Carb tuning help

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Jay_340

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Hey all. I have a 71 Duster with a mild 360. It has about 9.8:1 c.r. mildly ported J heads, a Lunati Voodoo cam with 268/276 adv. duration, 226/234 duration @ .050" and .494/.513" lift, Eddy Performer RPM intake, stock 340 HP manifolds and 2-1/4" exhaust with Magnaflow mufflers. I have two different carbs, an Edelbrock 600 AFB style and a Holley 650 double pumper. The Holley makes this car an animal, no hesitations, power from bottom to top of the tach, but its lacking in street manners. The Eddy 600 has very good street manners, great off-idle transition, but it starts pinging hard after getting up in the rev range. I put in richer metering rods, but it still pings. Either I need to jet it up more, or get a bigger carb if I want to keep with the style of the Carterbrock. Does anyone have good experience tuning the AFBs? If I need a bigger carb, then I'll use the Holley. If I can tune the AFB a little better, I kinda want to keep it on there. Help a guy out, who knows the AFB?
 
Is it electric choke / those are jetted leaner. I agree the Carter / Edelbrock carbs are better for idling...the Holley can be made to idle very well but the Edelbrock carb will always be a bit better.

The secondaries may need to be jetted richer..maybe my eyes are shot but I can not see those tiny numbers on the jets. I use wire drills and a mic to find the size I want. Small changes make a big difference and both the primaries and secondaries need to be right for best power.

Try going up .003 on the secondary jets..might need to go .006...each jet is .003 larger.

To get the Holley to idle better the idle feed restriction brass hole in the metering block might need to be open up a few thousands..like .003...helps to decease the idle air bleed but only HP carbs have removable air bleeds in the air horn...you can tap them thou or use epoxy to plug and re-drill.

Shot for ,065 on the low speed air bleeds..those are the outside bleeds..and .030 to ,035 for the meter block idle restriction holes..you might want to google for more infor.
 
If it doesn't ping with the Holley but does with the Eddy it's most likely just running lean. That's providing the Holley wasn't running so pig rich it drowned out spark knock. Generally when you jet a carb up you should do all corners, not just the front's. Otherwise you have an imbalance. Try jetting up the secondaries too and see what happens. I have noticed every Eddy I messed with was jetted pretty lean out of the box.

BTW: What's your timing set at? I have a 360 very similar to yours (9.8 to 1, mild ported X heads, Lunati 60404 cam which is one size bigger than yours) and mine won't tolerate any more than 34 degrees total timing on 93 octane.
 
Like dodge freak said, the electric choke eddy's are 2 sizes leaner than the manual choke ones. For what you have though, a 600 might not be enough.
 
Thanks for the responses, guys. I like the Eddy carbs for their street manners and drivability, so I appreciate the help. Plus, being able to change jets without draining the fuel is a plus. :)

dodge freak said:
Is it electric choke / those are jetted leaner. I agree the Carter / Edelbrock carbs are better for idling...the Holley can be made to idle very well but the Edelbrock carb will always be a bit better.

The secondaries may need to be jetted richer..maybe my eyes are shot but I can not see those tiny numbers on the jets. I use wire drills and a mic to find the size I want. Small changes make a big difference and both the primaries and secondaries need to be right for best power.

Try going up .003 on the secondary jets..might need to go .006...each jet is .003 larger.
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This carb does have the electric choke, so it is set up a bit leaner. I'll try bringing the primary jets up a size and a size or two on the secondary side.

fishy68 said:
If it doesn't ping with the Holley but does with the Eddy it's most likely just running lean. That's providing the Holley wasn't running so pig rich it drowned out spark knock. Generally when you jet a carb up you should do all corners, not just the front's. Otherwise you have an imbalance. Try jetting up the secondaries too and see what happens. I have noticed every Eddy I messed with was jetted pretty lean out of the box.

BTW: What's your timing set at? I have a 360 very similar to yours (9.8 to 1, mild ported X heads, Lunati 60404 cam which is one size bigger than yours) and mine won't tolerate any more than 34 degrees total timing on 93 octane.
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I'll have to recheck, but I'm pretty sure it's set at 34 degrees. I DO have a heavy spring on the advance mechanism, so it could be possible that it's advancing more than I think it is higher in the rev range.

64physhy said:
Like dodge freak said, the electric choke eddy's are 2 sizes leaner than the manual choke ones. For what you have though, a 600 might not be enough.
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Yeah, it is the electric choke version. Now that I think of it, I think I remember seeing a chart for carb vs. cam size, and the Eddys did seem to recommend larger carbs than Holley does with their double pumpers. IE: Edelbrock would say to use their 750AFB for this cam vs. Holley saying to use a 650 DP. Maybe I should try to jet this carb a few sizes up with the expectation of going to a 750?
 
Well, I'm more interested in good street manners along with good performance. As where the Holley turns this combo into a beast, most Holleys I've used aren't quite as good as the Eddys are in everyday street manners. I'm not opposed to using the Holley, but if I could stick with an Edelbrock, I would rather.
 
For your combo, I'd just go straight to the 750. An Eddy 1407 or Holley 3310 should fit the bill nicely.
 
Jay_340 said:
Well, I'm more interested in good street manners along with good performance. As where the Holley turns this combo into a beast, most Holleys I've used aren't quite as good as the Eddys are in everyday street manners. I'm not opposed to using the Holley, but if I could stick with an Edelbrock, I would rather.
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I would drop a 750 on that combo, i also agree with wild&crazy, spend the money, get an adj. holley 750dp. with all the good stuff, you'll be much happier with a tuned holley then an eddy, all my holleys had VG street manners, sure the eddy might idle better, but for all around perf., you can't beet the holley, make sure the dist. is curved right for the combo 1st., then get a holley with screw-in Air & fuel bleeds, if you look on the boards, they come up 4-sale, some are really nice & hardly used for alot less then a new one.
 
I ran one Carter 500 on my hot 318 with 360 heads and it was just fine...down on power but ran fine all the way to 6500 like my DP Demon.

I now have two Carter 500's and feel power is right up there were the Demon was (after much tuning) I know for sure it idles better cold cause it used to stall the first few mins if it idle at 900 for too long without blimping the throttle now and then...now it idle just fine cold..both my Demon and Carters have no choke.

I would jet up the Edel two sizes in back...or just jet it to the manual 600 choke specs and go from there. Funny with two carbs the primary was very close..need a bit richer one step on both low and high power but have to go from .094 secondary jets to .077...I tried many combs but that is works best when its 80 degress outside or 55 degress.

BTW I sold my 750 Holley and my 650 Demon and all my metering blocks, jet kit and gaskets cause I see myself never going back to one Holley / Demon carb..why when two Carters make as much power but idle better and get 1 mpg more..and that is not taking it easy...might be 2 or 3 mpg better going a steady 60 mph. And I was a Holley lover for 25 years.
 
dodge freak said:
I ran one Carter 500 on my hot 318 with 360 heads and it was just fine...down on power but ran fine all the way to 6500 like my DP Demon.

I now have two Carter 500's and feel power is right up there were the Demon was (after much tuning) I know for sure it idles better cold cause it used to stall the first few mins if it idle at 900 for too long without blimping the throttle now and then...now it idle just fine cold..both my Demon and Carters have no choke.

I would jet up the Edel two sizes in back...or just jet it to the manual 600 choke specs and go from there. Funny with two carbs the primary was very close..need a bit richer one step on both low and high power but have to go from .094 secondary jets to .077...I tried many combs but that is works best when its 80 degress outside or 55 degress.

BTW I sold my 750 Holley and my 650 Demon and all my metering blocks, jet kit and gaskets cause I see myself never going back to one Holley / Demon carb..why when two Carters make as much power but idle better and get 1 mpg more..and that is not taking it easy...might be 2 or 3 mpg better going a steady 60 mph. And I was a Holley lover for 25 years.
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To each his own 8)
 
What the initial timing set at on this combo. I see tons of "carb" issues that are rooted in poor ignition timing settings. Total timing is the wrong method to use on a street car with mechanical advance in the distributor

Timing almost always affects carb, carb rarely affects timing.

I'm going to guess that combo needs at least 16-18* initial, maybe more.

750dp on a 360/xe268h/2500 verter/2.76 gears, idles fine and getting 20 mpg on the highway with great street manners. That was out of the box, no jet, pv changes. Set the floats, idle and mixture screws and pound on it.
 
Yeah but how does the 750dp take off from a dead stop with those 2.73 gears.

Do you think these new 5.7 Hemi cars are "fast".

I have 3.91 gears and now wish I went with 4.10 gears..not much change but seem the more gear the better. I went from a 29 inch tire to a 26 this year (I did change the speedo gear) and it woke it up even more.

Yeah the motor spins fast on the highway, 20 mpg is a dream, ha ha but with my **** light set at 6500 and being its good for a bit more rpms (but risking a rod breaking) I find it has more than enough top speed 95% of the time.
 
dodge freak said:
Yeah but how does the 750dp take off from a dead stop with those 2.73 gears.

Do you think these new 5.7 Hemi cars are "fast".

I have 3.91 gears and now wish I went with 4.10 gears..not much change but seem the more gear the better. I went from a 29 inch tire to a 26 this year (I did change the speedo gear) and it woke it up even more.

Yeah the motor spins fast on the highway, 20 mpg is a dream, ha ha but with my **** light set at 6500 and being its good for a bit more rpms (but risking a rod breaking) I find it has more than enough top speed 95% of the time.
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:sleepy5:

This is what he needs 8)

This is just 1 of the many holleys i've built, tested it out on my stock 440, in the dead of winter, fired up after sitting 2 weeks & purred like a kitten. Fully adj., 4 corner idle, screw-in ABs, PVRChannels, IFRs, leveled & polished boosters, high flow throttle shafts & blades, had about 300.00 in this one.

100_0450.jpg
 
dodge freak said:
Yeah but how does the 750dp take off from a dead stop with those 2.73 gears.

Do you think these new 5.7 Hemi cars are "fast".

I have 3.91 gears and now wish I went with 4.10 gears..not much change but seem the more gear the better. I went from a 29 inch tire to a 26 this year (I did change the speedo gear) and it woke it up even more.

Yeah the motor spins fast on the highway, 20 mpg is a dream, ha ha but with my **** light set at 6500 and being its good for a bit more rpms (but risking a rod breaking) I find it has more than enough top speed 95% of the time.
Click to expand...

It roasts the tires from a dead stop with the 3.23 sure grip in the car now.

So, I'd say it runs pretty darn good.

I've had cars that run deep in the 9's, so I don't think many, if any, production cars are "fast".

I'd run a 950hp on the OP's set up if it was in one of my cars, but, that's just me.
 
dodge freak said:
Yeah but how does the 750dp take off from a dead stop with those 2.73 gears.

Do you think these new 5.7 Hemi cars are "fast".

I have 3.91 gears and now wish I went with 4.10 gears..not much change but seem the more gear the better. I went from a 29 inch tire to a 26 this year (I did change the speedo gear) and it woke it up even more.

Yeah the motor spins fast on the highway, 20 mpg is a dream, ha ha but with my **** light set at 6500 and being its good for a bit more rpms (but risking a rod breaking) I find it has more than enough top speed 95% of the time.
Click to expand...

What does a new hemi car have to do with this thread, there FI, makes no sence, it just sounds like your trying to convince holley guys to convert to Carters because you couldn't tune them, because in reality, that would be the only reason, i'll be the 1st. to admit i litteraly HATED holleys, couldn't stand them, but i didn't know how to work on them neither, & i'll also add, eddys or carters always run good "paired" up, thats a given, because there too scared to run alone like a holley :-D.
 
No one Holley / Demon DP carb will make more power than any Edel / Carter carb.

I will just say the Carter / Edel carbs do seem to run better at the 1500 rpms and under range.

3.23 gears are far better than 2.73 gears....

F.I. isn't "better" than carbs..was a long debate on speedtalk about which is "better" not all agree but many pro racers were saying a big carb will make more power than F.I.

F.I. are a pain cause you are limited on the injector sizing, too big low speed and idle is poor but then too small and you are giving up top end power, now remember pro racers turn their motors to 9,000 rpms. (there was a few other reasons why carbs were better, something about the ram effect and how a carb can keep adding more fuel as more air goes through it, while F.I. can not keep up with the A/F ratio changes)

Like I said, it was a long debate..like 20 pages.
 
dodge freak said:
No one Holley / Demon DP carb will make more power than any Edel / Carter carb.

I will just say the Carter / Edel carbs do seem to run better at the 1500 rpms and under range.

3.23 gears are far better than 2.73 gears....

F.I. isn't "better" than carbs..was a long debate on speedtalk about which is "better" not all agree but many pro racers were saying a big carb will make more power than F.I.

F.I. are a pain cause you are limited on the injector sizing, too big low speed and idle is poor but then too small and you are giving up top end power, now remember pro racers turn their motors to 9,000 rpms. (there was a few other reasons why carbs were better, something about the ram effect and how a carb can keep adding more fuel as more air goes through it, while F.I. can not keep up with the A/F ratio changes)

Like I said, it was a long debate..like 20 pages.
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I don't race at 1500rpms and lower so that means beans to me, if fact It's a 4spd so.....

Your statement of eddy/carters making more/same power as a holley is unfounded, besides I never knew you could get a 1050 race carter/eddy.......

In the winners circle you'll find holley's or holley design based carburetors.

The only reason any carter is used in competition [thermoquad] is soley based on CFM otherwise if the rules said you could use a holley of the same cfm, they would.

There are street carbs and then there are true performance/race carbs and carter/edlebrock don't make those, they make street/stock carbs that are ultimately limited on tune-ability.
 
So going back to the OP's question.... You wil want to get eh strip kit if you dont have it, and more than likely the ping is a combination of the wrong step up spring and both primary jet and rod and secondary jetting. Also, the AFB uses the counterweighted air door and these can be slightly reduced in mass to get the secondaries to open faster, provided the fuell mix is correct. For what you have, I agree the Holley is not the best carb, and I'd wager it feels faster with it, but on the track isnt any faster. I also am a firm believer in timing first, and timing means the three prts: initial; centrifical; and total. You want at least 15° initial, and no more than 36° total. I'll add that if I had built it, it would have a 750 Thunder AVS on it.
 
I said my two 500 cfm Carters seem to make the same power as my one 650 DP Demon carb but give the motor a better idle and 1mpg more.

Now two Demons / Holleys might for sure make more power than two Carters on a tunnel ram set up.

I drive in parking lots and spend too much time waiting for the traffic lights to turn green..sometimes traffic is moving so slow I have to wait at a light for over 5 mins to get pass the intersection only to have to re stop again a min later. My car seems more enjoyable to drive now with the two Carter carbs yet it move as fast..maybe faster towards the top end now.

Too bad Edelbrock doesn't resell that D66 dual quad intake for SBM today. It is available for BBM.
 
dodge freak said:
I said my two 500 cfm Carters seem to make the same power as my one 650 DP Demon carb but give the motor a better idle and 1mpg more.

Now two Demons / Holleys might for sure make more power than two Carters on a tunnel ram set up.

I drive in parking lots and spend too much time waiting for the traffic lights to turn green..sometimes traffic is moving so slow I have to wait at a light for over 5 mins to get pass the intersection only to have to re stop again a min later. My car seems more enjoyable to drive now with the two Carter carbs yet it move as fast..maybe faster towards the top end now.

Too bad Edelbrock doesn't resell that D66 dual quad intake for SBM today. It is available for BBM.
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The demons are calibrated differently[lean] depending on model #,
If you had a mighty or race demon, it would have been different.

And from your last post I know it wasn't one of those.....
 
moper said:
So going back to the OP's question.... You wil want to get eh strip kit if you dont have it, and more than likely the ping is a combination of the wrong step up spring and both primary jet and rod and secondary jetting. Also, the AFB uses the counterweighted air door and these can be slightly reduced in mass to get the secondaries to open faster, provided the fuell mix is correct. For what you have, I agree the Holley is not the best carb, and I'd wager it feels faster with it, but on the track isnt any faster. I also am a firm believer in timing first, and timing means the three prts: initial; centrifical; and total. You want at least 15° initial, and no more than 36° total. I'll add that if I had built it, it would have a 750 Thunder AVS on it.
Click to expand...

Thats cool, but you can't argue that with the whole race community and come a winner.lol
 
Those Thunder AVS carbs are nice, I did grind some weight off both secondary weights.

Thunder AVS was too much for my budget, not when I got two brand new Carter 500 (with no choke or vacuum ports) plus two Carter strip kits for lets see, about $440.... twoThunder AVS 500's with no strip kits would have been over $700..plus they had chokes and vacuum ports.

How did I find two sellers on Ebay selling a chokeless 9502 Carter both brand new a few weeks apart / god must have been on my side, ha ha ha. I have yet to seen another one.
 
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