Carb tuning advice

[Dmichels]

I am winding down with all the little projects with the car. I now want to really get the carb dialed in. Carb is tunned to the pint where it runs well. It starts with no choke and will idle on its own in about 30 seconds. Drives and pulls hard.

Here is what I got
440 bore 30 over
stock heads
headers
MP old type 108 center line 509 lift 292 dur 4deg advanced
timing base 20   total 35
manual trans 4.11 rear
eddy ch4b center divider has a window
Holley 800 DP no power valve on the secondaries
50cc acc pumps pri and sec


Any input or starting jetting and pwer valve choice ?
any thoughts will be most apreciated?


As a side note why does everyone say this is not a good street cam? I drive the car hard and it loves it. I can also cruise around just fine.
Dave

[Cooter]

I am winding down with all the little projects with the car. I now want to really get the carb dialed in. Carb is tunned to the pint where it runs well. It starts with no choke and will idle on its own in about 30 seconds. Drives and pulls hard.



As a side note why does everyone say this is not a good street cam? I drive the car hard and it loves it. I can also cruise around just fine.
Dave

Poss. because what may seem Great to you, may not to someone else. Also, it is old tech. Rumor had it that they were ground using Chevy lobes/patterns. Go figure. Mopar engineered my azz.

[firefighter3931]

The 509 makes good power but it is a dirty old school grind. IN most cases it is a poor match but you have a stick and 4.10 gears so it works. Try running that cam with 3.23's and a 2500 stall automatic. 

As for jetting ; going with 72/80 on that 800dp would be a good starting point 


Ron

[Dmichels]

Thanks Ron
Any thoughts on power valve choice?
Dave

[elacruze]

I ran that combo with an out-of-the-box Holley 850DP, and never had to change a thing. I can't say what was in the carb. However, I changed out the CH4B for a single-plane M1 and it destroyed the jetting and drivability. I could never get the carb to work with that manifold. You could look in the old Mopar Engines book, I think they have jetting starts in the back for this combo.

[Dmichels]

Thanks for all the input. It is nice to have a known starting point when tunning things.
At idle I pull 6 to 7 lbs vaccum at 850 rpm
Depending on who you listen to I need a 3.5 to 5 power valve for the primaries.
any thoughts
Dave

[firefighter3931]

I'd run a 3.5 PV with only 6in of vacuum at idle 


Ron

[Dmichels]

I know thats what I should run but will it open soon enough so I do not get a bog? I got a vaccum gauge in the car right now and I really need to nail it to drop down to under 5. Not in any way normal driving, serious peddle to the floor stuff.  It cruises over 10 so I do not have an issue with it opening at cruise. I got a 5 in it right now and it feels ok. I will try your combo and see how it runs and take it from there. I have read up on holleys and tuned them in the past so I have an OK understanding on how they work. I take it it will be of little use to fine tune either cylinder bank because my manifold divider has been milled? Thanks for the input it has saved me alot of time.
Dave

[firefighter3931]

Hi Dave,

I wouldn't worry about staggering the jetting from side to side unless you are seeing one bank of plugs much different than the other.    Honestly, i haven't encountered that problem other than one time tuning a 6-pack which are known for uneven distribution.

You could try the 3.5 PV and see if it responds better to WOT bursts. It might or might not improve so the only way to know for sure is test and test again. I like to size the PV at 2in or so below idle vacuum....that way you know for sure it's not pulling in an extra fuel when it shouldn't be. 

Ron

[Dmichels]

Well
Got around to the carb today took out primary 74 and a 6.5 PV and on secondary 88 WOW I must have been running rich. Put in Ron's P72 S80. and a 3.5 PV I was most worried about the 8 size drop on the sec but did not notice a lean condition on my first "hot lap" I also did not see any drivablity issues with the new PV either. I need to take it out and drive it a bit and look for any problems
Thanks for the starting point Ron
Dave

[firefighter3931]

Cool stuff Dave....keep sneaking up on the tune and before you know it she'll be dialed in 


Ron