I have a 69 RS Convertible. It is basically in a stock/original configuration.

It has the 350 small block rated at 255HP. I also have the original 350 trans.
I am fairly sure I have a 2.73 or 3.07, 10 bolt rear. Two barrel carb and exhaust emissions.

I have big plans for the car but for the short term I would like to put a set of Summit stainless steel headers on and a carb/intake setup.

I am looking for recommendations for carbs and intakes.

I am building a 406 small block and would like the intake that I select to run on the current 350 motor and the future 406. (it may take me a year or more to pull the cash to finish the 406 but I need more HP now out of my 350)

Any recommendations?

I would go with an Edelbrock Performer RPM. If you don't like Edelbrock, Holley makes a similar manifold, Part # 300-36.

I would go with a 750 vacuum secondary carb. You can choose between Edelbrock or Holley on the carb. I prefer Holleys, but many people here really like their Edelbrock carbs.

Both parts should work equally well on both engines.

What about the Edelbrock Air Gap manifolds?

I know 10x more about fuel injection than Carbs but am learning fast.

I noticed that Summit has many Edelbrock Performer RPM manifolds listed.
It looks like there are two manifolds that will bolt up to my car.

part number at summitracing.com
EDL-7101
EDL-7104 (pic looks taller than 7101 and the intake wholes are shaped different)
What manifold should I go with?

I'm building a 350 from scratch (both parts and knowledge) and I asked a similar question over in Engines & Drivetrain title "What Carb Shoud I Use". I got a lot of good reponses. You might want to check that thread out.
I'm starting to lean towards the Eldebrock Performer RPM & Performer carb. It just looks like it might be an easier carb for the novice to tune.
Good luck

How do I know if I should go with a Manual or Electric choke for the carb?

Hey John,

I agree that the performer RPM is the choice to go with if you plan on putting it on to your 406 in the future. The stock 350 you have would probably be better matched to the standard performer intake, but the RPM would do much better on a hot 406 and probably wouldn't make too much difference on the current 350.

I don't think that the Air-Gap is much different in runner configuration, but simply isolates the runners from the engine oil, keeping the incoming charge slightly cooler. It also looks neat. Don't know how much power you would see over the standard intake.

If you want to use the same carb for both applications, I would probably go with something around a 750cfm. It might be a little big for your stock 350, but you don't want to under-carb your 406 in the future. Most people say that a holley will make more power for you, but the edelbrock is easier to tune. I don't really have much experience in comparing the two though.

With a manual choke, you will have to mount a knob in the car which you will pull to activate the choke. The electric choke just requires hooking up a ground wire, and splicing in another wire that will get juice with the ignition on. Then it will operate the choke automatically and you don't have to deal with cutting a hole in the dash or firewall to put in the manual cable.

I would go with the Performer RPM or Performer RPM Air Gap (the Air Gap might make a couple more HP but costs more). I agree that a 750 Holley vac secondary would fit both engines pretty good. The Holley # O-3310 would work nicely on your 350, but you will want to jet it leaner in the primaries, a #68 would be a good place to start. the Holley street avenger 670 would be even better and probably wouldn't need any jetting changes, but they are a bit more expensive.

I would get the electric choke, manual chokes have a pull cable that has to go inside the car. Manual chokes are a PITA in my opinion.

------------------
68 Camaro, 383 small block with TH350 trans. 11.98's at 111mph and never trailered.

Was up boodlefoof! (we have got to hit that Hooters again and get the pic with all the girls)

Thanks for the advise.

As you know my wife is expecting in 5 weeks and I now building the 406 is getting farther and farther away every day.
The current motor is ok but a bit of a slug.
It looks like I am going to go with the Eldelbrock 750, electric choke. The manual choke might be kind of fun if I wanted to shoot flames out of the tail pipes. http://www.camaros.net/forum/smile.gif

If the Air Gap manifold is comparable to the Performer RPM but will give me a bit more kick then I would lean toward the Air Gap.
Any opinion on Air Gap over Performer RPM?

Unless you plan on changing the rear gears any time soon, you are not really going to benift any from the change to a performance type intake and carb.

I recommended finding a used GM aluminum 4 barrell intake (alot of the 305 engines came with them) and a good pre-74 Quadrajet that maybe just needs to be freshened up. This intake and carb will match your stock cam
as well as the stock gears and transmission. If you know how to work on, tweak and tune Quadrajets, and get it operating like it should and modify it to prevent the bog, will probably want to keep it for the 406.

*Personal note: I love Quadrajets, best carb ever built, pre-74 that is)*

Save your money on the intake and carb until you have the whole combination: Car, rear gear, transmission, weight, etc on paper. See if the combination will perform as you would like. It maybe that your intake and carb might change from what you have planned.

I like the RPM manifold as well for either motor. I did the same thing - put it on a 327 first and then on my 400. I'm still struggling to see the advantage of the air gap version. Yes, I understand the cooler manifold part but the mags seem to report only a few HP (like 3) gain. It just deson't seem worth the extra $$ to me and seems to come down to the cool look factor.


I would give a smaller carb some serious thought. I realize there are a lot of guys running 750's who swear by them but if you run through one of those carb size calculators even the 400 comes up needing only a 600 or 650.

I ran both an Edelbrock 600 and 750 on my 400 - swapping them out and trying to determine the real difference. There was a slight top end performance increase with the 750 but it's not as responsive at low speeds and it really kills the mileage. The 600 was much more responsive off-idle and at lower (read: normal driving conditions)RPMs and the gas mileage was much better. I really didn't feel like I lost much if any overall power.

My opinion is that unless you're running a real hot 400 or you plan on spending a true majority of your time at high RPMs, the 600/650 will be a much better setup. And definitely get an electric choke.

------------------
Scott
'69 400SB, Richmond 5-speed
www.geocities.com/sdenning1 (http://www.geocities.com/sdenning1)

this summer we will definately need to hit up that Hooters again. http://www.camaros.net/forum/biggrin.gif

Hey guys,
Do you think a 750cfm carb is a bit much for a stock 350....

Well, my friends dad has a holley 750DP on a stock 350 in a work truck. Works fine so I would imagine a 750 edelbrock would be ok, may need to be tweaked a bit though. I used a 700 Q-jet on a stock 350 and it ran ok.

750 is rediculas for a stock 350. Most naturally aspirated engines run at about 85-90% effeciency at the most. Use that in a CFM calculator, and it'll say that you'll need about 500cfm.
I'd recommend nothing bigger then a 650cfm carb, even for a hi-po small block.
The thing that requires a bigger carb is when an engine is blown, or runs at high RPMs.

A stock 350 may only NEED 500cfm, but how often does a "stock 350" stay a "stock 350"? Not long . . . especially around here http://www.camaros.net/forum/biggrin.gif

So buy a carb that you can grow into a little and IMO a 650 would be just about right if you want a double pumper. A 650DP can probably support 350 or more HP without a problem. The 750 vac secondary is probably a little bigger than ideal, but you can oversize a vac secondary carb quite a bit without a problem. Holley (or Edelbrock for that matter) doesn't offer a lot of choices in vac secondary carbs between 600 and 750 cfm.

------------------
68 Camaro, 383 small block with TH350 trans. 11.98's at 111mph and never trailered.

[This message has been edited by Eric68 (edited 03-15-2002).]

The 650 CFM carb may be better for my stock 350.
I guess I should get a carb for the 350 and worry about the 406 when the time comes. I can always sell the 650 on eBay if I need a later carb like the 750 for the 406 later.
I just want a good bolt on for now on the 350. I will plan and calculate for the 406 later depending on how far I will take that motor. It may be a year or more for my 406 build.

I had a friend with a 350 in his Jeep. He pulled the 750 carb off the jeep for a 650 and the motor ran much better and faster. I guess bigger is not always better.

Thanks all for the great feedback.

If we take the recommendation of going smaller on a 350 (like Edelbrock Performer 600 cfm) should we drop down to a Performer intake or can we still use the Performer RPM?

I would love to comment on this, but with no speck's on how built this 406 will be... I will refrain.

I have only one rebuttal for everyone knocking the 0-3310 carbs all the time. Guess what GM put on their high performance cars in the 60's? Not a 600 cfm VS. Not a 650 dp. A 750 CFM VS carb. Overcarbed? I think not. Any of you saying that it's too much carb, ever ridden in a DZ302 car? Guess what? Yep, 750 Holley. How about an L78 big block car? 750 Holley on that one too. Neither of those cars exhibit any sluggishness.

So, seeing how GM obviously didn't feel like the 0-3310 was too big of a carb for a street driven small block, I don't either. My 750 Holley will be back on my car next week after I have it rebuilt, and then I'm gonna tune the sucker correctly.

Cya at the track. http://www.camaros.net/forum/cool.gif

------------------
79' Z28 4-spd- built 355, TRW 10:1 forged flat tops, WP SportsmanII heads, Crane Energizer 228* duration .480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :) 3.73 Posi 10-bolt

joesmith69,

Good point about the Z-28 engine's carb. but it was a 780cfm, 3310-1 style one (I think).

The original 3310-1 has the rear removable "jet-pill" plate vs the jet plate so is easier to tune and turned it into the 4150 (or is that 4160) series carb(??). Holley just used "dog-leg" primary boosters in the 3310-1 to get the extra 30cfm out of the carb. Thats all.

Yes, a 3310-2 needs to be jetted and secondary springed down to match the engines size, thats all. It should come from the factory set up for a 375hp/396 BB so is a schosh big for the 350.

I added the rear jet plate to mine so that it would be easier to tune by just changing "jet-pills" and not have to buy different rear jet blocks. IMHO. pdq67

PS., and as "Honest Charlie" used to say "it is the runninest carb. ever!"

Big difference in the application between a "more or less stock 350" with a set of 3.08 gears and a 302/290 or 396/375HP big block. Every owner of a Z28 will tell you that the 302 is a dog below 3000 rpm. Now we know that is a function of the engines stroke length, cam profile and size of the carb. The 302 was designed to run at 4K and up in competition, not putting around the neighborhood. Same deal with the big block. Add another 20% more volume and you can live with a 20% bigger carb without giving up any driveability. Don't ever tell someone that because GM put a 750 Holley on their hottest or biggest high compression, performance engines it will work fine on your stock smallblock. No one will be happy with the results.

You could live with a 750 CFM Rochester/Edelbrock because of the spreadbore configuration and the fact that the Rochester's secondary air doors act to limit air flow through the carb to exactly what the car needs.

------------------
Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine (http://www.townisp.com/~markcanning/camaro/transparent%20air%20cleaner3.jpg)

If the 302 was a "dog" below 3000 RPM it certainly was not because of the carb. When you nail the gas on an engine with a Holley O-3310 the primaries (roughly 390cfm) open immediately (the equivalent to a dinky two barrel). The secondaries open only when the air velocity through the primary venturi creates a signal strong enough to overcome the seconadary spring and pull the diaphram up. You could probably put an O-3310 on a little 4 banger and get it to run fine - just the secondaries would probably never open up.

An O-3310 has much less flow off idle than a 650 DP, that is why you can "overcarb" and engine with a VS carb.

------------------
68 Camaro, 383 small block with TH350 trans. 11.98's at 111mph and never trailered.

DZ302's had a 750cfm, becuase they we're made to rev to the moon. Rev's require CFM. with 4.10's out back and a solid lifter short stroke high compression engine they werent too worried about low RPM's.

On an engine with a 3.08 gear out back, stock torque converter, and basically stock equipment the engine isnt going to respond well to a 750cfm carb!

Back again, Just go to your local parts house and order a rebuilt stock, 275hp/327 or 295hp/350 Q-Jet! I bet you will really like it. pdq67

Thankyou Eric...

I've been there, done that. I had my victor jr./750 4160 carb on my car with nothing else done but a set of headers. The engine ran fine. Was it a bit soft below 3000rpm? Ya, but not because of the 750 carb.

New motor goes in. Big(ger) cam, sporstman heads, more compression. Was it a dog below 3k rpm? Yep. Due to my 750 developing a leak, I put a 600cfm VS carb on my car. Is it still a dog below 3k rpm? Yep. And it always will be with my cam/intake combo. My soft bottom end is not caused by my large VS carbuerator. Same as the DZ302.

I'll stick to my guns when I say that this carb could easily be used on anything from a stock 350 to a 7,000rpm 350.

------------------
79' Z28 4-spd- built 355, TRW 10:1 forged flat tops, WP SportsmanII heads, Crane Energizer 228* duration .480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :) 3.73 Posi 10-bolt

another vote for the 750. reason #1, unless you get real radical on the 406, it'll be a good sized carb. for it. reason #2, my old motor was a real stock, fairly tired 350, maybe a small cam, and i bought a 750 demon DP, and had my team G (single plane) waiting patiently for my 406, but decided to throw them on just to baseline tune my carb for the 406, and mostly cause i just hadda do it. i was amazed at how well it ran. killer throttle response and idled flawlessly, w/ a single plane intake none the less. sure it wasn't the optimum setup for that motor, but it worked fine untill i put in the 406. just my .02

<BLOCKQUOTE>quote:</font><HR>Originally posted by CamaroNOTcamero:
DZ302's had a 750cfm, becuase they we're made to rev to the moon. Rev's require CFM. with 4.10's out back and a solid lifter short stroke high compression engine they werent too worried about low RPM's.

On an engine with a 3.08 gear out back, stock torque converter, and basically stock equipment the engine isnt going to respond well to a 750cfm carb!<HR></BLOCKQUOTE>

1st - DZ302's had a 780cfm carb, not 750cfm.

2nd - a stock torque converter and a 3.08 gear, if anything, demands a vacuum secondary carb.

3rd - even at 7000 RPM a DZ302 does not "need" 780cfm.

So what was GM thinking and why would they put a carb that was too big on the DZ302? Don't say they needed a bigger carb for Trans am racing - that's not true IMO. GM didn't put anything smaller than a 750 Q-jet on any 4 barrel V8 that I am aware of. That includes those late 70's 145 HP smogger motors with 2.56 gears, etc. Yes, the Q-jet has smaller primaries than the Holley, but that won't make that big a difference IMO.

My point is that it's not "rediculous" to put a 750 cfm carb on a stock 350. A carb with smaller primaries, like a Q-jet or 650 Holley, may be marginally better out of the hole but the Holley 750 will work just fine. I know because I have run them on mild 350's before!

The only fault the O-3310 750 has in this application (or any small block application for that matter) relates to the fuel curve - not the carb's size. The O-3310 does tend to be a bit rich out of the box on small blocks since they were originally calibrated for the 396. Change the jets though and you're golden.

------------------
68 Camaro, 383 small block with TH350 trans. 11.98's at 111mph and never trailered.

I'm more then certain then didnt put anything smaller then a 750 vac. sec carb is becuase the primaries in that carb were small, and it didnt bog on the low RPM's like a square bore would.

UHH...a square bore carb(Holley) won't bog either if it's tuned.

------------------
79' Z28 4-spd- built 355, TRW 10:1 forged flat tops, WP SportsmanII heads, Crane Energizer 228* duration .480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :) 3.73 Posi 10-bolt

I'll have to put in another vote for the 3310 750 Holley. I have one on my 406 and I love it. I have the lightest secondary spring in it with stock jetting and it runs flawlessly. There is no doubt in my mind that you could get it to run fine on a stock 350. There may be some tuning involved, but I would rather tune one carb than buy two.

Also, I had a 600 cfm double pumper Holley on my 406 for several months. I put a 750 cfm vacuum secondary (3310) on my motor a few months ago and I couldn't be happier. Low end response and power is similar to the 600 with better top end horsepower.

you guys are miss understanding me.
1st, YOU DONT NEED A 750CFM CARB FOR A "STOCK" or even modified 350.
What i meant was the small primaries of the quadrajet help it get better off idle response then a square bore.

Cameron, compaire apples to apples, saying that he should use a 750 on a stock 350 shouldnt be based on the fact that your modified 406 (56 more cubes) runs good with it. Part of the fact that your still getting a pretty good low end response is the fact that its a 406 and has plenty of cubes, which also happends to need more carb then a 350 at a given rpm (on the top end).

Unless you modify the 350 to have large cylinder heads (like 230cc) with big valves (like 2.10) and spin the sucker to 7500 rpms, then your not going to NEED that large of a carb.

The CFM requirement of a 350 with 100% volume effeciency at 6000rpms is 607cfm. Now that same engine may like a 750 on the top end, but i think that proves its unnecessary.

YOur 406 at 90% effeciency (kinda high) at 6000rpms only requires 635cfm, but since you had a 600cfm on it, it responded well to the bigger carb.

[This message has been edited by CamaroNOTcamero (edited 03-25-2002).]

Run as many formulas as you like. That isn't gonna change what works in the real world.

What you seem to be forgetting, is that he's building another motor. In fact, that motor is gonna be a hot lil 406. That said, he asked for a carb which WILL work, and WILL work WELL, on both motors.

I know you mean to help. But your speaking from formula's and computer programs, not from any real world experience you've ever had. I DID run a 750cfm VS carb on a STOCK 350, with a single plane intake, and headers. The motor ran GOOD. I don't care if it only required 500cfm or whatever. The motor ran GOOD with a 750. Better than with the stock Quad in fact.

Now I have run that same 750 on a much more powerful 355 setup. It also runs good. In fact, better than the 600 that's on it for the moment.

I'm not trying to dis you. I'm just saying that I'm speaking from experience, while I'm not sure you are.

------------------
79' Z28 4-spd- built 355, TRW 10:1 forged flat tops, WP SportsmanII heads, Crane Energizer 228* duration .480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :) 3.73 Posi 10-bolt

why do you keep assuming i have absolutely no experience with engines? i do actually, and they dont have 750's on them. The roller 383 me and my brother are building is going to be topped off with a VS 625 road demon, so we'll see.
I'd rather use computer programs and forumla's to figure out where i am, then walk blindly, and see "what might work" I dont have the money to spend on just whatever might work, and try and try again until something does, so i like to use my formulas to see what i actually need.

Why spend the extra money on a 750cfm carb, if you only need 650cfm, even with the 406.

[This message has been edited by CamaroNOTcamero (edited 03-25-2002).]

I believe that he is saying that the motor will tolerate a smaller carb and still make good power, but it may not produce the best power.

I hope by now it is largly known that Holleys formula for cfm is admittedly on the conservative side so that someone whith no to low experiance does not wowfully over carburate there combination. Edelbrock's formula is little better for someone with decent knowledge and experiance, though it may be a little optomistic.

Carbs are very total combination dependant. By this I mean engine C.I.D, build configuration (stock/mild/wild), weight, trans ratio, how many gears, stall speed, rear gear ratio, ETC, ETC.



[This message has been edited by mutant 68 (edited 03-25-2002).]

i'm not using there formula's, i'm using smokemup.com's calculator.

I know that they're combo dependant, barry grant's website recommends a 650cfm carb for up to 400ci (i'll assume 406 included) and up to 235 duration with a 3000stall.

[This message has been edited by CamaroNOTcamero (edited 03-25-2002).]

jrager never says what his 406 combo is going to be, if its going to be a torquer then the 650cfm carb would be better ontop of it.

If its going to have a 250 duration solid roller cam, 230cc heads that flow 325cfm on the intake, a large intake like the super victor then sure he's going to need a big carb.

This is why volumetic effeciency is figured into these equations.

Get a 670 cfm Street Avenger and be done with it. http://www.camaros.net/forum/biggrin.gif A little more seriously though, I have a mild 350 with a 600 cfm VS Holley and it runs great. Just for kicks we put in a 750 cfm and, at least out of the box, it does not perform as well as the 600. Now on a 406 I would lean towards the 750, especially if the engine is going to be performance oriented.

I hate to tell you this, but in Holleys formula a 350 spinning 6000 at 100% VE is 607 cfm.

A 406 and even a 383 responds very well to an 830 annular holley

------------------
78 Camaro hyd cam 406
TH350-3.23 gear
11.86 ET
116.7 MPH

MY point is that you do not NEED a 750cfm carb on a 350, or a 406. While its not TOO much on the 406, and it'll run fine, YOU DONT NEED IT! can i back up my opinion with these formulas, or are you just going to bicker about the small stuff.

WHat you have to understand, is that jrager, as far as i know is not going to the track to run his car, he's building a street performance motor. A big concern of someone whose building a street motor is trottle response, and low end driveablity.
which is going to give you BETTER throttle repsonse and driveablity? a 650 or a 750? i'm more then certain the 650 cfm will do that, along with the fact that it will be better on gas (a street motor concern) and be enough for the 406 when he builds that.

an 830 annular holley is rediculas for a street motor, dont even get me started on that, not to mention the cost. If you were going to spend that kind of money, buy a Race demon with interchangable venturies, so you can try out whatever CFM you like.

What I meant was you've never owned a car with a 750 carb. Not that you had no experience with cars/motors.

And nobody here is walking blindly. Those formulas, as already stated, are conservative. I am stating my opinion based on what I've used, not what a calculator tells me.

Oh, and one other thing. A 650DP is MORE expensive than a 4160 750cfm VS carb. Going by summit pricing(commonality), the DP is $298.95, the 4160 is $223.95. So, well, I guess that says it all...

I don't have anything more I can say to make my point. We are simply running in circles here.

------------------
79' Z28 4-spd- built 355, TRW 10:1 forged flat tops, WP SportsmanII heads, Crane Energizer 228* duration .480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :) 3.73 Posi 10-bolt

yeah i agree, this is just frustrating me, and i'm sure its no different for you.
a 650vs is cheaper then a 750vs,

By the way Camaro what is trottle response http://www.camaros.net/forum/smile.gif

[This message has been edited by mutant 68 (edited 03-25-2002).]

hehe i was rolling with that one http://www.camaros.net/forum/biggrin.gif you big meany!

Camaronot.... You need to get away from the key pad my boy.
Half the time you`re dweebing, the other i don`t know what!! Don`t even get you started??? get real!!
An 830 runs like I said and for your "Lack "of information they are less than a 4779
1660 some odd posts!!! you need to get your hands dirty for a long while in order to be the expert you try to present yourself as!!
No respect

------------------
78 Camaro hyd cam 406
TH350-3.23 gear
11.86 ET
116.7 MPH

hard to get my hards dirty when i've been having lung trouble, my appologies, i've been in a state of pretty bad health for the past 5 or 6 weeks, i'm converting the front brakes over to disk, and changing the master. After that i'll be building my 12 bolt posi rear (my apoligies again, the $$$ income is slow becuase of my recent bad health, so i havent the money to work on my 12 bolt yet).
1st off, the need for an annular 830 is really unnessesary on a stock 350, and even still on a 406.
Gotta love the post comment, "the expert i present myself as" i present myself as an expert? i believe i made a comment on how i was using programs and calculators to help myslf through some of this...becuase i havent tried it yet.
I've been listening to engine builders, and letting everyone have there say on what they feel i should do with my engine, and alot of those guy have been doing this since the 60's, these are who i get my opinions from. I hang around in shops, and i do get my hands dirty, i've been a metal worker for quite a few years, and i'm no newbie to this stuff. You dont have any idea who i am, i dont go around judging you.
BTW, am i wrong?
If you want to prove me wrong, explain why i'm wrong, dont tell me i'm wrong becuase i'm a dumb kid with no experience, and "this is how it is".
I have alot of repsect for the guys that prove me wrong, and explain to me, why they are right. I dont have any repsect for the people who just flat out tell me i'm a geek and need to go get dirty.

Does Holley make a 650 VS????

Red, let's keep this civil.

------------------
79' Z28 4-spd- built 355, TRW 10:1 forged flat tops, WP SportsmanII heads, Crane Energizer 228* duration .480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :) 3.73 Posi 10-bolt

they have a 600vs, forgot to check on that, they also have the street avenger 670, but thats a bit pricey.

I sympathize with you on your poor health.
But sometimes you have have a "know it all" attitude.
The guys that have been doing this stuff since the 60`s, that you say you respect, are the same ones you take issue with on nearly any subject posted. They have real "experience" whereas you have "opinions". Largly from computer programs and thereory... Huge differance. That`s where the respect issue lies. And at 17 years of age how can you have "years" of experience as a metal worker??
That`s EXACTLY what I meant when I said that you try and pass your self off as one that has more experience and hands on ability than you actually do.
Done...


------------------
78 Camaro hyd cam 406
TH350-3.23 gear
11.86 ET
116.7 MPH

exactly my point, i'vbe been a metal worker for about 5 years, maybe a little longer, i've been making all sorts of wood things too, and have been making knives for about 4 years. I've worked with everything from pig iron (on trial things) to BG-42 stainless, along with tool steels, and 440C and AT-34 stainless.
YOu may precieve some of my posts that way, but i dont have a know it all attitude, on this particular subject i know that i'm not wrong.

To get back to the topic: How does one know he has undercarbed? I'm thinking of putting an Edlebrock performer 600 on a performer RPM atop my 355 built for moderate performamce*. What would be the sypmtoms to tell if I should have bought a 750?

* = 355 with forged flat tops, TFS 23* heads, CompCams 282S and 1&5/8 headers.

Realistically you probably wouldn't know except on a dyno or at the track.

------------------
79' Z28 4-spd- built 355, TRW 10:1 forged flat tops, WP SportsmanII heads, Crane Energizer 228* duration .480" lift, Edelbrock Victor Jr., Holley 750cfm, Dynomax headers, dual 3" flowmasters :) 3.73 Posi 10-bolt

Don't check in for a couple days and miss out on all the fun http://www.camaros.net/forum/wink.gif

Lets define the difference between what an engine "needs" and what an engine will run best with. I think were talking apples and oranges here.

A mild or stock 350 may NEED only 500 cfm, but (based on my EXPERIENCE) there is a chance that it will run better (better = faster in the 1/4 mile) with a VS 750 carb as opposed to a VS 600 carb. Even if it doesn't run faster, the engine will certainly live just fine with a VS 750 carb. The only way to know for sure is to try it.

To say an engine will be a dog with the 750 carb is to say that the engine would be a dog with a 390 two barrel - because that's exactly how a 750 will respond when you mash the pedal off idle on a mild 350. You see that's the magic of the vacuum secondary carb - it will ONLY add airflow through the secondaries when the engine demands it. If the engine is too small or too mild to demand it then they will not open - its that simple.

My advice Camaro - stop arguing and lecturing so much about things you have little experience with and LISTEN to guys like Big Red and some of the other old timers around here. Hope your lung problems work out OK.

point taken. Thanks, i'll be doing better soon, then working on the camaro, plenty of new toys to install.
I dont have respect for anyone that implies that i'm a dumb kid. Eric, you on the other hand, explain things to me, and you dont treat me like i'm a moron. thanks.

Just want to say sorry if that's how I came off in any of my posts. I too am a 'dumb kid'.

-Joe

dont worry about it Joe, i didnt precieve any of your posts that way. I repsect anyone who will apologize like that.

Camaro - didn't mean to sound harsh if I did. Actually, when someone mentioned you were 17, I was a little shocked. You have a very good understanding of how an engine works for your age. Thought about a career in an engineering field?

thanks eric, i appreciate the complement http://www.camaros.net/forum/smile.gif

I've been planning to go into engineering, i like auto, and mechanical, i do alot of drafting also, only been in drafting class for 2 years though, i work on auto cad, and the board. Been looking around for engineering classes in Jersey, although, i'd rather go down south, becuase they're more laid back down there.

Thought I would see where this ended up before posting. In a resent article about BG Demons (sp). Towards the end of the article it stated that BG says that most 350's with a dual plane intake and moderate gears can use a 750cfm carb. He didn't say anything about it making more or less power. Also in the article it stated that if a mach. secondary carb can be cracked open without any bogging that the motor will rev faster than with the same size carb useing vac. secondarys. Thought it was an interesting article.

Shane

I didn't wan't to post (AGAIN) since I am somewhat long winded, but I thought this might help shed a little light..Keep it in mind that I am not trying to step on anyones toes, just stating what I found out years ago...

My 355 was in a 79 El Camino that weighed 3365 with me in it.

TH-350, 2400 stall, 3.42's, 26 tall tire.
10:1 comp, Cam Dynamics Energizer 278H, Performer RPM, S/R Torquers-Pocket Ported 202/160's, Hooker 1 3/4 headers and 2 1/2 exh. Shift points were 5800-6000.

I tried these carbs on it 600VS, 650 DP, 3310-1 (780VS CFM), 750DP. You can bet that I would have tried a 700DP if I had one at the time. All of these carbs were dialed in to the combo withought drilling anything, just streight jetting and the other standard caliberations.

What I found was that the 600 had realy good responce and good low end, but of course the midrange and top end suffered compared to the larger carbs.

The 780 VS was not a good performer even though it was a VS model. It came on pretty good in the upper mid to top end. The bottom end felt lazy on the street, this could have been because of the dropped leg boosters. If I slightly lifted when in the top end it seemed to accelerate a little quicker. This is a sure sigh of being over carbed.

The 750 DP actualy felt a little stronger in the bottom end if you didn't nail it. It was more tractable.

On went the 650DP. Well WELL what a difference. Snappy low end, good mid, and a good top end. The EL now became quite the tire fryer. The top end might have been SLIGHTLY down on power compared to the 750-780. Still, this carb was clearly the winner.

I sure wish I had that 700DP to try.

Now if you use the typical formula at 90% VE then my engine was over carbed by about 100 CFM with that 650DP. But yet it was the best carb. Ever since then I have been a BIG DISBELIEVER in the typical formulas. Experiance and testing seem to be your best friend when it comes to picking a good carb.

There was a brief discussion about this same subject in Team Chevelle a wile ago
http://www.chevelles.com/forum/Forum4/HTML/006582.html


[This message has been edited by mutant 68 (edited 03-28-2002).]