Super stock crossram jetting for dual AFB chokeless 750s

prostockstan · Oct 20, 2017

I have seen so many different jetting schemes out there. From what I have seen the one carb has straight jetting the other carb has staggered jetting but the articles say left or right carb. I need to know drivers side or passenger side and how much stagger in jetting on the secondaries. It runs great now but I'm in search of perfection. Which carb has the staggered jetting and which jet is smaller and where is the smaller jet in relationship to the passenger or driver header location.
Thanks: Stan

not so famous bob · Oct 20, 2017

prostockstan said:
I have seen so many different jetting schemes out there. From what I have seen the one carb has straight jetting the other carb has staggered jetting but the articles say left or right carb. I need to know drivers side or passenger side and how much stagger in jetting on the secondaries. It runs great now but I'm in search of perfection. Which carb has the staggered jetting and which jet is smaller and where is the smaller jet in relationship to the passenger or driver header location.
Thanks: Stan

I will be no help on ur combination, but the old ratroasters needed staggard jetting on both carbs. Very few of the jets were the same size.

dvw · Oct 20, 2017

I ran the old Direct Connection carb tips jetting. You have to solder up at least one secondary jet as they don't make one that small anymore. Granted this was for 3705 Carters but it ran fine.
Doug

stage3 · Oct 20, 2017

go to Chrysler power magazines web site,,they did an article by dvorak racing on setting up orginal and edelbrock afb carbs,,very informative...its what I based my set up on..

http://chryslerpower.com/webstore/Magazines/Best-of-CP/Carburetion-Dvorak-D

Diodedog · Oct 21, 2017

The stock 3705s used 104s in the primary with 16-76 metering rods which were .053" on WOT, the secondary throttle side was .089" and the choke (outer) side .063", this jetting is a great place to start.

prostockstan · Oct 26, 2017

stage3 said:
go to Chrysler power magazines web site,,they did an article by dvorak racing on setting up orginal and edelbrock afb carbs,,very informative...its what I based my set up on..

http://chryslerpower.com/webstore/Magazines/Best-of-CP/Carburetion-Dvorak-D

Well this past Sunday we tuned the 512 with some friendly advice from the legend Dan Dvorak. We ended up with 107s in the primaries. .095 on the secondaries on the throttle side of each carb and .089s on the secondaries of the of the choke side of each carb. The rods are the .065 x .052 He told us to originally go with this jetting scheme with the stock .071 x .047 rods but it had a lean pop at around 4000-4500 RPM so all we did was switch to the .065 x .052 rods which richened up the bottom end RPM with the smaller .065 diameter of the big end of the rod. The top end RPM was leaned out a little more with the .052 diameter of the small end of the rod versus the .071 x.047 rod. We could have gone with .110 mains and the .071 x.047 rods but the difference would have been about the same. The rod swap also saved us a lot of time not having to pull the tops off of the carbs again. Dan Dvorak spent a good time with us on the phone and we purchased one of his dual quad syncronizers for future use. I wish more people were like Dan Dvorak, he is a blessing to the Mopar world. The 512 now screams and I couldn't be happier!

Stan

Ski 61701 · Oct 26, 2017

I have his carb hat. Looking back at things I couldve made it myself and saved some $$$.it does save you a bunch of grief getting them balanced. I did get to meet him, snd yes he is a wealth of knowledge. He has forgotten more than I will ever know. So spending extra cash with him was worth it to me, just to learn.

I did run into a small prob with his sync tool. The top of the cylinder the top can be removed. The fit was horrible and it did not work. I put a little silicone on the top of the cylinder and put the top back on and it works as designed. Not Dans fault, its the Chinese quality control. You might want to look it over real close if you have an air leak anywhere the sync tool will not work.

Glad you are on the right track. What colour step up springs are you using?

prostockstan · Oct 26, 2017

Ski 61701 said:
I have his carb hat. Looking back at things I couldve made it myself and saved some $$$.it does save you a bunch of grief getting them balanced. I did get to meet him, snd yes he is a wealth of knowledge. He has forgotten more than I will ever know. So spending extra cash with him was worth it to me, just to learn.

I did run into a small prob with his sync tool. The top of the cylinder the top can be removed. The fit was horrible and it did not work. I put a little silicone on the top of the cylinder and put the top back on and it works as designed. Not Dans fault, its the Chinese quality control. You might want to look it over real close if you have an air leak anywhere the sync tool will not work.

Glad you are on the right track. What colour step up springs are you using?

I will give it a good looking over first. Thanks for the info. I was under the impression that they were made in the USA.

prostockstan · Oct 26, 2017

Ski 61701 said:
I have his carb hat. Looking back at things I couldve made it myself and saved some $$$.it does save you a bunch of grief getting them balanced. I did get to meet him, snd yes he is a wealth of knowledge. He has forgotten more than I will ever know. So spending extra cash with him was worth it to me, just to learn.

I did run into a small prob with his sync tool. The top of the cylinder the top can be removed. The fit was horrible and it did not work. I put a little silicone on the top of the cylinder and put the top back on and it works as designed. Not Dans fault, its the Chinese quality control. You might want to look it over real close if you have an air leak anywhere the sync tool will not work.

Glad you are on the right track. What colour step up springs are you using?

We are using the lightest springs the blue ones. We were using the yellow springs with the old jet scheme but after changing to the jet scheme above the rods were dancing a little at around 1000 idle RPM and the idle was rough and uneven. We then switched to the blue lightest spring and the idle is as smooth as a kitten. Our timing is 22deg initial 36deg total. I can't beleive how good this thing runs now.

Ski 61701 · Oct 26, 2017

Mine wasn't maybe things have changed since I got mine. My pop has an old school sync tool , its a nice heavier metal, the float ball is metal not plastic. Regardless once my air leaks were sealed, works as designed.

stage3 · Oct 26, 2017

prostockstan said:
Well this past Sunday we tuned the 512 with some friendly advice from the legend Dan Dvorak. We ended up with 107s in the primaries. .095 on the secondaries on the throttle side of each carb and .089s on the secondaries of the of the choke side of each carb. The rods are the .065 x .052 He told us to originally go with this jetting scheme with the stock .071 x .047 rods but it had a lean pop at around 4000-4500 RPM so all we did was switch to the .065 x .052 rods which richened up the bottom end RPM with the smaller .065 diameter of the big end of the rod. The top end RPM was leaned out a little more with the .052 diameter of the small end of the rod versus the .071 x.047 rod. We could have gone with .110 mains and the .071 x.047 rods but the difference would have been about the same. The rod swap also saved us a lot of time not having to pull the tops off of the carbs again. Dan Dvorak spent a good time with us on the phone and we purchased one of his dual quad syncronizers for future use. I wish more people were like Dan Dvorak, he is a blessing to the Mopar world. The 512 now screams and I couldn't be happier!

Stan

thanks for the info...dan is a nice guy who's easy to talk to on the phone..i bought his syncroniser also..hes right,,u cannot equalize the tune without it..I think im going to replicate your settings in my 3705's.and go from there....I would ask what springs u used on the meter rods but,because of cam's..im sure there all different..

prostockstan · Oct 26, 2017

Ski 61701 said:
Mine wasn't maybe things have changed since I got mine. My pop has an old school sync tool , its a nice heavier metal, the float ball is metal not plastic. Regardless once my air leaks were sealed, works as designed.

stage3 said:
thanks for the info...dan is a nice guy who's easy to talk to on the phone..i bought his syncroniser also..hes right,,u cannot equalize the tune without it..I think im going to replicate your settings in my 3705's.and go from there....I would ask what springs u used on the meter rods but,because of cam's..im sure there all different..

Dan also told us that if your close with a certain color spring, you can clip off 1/4 to 1/2 or a whole coil of the given spring your running to dial it in perfectly. Leave the rod covers off half way and tighten them so you can see the center of the piston dancing. At idle speed the rods should be completely down and not dancing upwards at all and as soon as you touch the throttle they should shoot up to the top. Great information was passed down to all of us here at B-Bodies from a guy like Dan who has been running and tuning these things for years. He really stressed that you have to seal up all possible leak areas especially the manifold stud with sealer so you have as much manifold vacuum as possible at idle. This will pull the rods down easier at idle making the car more driveable. We did all the tricks. also the rod springs atop the rod he discards altogether because it side loads the piston and totally changes the spring color you are running. When we removed the top rod retaining spring we went from yellow to a blue spring which is the lightest. He did not understand why we had to run the lightest spring. I guess no side loading of the rod piston allows a little more air to go around the piston. But we noticed a much crisper throttle response. We are going to check all items attached to the manifold that could possibly leak. I can only say if it is leaking it sure runs like a rabid animal.

Stan

stage3 · Oct 26, 2017

@prostockstan.
all good info right off the article from Chrysler power magazine..
I just rejetted my carbs to what u posted above,with metering rod reccomendations....I put in the orange lite weight springs from the assortment kit I had,,1 step up above the blues.per dvoraks instructions.much liter than the 1 that was in it...will run it tomorrow and check the dance of the metering rods..i think that it will depend a lot on cam ,, vacuum generated...what cam r u running...must be fairly stout to go all the way to the litest spring...mines a .650 roller. with 280-290 at .050...low vacuum..my synchronizer I bought from him,i had to drill a hole in it to be able to get the orange ball in the middle.could not idle it below 1500,,probably due to the springs and cam?..we will see...thanks for sharing...will post after the run tomorrow..

prostockstan · Oct 27, 2017

stage3 said:
@prostockstan.
all good info right off the article from Chrysler power magazine..
I just rejetted my carbs to what u posted above,with metering rod reccomendations....I put in the orange lite weight springs from the assortment kit I had,,1 step up above the blues.per dvoraks instructions.much liter than the 1 that was in it...will run it tomorrow and check the dance of the metering rods..i think that it will depend a lot on cam ,, vacuum generated...what cam r u running...must be fairly stout to go all the way to the litest spring...mines a .650 roller. with 280-290 at .050...low vacuum..my synchronizer I bought from him,i had to drill a hole in it to be able to get the orange ball in the middle.could not idle it below 1500,,probably due to the springs and cam?..we will see...thanks for sharing...will post after the run tomorrow..

I'm running a Howards 263 276 @ .050 advertised 295 304 lift .640 .630 Is your motor also a 512ci ?

coloradodave · Oct 27, 2017

Make your own carburetor synchronizer:
http://www.forbbodiesonly.com/moparforum/threads/diy-carburetor-synchronizer-cheap.75710/

stage3 · Oct 27, 2017

prostockstan said:
I'm running a Howards 263 276 @ .050 advertised 295 304 lift .640 .630 Is your motor also a 512ci ?

no,,its a 440 with stage 2 ported max heads with stage 3 c/ram and 3705's...ran it today!big diff from before..no more pinging!and runs cool but...using the orange springs..at idle,they r down no dancing,,whack the throttle and up they go but, they go right back down..is that what yours do?or do they stay up?plugs r now blackened..i thought it was a little lean..white before..need a lesson on metering rods..how to lean it down a little without changing jets..how many jett sizes does a rod equal...only problem I had today was by the end of the run..at least 2 spark plug boots backed off and started dropping cylinders...thought I was fouling plugs..but at freeway speeds,that probably isnt possible..

prostockstan · Oct 27, 2017

stage3 said:
no,,its a 440 with stage 2 ported max heads with stage 3 c/ram and 3705's...ran it today!big diff from before..no more pinging!and runs cool but...using the orange springs..at idle,they r down no dancing,,whack the throttle and up they go but, they go right back down..is that what yours do?or do they stay up?plugs r now blackened..i thought it was a little lean..white before..need a lesson on metering rods..how to lean it down a little without changing jets..how many jett sizes does a rod equal...only problem I had today was by the end of the run..at least 2 spark plug boots backed off and started dropping cylinders...thought I was fouling plugs..but at freeway speeds,that probably isnt possible..

They should stay up as long as its on acceleration, down when it goes back to idle.

prostockstan · Oct 27, 2017

Let me know how it runs. Our motor is much bigger but has a smaller cam. Your motor is smaller but has a bigger cam. You might try the .071 x .047 rods if it is too rich. if it is too rich with the .071 x .047 rods go down to 104 primary jets with that rod.

prostockstan · Oct 27, 2017

I like to get to the point where it pops lean and go up larger with the primary jet or smaller with the rod. The larger diameter of the rod is the low rpm diameter of .071 the small diameter of the rod is the high rpm end of the rod. The high and low numbers of the rods switch around so see what rpm is the issue and tune the rod according. Smaller diameter rods flow more fuel around the rod. The larger the rod end the leaner . Remember the rod goes down into the primary jet and fuel is flowing around the rod ends.

stage3 · Oct 27, 2017

prostockstan said:
They should stay up as long as its on acceleration, down when it goes back to idle.

o.k.but all we can do is see it in the shop so..when the throttle is cracked open,,should the piston stay at the top?mine does not..but its not dancing either..I have .065-.052 in there now...to lean it out some what....075-.065?

Super stock crossram jetting for dual AFB chokeless 750s

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