w30442

I presently run 21 initial and 12 mechanical advance timing on my 455. I was thinking of locking out the timing to 33 total to cleanup the idle due to a high duration solid cam and low vacuum. Anyone run a locked out distributor on the street. Any pros/cons ?
It seems to be more a street car nowadays than the track. Car has an 850 DP Holley.

fleming442

34⁰ locked, here. Works well. Engine pulls about 12-13hg vacuum at idle.
Just my opinion: I would think it works better in a mechanical situation (carb secondaries and transmission). Vacuum secondaries and an auto trans might like vacuum advance, as well? I don't know, but it sounds good.

Rallye469

Locked out MSD as well.
No trouble at all on the street. I don't require vacuum for anything.
My brakes are manual disc, TH400 is mostly shifted by me manually.
If I put too much timing in hot starts are tough...but usually not a problem.

w30442

Thanks Gents for the feedback, I have changed to Manual brakes years ago due having power brakes with old 328 W30 cam you needed a leg like a horse to stop the car. Car has a manual auto as well

Duh

Running locked out distributor on the street is not a problem with higher stall and steeper gears.

70W-32

If you have hot start issues with locked out timing, MSD sells a start retard to alleviate that issue

matt69olds

I ran the timing locked on the HEI for years. I also retained the vacuum advance to keep the part throttle efficiency. It worked well. I have a MSD6AL box, with a MSD retard box for the nitrous, it also had a 20 degree start retard. If I remember correctly, my particular combination seemed to work best with 34 degrees.

fleming442

While we're on the subject, what causes the hard start? I've never had a problem, but also have a Powermaster 9510. I did have to replace the contacts recently after 5 years, 20k-ish miles....

Mr Nick

My best guess... slow cranking speed means slow piston speed. Igniting the mixture 34* BTDC while the piston is moving so slow allows peak combustion to occur before the piston gets to TDC and as a result may try to push the piston back down, before it ever reached TDC.

olds80six

32° locked. Motor pulls around 6 inches of vacuum. I used to run some mechanical advance, but decided to lock it to clean up the idle and keep it from tickling the power valve opening when pulling away from stop lights.

I tried using later opening power valves, but didnt get the result I wanted. Locked timing gave me the result I was after.

w30442

While I am at it I think I will block the rear power valve as well and jet up the secondary. Car has 3.73's and a 3400 stall. I believe I will put a kill button on the ignition just in case and fire it while the car is cranking in case of hard start. I am still using a stock starter. Those pigs are heavy.

w30442

I took my distributor out and locked out the timing. I set it for 33 deg. It moves around a bit between 33-34 deg. I did notice that while trying to get a read on it at lower rpm its somewhat all over the place after you rev it up and let off the throttle. I believe this is the MSD-6AL box causing issues with my timing light. but at 3000 up it holds steady. I put my distributor back in at TDC at 0 deg on the balancer but this seems to have limited my range on the timing as it retarded all the way to get 33 deg. Perhaps you supposed to drop the distributor in with the balance at the 15 or higher mark to give yourself a bit more range ? What does everyone else do ?

I also took my 850 DP apart and drilled out all the factory fixed bleeds and restrictions on the metering plates and throttle body.

I set the idle at 1000 rpm and adjusted the 4 corner screws for best vacuum and ended up with 9 lbs. When I dump it in drive it goes to 5 lbs . I have a 4.5 power valve in the primary and the secondary is blocked. I haven't had it out yet just tuning in the yard. The power valve may possibly have to move to lower I guess I wont know till I drive it.

Jets are 76 front and 84 rear
HS Air Bleed 0.033
Idle Speed Air Bleed 0.073
Idle Speed Restrictor 0.031
Power Valve Restrictor 0.053
Rear power valve blocked

Carb previously was always rich and factory stuff was set at
Jets 80 front and rear
2 power valves 4.5
idle jet 0.037
PVRC 0.066
Idle air bleed front 0.077 - Rear 0.065
HS air bleed front 0.026 - rear 0.023

w30442

Drilling out the idle air bleed
Not alot of meat around these - I went with 8-32 on the HS bleeds and 10-32 for the Idle Air Bleeds
PVRC and Idle jet are 6-32
All are brass set screws with a 3/16 length


Back together
but jets and PV's not as marked
No real trick stuff here just the heavy holley.

RW Tech

Locked out timing on a street car is not a good idea unless you absolutely do not care about fuel economy or how well it runs during light load/low throttle. If it needs a lot of initial timing to idle, you can limit the amount of centrifugal (mechanical) advance and/or connect the vacuum advance diaphragm to intake manifold vacuum. Otherwise, you will be cruising at light load with about 15 degrees less timing than it will actually want at that RPM/engine load.

teamwieland

Olds80six I’ve never had a great idle. High compression 455 runnng e85 (more like e60 at the pumps here). Been fiddling with my Holley carb with vacuum secondary to no success. Just locked the timing at 35 degrees and it solved my idle and motor runs fantastic. I have 4.10s in rear with TH400 so that helps. What are you referring to when you say “keep it from tickling power valve”. I’m still trying to get rid of the lean bog when transitioning to secondaries and wonder is power valve could be the issue.

olds80six

I'm referring to the power valve starting to open prematurely, causing an overly rich condition during normal driving.

teamwieland

What does the locked out timing have to do with the power valve staying closed? I’m running way rich at idle and light cruise, with a lean bog when I get on it at low rpm. Once past that it runs beautifully. Locking out the timing really cleaned up the idle and I don’t notice any trade offs so far, but Im still rich at idle with a lean bog. Almost sounds like Im having the opposite problem you were having.

olds80six

Increased idle vacuum and torque, requiring less throttle angle when pulling away from stops. Doing so keeps the carb more on the transfer slot, as opposed to a greater throttle angle causing it to start pulling on the booster (main jet/power valve) sooner than o preferred.

rfpowerdude

Get one of these and set it however you want with your handheld or tablet.
https://progressionignition.com/
I bought two and can't wait to get one in to test it out.

matt69olds

years ago I locked the timing on my HEI, but kept the vacuum advance functional. I ran 35 timing, with a 15 degree vacuum advance canister. The MSD 6AL ignition system with the 3 stage nitrous retard (which includes start retard) worked great.

Run to Rund

Another approach would be 10-12 degrees initial, and 24 in the distributor. With very light springs, half of that would be in by idle speed at 1200 or so, and the total around 2400 rpm. Meanwhile, you would have just the 10-12 deg when cranking and starting.