Carburator size

-
B

BobbyY

Old Mopar guy
Joined
Apr 16, 2013
Messages
122
Reaction score
2
Location
Austin Texas
I know carbs are like a religion, but, I need some help. Lets start with as much as I know about the engine build.
360 LA, with [FONT=&quot]hypereutectic pistons[/FONT], [FONT=&quot]Comp Cams Hi-Lift series 275HL hydraulic flat tappet cam.
[/FONT][FONT=&quot]Edelbrock # 60779 Performer RPM heads, Elderbrock # 7176 Performer RPM intake[/FONT].
A727 3000 RPM stall converter and 3.91 rear end.
The engine currently has a Holley 4150 Series 600 CFM double pumper with a fresh rebuild kit. I have been told the engine should be in the 420 hp range but I don't know.
For all I can tell sounds like it runs strong, with that said I am unable to take it out a romp down and hold it so I have no way of knowing how the 600 will hold out at extended high RPM's. Also this series does not have a choke of any kind and I don't think one can readily be added (could be wrong there). In any case I would prefer to have a carb with an electric choke, and vaccum secondaries I really hate having to pump it until it is really wet then have to bayby it until it comes up to operating temps. I have a chance to pick up a like new Holley 85670 STREET AVENGER ALUMINUM 670 cfm. Is this enough carburation or do I need to be lookingin 725/750 range.

Help,
Bobby
 
I have a built like yours and I am running the holley 770 street avenger. I dont run a choke on it even here in pa but I have to play with it when cold for about a minute. I love the carb and it works flawlessly. In the summer Its starts and goes fine. It was my choice to take the choke off.
 
Holley 750/780 - 3310(?) w vac sec, and elec choke.. nite and day diff to 600..

Your motor wants too breathe,, you got big money in those heads,, take advantage of them..

hope it helps''
 
Thanks for your inputs. I think the idea of a really good deal and thinking that a lot of times we tend to over carb engines, I was hoping 670 would be more than enough. When I go to the Holly Website it shows to be right in the middle of what they recommend for a decent built out engine up to 6000 RPM. I also forgot to mention that this will be a 90% street car with maybe a occasional visit to the strip. Will most likely pull the 3000 RPM stall converter out and maybe re-gear to 3.55. I guess I'll look for something more in the 750 range.
 
I'm sure it'll run fine with the smaller carbs,.. ,, my thoughts are,, if you spent big bucks putting on hi-flow heads - hi-flow manifold, and presume hi-flow exhaust,, why would you put a pea shooter size carb on it, when all the parts you put on it indicate you wanna get top h/p outta your engine,, ergo,.. bigger carb,,.. for 420 hp you need a bigger carb.. my .02..

hope it helps..
 
Put a 750DP carb on it.

It likely won't make it to 6K RPM. Max power will probably be around 5700.
 
My 340 isn't that far off of your 360 build, specs are

'68 340, .060" over with KB 243 hypers, .018" over the deck, ~9.8:1
308 heads, 2.02/1.60 valves, 65 cc's chambers, stage II ported and flowing 264cfm at .500"
Harland Sharp 1.5 roller rockers, Smith pushrods
Lunati 60404 Hydraulic cam, .513/.533", 276/284 advertised duration
Doug's 453 headers
Edelbrock air gap rpm intake

Hp should be in the 420-430 range as well. I tried running it with a 670 Street Avenger, was way lean out of the box. I had a 770 street avenger on hand, so rather than start with a big tune on the 670 I put the 770 on it. Runs pretty well right out of the box with the 770, but if I change anything it'll be to go up a size on the primaries. Seems pretty close, but its definitely not rich as the plugs are still bone white. It's getting a wideband A/F gauge here in the next few days so I'll have a better idea of where I'm at.

With your set up I don't think a 670 is going to cut it.
 
The smaller exomended carb is a pure street recommend size carb, for some strip or a mean street machine, go up 50 CFM. Etc...
I'm with the guys on going with a 750 or the 770 Avenger.
 
I like stickin with VS carbs with an automatic. I think the good old 3310 would be perfect. They are tough to beat, IMO.
 
i could not be happier with my street h.p. 750 holley 750 vac. sec.although it was reccommended a d.p. would be the better choice with my 3400 vert and 391 gears with my built 727
 
Rusty, In several of your post I see you referring back to the 3310, what is the application/performance advantage/differences between the 3310 series and the street avenger 770 series, or the square bowl single inlet 750 (0–80459SA ). Just trying to educate myself. Keeping in mind 95+% is street crusing, if it makes it to the track once or twice that will be about it. So ease of setup/use, start-up and idle very important. I must also say I'm intrigued by the Holley square bowl and the Street Demon's looks, Kind of a throw back to the Carter AVS.

Bobby
 
ANY single inlet dual bowl Holley has a serious flaw. Fuel in the secondary bowl just sits there, unless the secondaries are opened. I have taken 1850 Holley 600s apart so many times that have 1/4" or more varnish and crud in the bottom of the rear float bowl it's pathetic. It's really a bad design, because usually people buying a single inlet carburetor are looking for the cheapest, most streetable carburetor and are not really concerned with cracking the secondaries much.

Nothing at all wrong with the Street Avenger carburetors. I like them. I always use the 3310 though for recommendation because of its sheer simplicity and cost effectiveness. Lets face it. How many people really NEED to spend the extra money on a Street Avenger? Most average Mopar guys can turn a wrench good enough to buy a 3310 used and kit it themselves saving them even more.
 
For a street car I'd recommend the 3310 as well. Ran one for 6-8 years on a 360 before I went 4 speed. Was the most reliable carb I've ever run. It was a 509 cammed, 3000 stall, 3:55 posi car at the time.
 
I hope this doesn't post twice. I thought I sent a similar post to below earlier but don't see it.
Rusty, I’m going to show my ignorance here with regards to carburetors. I’m not questioning your thoughts, I’m trying to understand and learn from your experience. I fully understand what happens to gas when left to sit, especially with the crap they are selling us now and calling it gas. What I don’t understand is, if there are two bowls, what difference does one or two inlets make. If the secondaries are vacuum operated you are still going to have to use the right foot vigorously once in a while to replenish the supply with fresh gas. Now if it was manual secondaries I could understand it. Thanks for taking the time to educate me. I may be slow but I am trainable.

Bobby
 
Any good fuel system needs a fuel return. People on this forum have argued me down on it, but I stand by it. Even with a fuel return, the single inlet carbs do not circulate fuel as completely as a dual inlet.....speaking strictly of Holleys here. A top plate bowl carburetor such as a Carter or Edelbrock, they are different entirely. When you have a dual feed inlet, even with no return, they generally move fuel enough to keep the rear bowl from crudding up. But the single inlet carbs have a complete disadvantage. Even when you add a return, they never fully circulate fuel like they should.
 
You must log in or register to reply here.
-

Back
Top