fine for me.

If you go to the main site, it's easy enough to find the tuning tips.

http://www.mortec.com/

Confuzed1

iTrader: (4)

I'm no expert when it comes to carbs, at least so far as getting them tuned right.

I've been struggling with mine since the day I put the thing on. The only thing I've consistantly noticed is it wants to run pig rich at idle no matter what I seem to do. If I lean it down with the A/F adjustments on each corner idle quality sucks.

Then when I lay into it, according to my cheap narrow band A/F ratio gage, it goes full lean. I think part of the problem is the shop that dynoed the thing set the carb up for WOT power and that was it - and I think they may have messed with other things like idle air bleeds or.... something. I mean c'mon - they had 80/94 jets in the thing when I got it...that's like 14 steps up from the stock jets, which is fine if your running straight headers with no mufflers and a velocity stack like on the dyno. Put that same engine in a car with a more restrictive exhaust and intake - and you'll have tuning problems - or at least I do.

I guess you guys can say his mechanic is wrong when he told him to go with a 650 carb, but I'm here to tell you he's NOT the only one I've heard this from. I called Demon techline and THEY recommended a 650 for mine too, so I guess they don't know what they're talking about either. If you look at the carb selection sheet on thier website - it will also direct you towards a 650 cfm for a 400 CI engine. I wish I knew what the real truth was too. BTW....my setup had no problem making torque with a 650, but I gotta wonder if there's more power to be had with a 750. I may never know because I'm looking into EFI now for better streetability, and hopefully a bit more power.

1982TA

iTrader: (1)

As am I. What type of EFI are you looking at? I was looking into CFI or TPI. I'm not looking for a high revving engine, and want to keep low end torque. My redline is at 4500 anyway.

Confuzed1

iTrader: (4)

I'm not looking at any stock EFI systems. You'd need to do some porting on either CFI or TPI to provide enough flow on a 400 I'd think, along with larger injectors and other tuning. But it can be done it here and I haven't heard them complain.

I'm looking at getting either HSR or a Miniram for mine because I'd like to keep my torque also, but pull to 6K rpms. But my 400 is far from stock too. Still researching on which will better fit the bill.

F-BIRD'88

You need a new mechanic, not a new smaller carb.
A 750cf carb is not "too big" for a 400 or even a 350.

750's were factory installed on 302's back in the day.

The holley 3310 is a very versitile universal performance carb. It's out of the box calibration is * a little rich*
" A LITTLE RICH" not too rich. It's made a little rich for a reason. So anyone can bolt this carb on just about any V8 motor and not damage the motor from being Too LEAN.

That being said: the stock jetting on a 750vacuum carb is 72Pri and either 76 sec or a #21 sec metering plate.

This works well for most applications (out of the box).
You can and should fine tune it to your car.
In the 30 some years, using this carb on many motors, I've
found this carb likes 69 to 74 primary and 76 to 84 secondary jetting.
Try slightly leaner #70 primary and a #80 sec jet on yours.
The "bogging" you are experienceing is not from an over rich condition. The carb is going lean when you're opening the throttle. This the accelerator pump, not the jetting.
read the Holley manual online, on setting up the accelerator pump linkage and shooters. many times the linkage gets bent and out of wack from improper adjustment. Bend the linkage arm so that you get a full shot of fuel, starting as soon as you first move the throttle. then readjust the screw and spring combo to allow a .015" clearance on the pump at WOT. A .025" to .035" pump shooter should work well. Make sure the accel linkage spring is not wound tight.
(liquid fuel will not compress and the linkage arm will bend out of wack if the spring is adjusted too tight.)
Many people do not understand this and miss adjust the linkage.

Check the seconday diaphram housing for a good seal. Either the top is leaking, or the lil cork ring gasket between the housing and carb body is bad. A Plain , purple or long yellow sec sping is usually the right one.

Make sure the floats are adjusted right and the fuel inlet needle and seats are good. make sure the fuel pump is supplying enough fuel to the carb to keep the fuel blowls full even at WOT. ( VOLUME not pressure)

Until you understand and can make a simple carb like a 3310 work well, a different carb will not help and setting up and tuning fuel injection even EFI is not going to be any easier. Replacing a few service parts and gaskets and retuning your carb is way cheaper then droping a big $load$$ on a new carb or EFI.

Rest assured this carb is not too big.

What intake manifold are you using?

If you have a big "hi performance cam", with a rough idle in your motor, then your ignition timing advance curve needs to be retuned form stock to match this. usually requiring a mechanical curve setup with much more initial advance at idle and less mechanical advance travel in the distributor.
something like 20deg initial at idle and 32-36 at WOT works well for a SBC. (12 to 16deg of travel)

20 to 24 is typical for a stock out of the box distributor.

katman

I have a 750 HP on my 359ci and it runs 12s. I cruise the Sonics and car cruises just fine.

HorseflyDF

I have a 600cfm 2160 holley on a 350 sbc goodwrench motor.
which has around 250 hp.
The previous owner said he tried a 750 carb on it but
it didnt run right.

I went to wot last night when a new lexus coupe
tried to over take me.............so I punched it, then I went to
wot because he was still on my bumper..I looked in
my mirror to see his headlights and all I saw was lots of
smoke from my tailpipes.. I dont know to much about carbs
or tecnical stuff either but my guess would be I was running to rich..The car didnt missfire or bog either.

swimster

You'll ahve to have someone behind yu in the daylight and see what color smoke.. Grey is too lean and black is too rich.. you DEFINITLY don't want too lean.... As far as the 750 going on that goodwrench engine, the guy just never tuned it right. I can run my 800cfm Q-jet on a 305 and get 28mpg all day long and get great WOT response... It's all in the tuning.

1982TA

iTrader: (1)

so is it possible that I'm running lean? My fuel pressure is about 9psi. Also when I'm stopped and want to get on the throttle it bogs a little and then takes off. I've heard different things about taking off, such as easing into the throttle rather than punching it to the floor. What is the truth on this?? Sometimes when I've been driving for a long periord and try to restart the car after I've went to the store or something it's hard to start. It will crank over very slow and I basically have to hold the pedal to the floor and crank it over. Usually when this happens it will start but immediatly die if I let off the gas. It's starting to be a PITA. That same mechanic friend said the carb is being flooded, hence I'm running too rich. But it sounds as if I'm running lean at WOT. I also understand the heat issue with the starter, since it's right next to the headers. I have a heat shield and the seloniod is in the back. The same mechanic said my timing could be off. I don't see how since it starts up fine everytime...just when it's hot and driving for a long time does it act up. I would guess my carb needs a tune up...probably a rebuild. I have no idea where to start or what parts I need for a rebuild. I've been searching but don't know what I need. Also, I have 2 blocks, one on the primary side and one on the secondary. I don't believe these are stock since stock had plates correct? Or one plate on the secondary side. I guess this is for the jets?? Also, what is a good book for holley carbs? I've read one holly book, but it's basically a tune up book and performance type deal. It doesn't go throught the operation and all of the parts of the carb. Since mine is a 3310 it doesn't seem like there is a lot of info, more on the 4160/4150 carbs. Also, I have no choke on the car and not sure if it is really necessary. I guess technically it could be but I usually have to hold my foot on the gas and let the car warm up before I can go otherwise it will die. Also I think my power valve might be blown. If this is the case I should be running rich all the time right? I know under load it opens to allow more fuel in. One time on the expressway I was driving and pushed down on the throttle and hear a loud pop under the hood. I didn't really know what it was at first but reading about the carb I am gussing it would be the power valve. This was a long time ago, like right when I bought the car. This was before the winter so I had it stored over winter and drove it minimally in the spring now. It's garaged right now since I don't have plates for it yet. It has a quick change secondary spring device as well. I've tried all assortments of the springs, and I don't really notice any difference between them. What are some good rebuild kits or replacement parts? I've checked out Proform and quick fuel technology. I've also seen some stuff from Barry Grant. Rather than buy a new carb I'd like to keep this one and rebulid it, if it's worth it.

Here is something I thought was interesting
Proform Holley Carb upgrade

RB83L69

9 psi is WAY WAY WAY more fuel pressure than you need. Carbs don't work on the basis of fuel pressure, like injection; all the pressure it needs, is enough to keep the fuel bowl (which is at atmospheric pressure ... 0 psi) full. If your fuel system would deliver enough fual at ¼ psi to keep the bowl full, then ¼ psi is all you need. In the real world, that carb needs about 3-4 psi to flow enough fuel to feed a 427.

Earlier production ones of those had metering blocks. They switched to plates much later on.

Ignore the starter problem for the time being. Sounds to me like you have too much fuel in the bowls, from the excessive pressure; and it's running over into the intake when you turn the key off. First thing you need to do, is get the FP to a reasonable value, and then get the floats set right.

Right here is everything you could possibly need to know about your carb. What jets it came with, what kit it uses, etc. Your carb is a model 4150 if it has metering blocks; a 4160 if it has plates. 3310 is the list number (or part of it at least), not the model #.

Best book I know of for Holley carbs is by Alex Walordy. I can't recall the name of it. Put his name into amazon.com or something and see what you come up with.

Best thing you can do right now, is to go get yourself a rebuild kit and learn to work on it. It's incredibly easy. That's why Holley carbs in general, and that exact list # in particular, has been so popular with hot-rodders for 40 years now. Posting here is only good for just so much. Sooner or later you're going to have to walk out there and put it into effect. Sooner is better than later.

1982TA

iTrader: (1)

I'll regulate it down and see what happens. Also, is it necessary to have a return line? I have the original fuel return line still on the car, but there isn't a line from the carb to the return line. Also are block better to have than plates? I've seen carbs without the secondary block. Mine has one, so I take it that it has more "tunability"?

also looking at the PDF file, it seems I have the 4160 since my list is 3310-2. If this is the case, then someone put the metering block on the secondary side. Are all metering blocks essentialy the same? Are there aftermarket ones that are better in anyway or do they basically all function the same?

RB83L69

Holley sells a kit to turn a 4160 into a 4150, very popular. If I somehow got stuck with a 4160, that's one of the very first things I'd do to it, specifically for "tuneability", since you can't change the jets in a plate; along with a rebuild kit (duh), PV protector if it didn't have it, etc. Most likely, that's what you've got. If you cruise th ecarb parts area of Holley's site you'll see it.

It's not "necessary" to have a return line; but it DEFINITELY makes the whole fuel system work better. It allows fuel to circulate constantly through the fuel system, thereby keeping it cool. About the worst thing that can happen, is for the fuel to get hot in the lines, under pressure; because if it does, it will boil violently when it reaches the fuel bowl and the pressure suddenly goes to zero. You'll have boiling fuel gushing out the top of the carb into the intake, and make the engine run unbelievably rich, and then starve because there's none left in the bowl for a few seconds.

The return line hooks up to a fitting on the pump.

If you don't have the stock pump, that would be a great place to start. Just go to the store and get a $12 stock replacement pump, hook it up right, and see if the car works any better. Simplify. Get rid of extra unecessary parts and plumbing.

Did this car come with the LG4, or the Cross-Fire motor?

1982TA

iTrader: (1)

Yes, the car originally came with the crossfire engine. It's been swaped out obviously but the fuel pump is stock and I still have the original fuel lines, at least the source but it's cut back in the engine bay. Also I noticed the source line is VERY close to the headers, while it's not touching them it's close. Is this a concern since you said the fuel can boil? As for the return line, there is a fuel line to the left side of the bay that isn't hooked to anything, it's just got a length of rubber fuel line and is capped off. I would assume it was the return line. There is also a line to the charcoal canister but it seems to be just for looks as it doesn't work and the lines don't really goto anything as far as I can tell.

RB83L69

Hmmmmm..... a hack job... sorry to hear that... may take a little work to un-sodomize it....

So you might still have the electric in-tank pump in there, do you know whether you do or not? and if so, is it working?

1982TA

iTrader: (1)

I'd guess that it's the original pump, at least that is what the previous owner said...but he said the motor was a pontiac too and it's a Chevy. As far as I know it's the original pump, and yes it does work. I know because I had to trace the pump wire to the relay because not too long ago I wasn't getting any fuel pressure. I thought my pump had gone out but I wanted to make sure it was actually the problem before I have to go through all the trouble to drop the tank...not fun. Anyway I was messing with the relay and got power to the wire and it works just fine, it turns on and makes fuel pressure. While my car does seem to be a hackjob it's probably not that bad. I thought about restoring the Crossfire setup but when I found the ECM wiring hacked and the ECM missing I decided against it. I don't even have the computer port, and finding a good wiring harness isn't that easy. While I was kinda disapointed in the hackjob, I learned to deal with it. I was thinking about maybe going EFI in the future so I'd need to get a new wiring harness and computer anyway. The only thing I don't understand now is the TCC lockup control. It's controled by the ECM and if I'm not getting power to it...or it's missing, how is the TCC function completed? I've got a 700R4 and it's been shifting funny. I've heard so many different things on what it's doing and why I don't know who is right, but that is a whole other thread

RB83L69

Well, a good way to deal with the fuel pressure issue, is to use a Mallory 4309 regulator; and hook its return fitting to the return fuel line. Set it to around 4-5 psi, or lower if it will go lower; and see if that doesn't make the car alot better-behaved and more tuneable.

Yes if you have a fuel line going too close to the header, it will boil the fuel. If you can, get it separated.

1982TA

iTrader: (1)

well, I might have to do some re-routing. The source line comes up on the right side of the engine bay and runs along the right fender. This is also where my fuel filter is located, just before the regulator. The fuel line Is VERY close to the header, I just noticed this the other day because I was replacing all the rubber hose line and checking the fuel filter. It is actually held away by a bolt.... I guess this would be the stock position for the fuel line. Up near the headlight is my regulator and it has a small length of rubber hose then goes to solid line up to the carb. It almost looks like it's the stock piece from the crossfire, just because of how it is bent. Then it hooks into the 2 fuel fittings on the side of the carb. My fuel pressure gauge is hooked to the "fuel log" On the right side is the return line and I guess the vapor line connecting to the charcoal canister. I don't want to have line going all over the place and would like it as neat as possible, but also a short of run as I can get. Where is a good place to locate the regulator?


edit
I found this regulator bracket I thought was kind of cool
AED

Also, I have the dual feed float bowls. Any advantage to this vs single feed? What is the purpose of dual feed, just to have the fuel lines on either the left or the right side?

ECHO71-11BRAVO

[quote=1982TA;2358527]I was talking to a guy at work...


ME TOO BUDDY,
ok, so here's my schpeal.

my little brother is an Army Airborne Ranger, in the 1st Infantry Div. Active Combat, and i thought that if i built him a sweet welcome home present, providing he doesn't get his 6 o'clock shot off.
the dream follows, as;

1987 k5 Chevy Blazer, 4 in. lift, rancho shocks, 308 Overn locker, many extras...
305 H.O. with a hot cam. i stacked a 750 on top, thinkin' i could get away with it, i am having many of the same problems as you mega racers are, and have pulled almost all of my hair out, along the way.
i have yet to jet down, i hope this will work, for fear that the project will run out of cash. i have an old 650, but if you can stick one on a sb 302 Ford, then what is my prob?
you say it is all in the tune? if you can look past your ford rivalry, a Chevy man would owe you a favor bro. help a soldier out?

ECHO71-11BRAVO RANGER BAT.

peter355camaro

i would like to know if a 750 cfm holley 3310 carb is'nt to big for me?

i got a 350 with flat top pistons, ported camelhump 370 heads 1.94/1.50 , 280h compcam, edelbrock 2101 dualplane intake,

maybe it's a dumb question because you sad it's even good for 302 chevy's but i want to be sure that it will be good for my 355!!

thanks a lot!

Air_Adam

It will be just fine. I used that carb on my 350 when it had only 180hp, and up untill it had the 400hp its got now. Worked fine all the time with proper tuning.

chaoz28

...i had an edelbrock 600 cfm on my camaro before i switched to the holly... had the saem EXACT problem id hit 70 and it would start bogging and sometimes even kill on the highway... NEW ACCELORATOR PUMPS you accelorator pump isnt working correctly for one reason or another or more i had plans to switch to a holly anyway so i just did that but i rebuilt the edelbrock for future use.. lone behold ACCELORATOR PUMP clogged passages

F_N_JUNK

iTrader: (4)

850 should be fine... BBC pull lots more vaccuum than SBC motors......
----------
Your secondaries are opening too quickly !!

Batass

Just sounds like you need to learn how to tune your carb. Maybe check the timing too. A 750 isnt too big for a 400 or a 350 but if you arent taking your engine past 4500 rpms.....then I would say that a 650 is definitely a better choice for you. You will gain more low end torque, it will be more responsive, and easier to tune due to more of a pulling signal. Not to mention better gas mileage.

I would recommend doing a lot of reading on carb tuning, the more you know, the less BS you have to sift through, and you won't take as much crappy advice.

Air_Adam

Accelerator pump may just be out of adjustment if thats the case. Check for play in the linkage, and adjust out any play that might be there and see what happens. Its quite easy on a Holley.

327_TPI_77_Maro

iTrader: (8)

I ET'd several tenths faster w/ a 750 vs a 600, back to back, on a little high revving 327. A 600 would be too small for a 400. A 750 is going to be totally fine.

88IROC350TPI

holy 2005 thread batman!