Distributor curve

[CamaroAdam73]

Ok i finally got ahold of some timing tape..

I backed off the initial timing down to 18. My dist advance is coming in at 1500 RPM and all there by 3000 RPM. I'm getting 14-16 degrees from the dist advance, i cant be any more precise because my timing light kinda sucks.

So my total timing is 32-34 degrees right now.
I pulled plugs again and it's showing signs of running lean.
When i put the car in gear it's still dropping from 1100RPM down to a 600-700 fluctuation in gear.

Took it for a drive..

If i accelerate hard from a dead stop and hold it in 1st letting the engine spin up to about 4000 RPM then letting off the throttle, it pops through the exhaust like a machine gun.
From a cruise in 3rd gear giving it hard acceleration but not enough to down shift, it acts sluggish and doesn't want to rev up.
What confuses me though, if from a dead stop i put it in 1st and give it WOT it just rolls the back tires until i let off. How can it pull so good in 1st and just fall on its face in 3rd?

I have to note, when pulled back in after the test drive i brang the car to a stop and kept in gear, it would fluctuate between 600 and 500.
I put a longer line on my vacuum gauge, when i put the car in gear and the RPMs drop to 600/700 the vacuum signal drops to about 6" of vacuum.
I also tried ported source of vacuum, the car stalled as soon as i put it in gear, that shouldn't happen.

What do yall think now? I'd have to agree at this point i think my problems are in my carb.

 

[Fox80]

I would agree, I think now you need to move on to the carb, the dist sounds like what I would want to see. If you look at all the things you stated, popping in the exhaust, sluggish under heavy load, all sound like a motor that is very lean. I don't recall what you have for a carb but I would start with a jump up of 5 jet sizes all four corners if its a Holley, If its a Quad, or an Edelbrock maybe some of these guys can chime in on how to tune it, I know nothing about them carbs I've only ever used Holley carbs on every car I've owned

 

[DoubleV]

Carb
Factory 800 CFM 403 Q-jet, built to this motors exact specifications

Who built your carb? Do you have any details on what was done? On a Qjet, there are lots of little things many never really think about when modding them for performance use such as the size of the idle circuits, air bleeds and other things like that. These late 70's carbs were all calibrated for strict emissions. Put one on a built motor, especially one with a radical cam, and they usually don't do too well ( even if you up the jet size ). This is where much of their bad rap comes from.

As far as your idle goes, if I were to just guess, I would say it's possible your idle circuit needs going through. You're probably just not getting enough fuel at idle even if you pulled the idle screws all the way out. Cliff Ruggles is a great guy to talk to about the specifics of that kind of stuff.

Your timing seems to be good. Personally I would think running manifold vacuum would by far be the way to go for you. You most likely could run a bit better with closer to 36 total, but that's just icing on the cake. You have bigger fish to fry first.

 

[CamaroAdam73]

The carb was built by ken at EverydayPerformance, memberlist.php?mode=viewprofile&u=11887#.UfznFJKp9N8 . He's TechG8 on here.

As for what modifications have been done to the carb i'm not 100% sure. I called him and told him what the carb was going on, sent him my cam card/engine spec and told him to set it up to run best with this setup, so hopefully the carb just needs bigger jets/ idle tubes.

DoubleV, i think you're right about the idle circuit. Yesterday i adjusted the mixture screws out (rich) some more and got my vacuum signal up to steady between 14.5 and 15" vacuum. If the idle circuit is lean, can that be solved by bigger idle tubes?

I know of Cliff Ruggles, I've always bought my rebuilt kits from him for previous Qjets I've rebuilt. I picked up his book too, lots of good info in there. I've had success in the past with rebuilding Qjets to run on STOCK application engines, being this was my first real performance build i wanted some outside help..

As far as my timing goes, i didn't want to make any moves until i knew for sure the problem wasn't in timing. Once i get the carb straightened out i'll tweak timing closer to 36 total.

I won't be able to get ahold of ken until Monday and i don't have anything other than stock replacement Qjet parts laying around so i'm dead in the water for now.

My friend has a holley 750CFM 4150/4160 vacuum secondaries, i was going to bolt that on today in place of the Qjet for now and tune it in to see what kind've a difference there is between it and the Qjet.

 

[Fox80]

Your timing seems to be good. Personally I would think running manifold vacuum would by far be the way to go for you. You most likely could run a bit better with closer to 36 total, but that's just icing on the cake. You have bigger fish to fry first

See Double V we can agree on something lol, If you have a donor carb that would give you an idea if it is for sure the carb you have needs work. Sounds like you have some money in the carb you have so getting that one to works would be the cheapest way to go, and them carbs do work well when tuned right

 

[CamaroAdam73]

If you have a donor carb that would give you an idea if it is for sure the carb you have needs work. Sounds like you have some money in the carb you have so getting that one to works would be the cheapest way to go, and them carbs do work well when tuned right

Pretty much. I've got 400$ into this Qjet right now, i know when they're tuned in they run really good for street usage.

 

[olds307 and 403]

Definitely sounds lean. Sounds like 20 base timing will put you where you need to be. I bet a Holley will be much better with such a big cam with mild compression. Plus everyone knows how to tune them.

 

[CamaroAdam73]

Do yall think a Holley would better suite my setup than the Qjet tuned in?

 

[Fox80]

I would put a Holley on it if it were my car, its times like these I think a Holley wins over all other brands, things like jet changes, fuel bowl level, and accelerator pump adjustments are ten times easier on a Holley carb. Like I said tho I have never had trouble tuning a Holley and keeping it tuned for any combo I had, yet have had nothing but horrible luck with Edelbrocks for sure and even Quad's on non-stock combos. Now that Summit sells the re-man style Holley carbs at such a reasonable price I think its hands down the best choice for motors like you have.

 

[DoubleV]

Do yall think a Holley would better suite my setup than the Qjet tuned in?

Not really IMO. I've seen Qjets run incredible on engines much wilder than yours. It just boils down to tuning and that's where a Holley shines. They're easier to tune and you can buy them already setup for 'racier' engines. With the Qjet, the starting point is usually much further away from where you want to be.

Just curious but have you tried the tip in preceedure with the APT as shown in Cliff's book?

Slapping on your Holley may be a good idea to help determine if you do in fact have carb issues. If it runs better, then you know it's gotta be something about your Qjet ( setup, tuning, or actual problem ).