car slower after carb change ( update )

[69chargerR/T]

Hi guys, I made some of the carb adjustments that Ron and jg68 said,now the car runs great I did make one dumb mistake Ron, I adjusted the secondary throttle plates so they are almost strait up and down at full throttle, they are pretty close. I had to bend the secondary link a lot to get the secondary throttle plates where they are now, I was afraid to bend the link any more because I thought the secondary would come in too soon and cause a bog when the secondary came in. I took the car out to try it,car definitely  seems quicker and it seems to pull harder right to the top off the power band And no bog when the secondary comes in, and now you can feel the secondary kick in, so I may try bending the link some more and get the secondary plates all the way strait up and down, they are real close now so I may just leave it alone. Now this is the mistake I made, awhile back I was having a problem with my 4 corner idle screws, jg68 told me to make sure the primary and secondary throttle plates where even, they where not. So I adjusted them like jg68 said to, now my idle screws work good. BUT!! I forgot to  readjust the accelerator pump adjustment  That why I was getting the off idle back fire and wasn't getting a good off idle acc. pump shot!!!!! Now the car runs awesome From a dead stop I stuffed the gas pedal to the floor no back fire or hesitation, the car just smoked the tires in first and second gear and pulled good all the way to the top of the power band Now I know why my 770 avenger also back fired because the cam I have I had to turn the idle screw in so far that the acc. pump was out off position to give a good pump shot off idle, thats why I was getting the back fire. Ron and jg68, thanks a lot for all you help and tuning ideas I don't think I would have figured this out with out your help guys Now I have to install the NGK xr-5 plugs I just got and do a new plug check to see how the jetting is, I still have the stock jets in it 71s front 80s rear and see how it is Again thanks a lot the car runs awesome the throttle response is great now, who ever said you can't run 750dp on street car was wrong and you guys are awesome for helping me out



                                                                 Thanks,Alan


 



   

[jg68]

Glad to hear you got it running better, now just jet for best MPH, sometimes this is best done at the track, yeah, those acc. pump arms need to be right, sounds like you most defenitly had a lean stumble causing the pop back, now is this with the orange cam or the pink one?

Joe

[69chargerR/T]

Glad to hear you got it running better, now just jet for best MPH, sometimes this is best done at the track, yeah, those acc. pump arms need to be right, sounds like you most defenitly had a lean stumble causing the pop back, now is this with the orange cam or the pink one?

Joe

jg68, I still have the pink pump cam in it, after readjusting the acc. pump the back fire is gone, and no hesitation at all so I didn't change the pump cam. Also, I still have the #35 pump nozzle in it I'm going to change it to a #31 and try it and see if the back fire is still gone, if it is and no hesitation I may even drop it down more to a #28 and see how it is I'm going to do that today, and then change the plugs and see how the jetting  is Joe, again I thank you a lot for your help I don't  think I would have gotten this figured out with out your help I saw the pics. of the carb you built, that think looks awesome what is the cfm on that carb I would love to have a carb that looked like that, that thing is cool. Next year I'm thinking of rebuilding my motor and maybe stroking it, and have you build me a carb like that  Again, thanks a lot for your help!!!!!!!!!!!!


                                                                Thanks, Alan

[jg68]

Glad to hear you got it running better, now just jet for best MPH, sometimes this is best done at the track, yeah, those acc. pump arms need to be right, sounds like you most defenitly had a lean stumble causing the pop back, now is this with the orange cam or the pink one?

Joe

jg68, I still have the pink pump cam in it, after readjusting the acc. pump the back fire is gone, and no hesitation at all so I didn't change the pump cam. Also, I still have the #35 pump nozzle in it I'm going to change it to a #31 and try it and see if the back fire is still gone, if it is and no hesitation I may even drop it down more to a #28 and see how it is I'm going to do that today, and then change the plugs and see how the jetting  is Joe, again I thank you a lot for your help I don't  think I would have gotten this figured out with out your help I saw the pics. of the carb you built, that think looks awesome what is the cfm on that carb I would love to have a carb that looked like that, that thing is cool. Next year I'm thinking of rebuilding my motor and maybe stroking it, and have you build me a carb like that  Again, thanks a lot for your help!!!!!!!!!!!!


                                                                Thanks, Alan

Thanks Alan, that carb inthe pic is an 800 4780, i also just put the 850 4781 main body on e-bay for a BUY IT NOW for 100.00, that 850 main body should flow 910+ CFM with the Quikfuel stuff & Billet base, perfect for a 500+ stroker, its all done & ready to go, you can get all the QF stuff for around 300.00 & thats with the Aluminum bowls, all you'll need is the floats, float hangers & needle valves & jam nuts & lock screws, squirters, now you could just use the bowls off of your carb, then all you will need is the 1.3/4 Billet base & Billet M.Blocks.

Yeah, go ahead & try a smaller squirter, i would leave the cams be, i would say 31s F&R should work great with the pink cams in #1 hole, heres a few pics of the 850 MB.

[69chargerR/T]

Joe, tried a #31 squirter with pink pump cam, back fire is back but not as bad changed the pump cam to the orange one made back fire worse. So I put the pink cam back in and the #35 squirter, no back fire I guess my motor likes fuel!!!! I'm going leave like it is now car runs great, I might get a #31 and #35 tube type squirter's and try those and see what happens Thanks again for all your help


                                                            Thanks, Alan
                                                                                       

[firefighter3931]

Alan, glad to hear the 750dp is working better for you. I knew it would scream once all the bugs were worked out. 

FWIW, the pink cam will deliver more fuel and it seems to be working better so stick with it.    From your description the engine is wanting a big pump shot (#35 squirter) which isn't necessarily bad....it is what it is. Just tune it for best performance and don't worry about what should be in there...just use what works. 

So where's the proof...we need pics ! 



Ron

[69chargerR/T]

Alan, glad to hear the 750dp is working better for you. I knew it would scream once all the bugs were worked out. 

FWIW, the pink cam will deliver more fuel and it seems to be working better so stick with it.    From your description the engine is wanting a big pump shot (#35 squirter) which isn't necessarily bad....it is what it is. Just tune it for best performance and don't worry about what should be in there...just use what works. 

So where's the proof...we need pics ! 



Ron

Ron, just got done putting a set of NGK xr-5s in, going to drive car to work tomorrow its a 20 minute ride to and from work so I can do a plug check and see how the jetting is I'll try to get some pics. of my car and post them, I'm going to have to get one of my kids to take some pics. and try to post them. I have no clue how to do it, I have a hard enough time typing and making posts it takes me forever, my kids make fun of me when the see me typing my posts  me and computers don't get along I'll try to get some pics. up tomorrow Thanks again for all your help!!!!!!!!!!


                                                          Alan

                                                         

[firefighter3931]

I'll try to get some pics. up tomorrow Thanks again for all your help!!!!!!!!!!


                                                          Alan

 

You're welcome Alan....looking forward to the pics ! Don't forget the tire smoke ! 



Ron

[69chargerR/T]

I'll try to get some pics. up tomorrow Thanks again for all your help!!!!!!!!!!


                                                          Alan

You're welcome Alan....looking forward to the pics ! Don't forget the tire smoke ! 



Ron

here are some pics...

[firefighter3931]

Alan, that car is sweeeeet !!!    Red and Black are my favorite colors !  The old school M/T valvecovers are cool...i have a set but the won't clear my roller rockers and .580 lift cam ! 

Nice job on the car and motor !   



Ron

[jg68]

Sweeeeet Alan

[69chargerR/T]

Alan, that car is sweeeeet !!!    Red and Black are my favorite colors !  The old school M/T valvecovers are cool...i have a set but the won't clear my roller rockers and .580 lift cam ! 

Nice job on the car and motor !   



Ron

Thanks guys, heres a couple more. Ron, I'll try to get some pics. with tire smoke this weekend lkie you asked

                                                                         
                                                                                       Alan

[69chargerR/T]

Joe, or Ron, I pulled a couple plugs today to see how the jetting is the outer ring turned a little light tan and the strap is kinda white. I went back to my first car slower thread and looked at Joe's plugs, and my plugs  color is not close to those. Joe, how long or far did you drive before you checked your plugs, I drove my car to and from work its 24 miles round trip, drove car easy didn't get on it the outer ring has changed slightly tan, like its just starting to change color. I think it my be a little lean, or I have to drive car more. Should I try to get my plugs to look like Joe's   



                                                                             Thanks Alan

[firefighter3931]

Alan; i would try jetting up 1 size on the primaries....sounds like you're close with some tan color on the threads.   


Ron

[jg68]

Yeah Alan, jet it up to a 72, thats another .003" then a 71, on mine, the 71 was just a tad too lean

[69chargerR/T]

Yeah Alan, jet it up to a 72, thats another .003" then a 71, on mine, the 71 was just a tad too lean

Thanks, guys I'll try  jetting up to a #72 on the primary's Joe, what are you running for secondary jets, it sounds like your engine build is  almost the same as mine.


                                          Thanks, Alan   

[jg68]

Yeah Alan, jet it up to a 72, thats another .003" then a 71, on mine, the 71 was just a tad too lean

Thanks, guys I'll try  jetting up to a #72 on the primary's Joe, what are you running for secondary jets, it sounds like your engine build is  almost the same as mine.


                                          Thanks, Alan   

Alan, i have mine jetted 72/84 PV up front, it seems to run pretty good at WOT, are you running a jet plate or metering block in back?

[69chargerR/T]

Yeah Alan, jet it up to a 72, thats another .003" then a 71, on mine, the 71 was just a tad too lean

Thanks, guys I'll try  jetting up to a #72 on the primary's Joe, what are you running for secondary jets, it sounds like your engine build is  almost the same as mine.


                                          Thanks, Alan   

Alan, i have mine jetted 72/84 PV up front, it seems to run pretty good at WOT, are you running a jet plate or metering block in back?

Joe, I have a metering block in back with #80 jets in back. I have the 750dp set up stock 4 corner idle 71s front 80s rear 6.5 PV in front, car has 12.5/13.0 inches vacuum in gear at 700 RPM 14.5/15.0 in park at 850 RPM, Ron, suggested  that I might want to go up to a 8.5 PV what do you think. The car runs great, idles great, I just think it may be a tad lean, the throttle response is great!!!


                                                                             Thanks, Alan


                                                               

[jg68]

Yeah Alan, jet it up to a 72, thats another .003" then a 71, on mine, the 71 was just a tad too lean

Thanks, guys I'll try  jetting up to a #72 on the primary's Joe, what are you running for secondary jets, it sounds like your engine build is  almost the same as mine.


                                          Thanks, Alan   

Alan, i have mine jetted 72/84 PV up front, it seems to run pretty good at WOT, are you running a jet plate or metering block in back?

Joe, I have a metering block in back with #80 jets in back. I have the 750dp set up stock 4 corner idle 71s front 80s rear 6.5 PV in front, car has 12.5/13.0 inches vacuum in gear at 700 RPM 14.5/15.0 in park at 850 RPM, Ron, suggested  that I might want to go up to a 8.5 PV what do you think. The car runs great, idles great, I just think it may be a tad lean, the throttle response is great!!!


                                                                             Thanks, Alan


                                                               

Alan, an 8.5 PV wouldn't hurt anything with that much vacuum, But just remember, the PV & there Channels are an inrichment circuit, they control the transfer over from the idle circuit to main metering, what you want is a smooth transition without it feeling lazy, i would jet it up F&R 72/82 for your combo, don't worry about it being a 10 point spead, it'll be fine, i'm running an 84 jet in my 750 as a baseline, only because this carb came factory with a 76 rear jet & a PV, so 8 points being the norm puts it at 84 blocked off, so if you feel its lean, DON'T hesitate to put in more jet, it won't hurt, you might just be surprized at the resalts

[69chargerR/T]

Yeah Alan, jet it up to a 72, thats another .003" then a 71, on mine, the 71 was just a tad too lean

Thanks, guys I'll try  jetting up to a #72 on the primary's Joe, what are you running for secondary jets, it sounds like your engine build is  almost the same as mine.


                                          Thanks, Alan   

Alan, i have mine jetted 72/84 PV up front, it seems to run pretty good at WOT, are you running a jet plate or metering block in back?

Joe, I have a metering block in back with #80 jets in back. I have the 750dp set up stock 4 corner idle 71s front 80s rear 6.5 PV in front, car has 12.5/13.0 inches vacuum in gear at 700 RPM 14.5/15.0 in park at 850 RPM, Ron, suggested  that I might want to go up to a 8.5 PV what do you think. The car runs great, idles great, I just think it may be a tad lean, the throttle response is great!!!


                                                                             Thanks, Alan


                                                               

Alan, an 8.5 PV wouldn't hurt anything with that much vacuum, But just remember, the PV & there Channels are an inrichment circuit, they control the transfer over from the idle circuit to main metering, what you want is a smooth transition without it feeling lazy, i would jet it up F&R 72/82 for your combo, don't worry about it being a 10 point spead, it'll be fine, i'm running an 84 jet in my 750 as a baseline, only because this carb came factory with a 76 rear jet & a PV, so 8 points being the norm puts it at 84 blocked off, so if you feel its lean, DON'T hesitate to put in more jet, it won't hurt, you might just be surprized at the resalts

      Thanks Joe, I'll just jet up  and try it, thanks again Alan
     

 

[firefighter3931]

Alan, an 8.5 PV wouldn't hurt anything with that much vacuum, But just remember, the PV & there Channels are an inrichment circuit, they control the transfer over from the idle circuit to main metering, what you want is a smooth transition without it feeling lazy

Exactly ! The way i like to tune the PV enrichment is to keep it close to the idle/cruise vacuum readings. That way, when you drop the hammer the enrichment circuit activates soon as the vacuum drops and bog is eliminated. If you have 15in of vacuum and a 6.5 PV you won't have any enrichment fuel until the engine vac reaches 6.5.....which can create a "hole" in the transition. That hole will often lead to a stumble or off idle bog.

That's the beauty of a holley carb....there are so many ways to tune it. 



Ron

[69chargerR/T]

Exactly ! The way i like to tune the PV enrichment is to keep it close to the idle/cruise vacuum readings. That way, when you drop the hammer the enrichment circuit activates soon as the vacuum drops and bog is eliminated. If you have 15in of vacuum and a 6.5 PV you won't have any enrichment fuel until the engine vac reaches 6.5.....which can create a "hole" in the transition. That hole will often lead to a stumble or off idle bog.

That's the beauty of a holley carb....there are so many ways to tune it. 



Ron

Ron, I'm going to change the primary jets to 72s, sounds like you and Joe think it wouldn't be a bad idea to change the PV to an 8.5 with my vac readings is this right ? If so I will get an 8.5 PV and change it when I'm doing the jets, that way I don't have to pull the fuel bowl twice.


                                                                                     Thanks, Alan
                                               

[jg68]

Alan, i would jet up the back to 82s while your at it, just take off the whole carb there for its easier for ya

[69chargerR/T]

Alan, an 8.5 PV wouldn't hurt anything with that much vacuum, But just remember, the PV & there Channels are an inrichment circuit, they control the transfer over from the idle circuit to main metering, what you want is a smooth transition without it feeling lazy

Exactly ! The way i like to tune the PV enrichment is to keep it close to the idle/cruise vacuum readings. That way, when you drop the hammer the enrichment circuit activates soon as the vacuum drops and bog is eliminated. If you have 15in of vacuum and a 6.5 PV you won't have any enrichment fuel until the engine vac reaches 6.5.....which can create a "hole" in the transition. That hole will often lead to a stumble or off idle bog.

That's the beauty of a holley carb....there are so many ways to tune it. 



Ron

Ron & Joe, I just want to make sure I understand what you guys are saying, I'm going to pull the the carb and jet up should I bump the PV up from the 6.5 to the 8.5 or should I leave it alone ? The car runs  good but, if you guys think it will help or perform better with an 8.5 PV then I will try it I'm wondering maybe if I up the PV I might be able to drop the acc. pump squirter to a 31 ? Just want to know what you guys think, I need to get some jets, and if I need the PV I want to get all the stuff from summit at the same time and pull carb and make all the changes at the same time


                                                  Thanks, Alan

[jg68]

Alan, i'm sure if you bump up the PV to a 8.5 & change to a 72 jet you'll be able to put back the 31 squirter, normally (if not most of the time) if you are needing a larger squirter, you'll just get an abrupt stumble right off idle, but it'll recover quickly once you get into the main circuit, Now this is only if everything else is were it should be, its very rear that you'll get a "pop back" threw the carb by just a squirter if its just off a little, i still think your going lean alittle too much under throttle & the larger squirter is compensating for it, so start off with the front first, 8.5 PV & 72 jets, then see how it runs, then try the 31 squirter, but make SURE you have the pump adj. right & float levels too

[firefighter3931]

Alan, i'm sure if you bump up the PV to a 8.5 & change to a 72 jet you'll be able to put back the 31 squirter, normally (if not most of the time) if you are needing a larger squirter, you'll just get an abrupt stumble right off idle, but it'll recover quickly once you get into the main circuit, Now this is only if everything else is were it should be, its very rear that you'll get a "pop back" threw the carb by just a squirter if its just off a little, i still think your going lean alittle too much under throttle & the larger squirter is compensating for it, so start off with the front first, 8.5 PV & 72 jets, then see how it runs, then try the 31 squirter, but make SURE you have the pump adj. right & float levels too

That's a good recommendation.  Like Joe says the large squirter could be covering up a lean condition at the transition. The 8.5 pv and 72 primary jets are a good starting point and you can fine tune from there. 


Ron

[69chargerR/T]

Alan, i'm sure if you bump up the PV to a 8.5 & change to a 72 jet you'll be able to put back the 31 squirter, normally (if not most of the time) if you are needing a larger squirter, you'll just get an abrupt stumble right off idle, but it'll recover quickly once you get into the main circuit, Now this is only if everything else is were it should be, its very rear that you'll get a "pop back" threw the carb by just a squirter if its just off a little, i still think your going lean alittle too much under throttle & the larger squirter is compensating for it, so start off with the front first, 8.5 PV & 72 jets, then see how it runs, then try the 31 squirter, but make SURE you have the pump adj. right & float levels too

That's a good recommendation.  Like Joe says the large squirter could be covering up a lean condition at the transition. The 8.5 pv and 72 primary jets are a good starting point and you can fine tune from there. 


Ron

Thanks guys, you guys have been right ever time I've made an adjustment!!! I'll change the PV to 8.5 and up the jets to 72s and try that, who knows the car may even get quicker than it is now!!!!!!!!!!!!  I'll let you know how it goes