650 or 750 cfm. carb??

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Galactic_eyes said:
As far as I know nothing has been done to it. The 360 had a Thermoquad that the previous could not get to act right. He had pulled the 600 off of his Montecarlo. It's been on there ever since.
What octane gas are you using? If I use anything less than 93 it will ping like a mother.
A friend of mine has a 650 DP that we were going to try on my car but we didn't have the bracket for the TV cable going to the trans.
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I use either 93 or 94 octane. Is your carb and electric choke or manual choke?
 
BJR Racing said:
IMO I think that you need to tell us what you have in mind for a cam and what amount of head work you plan on having done and is the compression ratio staying the same or is it going to be increased? I don't ever run anything smaller than a 750 VS carb on the street, and alot larger than that on the track. In order for anyone to tell you exactly what carb you really need is a shot in the dark until we know a few things as I mentioned above, as they all have effects on the carb. A 360 that I did with mild head work and a XE284 cam and a Torker II intake and shorty headders needed a minimum of 750 cfm's and we ended up using a 830 cfm carb. Throttle response was great and crisp as you would ever need one. We tried smaller carbs and they were flat just above 5,000 rpms, because they just couldn't flow enough air to satisify the engines needs.

If this is going to be a street only engine and less than 5,000 RPM's 98% of the time then I might consider a 650, but don't expect any big power from the engine. And as I stated before this would be in stock form only, without any considerations for improvements. But from what you stated that you have intentions of modifing your engine then I wouldn't even consider anything smaller than a 750 VS. In fact Holley recommends this for there street avenger carbs,

570 cfm's for 300 HP
670 cfm's for 300-400 HP
770 cfm's for 400 + HP
870 cfm's for 500 + HP

you can get anyone of these with electric choke. A buddy of mine had a 670 on a stock 454 and had problems pulling hills with a trailer behind him. This is in a Chevy Dually, he stated that he was getting 10 MPG with it but couldn't keep up with traffic on the interstate when a hill came up. Then I loaned him my race 780 cfm carb VS and he said man what a difference. Sure his gas mileage dropped but it was because of his right foot. He told me that he no longer had to keep his foot on the floor to pull the trailer, and that when pulling the trailer that he could pull hills at half throttle. He said that he could do 70 mph and it not back off at hills. And the engine was only turning just over 3,000 rpm's.

So my point being that reguardless of engine size a VS 750 is one of the best all around carbs for the street and power and IMO I would use a 770 street avenger. You have to look at it this way also, that your only running the engine on the primary front 2 BBL's most of the time, and if the engine needs more then this can be adjusted by the secondary diaphram springs for when you want it to come in. But it's a simple change.

On my 322 engine with 302 heads I don't run anything smaller than a 750 and in the last few weeks I have had a 9375 1050 Dominator on it, that a friend of mine was having problems with on his 540 BBC engine. I cured the problems with it and he told me to run it so I did. The result was that without dejetting it that it ran just as fast as the 750 did but believe me there was alot left in the engine with this carb on it. Had I been able to tune it to the engine it was on. I would say that with this carb on the little 318 .030 over that it would have run 1/8 mile times equal to low low 11's on 87 octane gas in a 3,330 lbs duster.

I guess I look at carbs differently than most do, I don't like to put the minimum cfm carb on a engine but rather I allow a couple of hundred cfm's more. And this usually is seen in the time slips at the track. If more airflow didn't or doesn't make more power then why did they put Q-Jet carbs on the 231 V-6 engine that Buick ran in there Grand National Cars. I had one of these cars without the turbo and it ran very well, and in stock trim could smoke the tires. The main thing here is to use what ever carb that you want, it's your car/engine and you have to live with what ever you choose. But I know what I would do. And this is comming from someone that has built many different engines and for different purposes and what they required to make them work well.

Oh ok 1 more, my 318 that I had in a 4,000 lbs truck was getting 17 mpg without a OD and it was a 750 VS holley. This was a stock 318 engine and a 727 transmission. And it passed 04' emissions better than the new cars did. It was a 3310-1 and had 78 and 84 jets in it with a 6.5 PV and the air bleeds were 72 and 32 idle and power, with the idle mixture screws turned out 1 turn. The engine had 20" of vacuume.
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Very well explained Bobby. Great points made. I too don't like minimum carbs on my engines also.
 
BJR racing thanks a lot for the info. it really sounds like you know what you're talking about which is good. Like i've stated a few times i'm in the process of switching my car from a /6 to this 360 so unfortunatly mods. such as a cam will come whenever budget allows. I'm 17 years old and at school 5 days a week and work a part time job so the budget is really restricted. I do NOT expect any more then 400 hp. out of this engine and i'd be surprised if i ever ran it higher then 6000 ever with the current rotating assembly that's in it now (bone stock). Also as far as compression goes and head work, again it really depends on budget. i'm hoping to give the stock heads a valve job (2.02/1.60 hopefully) and shave them to get me a better compression ratio but unfortunatly i really don't have the money to be doing a rotating assembly so i will have to build compression by shaving the heads, and when i can afford it. I'd imagine for the first year i'm just gonna throw the engine in and get it running and back on the road and do mods. a little at a time when budgets allow. I hope that this info. helps even though i'm kind of unable to answer your question. Thanks again guys all your help is really appretiated!!
 
Not sure if you or anyone else is interested? ,But I have a holley 750 double pumper carb with mechanical secondary,non electric choke.
Was rebuilt 2 years ago for a car I had.
Worked awesome,sold the car and I kept the carb.
It was painted black when it was rebuilt.
Has been sitting on a shelf in a heated garage for just under 2 years, All parts move free.
Should be able to pop it on and fire it up!.
oh and also, I have the dual feed chrome fuel line I would toss in on the deal also. If your interested,just make an offer.
Thanks
,Pat
 
where are you located IgotDUST? I might be interested but i'm a huge fan of the electric chole because it often gets kinda cold up here in canada and the old cars don't wanna stay running lol.


Again BJR racing thanks again for the advice, i've been told by other members that you are very knoledgable and really know what you're talking about and i really appretiate that. i only wish i knew exactly what my build would be because then it would be easier to decide, but hey you work with what you got right. Thanks again guys!!
 
ok guys so what i see a lot of you saying is that the manual choke carbs. are jetted higher then the electric ones or rather the electrics are jetted down? correct me if i'm wrong. So lets say i wanted to buy a manual choke, then i'd buy a 650, but since i am wanting an electric choke i should look more at a 750 because it is jetted down? You guys keep mentioning holleys, what line do you guys think is best. ie. double pumper, street avenger etc? Don't forget that this will be a mostly street car with some occasional fun track time, so good street manners would be fairly important.
 
I would personally use the 770 street avenger, this way you get the electric choke that you want and the tuneability that you need. These carbs have very good street manners and great drivability. I would put them against the Eddy's anytime. The 770 would be large enough for your engine at this time and give you what you want. Then later you can tune more to the performance side as your engine get's it's performance mods. 1 carb and inexpensive parts for the up grade later, by parts I mean sec. spring kit, air bleeds, and jets.
 
74scamp360 said:
where are you located IgotDUST? I might be interested but i'm a huge fan of the electric chole because it often gets kinda cold up here in canada and the old cars don't wanna stay running lol.


Again BJR racing thanks again for the advice, i've been told by other members that you are very knoledgable and really know what you're talking about and i really appretiate that. i only wish i knew exactly what my build would be because then it would be easier to decide, but hey you work with what you got right. Thanks again guys!!
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PM sent
 
This is an interesting thread. I'm in the same boat as this guy. I'm haggling over carb size. I have a 360 boared .40 over with a Comp 268 extreme energy cam, edelbrock rpm intake, rpm heads, headers, and currently have a 750 dp no choke carb on it. I'm adding 125 shot of nitrous in the fall. The 750 dp drinks gas like you wouldn't believe. Ran out yesterday on the way to the gas station.

My car is primarily a street car that will see occasional track time once I complete it. I contacted Holley for the best size carb and their tech recommended a 650. I bought a 670 steet avenger to go on it but noticed that the 670 was for a mild engine. I wouldn't consider my engine "mild". They recommend a 770 for a "hot" engine (I'd say that mine is hot). What would you guys say?
 
1ToughDuster said:
This is an interesting thread. I'm in the same boat as this guy. I'm haggling over carb size. I have a 360 boared .40 over with a Comp 268 extreme energy cam, edelbrock rpm intake, rpm heads, headers, and currently have a 750 dp no choke carb on it. I'm adding 125 shot of nitrous in the fall. The 750 dp drinks gas like you wouldn't believe. Ran out yesterday on the way to the gas station.

My car is primarily a street car that will see occasional track time once I complete it. I contacted Holley for the best size carb and their tech recommended a 650. I bought a 670 steet avenger to go on it but noticed that the 670 was for a mild engine. I wouldn't consider my engine "mild". They recommend a 770 for a "hot" engine (I'd say that mine is hot). What would you guys say?
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It's all in the tune, I tune to the edge of lean for power and milage.

My combo was 340 .030 9.8comp, .528 solid cam, 750 dbl ,3.73 gears, ported heads, 2 1/2 exhaust etc......

I got 15 miles to the gallon, varying only 1-2mph on the street only depending on how I drove it [now it's a 410ci]

This is with 26*initial & 8* full advance @ 2200rpm=34*total timing
no vac advance
And like I said... I tune it on the edge, sometimes when it gets cold out, it'll mildly surge here and there so I go up 1 jet size till it's smooth.
 
well BJR you've nearly convinced me to change and go for a holley. you guys sounds like you really like the holleys. The biggest reason that i was looking at an eddy. was my dad had amazing results with his. he bought a thunder series 850 to go atop his strongly build 440 in his 69' charger. It was so simple new gasket and bolt it down and it fired right up without touching it out of the box. we adjusted the idle a hair and leaned it out just a tad and it's worked awesome ever since. He said that it performed a thousand times better then his 850 holley ever did and he said he's probably got over $500 into it with some of the upgrades he put into it. That's been my experience with it and that was why i was so keen on using an eddy. But you guys have nothing but good to say about the holleys so maybe i need to give them a second chance lol. Thanks again for your help everyone it's been very useful!!
 
I have carb problems on my 360 / 395 hp crate motor. Had a 650 double pumper, a proform 750 and now 770 avenger series. For your app. 750 cfm. is what Id recommend. I personnaly do not like edelbrock carbs and would go with a Holley. Just my 2 cents
 
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