[DenRS]

Hi guys,

I bought the trickflow top end kit for my 69 camaro with a 350. Hopefully this year I will finally install it. I currently have a edlebrock 1406 600cfm carb on my engine now. I also have the calibration kit that goes with it. Originally I was just going to use that carb since that is what I had. However, my brother just gave me a edlebrock 1407 750 which has an electric choke installed. I'm in the process of rebuiding that carb. I know 650-670 cfm carb would be ideal, but since I have these two carbs, I'm gonna use either one. I don't have the calibration kit for the 1407, but if I decide to use it I would get it. Right now I'm not sure which of the two would be best for my combo.

Here are the cam specs
Lift
Intake @ cam 320 @valve 480
[email protected] cam 3294 @valve 494
ADv duration 284 Int 290 Exh
Dur @ .050 is 228 Int 234 exh
Springs 110 lbs closed 312 lbs open
1.50 ratio rocker

Cam timing opens closes
@0.004 Intake 32 BTDC 72 ABDC
Exhaust 75 BBDC 35 ATDC


Cam timing @ .050
Intake opens 8 BTDC closes 50 ABDC max lift 106
Exhaust opens 51 BBDC closes 3 ATDC max lift 114

The heads are Trickflow 195 with 62cc chambers however they are not cnc'd. I'm also using an edlebrock performer rpm manifold and trickflow 1.5 roller rockers. I have 1st design ST-10 4spd and 3.42 posi. This is for the street.

Thanks

 

[TJS69]

For the street I would say 600 CFM, for the drag strip I would say 750 CFM.
The best all around carb. would be a professionally tuned Quadrajet.

 

[dnult]

Excuse my ignorance but are those Eddelbrock carbs square or spread bore? The only Eddelbrock carbs I've had experience with are spread bore carbs like the Q-jet.

I use the following formula to estimate the maxium air flow of an engine. The VE figure is volumetric efficiency. On a stock motor, VE is about 85%. A normally aspirated motor with the right performance parts can approach 100% VE, but 90% is a typical figure. Anyway...here is the formula.

CFM = RPM * CID * VE / 3456

You'll see that on a 350 CID engine, anything over 700 CFM is non-typical for anything but a race motor. But spread bore carbs give you the best of both worlds -- you can afford to over size the carb a bit if it is a spread bore. Square bore carbs on the other hand are a bit more finiky if you exceed 700 CFM though they can be made to work. The primary venturi size is the determining factor in either case. If the primaries are too big, off-idle and part-throttle performance will be tweaky. Of course if you're destined for the 1/4 mile, it won't matter much since you'll either be at idle or full throttle.

 

[TJS69]

I agree with you on everything except all Edelbrock Performer series (which you have) carburetors are square bore. That is why I recommended the Quadrajet, which has very small primaries.

 

[Cal69]

I just went throug the same dilemma with my '69. I am running a 355, 10:1 comp with Voodoo 268 cam, Edelbrock RPM heads & intake, Edelbrock 1406, 1 5/8 headers to duals w/Flowmasters. Trans is a M-21 & rear is 4:11. The car runs very strong and I wondered if a 750 would be better for my application.
I was able to borrow a friends Edelbrock 750 which he has on his 350. He had already changed the rods and jets to lean it out a bit. Even with some minor tuning, I could not get the car to run as smooth. It might of had a bit more power on the top end (like 6K+), but was too soggy for mild throttle. Some guys run a squarebore 750 with luck on a street 350 but I just think it's too much carb for applications under 400 hp driven more street than strip.
Just my opinion here based on what I tried.

 

[68z28sd]

i have never seen edelbrock carb work except on a stock vehice. i you want to go and don't care about fuel economy 750 holly 3310 bolt it on and go.
no chrome avenger carb. the old style one. for milage ect. go q-jet

 

[ept000]

i have never seen edelbrock carb work except on a stock vehice. i you want to go and don't care about fuel economy 750 holly 3310 bolt it on and go.
no chrome avenger carb. the old style one. for milage ect. go q-jet

I agree, I have never seen one work well on anything but a stock motor. I ran a Edelbrock 750 on my 350 motor for a few years and I never got it to run right. The off idle/transfer stumble was terrible. Full throttle was not bad, but everything else was a total mess. I threw two hundred bucks worth of metering rods, jets and springs at it, and it never helped. Also, a restart after twenty minutes of sitting was never good. Put on a twenty year old, wore out Holley and it ran perfect. By the way, I am running a 350 with a TrickFlow top end, Performer RPM manifold, amd similar cam specs.

 

[DenRS]

I was wondering how my 350 would run with the 750 cfm carb. I'm sure the 600 I have would be fine since I'm only doing street driving, but I was curious about the 750 and my set up. Seems like I'll have more driveability issues using it. Since this is a street car, I'm willing to trade a few ponies for a driveability. I would love to buy a new holley, but with two edlebrock carbs already I can't justify it right now


Cal69,

What combo of rods/springs/jets are you running with your 1406. Right now I have a performer cam and performer manifold and my engine runs fine with it. Not sure what combo to start with once I add the new cam, heads, and manifold.

 

[Cal69]

Basically, I checked the tuning chart the comes with the instructions for tuning the carb. I was super lean in both drive and power modes. I just decided to do all the way rich in both areas and work backwards to lean it out. I got lucky and didn't need to change jets and/or rods after that. Can't remember the part#'s but I'll look it up when I'm at home. I've been reading my plugs and it seems like I'm right where I should be. I did move the acc. pump up for a larger off-idle shot.
I'll disagree with the comment that Edelbrock carbs are junk. That's just an opinion from someone who has a bad experience with them & everyone will have an opinion on what they like. I've had some experience with tuning both Holley & Edelbrock and the Edelbrock has been much easier for me. It has remained in tune longer than my Holleys and had better driveability. The Holleys I had did seem to make a little more power but it never drove as well. Some of that can surely be tied to my tuning skills (or lack thereof) at the time.
Since you have both, you can experiment with both and see what works for you, without spending too much more money.

 

[TJS69]

I had a Quadrajet originally on my 327 so when I had it rebuilt I thought a Holley 750 would be better, WRONG ! Now I had a square bore intake... so my quadrajet couldn't bolt on with out an adapter. I decided on trying an Edelbrock 600. It was a night and Day difference. I may go back to the Quadrajet someday but, who knows. What I'm trying to say is, you guy's with a Quadrajet... keep it !

 

[wildman926]

NOT THE FORMULA!!! lol...

Holley 670 Street Avenger

Nice compromise, 4150 style carb. It comes lean from the factory, so be ready to jet it up about 2-4 jet sizes. I had to use the green cam and a #35 squirter to get the stumble gone.

The 750/770 "Holley" will be great for the strip for max power, but the 670 will do you fine.

Here is a good write up where they test different sizes of carbs on the same engine, a 383.

 

[Cal69]

Thanks for the post on the article. Good reading!

 

[joe clance]

keep in mind, the testing was perfrommed with MECHANICAL SECONDARYS. Vacuume secondary set ups will not deliver the stated cfm's over the calculated values.
Other than idle and off idle response, performance gains were minimal over 650cfm.

Since vacuume secondary set ups will delivery less cfms, it would be interesting to see them repeat the tests with fixed vacuume secondary set ups.

joe c

 

[wildman926]

The article's point was that you could be within 2-4 hp on a carb that may be either too large or too small from optimum. What is given up is throttle response for going with larger carbs.

A vacuum sec carb car can be tuned to run just as fast as a mechanical sec carb, and still have decent street manners. It feeds your engine what it needs, not what you want it to eat.

 

[dnult]

The article's point was that you could be within 2-4 hp on a carb that may be either too large or too small from optimum. What is given up is throttle response for going with larger carbs.

A vacuum sec carb car can be tuned to run just as fast as a mechanical sec carb, and still have decent street manners. It feeds your engine what it needs, not what you want it to eat.

Good point wildman. Same goes for rejetting a carb to fit the motor. I think someone earlier in this thread spoke about rejetting a 750 to get it to run on a 350 motor. Rejetting won't fix the problems that come with an over-sized carb on a street motor. It might help with one problem, but it will create another somewhere else in the drive cycle.

 

[speedshifter]

The Edelbrock catalog suggests multiplying the formulated CFM by 120 to 150% for dual plane manifolds. Your cam looks like it should make peak horsepower at around 6500 rpm, so according to Edelbrock, 710 to 888 cfm would be right for this engine!

Chevrolet installed 780 cfm mechanical secondary carbs on 302 cubic inch Z28s (they all had 4 speeds) in the 60s, and they ran fine on the street.

 

[pdq67]

Fwiw, a STOCK Q-Jet off an engine that is PRODUCING the power you expect to get out of your's will be fine!!!

Be it any of GM's engines!!

I have a stock Q-Jet off a 403 Olds on my 406 SB and it ran GREAT before I switched engines!!!

And I think the big Buick's, Olds's, Pontiac's and Cad's have 800 cfm Q-Jets on them instead of the 750 cfm jobbers so check into it..

What you MAY have to do to make it run the BEST is to just take some time and reset the top rear air valve butterfly's so they kick in just where you want them...

And another point is that it used to be that the great old Holley 3310- carb was box stock to run on a 375hp/396 so tended to be rich on our smaller 302, 327 and 350 engines!!!

Years ago, "Honest Charley" said about the old 3310-, "That it was the runnin'est carb. ever!!!".......

pdq67

 

[Eric68]

The 600 carb is alittle too small and the 750 is a little too big. I would try the 750 and try to "tune through" and problems caused by the carb being a little too big.

PS. You Q-jet guys crack me up. He doesn't have a spreadbore manifold and already has two carbs to pick from!

 

[DenRS]

Since I already have the calibration kit for the 600, I think I'm going to buy the calibration kit for the 750 as well. Since I currently have both carbs, I can play around with both and find the one I like best. Thanks for the help.

 

[pdq67]

Eric,

Just info here is all.

pdq67