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Username Post: Ignition Timing '66 396        (Topic#370153)
Magnetocheck 
Silver Supporting Member
Posts: 19
Magnetocheck
Age: 68
Loc: Charlotte, NC
Reg: 09-05-22
11-23-22 07:18 AM - Post#2850378    

I am new to the forum. Just installed a Progression Ignition distributor (it is very cool!) and need some advice about initial and vacuum. I have a mild street cam in it (gives me 15" @ 800 RPM) but still struggling with rough and rich idle. What would you recommend for initial + vacc? I have initial @ 18 and Vacuum @ 8. Total is at 36 degrees and performance is good. All are real easy to change with this distr.

Bob
'65 Impala SS 396


 


Brickwhite 
Contributor
Posts: 285
Brickwhite
Loc: Colorado
Reg: 09-05-19
11-23-22 10:33 AM - Post#2850385    
    In response to Magnetocheck

Timing maybe a little high but not too bad.

I think my BBC 454 (mild cam, headers,ovalport heads) has 16 degrees of inital timing 36-38 w manifold vacc advance, with a HEI STD dist running a holley 750 DP.

What carb are you using?

That is going to be the place to start with idle.

If using a holley do you have the throttle plate closed enough to affect the idle circuit? Do the idle screws make any difference when turned?

Other factors
- ported or manifold vacc advance?
- Auto or manual Trans (vacc on some trans makes difference)
- Stock jets on carb?


Ted


Edited by Brickwhite on 11-23-22 10:41 AM. Reason for edit: No reason given.

 
Magnetocheck 
Silver Supporting Member
Posts: 19
Magnetocheck
Age: 68
Loc: Charlotte, NC
Reg: 09-05-22
11-23-22 11:03 AM - Post#2850386    
    In response to Brickwhite

What carb are you using? Holley 4160 650cfm with vac. secondaries on Edlebrock performance manifold (not hi-rise)

If using a holley do you have the throttle plate closed enough to affect the idle circuit? yep, closes all the way
Do the idle screws make any difference when turned? Yes but seem to run best almost all the way in,

Other factors
- ported or manifold vacc advance? manifold
- Auto or manual Trans (vacc on some trans makes difference) auto TH400
- Stock jets on carb? Yep 72 on primaries,not sure about secondaries. need to check
Thanks for the help!

Bob
'65 Impala SS 396


 
DHMelton 
Silver Supporting Member
Posts: 102
DHMelton
Loc: Central Arizona
Reg: 04-10-22
11-23-22 01:28 PM - Post#2850391    
    In response to Magnetocheck

Typical performance curve will have 10* static advance. Mech adv all in by about 3000 RPM, (but doesn't start until ~1000-1200 RPM), and with 15" idle vac, a vac can that is full open at 16* adv as about 12" vac.

So, at 800 RPM idle, your total advance would be about 26* BTDC. Note sometimes limit bushing are used with vac cans so full vac advance is limited to 12* or 14*, giving you total idle advance of 22*-24* total advance at 800 RPM

I don't know squat about that distributor, does it have some sort of vacuum transducer hookup that changes vac reading into advance curve?

An AFR meter would help with your tuning.

FWIW, the Holley 6210 spreadbore double pumper carb uses #60 (122-602 IIRC), main primary jets and the AFR is just about perfect out of the box.

Doug



 
Magnetocheck 
Silver Supporting Member
Posts: 19
Magnetocheck
Age: 68
Loc: Charlotte, NC
Reg: 09-05-22
11-23-22 01:43 PM - Post#2850393    
    In response to DHMelton

Thanks for the carb and timing advice. I may wind up replacing the carb anyway if I can't get the rich idle thing sorted out via timing and the 4160 carb rebuild. The vacc port on the diz runs a transducer that adds more advance, although it is really all electronic. You wouldn't even need it, as you can program the entire advance curve anyway you want w/o any "vacuum advance" but the transducer gives a manifold vac output to the app via bluetooth, along with RPM to use when tuning. More here if interested:
PI Link

Bob
'65 Impala SS 396


Edited by Magnetocheck on 11-23-22 01:45 PM. Reason for edit: No reason given.

 
DHMelton 
Silver Supporting Member
Posts: 102
DHMelton
Loc: Central Arizona
Reg: 04-10-22
11-23-22 03:16 PM - Post#2850399    
    In response to Magnetocheck

Interesting. It sounds like a programmable EFI without the injection part.

I would rejet your existing carb first. The 4160s come jetted really rich from the factory to deal with high overlap cams.

I really, really like the Holley 4165 spread bore 6210-3, but of course it fits a Q-Jet manifold. And costs about $750 these days.

Jets are cheaper. I would try #60 or #62 primaries.

Doug



 
Magnetocheck 
Silver Supporting Member
Posts: 19
Magnetocheck
Age: 68
Loc: Charlotte, NC
Reg: 09-05-22
11-23-22 03:31 PM - Post#2850400    
    In response to DHMelton

Again, many thanks for the jet advice. That was my plan, to rejet first after rebuilding to make sure I had no leaks, plugs, nor worn parts anywhere, but I didn't have any idea what size to go down to.
I'll give them a try and post back here

Bob
'65 Impala SS 396


 
62chevy427 
"15th Year" Silver Supporting Member
Posts: 2223
62chevy427
Loc: laurens sc
Reg: 04-13-06
11-23-22 05:03 PM - Post#2850406    
    In response to DHMelton

i run a 800 holley spread bore on my 62 impala with a 427. have had it for years. runs good. decent gas mileage with a 3.70 gear.

56 bel air ((since 2002)
62 impala ss (since 1965)
65 el camino (since 1969)
66 nova (since 1987)
67 malibu convertible (since 1981)
72 el camino ss454 (since 1985)
83 gmc 4wd (since 1991)
95 impala (new)
15 chevy equinox



 
toro455 
"7th Year" Silver Supporting Member
Posts: 885
toro455
Loc: Western NY
Reg: 06-15-02
11-23-22 07:12 PM - Post#2850410    
    In response to 62chevy427

Considering your idle vacuum your power valve number is probably not too high, even if you didn't change it, but those do need to be purchased/changed according to the vacuum level. They can also rupture and leak.

Another thought is float level. I don't love how the inspection plugs are set-up and the site glass set-up seems to be even worse. According to a Holley video the fuel should be at the very bottom of the inspection plugs. Essentially if something is running out the level is too high. If that's true you see nothing in the site glass.

What about fuel pump pressure? Doesn't Holley like a low fuel pump pressure; preferably around 5psig?

If it was crazy rich it could be a needle and seat issue. I had a small sliver of metal embedded in the seat cause a needle/seat sealing issue. I was actually able to find it. I was amazed but it could have driven me crazy if I didn't find anything.

Scott



 
Magnetocheck 
Silver Supporting Member
Posts: 19
Magnetocheck
Age: 68
Loc: Charlotte, NC
Reg: 09-05-22
11-24-22 04:45 AM - Post#2850414    
    In response to toro455

--My rebuild kit came with a 6.5 Power Valve, which I installed, even tho the old one looked OK. The original wasn't marked, so don't know if I'm going up or down! :laugh :
--I replaced the needles/seats/o-rings and before I tore the carb apart, I checked float levels. Primary was OK, secondary a little low. Agree with you on the sight glass. If you can see the level it's probably too high,
--Yep, everything I've read says Holleys like about 5-6 PSI, but my fuel pump is stock, so not likely overpressuring. I have a fuel pressure gauge, just been too lazy to get the hardware to hook it up and check.
Thanks for the advice!

Bob
'65 Impala SS 396


 
toro455 
"7th Year" Silver Supporting Member
Posts: 885
toro455
Loc: Western NY
Reg: 06-15-02
11-24-22 06:52 AM - Post#2850418    
    In response to Magnetocheck

Bob,
Power valve: Others who work with Holley carbs more than I do can correct me if I'm wrong but the power valve number is essentially the vacuum level which it should allow flow. Holley has a rule for it based on your idle vacuum. Your cam seems to make great vacuum. The big problem I had was mine did not. Anyway I wanted to make certain I remembered the rule correctly and I found a nice description here:

https://www.racingjunk.com/news/choosing-the-rig ht...

"To find out which power valve your high-performance engine needs, you first need to know the vacuum characteristics of your engine. Begin by hooking a vacuum gauge to an intake manifold-vacuum port. Warm up the engine and note the vacuum reading at idle. Automatic transmission equipped vehicles need to be in the Drive position for this test. Once you have a proper reading, divide the vacuum reading number in half. The divided number will determine the correct power valve that you need.

As an example, a vacuum reading at idle of 13-inches needs to be divided by two, which results in a number of 6.5. Therefore, you should have a number 65 Holley power valve installed in the carburetor. If your divided number falls on an even number, you should select he next lowest power valve number. For example, a vacuum reading of 8-inches, divided by two and you come up with a number of four. In this case, you would use a 35 power valve.
"

Site glass: According to what I found if you see anything in the site glass the level is too high. That's what makes it difficult. You don't see anything until the float allows the fuel level to be too high.

Needle and seat: That issue I described with finding a metal sliver in the needle can happen at anytime. If you have a new set-up any connection after the filter could be the cause. That wasn't my only issue though.

Return line/checking fuel pressure: One other thought... do you have a fuel return line and is it clear; not plugged?

To check for leaks and to set-up my regulator I made-up an adapter-gauge which I could snap my air compressor line on. I used a ball valve to slowly raise the pressure and I watch the the pressure on the adapter gauge. You can then see exactly when the regulator is opening. In your case it should show when the mechanical fuel pump is allowing fuel return or the pressure which the pump provides. I found it a lot more comfortable being able to check everything with the car off before I even filled the system.

Scott



 
bobb 
Super Senior Member
Posts: 6180

Loc: paradise
Reg: 09-05-03
11-24-22 10:13 AM - Post#2850430    
    In response to Magnetocheck

as i recall, a jet change will not help a rich idle. fuel level will probly have more effect. get a holley tuning book cheap from ebay. it may help. as i recall you need to restrict the idle fuel passage with a little piece of wire bent in a v shape. its crude but works. if you drill an air jet its premanent. you need to know your fuel pressure. air fuel meter is a good tuning tool that i use along with a vacume gauge. got one from ngk.

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
Magnetocheck 
Silver Supporting Member
Posts: 19
Magnetocheck
Age: 68
Loc: Charlotte, NC
Reg: 09-05-22
11-24-22 10:46 AM - Post#2850438    
    In response to bobb

Thanks for the insight! It runs rich all the time, not just as idle and gas mileage is terrible, so the smaller jets may help. Cheap fix if they help. They wire fix is pretty cheap fix too! I'll give that a try as well. Never had any experience with an A/F meter, but not too old to learn, I guess.
Happy TG!

Bob
'65 Impala SS 396


 
Magnetocheck 
Silver Supporting Member
Posts: 19
Magnetocheck
Age: 68
Loc: Charlotte, NC
Reg: 09-05-22
11-24-22 10:50 AM - Post#2850439    
    In response to toro455

Thanks for all the help and research. My 396 pulls 13" in Drive at idle, so a 65 should be good. Just re-did my fuel lines -- all brand new from filter to carb. Looks like i need to get busy and hook up my pressure gauge as a final check! Happy TG!

Bob
'65 Impala SS 396


 
bobb 
Super Senior Member
Posts: 6180

Loc: paradise
Reg: 09-05-03
11-24-22 01:47 PM - Post#2850447    
    In response to Magnetocheck

running rich all the time sounds like it could be a power valve or gasket issue. when idling try plug the air jets one by one to check if they are restricted. timing numbers are only for taking note of. experiment with advance and retard to see what the engine likes. if you have a stock type dampner you need to mark the inner part in reference to the outer part so you know if it slips, throwing all your timing numbers out the window.

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
FishFry 
Newbie
Posts: 41
FishFry
Loc: Augsburg - Germany
Reg: 11-01-22
11-25-22 10:15 AM - Post#2850487    
    In response to Magnetocheck

  • Magnetocheck Said:
I am new to the forum. Just installed a Progression Ignition distributor (it is very cool!) and need some advice about initial and vacuum.



I have a similar device called 123 Ignition from the Netherlands. It's quite popular here in Europe.

It may sound crazy, but I ended up with 13 deg. "mechanical", and 20 deg. via vacuum at 800 rpm idle. No initial timing.

So that's 33 deg.at idle.
And yes I know how that sounds, but she purrs like a kitten, and I get the highest vacuum reading that way.
This is an inline 6 though, but give it a try.

My "mechanical" timing curve starting point is always RPM /100+5.

So at 1000 rpm you have 10 deg.
at 2000 rpm 20 deg.
at 3000 rpm 30 deg. etc.

Those +5 deg. are from the initial advance my engine wants.

With those programmable distributors you have to relearn some stuff, but it's great fun to play with them.

Frank






 
Magnetocheck 
Silver Supporting Member
Posts: 19
Magnetocheck
Age: 68
Loc: Charlotte, NC
Reg: 09-05-22
11-25-22 10:19 AM - Post#2850489    
    In response to FishFry

Thanks for the advice. Yes, I am having fun playing with the new distributor, but with so many choices can be overwhelming. As soon as I get the carb back together, I'll try your suggestions!

Bob
'65 Impala SS 396


 


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