Blower timing

Now, I know I don't mail in much and always try to use the info already available but I realy do need some expert advice id any one out there has a good grounding in Blower set ups.

I am presently finishing off my 56 F100, it now has a 454 big block with a bds 871 blower. I am just in the process of changing fron two 600 holleys to hilborn blower efi and would like to know if anybody has run this type of set up and what timming they started out with.
I have run blown small blocks with good results and kept the vac advance on the dissy from ported vacuum. Plus a 6btm to retard on boost to keep from detonation.
On this system there is no provision for any ported vac and the manufacturer recomends locking out the vac advance, keeping the centrifugal at about 20 deg (crank degrees) in by 3000 and 10 initial.
I want to get it in the ball park for initial fire up as I have so much going on (rebuilt motor, new induction etc) I need to keep away from serious heat and detonation problems.
I am planning to use 92 octain gas (I am in the UK and we can get 91/91/95and 97 if required at the pumps in most places), so this could be increased.
My main concerns are that by locking out the vac advance I am making the motor all performance orientated and really want to keep the thing street only, so part throttle responce is key.
I have in the past run motors with the vac advance on inlet vac not ported which puts loads of advance on at low load/idle - closed throttle but allows retard on part throttle and loading up, this I have found to work well in practice on heavier stuff when going up hills or towing (not a requirement here).
I was wondering if this could be applied to this biger blower motor as as blower speed and presure increase it would also cancel the advance so the vac advance would be limited to off idle and sub 2500 rpm but do not want to try as never heard of anybody running blower timming like this.
Anybody any experiance of blower timming for street not race appications on higher output motors.
Not expecting the economy to be too good but it is always a concideration at our pump prices so this is another reason not to take the race set up route.

Any help apreciated.

Bailey40ford


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I ran a 671 at 1:1 on a street SBC. With CR of 7.5, it needed about 20 degrees of initial advance to keep from burning the headers, plus 20 more centrifugal in by 3000. Didn't use any vacuum advance, but did have an MSD 6BTM. Optimal initial timing goes up as the CR goes down: lower CR means the combustion proceeds slower and you need to start it sooner so it will be done before the burning gases are pushed out the pipes. I fried a new set of headers before I figured this out. Hope this is some help.

Blowers like a lot of initial timing. I run 12lbs of boost on pump gas. No vacuum advance, two Holley 750DP's (blower carbs). My initail timing is set at 20 with a total of 34*. If you try to run that blown engine at 10* initial you will have an overheating nightmare on your hands and your exhasut temp will be HIGH.

You will your car will still be streetable if you set the timing up correctly. If you don't run enough initial it will hurt low end performance and really run a lot hotter. I started off at 12* initial and I can tell you the difference between how the car ran with 12* compared to 20* is night and day.

The distributor I like to use is the Mallory magnetic pick-up. No vacuum advance. You can adjust the timing curve however you want with it. There are "keys" used to set the initial timing.

Royce

Aww lol, man bailey probably forgot about what he posted 2 yrs ago since no one answered him... Hate it when that happens.

LMAO!! Why did someone bring this post back from the dead? I guess I should have checked the time stamp. Since there was only one reply I figured it had to be from today. The good news is it is now in the post so if someone does a search they will find some info.

Royce

i just got my motor done by greesman motorsports 383 chevy makes 733 hp 599.5 ft lb torque..msd..pro engerneering carbs...stewart fuel pump.pistom......timing 32 degree total..light springs....timing is important on blower motor...fuel is biggest issue...ran other motor 355 with same blower.2 eldebrock carbs mallory dist.. msd al6 controll 16 years...pro street studebaker.....564 hp..502 ft lb torque....new motor same block dyno dont lie if used right....mitchymo

Mitch, the original post was in 2003, it died and was resurrected in 2005 briefly, and has now been dead for almost seven more years, I doubt the OP is even still around...

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Midnight Sun Street Rod Association

Thanks 68....Saved me from writing another 1/2 hour long post. haha

To put things in perspective- and to help someone who may find this thread while doing a search- what size carbs, what is your initial timing, what size/type is the blower and what is the blower drive ratio?