Choosing Carburetor for 1970 Road Runner 383

[RoadRunning]

Hello, I am new to the forum and this is my first post :headbang:

I am currently thinking about what carburetor to put in my 1970 Road Runner. The car is pretty stock except some minor changes. Here are my specs:

• 383 engine
• Edelbrock performer 383 intake (Part number might be 2186)
• Mopar "purple" Cam
• Mid size headers (do not know brand but probably about 1.75" diameter)
• Turbo Walker dual exhaust
• 727 Torqueflight with shift kit

We have the stock carburetor that we are saving for #s matching and we also have a Carter AFB Competition Series 9605s 3013 that is 600cfm. I am converting to electric choke since right now it is manual and think there might be some benefit to getting a slightly higher cfm carburetor while I am at it. What do you think?

I would like to go with an Edelbrock one with AVS so I was looking at the Thunder Series. Sounds like 750 cfm is a pretty popular choice but the Thunder Series only has the 650 and 800 cfm. Which one would you choose with my setup? Any other recommendations?

Thanks!

 

[DP78]

I have a pretty much stock 1970 RR 383 except for Cam and DP4B intake. I run a Holley 670 street avenger and I would say that's about perfect size for the motor. IMHO I think people tend to over carb all the time. Their is a formula to calculate carb size with engine size and someone on here probably knows it or you can Google it.

 

[HYRDGOON]

I also had a Holley Street Avenger 670 on my 383 and it worked well

 

[lewtot184]

the 650 avs is very close to 383hp avs. don't do the 800avs. the 750 edelbrock is ok but will need to be recalibrated. a good factory 383 avs is a good choice. the performer cam is a little less than a stock magnum cam but not a bad choice for a driver.

 

[RoadRunning]

Just edited my post to reflect the correct cam. I actually have the Mopar purple cam in the engine, not the performer.

 

[Phil McGrath]

Back in the day it was very common for 383 drivers too swap out there 625's, for the 440's 750 carb.

What size Purple Shaft cam, there are a few of them? Stock resto, Six-Pack- 474-484-509?

 

[RoadRunning]

Hi Phil, not sure which purple cam is in it. All the guy told us when we bought the car is that it was "one step up from stock".

 

[dburnett6263]

I'll throw in my 2 cents worth here. My 68 RR 383 is a moderate build, .040 over, comp extreme energy cam, crane & milodon valve train, etc. Very healthy but very street-able. Originally had an edelbrock 650, but just wouldn't cut it and the secondaries came in way to quick, no matter what we did to try and overcome it. After research went with the Holley 770 street avenger. Night and Day difference. Except for curb idle didn't have to touch it. I do agree with the above, so don't over carb, but this works well for my setup.
Also maybe a year ago Mopar Muscle had an article on 383 carburetors with dyno performance. Engine was a moderate build and the 750 cfm pretty much hit the marks. 850 cfm was about the same as 750.

 

[RoadRunning]

I would like to go with a 750 cfm from what I've read. The Edelbrock Performer is very tempting but it doesn't have the AVS. The Thunder series with AVS does not come in 750 cfm. Do you think I will need AVS or would the Performer do the trick?

 

[young99]

I just replaced my Demon Carburetor with a Holley 750 CFM Classic and I like it. If you decide to go this route you can order one through autozone for $263 if you don't live in a state with crazy internet tax.

http://www.autozone.com/fuel-delivery/carburetor-performance/holley-carburetor-performance/691574_563874_5972/

use the DRL2056 code on checkout. It must be shipped to your house to use this code.


One side note I did not realize is that the Holley Carburetors don't come with the mounting studs and nuts. So you may want to pick them up if you plan to replace them.

The benefit for me is that most chain part stores have a 90 day return policy. If you don't like it or is not working like you wanted you can take it to the local store and get a refund.

 

[RoadRunning]

I am starting to look at the 750 cfm Street Demon carb. What do you all think? There is a notice "Depending upon the air cleaner used, a riser or spacer may be needed for adequate choke andthrottle linkage clearance." Also "If installing the Street Demon™ on a factory castiron spread bore style manifold, a spacer may berequired for proper throttle opening."

Anyone have any feedback on the 750 Street Demon carb with my setup above?

 

[young99]

I have not used a 750 cfm demon but just returned my 625 cfm street demon. Maybe I just had a bad carburetor but the choke metal flap was not cut properly and kept getting hung so it would stop opening . I had to take it off or use a grinder to modify it to open properly. Drove the car probably 3 times within a 2 and half month period. Got ready to drive it noticed the carburetor was completely locked, up would not open or close. I returned it for a refund and picked up a Holley. Now when the carburetor worked the few times I drove it worked great and responded well.

 

[RoadRunning]

Resurrecting this thread as I have not bought a carburetor yet but I am ready to buy one now after a successful start of the engine. I am looking to buy 1 of the following:
1) Street Demon 625 CFM
2) Street Demon 750 CFM
3) Speed Demon 650 CFM
4) Speed Demon 750 CFM
5) Road Demon 725 CFM
6) Holley Street Avenger 670 CFM
7) Holley Classic 650 CFM
8) Holley Classic 750 CFM

Knowing my setup above, does anyone have any opinions? I am guessing the car is probably just under 400 HP. Thanks in advance.

 

[SlinktRR]

street demon 750 or avs 800. I run the 800 its fine on a 383. A 383 can move some air at high rpm so opt for more more cfm if you plan to rev it. Of the two, I would go demon.

 

[727]

I have a 750 street demon on my 440 and it is better than the Edelbrock carb. The price is cheaper than anything else as well (check on eBay).
Regarding automatics: What I have found with the smaller carbs, is when you roll into the throttle at cruising speed it's very easy to downshift with a 600 vs the 750 which allows more volume (span) before downshifting.

 

[moparwacko]

Resurrecting this thread as I have not bought a carburetor yet but I am ready to buy one now after a successful start of the engine. I am looking to buy 1 of the following:
1) Street Demon 625 CFM
2) Street Demon 750 CFM
3) Speed Demon 650 CFM
4) Speed Demon 750 CFM
5) Road Demon 725 CFM
6) Holley Street Avenger 670 CFM
7) Holley Classic 650 CFM
8) Holley Classic 750 CFM

Knowing my setup above, does anyone have any opinions? I am guessing the car is probably just under 400 HP. Thanks in advance.

Commitment issues? just buy one and endlessly fiddle with it like the rest of Us!
Seriously, on a mild build like yours, edelbrocks have worked fine for me, avengers also. My current 383 likes anew old 750 3310 Holley, until I fiddle with it some more............we're here to help whichever one you buy. But do go buy one.

 

[SlinktRR]

I have a 750 street demon on my 440 and it is better than the Edelbrock carb. The price is cheaper than anything else as well (check on eBay).

Agreed! I only keep the AVS because the 383 in my car is on borrowed time, my new RB goes in this winter and will be getting something bigger like a QF950 or equivalent. I like the design of the street demon it combines a lot of good ideas from holley, EB and carter thermoquads into a modern carb. Hughes built a stroker with the 750 street demon/edelbrock RPM and it made 585hp on the dyno. The carb was pulling 1.5" vacuum during the final pull so it was definitely too small for high RPM power, but on a 383 with headers and warm cam I bet that 750 would be just right.

 

[T Reynolds]

Hello, I am new to the forum and this is my first post :headbang:

I am currently thinking about what carburetor to put in my 1970 Road Runner. The car is pretty stock except some minor changes. Here are my specs:

• 383 engine
• Edelbrock performer 383 intake (Part number might be 2186)
• Mopar "purple" Cam
• Mid size headers (do not know brand but probably about 1.75" diameter)
• Turbo Walker dual exhaust
• 727 Torqueflight with shift kit

We have the stock carburetor that we are saving for #s matching and we also have a Carter AFB Competition Series 9605s 3013 that is 600cfm. I am converting to electric choke since right now it is manual and think there might be some benefit to getting a slightly higher cfm carburetor while I am at it. What do you think?

I would like to go with an Edelbrock one with AVS so I was looking at the Thunder Series. Sounds like 750 cfm is a pretty popular choice but the Thunder Series only has the 650 and 800 cfm. Which one would you choose with my setup? Any other recommendations?

Thanks!

I run a 650 Demon on a similar set up. It outperformed the 600 and 750 edelbrock. The 750 was the better edelbrock. In the thunder series I would run the 800.

 

[Lazerwolf]

I have a very similar set up to you. It's a 400 with E-Street heads, Performer intake and Lunati 702 voodoo cam. It originally had a Edelbrock 1406 600 cfm on there. Transmission has B&M shift kit. It always had a lean bog to it while normal to hard accelerating, even after tuning. I had a Holley 4160 750 cfm off a different engine so put it on. Not saying Holley is better than Edelbrock, just when putting extra ponies in there, it responds much better with the 750 cfm than the 600 cfm. Would like to try a Edelbrock 750 for comparison. Buddy of mine put the Holley 650 classic on his 66 El Camino with a 400 in it and is looking to upgrade to 700-750. Give Holley tech a call at 866-464-6553.

 

[RoadRunning]

I have a very similar set up to you. It's a 400 with E-Street heads, Performer intake and Lunati 702 voodoo cam. It originally had a Edelbrock 1406 600 cfm on there. Transmission has B&M shift kit. It always had a lean bog to it while normal to hard accelerating, even after tuning. I had a Holley 4160 750 cfm off a different engine so put it on. Not saying Holley is better than Edelbrock, just when putting extra ponies in there, it responds much better with the 750 cfm than the 600 cfm. Would like to try a Edelbrock 750 for comparison. Buddy of mine put the Holley 650 classic on his 66 El Camino with a 400 in it and is looking to upgrade to 700-750. Give Holley tech a call at 866-464-6553.

I emailed Holley tech. Their response was they would recommend the Holley Classic 650 CFM for my setup. They stated it "has good street manners and still provide good throttle response". I then asked directly if they would recommend the Holley Classic 650 over the Street Demon 750 and they said the 750 would be a bit much for a street car with mild modifications and that he personally liked the Holley better and that it would allow for more tuning ability later than the Demon would...