Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Dialing in your rebuilt Quadrajet carburetor => Topic started by: dwelch on September 26, 2019, 11:10:25 AM

Title: edelbrock 1904
Post by: dwelch on September 26, 2019, 11:10:25 AM
i have been running this 1904 for about 2 years now on my 81 malibu hot rod.blueprint engine bp3503ct1 385 hp @5200rpm turbo 350 3:73 open. when i bought this carb.i got a kit from cliff with a couple idle tubes and a set of 74 jets(73's were in it).opened up the new tubes a couple thou.and restriction to .054. this q-jet seems to be on the money.idle at 900rpm 16 inches of vacuum, cruse at 2400rpm @21inches of vacuum. lean into it at 2400 and it's gone. no hesitation. stomp it all the way at 2400 and it's has no hesitation,just gone. cam specs are hyd.roller intake .495 ex..502 dur at .050 is 221intake 226 ex. lobe sep.110. looks like a torque cam. i have never had a carb. that worked this well and has the manners this one has. so now your probably wondering why i have some issues. i get no action from the tip in method. i get no action from the idle mixture screws. nothing. this carb. runs perfect like is now but i have been wondering if something has been left on the table. i tune by the seat of my pants feel. wideband says 13's and plugs are pretty much white. don't go by plugs very much anymore(too many additives).just use the wide band to see if things are close.i'll check idle screw hole size this month. would really like to get some response from idle screw adjustments. once again i cannot say enough good about how well this carb. works. sorry for the long rant.
Title: Re: edelbrock 1904
Post by: Cliff Ruggles on September 27, 2019, 07:45:17 AM
How much timing are you running at idle?
Title: Re: edelbrock 1904
Post by: dwelch on September 27, 2019, 12:16:13 PM
locked at 34. thats what blue print suggested when i bought the engine.they did not recommend the locked dist.i do not run vacuum adv. performance is instant,no hesitation,no barfing or bogging. for such a fantastic operating both at idle and part throttle,and wot.i am at a loss why there is no change in the idle adjustment screws or tip in. try to get a change at 800 rpm idle,but nothing doing. i was thinking maybe a 48m pri. rod might change tip in,i run the stock 50m now. i am very happy with the performance of this carb. right now i'm retired and have some time to mess with it. very quick with the 3:73's. i have several perf. dist. but this one on it now works so good that i'll run it for a while. really have not changed anything since the install a few years ago.
Title: Re: edelbrock 1904
Post by: Cliff Ruggles on September 28, 2019, 04:38:53 AM
WAY too much timing at idle and why you have no control with the mixture screws.

NOT ENOUGH timing at light load so why you don't see control with the APT system.

Running a "locked out" distributor on a street driven vehicle is "stone age" and not a good idea.

Also a good way to bust the nose off the starter on an engine re-start fully heat soaked.

Nearly as bad is running a super quick advance curve distributor w/o a vacuum advance, which will also result in some tuning issues and lower than idea A/F for "normal" driving.

Can't really help out with tuning suggestions for the carb and I've never seen a street engine that needed, liked, or worked well with 36 degrees timing locked out and no additional timing from a VA for "normal" driving.......Cliff
Title: Re: edelbrock 1904
Post by: dwelch on September 28, 2019, 10:54:45 AM
totally forgot about the locked initial timing. just changed oil and went for a cruse. at 2400 rpm i'm at about 55 mph. engine smooth running,i'll lean into it enough to knock the vacuum down to about 5 inches and it's gone. there is no hesitation or bog. it's instant. same mph same rpm and this time i floor it and it goes to zero vacuum,barks the tires and then barks them again in the 2-3 shift. at first i did not think the cam was not quite radical enough for locked timing like my vette was. cam in vette has around 6 inches of vacuum at idle and shakes the windows in the house. was a pill until i locked the dizzy at 34. now it's very tame to drive now. no starter issues,even when hot (180),i'm talking about the malibu. i would love to have someone dial in an advance for that vette engine but we spent about 3 hours with numerous springs weights and cans. locked was the best for that engine. as far as street manners,this car is a joy to drive. no heat problems,no loading up,just nice idle and off idle. i credit the q-jet for that. "stone age"hell Cliff i'm stone age(lol). apt two turns,idle mixture screws,2 turns. wide band 13:1 through 13:9. go more by feel than the wideband. this engine likes locked. some of my friends engines did not. most with a lot of overlap liked locked.
Title: Re: edelbrock 1904
Post by: dwelch on September 28, 2019, 04:06:57 PM
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.
Title: Re: edelbrock 1904
Post by: Cliff Ruggles on September 29, 2019, 07:21:42 AM
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
Title: Re: edelbrock 1904
Post by: dwelch on September 30, 2019, 06:22:49 AM
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.   
Title: Re: edelbrock 1904
Post by: Cliff Ruggles on October 01, 2019, 04:02:56 AM
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
Title: Re: edelbrock 1904
Post by: dwelch on October 02, 2019, 10:44:24 AM
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.
Title: Re: edelbrock 1904
Post by: Cliff Ruggles on October 03, 2019, 04:11:34 AM
Most of the later carbs use the tamper proof screws with a double "D" head.  Some had a very small hex head but somewhat rare.

If you have a flex tool for the stock type screws they work much better to set the mixture screws than a screwdriver.

The hex head variety are also easier to adjust as you can use a nut driver with a universal wrapped with electrical tape so it doesn't flop around so much.....
Title: Re: edelbrock 1904
Post by: dwelch on October 03, 2019, 08:12:11 AM
i have about a half dozen spare and parts q-jets. are the mixture screws the same if i have a spare set from one of my parts carbs with the hex head? i'll follow up with how this distributor set up works with the edelbrock 1904.  thanks for your help. ps it's been about three years since i put this carb on and i like to freshen them up every now and then. i'll call around thanksgiving for a kit.
Title: Re: edelbrock 1904
Post by: 77cruiser on October 03, 2019, 11:57:14 AM
You'll have to compare the threads. Late carbs had fine metric & others were 10-32. Easy to tell when side by side.
Title: Re: edelbrock 1904
Post by: dwelch on October 04, 2019, 07:16:52 AM
thanks for the reply. i'll check my supply this weekend.
Title: Re: edelbrock 1904
Post by: Cliff Ruggles on October 04, 2019, 11:28:53 AM
1979 and later units (17059XXX and 17080XXX) will use fine pitch metric threaded idle mixture screws.

The hex head versions are pretty rare, most are the double "D" variety, and they require a very thin wall deep well socket or special tool to access and turn them......Cliff
Title: Re: edelbrock 1904
Post by: Kenth on October 05, 2019, 02:37:02 AM
For the double-D
Title: Re: edelbrock 1904
Post by: dwelch on October 09, 2019, 01:21:30 PM
ok i got 18 initial,32 at 2500 and 34 at 3000. i'm gonna leave it here for a while. still very quick with this dist. in but with the advantages of vacuum advance. at 2400rpm had no change at tip in. took a vacuum cap off and still no change of rpm. road test at 2400rpm then lean into it kinda hard and no hesitation, just gone.i think the 1904 works great. starts easy and does not run on when shut off. the idle mixture screws are 2 1/2 turns out now. vacuum is very good. will try the mixture screws later this week. i really have no issues with the way it's running. btw i do not run a choke and the apt is about 2 turns out. and last but not least the wide band reads 13.00 to 14.02 all the time.
Title: Re: edelbrock 1904
Post by: Cliff Ruggles on October 10, 2019, 02:28:32 AM
Why no choke, it hurts nothing to use one and makes for instant starts in any weather and fast idle for warm-up.

When you add vacuum advance you can lean up the APT a bit because it will allow the engine to burn a much leaner mixture w/o drivability issues.

Not uncommon at all to see 15-17 to 1 A/F at very light throttle depending on engine load, throttle position and RPM's.  Since the VA is a load sensing device, the additional timing drops right out and you go on the mechanical advance curve with any heavy throttle or heavy engine load. 

My engine makes over 550hp/600tq and I use an electric choke on it and VA.  It's higher compression (11.3 to 1) so I only add about 14 degrees from the VA at light load (ported vacuum), 10 degrees initial timing and a 20 degree mechanical curve all in around 3000rpm's. 

I ran a few years w/o a choke because I was racing the car a lot and not much street driving.  About 15 years ago I put the choke back on it because starting it up to move the car around in cool/cold weather was a serious PITA.  It will now fire right up in any weather, even tested it well below zero outside and it roars to life instantly.  Without the choke I'd have to pump it dozens of times and it would only run 3-5 seconds then stall out.  I'd have to repeat that cycle and "feather" the throttle to keep it running till some heat got into the engine. 

I thought the choke might slow it up some at the track, but it runs exactly the ET and MPH with or without it.......FWIW.......Cliff