ok guys i have a 750 edelbrock carb 1407 and my car seems to run rich liek if i rev it re4 i come to a stop it really stinks, now with the combo on my 350 in my sig should i have to re jet this thing or shoudl i be fine??

 

Adjusting the idle, main, accelerator pump and power circuits of a carb should be expected when modifying an engine. It is also unreasonable to expect a carb to work correctly "out-of-the-box". If you're not sure how to approach it, check out Edelbrock's website for the procedures.

 

The gas smell is not from rich jetting.
If you are near sea level your jetting is not too rich.

Edelbrock carb don't like more than 6/7 psi fuel pressure.
If yours is more at an idle, get a regulator.

If you don't have a PCV valve hooked up get one and hook it up and vent the other valve cover.
The carb is designed to idle properly with this hooked up.
{Not hooking it up causes the idle to be too rich and the throttle blades to be too far open at idle.}

When your car is idling the fuel is controlled by the idle circuits not the main jets. {idle feed restriction and air bleed}
Change the primary metering rod to 1 stage leaner at cruise

This would be a .073x.047 rod.

Change the pri step up springs to a 4" spring (yellow) to hold the rods down in the jets at idle (lean). ( {5"} orange is stock)
Your cam has enough vacuum reducing overlap to require this.

Most of the smell is from the carb getting too hot on the manifold
over-vapourizing the fuel in the fuel bowl. (fuel perculation)
If your manifold heat raiser passages are open (intake manifold gasket),, block them off to stop the intake manifold plenum from being heated. Get a Edelbrock Wooden carb spacer ( a divided one) to isolate the carb from the hot manifold. This will help a lot.

Normally these smelly gas vapours are collected in the Charcoal fuel vapour control canistor, but I'll bet it's not hooked up.
This is why you didn't have the problem with the origonal Q-Jet
carb.

Divided 1/2" Spacer, Wood Fiber Laminate Edelbrock #8725

 

i had tbi be4.i have a vent on both valvecovers. now u are sayin use a pcv valve and run it to the big vacum port on the carb?? my car also doesn;t really idle consistantly its likebetween 1000 and 650 but if i rev it in nuetral be4 i stop it will idle back down to liek 750 800 where its should be.

 

I have a holley 750 DP. What adjustments can I make? My car dies towards the end of the track. I eliminated timing and fuel pressure and spark. The only thing left is the carb. Whats screws on the cab do what? What size jets should I start experimenting with if any? Mods in sig

 

yes hook up the PCV system. It will clean up the idle, and reduce the fumes.

the idle is going up and down because the metering rods are
opening and closing (power step up spring).

In addition be sure vacuum advance is plugged into "ported vacuum".

also if you have the light (fast) advance weight springs
in your distributor replace one of them with a medium tention spring. The lightest ones are unstable at idle.
One light and one med spring usually is the best for overall performance.

Do each of the things I suggested and you'll find it will be a lot more street friendly.

Also check the routing of your fuel lines. if they are getting hot
move them elsewhere.

Putting the effort into these details is worth the time and money trust me. Good Luck

 

1. If your car actually has a true cr of 11.5:1 you will need high octane race gas to avoid detonation.
Even if you can't hear it, it will flatten the power curve if it is.
You may be able to just mix it 50/50 with 92/93 octane
pump gas. You need about 100 to 104 octane.

the practical limit with alumium heads and a carb is around 10.5:1 +/- a smuggin' 11.5 is a little high for pump gas.

If you're setup is actual able to opearate fine at 11.5:1 on pump gas without detonation, more power to ya.
But I would try some racing gas.

2. you need fuel flow (volume) not just pressure all the way down the track. Check all fuel lines and fittings for flow.
Check that the pump actual flows lots of fuel.

3. what rpm does it flatten out. You may be floating the valves.
and what rpm do you cross the finish at?

4. I would be useing #72/74 primary jets and #80/84 sec
jetting.

5. your timing may be over advanced. Try retarding the timing 2/3 degs and see if the MPH improves.

should be 32 to 36 total.

6. your problem has nothing to do with the lil' screws on the carb.
they are for the idle mixture and speed.

You are pulling my leg right.

with all the hi tech expensive stuff in your ride, you should be well aware of the ins and out of a holley by now.

If not and you really are a newbie to carbs I'd buy a book on
holley carbs. You can get them online or from most speed shops.

How does the car run in the quarter

60' ... 330ft....1/8 et 1/8 mph 1000ft et/mph 1/4 et mph

times if you got them. you can tell a lot from the time slip
if you know how.

Was this combo ever dyno tested?

 

1. My car is truly 11.5: 1. The guy who built the motor has a very reputable business and great tools. It is also a zero deck block.
2. I just installed a new fuel system. Its the summit fuel pump that flows at 140gph. Theer are no leaks and pressure remains constant.
3. Car does not flatten out until the end of the track after it has been floored for a while. Midway down trhe track I get great power and decent power off the line. When it does start to die off (towards end of the track after being at WOT for a while) I am at about 5500-6000RPM.
5. What would you reccomend for initial timing?" It is at 10 advanced now. Also, I have the weights and bushings in the distributor so that I get total timing of 36 at 2500RPM.
6. As far as screws on the carb, I know how to use the A/F screws and idle screws but are there any others that may require adjusting? The carb is new. Do I have to adjust when the secondaries open. It's a 750 DP mechanical secondaries. And yes, this is my first experience with carbs.
7. Heres the 1/4 mile slip before the new rear and fuel pump. The car was dieing off here. After the rear and pump I ran 13.9.
R/T .837
60' 2.083
330 5.717
1/8 8.728 MPH 81.5
1000 11.351
1/4 13.625 MPH 96.6
8. More than once, when I floored the car, I had a backfire out of the carb and a fire. It this because the fuel pressure was too high. It wouldn't happen unless I stomped it. If I eased into it, it was ok. I was also burning my eyes with the exhaust fumes. I ordered the A/F ratio gauge so that should help me with adjusting the carb a little.
9. The computer in my car is still hoooked up to avoid VATS problems. I highly doubt this has any effect on my car but just checking.

 

The guy who built the motor may be the best in the world,
but he can't change the laws of physics.

trust me 11.5:1 is really pushing it on pump gas.
Try some race gas..... see what happens

If ya make a lier out of me I can take it.

This is not to knock you, or your engine builder, it's just physics.
If the fuel does not have enough octane the motor
will detonate (spark knock) and be down on power. It may damage the motor too. You may not hear this knock.

Based on the parts list, you have a pretty stout motor.
Should run high 11's or very low 12's minimium
with what you have.

There is some thing seriously wrong here.!!!

Traction besides, your times are way off what this motor should be doing. At all points on the track.

The back-firing is probabily caused by a lean condition when you floor the throttle. You have to increase the accelerate pump shot by trying different accelerator pump cams and bigger shooters.
You probabily have a .028 shooter in there.
Step up to a .037" and see if that helps.
Check the linkage to see if the fuel comes out of the shooters
as soon as you move the throttle. It has to.

More initial advance will help here too.
Don't be shy 16/22 initial with 34/36 total is where you want to be. If you have vacuum advance plug it into Ported vacuum.
On a holley that is the one on the side of the primary metering block, not on the baseplate. You say you have 36* at 2600 rpm, what is it at 4000 rpm. If it increases you need to rework your advance curve.

Be sure the timing does not exceed 36 * at higher rpms.


You really need to invest in a Holley book 'cause these are just basic tuning proceedures. No rocket science.

You may find the answer on carb set up on the holley internet site. there is lots of tech info there.

I still suspect a fuel flow (volume problem) at high rpm.

Tell me about your headers,, exhaust system.

 

Where can i buy accelerator pumps and shooters? How many are there in the carb and where are the pumps and shooters located?
I have supercomp long tube headers. No cat. 3" to 2.5" then back to 3". I have all the goodies thats why this is bumming me out!
Do you think it's the carb that is a problem or something else?

 

You can buy holley carb tuning parts thru most any local speed shop
or online from Jeg's or Summit.

Your exhaust is two 3" pipes mergeing into 1--- 2.5" pipe
then back into 3"pipe (s)????

If so that 1 2.5" pipe is a big restriction.

Not near enough flow for your motor.

Thats really going to limit your power.

Uncap that puppy and let the Lobster Loose!!!!

 

hey f-bird88 why would i only replace 1 of them??

 

GTA badboy

tell me about those pistons in your motor.
Are they flat top with valve reliefs?
Do they have a dome top?
DO they have a dish on the top?

There should be a 8 digit part number stamped on the end of your Dart heads. What is that #.?

 

Does your exhaust look sort of like this?

 

One light advance spring and one medium spring is usually just right.

 

My exhaust looks sort of like that but it's kinda hacked. I plan on going with the SLPs because it wont be a complete hack job and I drive the streets alot. The headers scrape horribly on bumps. I will get you the head # when I get home saturday. Im at school now. On the other hand, they are the Dart Pro 1 aluminum heads with 230cc runners 64cc chambers. The were purchased bare, the P/N from Summit is DRT-11710040, but the engine builder bought them directly from Dart. I have Comp Cams Hitec pushrods, Ferrea valves 2.08/1.6, Comp Cams Pro Magnum full roller rockers 1.52 ratio, Lunati Roller Cam P/N 50169 with .606 intake and .585 Exhaust, Adv Duration 248/252 I believe 110 lobe seperation (not sure it may be 112). Hope this helps. I do not know about the pistons. They are JE light weight forged pistons with 11.5:1 CR.
How about my accel header shorty plugs. Are they ok for the heads? What should I gap them at with this CR and an MSD pro billet distributor and digital 6+ box?

 

Well I think your ehaust is a major factor here.

One 2.50" exhaust pipe is really going to choke the power.

that pipe should be 3.5" to 4" diameter.

The long tube headers are fine (I'd keep them)

You can increase your ground clearence by notching the crossmember where the "Y" pipes pass under it.

You can buy a 2 into 1 merged collector from flowmaster.

3.5" to 4" manderel bend pipe can be bought from a
shop that does truck exhaust. It's not expensive from these shops.


The rest of it sounds fine.