View Full Version : lock out distributor on a Procharged car?

02-14-2007, 05:10 PM
I talked to Kevin from CSU, and with my MSD BTM he said I should lock out my distributor. Now I have the Mallory Unilite 9000 model, can that be locked out or what should I do?

I have the MSD 6 BTM and the MSD Blaster 2 coil too, just in case that is asked next....


02-14-2007, 08:00 PM
I don't know for sure, I have a Comp 9000 also and am wanting to get a BTM instead of the 6al that I have. It may be ok to be locked out, but wouldn't that give it too much timing when you go to shut it off and make it "diesel"? I am curious to this also, let me know what you find out.

02-14-2007, 08:14 PM
It is better to lock it out so you are not chasing timing and boost. I run 40 locked on my street racer with no start retard with no issue, but you may find is neccesary to use a start retard.

02-14-2007, 09:43 PM
It will work locked out, but you're going to give up some mileage and throttle response. I mean, you may only be running 28 degrees at wot so now instead of having 36-40+ at cruise and light throttle you're stuck with 28.

I guess it would depend on your compression/boost and how much timing you can have at wot. One more big advantage of EFI and not having a btm.


02-15-2007, 11:30 AM
Never thought of that Jody, good point.

I was wondering about dieseling as well Jimmy, another reason why I posted this up here.

So with the MSD BTM and still have adjustment in my timing, should I try running the softer springs 1st? (That is what I have setup now for starters)

02-15-2007, 12:21 PM
My suggestion is to lock it out but leave the vacuum advance hooked up.

The reasoning being is that if your combo is "right" the engine will be undercompressed/overcammed when not in boost-- That means it will tolerate and most importantly run most efficiently with lots of timing. Too little timing with the compression/cam combo means inefficient combustion and worse mileage, more of a chance of fouled plugs, etc. And without a vacuum advance you will never get enough timing at light load for things to burn efficiently. I'm a firm believer that *all* street cars should have a vacuum advance for maximum cruise/light load efficiency.

When I was still running blowthrough carb'd I had the distributor locked out at 37 degrees plus the vacuum advance gave me about 50 degrees under cruise, and I used the BTM to pull the timing out under boost. Never had any problems at all with either the starter or anything else and I drove it daily for a while. I did have to shut the engine off in gear though to avoid dieseling when I had the automatic and when I changed to a stick I'd just "drag" the clutch a little when I'd shut the engine off.

A little bit of mechanical advance wouldn't be bad (maybe 24-26 initial and 34-36 total) but I don't think MSD makes a 10 degree bushing-- so you'll have to make your own.

Turbo Hen
02-15-2007, 02:43 PM
I use the MSD Digital 7 with my timing locked @ 40*

I make my own ramps with the MSD, so i run 38-40* @ part throttle & cruise and then timing comes out as boost comes on.

No Efi here, just a CSU 750 & an MSD Digital 7 :)


02-15-2007, 07:48 PM
Wow! That is alot of timing! I have mine set at around 26* and goes to about 28* under load. Without a BTM. I guess I should get one! If I give it much more timing than that on pump gas, it rattles under boost. How much power am I loosing at that setup? It did about 475hp/575tq at the wheels with that and pig rich from a too small regulator. Like not even on the wideband too rich!

02-15-2007, 09:24 PM
You are losing quite a bit of throttle response and cruise efficiency with that little timing. If you set your timing to the mid 30's (or whatever your engine likes best, but it will probably be in the 36-38 degree range) I wouldn't doubt your cruising mileage picks up significantly and the engine will feel much more "snappy" when not in boost.

Also, the significantly higher cruise timing will really cut down on EGT's especially on the freeway... your current 28 degrees is probably just over half of what is really needed!

50 degrees (or more!) of timing at steady light-load cruise is not at all out of the ordinary and it will also produce the best mileage numbers. That's where vacuum advance is your friend, it gives the engine the extra timing for maximum efficiency during light load (high vacuum) conditions, but that extra timing goes away as soon as you put your foot in it and the vacuum drops.

With the EFI now I'm running about 30 degrees at idle increasing to 50 degrees at freeway cruise speeds & during overrun (50 degrees is the max I can run with my FAST box with the crank reference lead maxed out at 60 degrees), timing is in the low 30s at no-vacuum medium load areas, and ramps down to 22 degrees or so at 15psi of boost. I used to run about 27 degrees of timing under max boost with the blowthrough carb and a different cam & intake, but with the new cam and EFI tunnel ram intake the engine just doesn't tolerate as much timing when under boost.

The BTM boxes work but are a compromise. They take timing out linearly in proportion with boost, (i.e. X many degrees per psi of boost) but typically you don't need to start taking timing out until you reach a couple PSI of boost, so the BTM will leave a little bit of power on the table. The Digital 7 (as Carm recommended) or a similar programmable timing box is the hot ticket IMO for a carb'd boosted application as you can precisely tailor your timing curve independently at all load conditions as you could with EFI.

Even with the EFI I still run my 6BTM-- partly because I didn't feel like removing it, and partly because if I ever get a bad batch of gas rather than pulling my laptop out and dinking with the timing I can just dial in a little retard on the knob... not that I would be smart to put my foot in it anyways with a batch of bad gas!

02-16-2007, 08:52 PM
Thanks for the info. I know that mine is slow, but did not know it was that bad. The EGT's are freakin' crazy! Cruise'n down the highway it is around 1100-1200 and goes up from there. But there wasn't much I could do with what I had to work with. The Comp 9000 dist doesn't have vacum advance and that is why I locked it down to where it was. May have to look into a digital 7!

02-17-2007, 04:43 PM
Also, the significantly higher cruise timing will really cut down on EGT's especially on the freeway... your current 28 degrees is probably just over half of what is really needed!

50 degrees (or more!) of timing at steady light-load cruise is not at all out of the ordinary and it will also produce the best mileage numbers. That's where vacuum advance is your friend, it gives the engine the extra timing for maximum efficiency during light load (high vacuum) conditions, but that extra timing goes away as soon as you put your foot in it and the vacuum drops.

Blown353 - What heads are you running? Do you think the "fast burn" style heads need that much advance during light cruise? The Edelbrock manual says 34 max. I'm running a locked-out MSD with the Holley 950 controlling the timing.

Good thread!



Turbo Hen
02-18-2007, 07:31 AM
"fast burn" style heads - i say its just a marketing clause.....everyone has these style CC now.

I'll tell you, the difference in EGT between running ~13.5:1 @ cruise with 32* timing & ~14.5 with 40* timing is abut 200-250*


02-18-2007, 11:44 PM
Jim-- I'm running ported 200cc Dart Pro-1's.

I really don't have much experience with fastburn heads, but I can say that darn near every street application small block I've ever worked on, even stout ones, have no trouble supporting mid to high 40's and sometimes more (depending on the vacuum advance can) for timing during light load cruise with the vacuum advance connected. Under load however, 34-38 degrees for naturally aspirated small blocks seems to be where most combos end up making the most power... but not all. My old originally naturally aspirated engine combo which was overcammed/undercompressed (like most people's first engine builds, LOL!) made the most power on the dyno and posted the best MPH at the track with 40 degrees of timing with the distributor locked out. It would tolerate up to 43 degrees locked out without pinging but didn't pick up any trap speed going from 40 to 43 degrees.

02-19-2007, 10:24 PM
Cool, thanks, I've got some experimenting to do. I've been playing around with low-load cruise AFR's of 15.75-16, but haven't tried increasing the timing over 34.


02-23-2007, 05:27 AM
Ok Guys...

I've been reading this and I'm not sure if I should run what I've got or look into another distributor or add a vacuum advance can if possible ...

I have the MSD-85551 Billet Dist (does not have Vac. Advance) ... The MSD 6BTM and the MSD Coil Blaster MSD-8252

I locked out the Distributor and was planning on going that route but after reading this I might should have went the vac. advance route ...

If it would help ... the engine will see approx. 15 lbs. of boost, has a 3000 stall converter but will act as a higher stall thanks to the boost, and the cam specs are Lift .564/.582, Duration 244/253 @ 0.50, LSA 114 ... also this is an automatic tranny ride ...

Input welcomed ...

02-23-2007, 08:03 AM
I am starting to wonder the same thing. I have the Mallory Unilite 9000 mechanical advance, running to MSD Blaster 2 coil, and MSD 6BTM. I am running 10:1 compression, F1R procharger, Devil's Own meth injection, 8-10 psi boost, and I will have to find my cam specs again.

Currently I am running softest springs, hitting full advance (36 degrees) at 2800 RPM. Initial timing is set @ 12 degrees. I know I have little vacuum maybe 4 psi at idle....

Turbo Hen
02-23-2007, 03:34 PM
Vacuum advance is NOT the best way to control timing on a car with Forced Induction.....those springs can break or stick or anything then its over.

Lock out the distributor, get a digital igntion & make your own curves......this is the most reliable way in my eyes.

I use the MSD distributor without vacuum advance.....have it locked, then use my MSD Digital 7 to make my curves


02-23-2007, 04:36 PM
Running boosted engine require a lot of tuning work.
But if you dont have forced induction. I try to run my Chevys(this depends on the burn characteristics of the heads) with about 14 to 18 initial and I generally use stock weights with aftermarket springs (and those springs can be mixed) to get your proper curve. I have generally got engine in the mid 30's before vacuum advance. Then add in your vac adv and tada when you mat it your vac goes and so does the advance. When you are back on light throttle you get it back.
Every engine needs timing and figure it this way some of current EFI cars will add as much as 60 to 80 degrees advance at times. I had my brand new Snap-On Solus scanner on a Corvette that had been reflashed and at 168mpg it was cruising with 78 degrees of advance!
timing addition will effect power ,economy and emissions.
See if you advance an engines timing it "sees" the mixture as richer. The reason it "sees" this is because the cylinder isnt in "blow down" or the loss of combustion mixture due to overlap.
I have always tuned engine with as much timing as they will run hard, not buck the starter, and not spark knock.
I used to not understand timing and I was having problems 20 yrs ago getting my Pontiacto run good ,not drink gas and start well. It called for something like 6 or 8 deg of initial, and a stock dist and I was messing around under hood and it started running better, but was idling higher. I had just replaced the vac advance and inadvertantly moved the dist. I had it up around 24 deg but it would buck the starter, so I backed it back to 20 and it was till bucking, so I took it back to 17/18 ish by the timing tape and marking #1 on the dist. I forgot to hook up the vac advance but it ran like stink then and I had to readjust the carb too. I then found I had left the vac off and hooked that up and it started racing up some so I reduced the idle again!
This car went from (stock 400 2bbl but it had a Carter AFB from a 67 340 Buick) 8 or 9 mpg to 14 t o16 and it would light the rear tires for BLOCKS then. After hooking up the vacadvance it went to 18 mpg in a 69 Executive with stock tires and 2.93 limited slip rear.
I probably could have got 20 out of it with headers and duals.
A full size with almost double the mileage was a learning experience for me.
My next car was a 66 Galaxie 289 2 bbl, I figured out how to recurve Ford dists (points even), I added a 4 speed in place of the 3 , a 4 bbl from a 73 429/460 Autolite car b i got for free from my uncle.
That ar had 3.00 to 1 gears and single ex and it got average of 22 mpg .
Then I built my second Pontiac as the first broke the frame, anothr 69 but it was a Ventura and I still have it. Then I got my 61 Ford F100 for towing my race car, it got a recurved dist too and with a granny low trans and what ever gaers it got in the 15-16 mpg range.
MY race car was a 76 Buick Skyhawk (Monza clone) with a 327 and when it went on the road it was getting 21 or 22 mpg even with a solid lifter cam and all.
The same engine went into a 70 Monte Carlo and with 355 gears it got around 18 or 19 mpg with duals but before before the duals it had singles and only got around 15 to 17.
I dropped a valve in that engine and borrowed a stock 350 and that engien with same carb/intake/headers as the 327 went up to 22.
That engine got replaced by my 402 BBC with 84017 800DP Holley 4011 carb and it was getting avery nice 14 to 16 after I had to install a new tranny 2 weeks after putting the BBC in, and eve with the saturday Night Special converter it was very well mannered and it had the self same distrivutor the 327 had, curved by me 4 yrs before.
I later on tweaked the dist to get a few moreegrees of vacadvance and had it up to the 58 to 60 degree range and it always got same mileage.
Timing locked is an old time thing for race cars. Now locking your dist and using an electronic timing set up to dial in your curve (it also helps if you can use a knock sensor to) but dont forget to use the timing to your advantage.
I drive 78 C10 with a 355 with LT4 HOT roller and the same 800dp and a tall Street Dominator intake, duals and Flowmasters and headers and it run normally a 14 to 15 mpg.
I hope to get back to work soon and fins decent 4L60 or 700R4 to swap in or maybe even a 4L80E. I also hope to rebuild the diff and add some lower gears for towing after putting in the OD.
Timing is your friend.