[dv657172]

Question - Would you lock out the timing and if so what would be an initial setting to start with?

100% dedicated race car
1965 GTO w/68 400 (462")
TH400 with 3500 stall
Launch off a transbrake around 3800
Hydraulic cam but unknown specs unfortunately
MSD 6AL box with MSD distributor

Car has not had much track time at all and from my OLD notes timing was set at 20 degrees initial and 36 total

Pulled engine in the offseason to replace a leaking rear main seal and have it all back together and re-checked timing and now it reads 18 initial and 40 total at 2500 rpm.

Distributor never came out when changing rear main seal and timing gear marks were definitely set at 12 oclock on reassembly. Confident in current timing readings but not sure how good my old notes are.

Should I just lock it out and be sort of done with it? If so where would you set it initially as 40 sounds high

I know getting the timing right is a matter of trial and error but given the few opportunities to get to a track during the season I would like to at least start from a reasonable point. Thanks

[steve25]

Let others chime in here, but I would not lock out the timing on a motor such as your which will not be having a narrow power band from running above 6000 rpm on up all the time.

[Elarson]

My thoughts:

34-36 degrees total timing sounds reasonable, 40 sounds scary.

In a normal distributor, the full timing is usually in by 3000 rpm or sooner; and it sounds like you'll be above that. So my vote would be locked timing for simplicity and repeatability. The only downside might be hard starting if your battery and starter aren't up to it.

All that assumes you don't have vacuum advance. If you do, having the mechanical advance locked would give you too much at low rpm.

Eric

[AG]

Mine is locked out at 38 degrees race only. Lock yours out at whatever your total timing is and you should use a start retard, i use a MSD Digital 6 that has 20 degrees start retard.

[Dragncar]

What is the advantage to locked out timing. I tried it once and my car did not like it.
Why not just have a good distributor with the right curve, right amount of advance where you can start your car normally.
Since we race these things what really matters is the total advance. We take off under full advance.
I only check total advance at 3000 RPM. Have not checked at a idle in 25 years. I don;t care what it is.

[TinInjun]

Lock it out. Install MSD starter saver and cut the blue wire for 20 degrees of retard during start. Set the timing and your done.

[Johnny406]

I have mine locked out at 31.5 degrees (KRE D-ports) running E-85. I use a RobbMc starter with a pinion support. When the motor is cold, I have a ignition kill switch to allow the starter to get the motor cranking before giving it spark.

[OCMDGTO]

I've been running mine locked out at 37° for the last few years with 10k+ street miles. No issues other than a couple broken teeth on the flywheel

[dv657172]

I appreciate all the replies!

Definitely going to bring the total timing down to the mid 30s to start with the next time out and try to figure out what the car likes best.

Leaning towards locking it out and adding an MSD Starter Saver once I get that figured out.

[Dragncar]

Originally Posted by OCMDGTO

I've been running mine locked out at 37° for the last few years with 10k+ street miles. No issues other than a couple broken teeth on the flywheel

What ? Sounds like a real issue with no benefit to me.
Still trying to find someone to explain the advantage to locked out timing vs a simple distributor that has the proper advance curve so you can start you car like it was meant to be started.
I am open minded about it. If someone can explain the benefit that would be great.
I found nothing but a hard crank issue vs a distributor Whitmore set up for me. I even cranked it with ignition off and ht the ignition. Not worth it and yanked that stuff out.
Its the race section and unless you are foot braking it and taking off at 2000 RPM or something where there is a difference we all take off past full advance anyway on a 2 step.

[TinInjun]

Originally Posted by Dragncar

Its the race section and unless you are foot braking

You just answered your own question. Locking out the timing when the rules do not allow trans brakes and two steps makes a car more consistent when racing in index classes. Much easier to tune for weather changes.

[AG]

My converter stalls to 5000 rpm, no need for mechanical advance and it idles better with full timing.

[aaronman]

Walk the staging lanes at any bracket race and talk to racers. You will find that most all have their timing locked. Just one less variable when races are routinely won or lost by a few thousands of a second. It also eliminates one variable when you do run into problem.

[OCMDGTO]

I run mine locked out as recommended by the builder. Gaydosh had built this combo before and said it picked up et wise

[lust4speed]

As far as timing, my 670 semi-open chamber street heads run best at 38°. My first generation Edelbrock round ports that flow 349cfm liked 41° on the dyno and at the track. Most of the Kaufman heads were between 31° and 32° on the dyno, and the later generation Edelbrock heads ended up at no more than 34°.

My MSD Digital 6-Plus had a strange quirk where it would not always do the 20° electronic retard. Did enough checking where the failure to retard had to be inside the box itself. I gave up fighting it and went to a set of springs just strong enough to bring the weights back on shutoff. When the box retarded the timing the locked distributor worked great, but when it didn't work the engine was really unhappy on start up.

[Tim Corcoran]

I tried locking out my MSD Pro Billet and it was hard to start and idle was not good at all. Went back to mechanical advance and all is good. This is a race only car that is foot braked and I bring the RPM up to 1100 and hammer it and it spools up instantly, when it was locked out it didn't spool as fast. Timing locked out did not work for me.

[dv657172]

I launch of a transbrake at around 4k so my centrifugal is basically fully advanced from launch through the full run. IF I do lock it out I will definitely try the MSD Starter Saver to make start up easier.

DV

[Don 79 TA]

i have had mine locked out. i dont use a start retard, don't really get any kick back either
fires up all the time
i've also used it curved, no issues either way, used the bushings from 4seconds flat that reduced the amoutn of advance, they are nice indeed
only thing i recommend is to check rotor phasing with locked timing, be surised how off that is sometimes, i've found the marks on the edge when locked, and more in the middle with a nice sweep when using advance, but thats just my observations with the MSD dist.
i also prefer to use the largest size caps i can
i use MSD distributors

[KGTO]

Mines been locked out since early 2000s. I ran a Jericho, always used the start retard with the digital 6 box and 2 step since I'd launch above 5k. It had a 150 shot, iron heads and ran mid to low 10s. Mostly a street car.

It no longer goes to the track, no more nitrous and has a TKX. Been thinking of pulling the pro billet distributor and installing one with VA. Has a good sized solid with 108 LSA. Runs awesome, never a starting issue, never banged the teeth, also use a good mini starter. Only thing cruising is a little chug which could probably clean up with a good curve. My other race cars were all in too. I'd lock it out.

[lust4speed]

For whatever reason when I tried the locked out distributor the Digital 6 box wouldn't always pull the timing back. Sporadic and sometimes would and other times it wouldn't. The wiring checked out good and it was inside the box so I gave up on the locked out ignition. Put in some very light springs just enough to bring the weights back and lived with that. My son's Firebird with the same box worked every time.