You need to get the carburetor sorted out. No way does the engine require 42degs at idle. no way no how.I need to use MVA in order to run a hight advance at idle
You need to get the carburetor sorted out. No way does the engine require 42degs at idle. no way no how.I need to use MVA in order to run a hight advance at idle
no way pingity pingity ping.ight. And why does an engine cranking 200 psi need all that idle timing.
It's a carburetor issue. 99%converter issue
I can agree with both of you. The converter is a drivability issue for sure. The carburetor I am sure could use more tuning. This is my first time working with a Holley. I only have worked with a few Rochesters in years past. So I am trying to figure out this as well. Lots to learn all at once…. Wish you guys could come over and just freaken show me. So I will keep trying to learn here and in books etc.It's a carburetor issue. 99%
NoDo we know the specs or at least approximate specs on the cam ?
Sounds right … Turk is giving me good guidance to visit the balancer checking the advance of the motor.You need to step back , take a deep breath and cover the basics again . Check the TDC mark on balancer , set dizzy manual to 17-20* , pull carb and check transfer slot opening ( .025ish …. ). . Probably needs work on idle air bleeds .
Sounds right … Turk is giving me good guidance to visit the balancer checking the advance of the motor.
Ive been reading about making sure the transfer slot is like 1/16 no more at idle. The way I understand this is that if there is too much transfer slot opening it will not allow enough flow to the pilot idle path down the emulsion tube/path. Is that what you’re thinking?
I was going to look at the carb after I got it to a point I can run it. Looks now maybe the initial advance is too high at 42°. I e just had it hammered in my head to give the motor what it wants and was using vacuum as part of the process. When is too much I don’t know. Some have said my motor could want as much as 50°???..??
Ok, that’s another rule of thumb as far as T slot exposure.
I start with a square slot and then open the throttle to get it to idle.
Once I finalize everything I verify the T slots are not open so far that the mixture screws don’t work.
There is no tuning magic in T slot exposure. They can’t be open so far the mixture screws don’t work but they don’t need to be damn near shut to work properly either.
Edit: if you end up with the throttle blades too far open and mixture screws don’t work, we do t just grab the vacuum hose and hook it to manifold vacuum.
I drill holes in the throttle blades so they shut further and correct T slot exposure.
Resorting to MVA to get one to idle is my last resort.
Because in the end, most time guys end up right where you are. It’s not a fun place for sure.
What would the mechanical curve on this set up look like?Thousands, if not millions of GM cars, came with MVA. Below is a page out of the 1967 Pontiac manual stating the use of MVA. These cars had 6* initial & 20* MVA added so that they idled with 26*. Small cam, 197 @ 050, 10.75:1 CR.
You say you're having some brake issues... what kind of issues? if you have power brakes, are you sure there's not a vacuum leak to the brake booster? Because that could sure make a HUGE difference here. I also agree that you need a looser converter, which will also make another big difference for your setup and the way it idles in gear.I pulled my number one plug to look at it but honestly, I have almost no time on this motor as it is this may be 20 minutes of tuning and driving around about 7 miles. I don’t trust you yet for high uses. I’m having some brake issues and I’m working through.
340,
You have let yourself be brainwashed by Turk & his nonsense. For the other MVA non-believers, we should say a prayer for them & hope they have a quick recovery......
These people do not understand the combustion process & WHY more timing is needed.
Thousands, if not millions of GM cars, came with MVA. Below is a page out of the 1967 Pontiac manual stating the use of MVA. These cars had 6* initial & 20* MVA added so that they idled with 26*. Small cam, 197 @ 050, 10.75:1 CR.
Your 42* sounds right & do not let some dumb a**e talk you out of it. My own car has 48* at idle, has had it for the last 15 yrs. Another car I tune for drag racing 3950 lb without driver, 3.31 diff, street driven & does 1000 mile return trips, has run 11.65 @ 119 mph. No tuning at the track & the driver was new to drag racing. It idles with 48* via MVA @ 900 rpm in gear.
I did a final tune recently on a 440 I built. TF 240 heads, 10.X:1 CR, Mopar M1 4500 intake, TQ carb. It idles with 42*. I think stunned would be the right word....The owner was stunned at the improvement in idle quality, vacuum etc between 12* at idle & 42*...
Lets do a little experiment. I have a digital ignition so it’s easy to modify my curve . I will post the stats on my engine and you recommend a curve . If it runs better without pinging we will know you are correct . Don’t get me wrong … I believe you know your stuff . But it will be a fun and informative experiment. Worst that could happen is my car runs better .
360 based 408
W2 race heads / closed chamber
9.75 compression ...045 quench
246/250 @ .050 .648 lift on 108
Victor W2 intake
TTI 1 7/8 headers theu 3” full exhaust
Pro Systems 850 carb
Daytona Sensors CD1 ignition
Mopar dist with 8.5 VA can on manifold vacuum .
21 intial at 1000 rpm
32 total by 3000 rpm
4sp and 3.91s. 27” M/T drag radials in 69 Swinger.
Did I forget anything ?
Yes but dyno testing doesnt cover off idle and low speed cruising .Didn’t you test this stuff when you had your engine on the dyno?
IABs?3500 rpm up is the easy part to tune . Thats where the dyno pull started . I have picked up significant low rpm performance adjusting ign curve and IABs/transition slot .
Yes but dyno testing doesnt cover off idle and low speed cruising .