Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

edelbrock 1904

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dwelch:
just keep thinking this engine is not equipped with that hot of cam. i run a old aluminum points dis. fired by a msd street fire box with jacobs ign. stuff. i have a rebuilt first gen. camaro sb alum.dist. that i will get ready to get a good curve on. should be an easy swap. then i'll see what i get with  tip in and idle mix screws. been a while since i did an advance curve but should be plenty of advice on the web.

Cliff Ruggles:
An engine distributor has an advance curve and vacuum advance for a reason.

Very, and I mean very few engines will crank with locked out timing full heat soaked w/o "bucking" the starter.

36 degrees is too much timing at idle for most as well.

You are missing another 10-20 degrees timing at light load which hurts engine efficiency and fuel economy.

That's just the way it is with this stuff.

If you are getting away with locking out distributors it's something I've never had any success with except in full race applications, and even they we put the ignition switch separate from the start switch so we can roll the engine a bit before firing the distributor to keep it from cranking hard.......Cliff

dwelch:
the locked out dist.method was used on my full race bbc. 14:1 with big roller cams at big lift numbers and 300+dur. vette also has a big cam and compression and is locked. i have just about everything ready to swap out the locked and install my new one with va and lighter springs and my timing light in hand. some say the B1 can is good for what i'm doing. i'll try to hit 34 total,14 initial and 20 in the dist. the B1 can says it starts at 8-11 and in at 16-18. i also have a few gm cans that i might try if problems with the B1. of the three numbers i was told that the last two are the dist. degrees. example is 201-15 would be 15 degrees of dist. degrees which would be 30 degrees at the crank. i have also heard the the 15 is crank degrees. pretty reliable source said it was dist. degrees. i'll try to get this done soon and reply later.  thanks for your help.   

Cliff Ruggles:
The B-1 can is about all that is left unless you can locate some of the lighter "high performance" cans that are NLA on Ebay.

I'm not overly fond of the "adjustable" VA units and don't use them.

Setting up a distributor is pretty easy, I've done thousands of them over the years and have always offered this service, but I only do original units, nothing aftermarket.

Lot's of folks who send carbs here also send their distributors to be set-up for what they are doing.  I do not like or use aftermarket spring/weight kits and stick with OEM parts.  I set-up custom curves by using a MIG welder to reduce the travel of the advance pin, then open it up if/as needed so it adds the timing we are looking for.

I verify this with a degree wheel, then select the springs to get the advance in when we want it. 

Well thought out engine builds will not like, want or need a lot of advance or having it "all-in" early.  These super light spring kits to get it all in around 1500-2000rpm's do not work as some of it will be in at idle speed making tuning difficult if not near impossible.

For most well thought out engine combo's I shoot for 10-12 degrees initial timing, 10-11 from the mechanical advance (20-22 at the crank), and 10-15 degrees from the VA.

Engine with tight quench, decent compression and well chosen cam will usually make best peak power around 30-34 degrees total timing.  This assumes optimum compression for pump gas and good combustion chambers.  Some of the "old" combustion chamber designs developed for emissions will not fair well with those numbers and need considerably more timing for best efficiency.  Problem is that some of those designs have WAY too much squish area and tend to ping on pump gas even when you are doing everything right. 

I've ran into several engines that were nearly impossible to tune with pump fuel even though the static compression ratios were pretty "low" and cam choice looked good for them.

Couple of years ago I opened up my Saturday mornings to custom tuning troubled engine combo's and have had vehicles brought here, some from great distances.  Of course this was after the owner exhausted all locally available resources to get them working well, including all his beer drinking buddy's and any local shops or "guru's" who do that sort of thing.

The common denominator with nearly every single one of those troubled engines was using some cheap-ars Mr Gasket or similar weight/spring kit in the distributor.  Adding Petronix was another big problem I found with them (insufficient dwell across the RPM range). 

The spring/weight kits in every single case were allowing some timing in below 1000rpms making idle tuning a lesson in humility.  Some of them were even adding timing when cranking making restarts difficult!  A good advance curve can NOT start below the idle speed or timing will fall-out when the trans is placed in gear or engine tries to "settle down" at idle speed.........Cliff

dwelch:
ok out came the locked out dist. and in went the stock points dist. fired through the street fire. here are the specs. i came up. this alum. dist has about 28 degrees in it (1111150 casting number.).i welded up a small slot with the mig and cleaned everything up. wanted to get to 20 degrees in it but came up with 18. what i tried to get was 14 initial,20 in dist to give me the 34 total blue print engines suggested. stock weights and one stiff and one a little softer. so 14 initial,18 in dist for 32 total,idle at 900 rpm.B1 can has 14 degrees in it. so 14 initial plus can hooked up is 28 at idle. 1800rpm is 24 degrees,2200rpm is 28 degrees. i kinda wanted wanted everything in at about 26 or 28 hundred rpm.idle vacuum is 15. 2400 rpm on cruse is 20 inches vacuum. gonna put a few miles and see how it goes but would like to get that extra 2 degrees back into the dist. for now i'll set the total to 34 and let the initial fall where it falls. looking forward to tweeking this some more.one thing for sure is there are some pia fixtures in front of the carb. that makes it tough to adjust mixture screws with a small screwdriver.thermostat housing,hoses,fan and shroud  ect. was wondering if there are mixture screws that can be adjusted with a nut driver instead of a screw driver. would like opinion on a better VA can.

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