77 350 w holley street avenger. wanting to get everything running perfect. if i set timing at 6 and then try to set at about 32 at 3000 rpm the idle timing is way off 6. ?????? now when i set air/fuel mix i hook vac gauge to vac line coming out of manifold right? then keep turning both screws till i get the gauge to the highest point??? right any hints advice appreciated thanks

 

The initial timing is probably moving when you set the total timing because your trying to get a total of 24 degrees advance. Your distributor may be set up to only allow less than this. Maybe 20 total.

How big is your cam? 6 initial isnt much. You may be able to put more timing in it than that.

For the idle screws, what you said sounds about right. Set the timing first, then set the idle rpm you want. Then adjust the screws for max vacuum at idle.

 

Set it to as much centrifugal advance as it'll take (32-34 degrees or so), as quickly as it'll take it (2500 RPM or so), and let the initial advance be wherever it ends up to achieve this.

 

going to buy an advance timing light tomorrow. SUBSCRIBED!

 

You don't even need an advance light, you can mark the balancer at 34 degrees if you prefer.

 

sorry to hyjack usmc949803.... but how?

 

Accurately measure the diameter of your balancer, multiply by pi, divide by 360, multiply by 34. Accurately measure this distance from the zero degree mark on the balancer, and make your mark.

 

i will do that in the morning! THANKS!

 

hell... cant sleep, i have 8" balance and came up with 2.373". is that right? and do i mark clockwise or counter from zero

 

That's right for an 8" balancer. The engine rotates clockwise, so you want to make your mark 2 3/8" clockwise from the TDC mark to get 34 degrees BTDC.

 

If you have ANY kind of performance cam in that engine (especially if it is still a low compression 1977 350), you will need a lot more than 6* initial advance. If this is an HEI distributor, it probably has around 24* mechanical advance. That means you can set your initial at 12* and get 36* total. 12* initial still isn't great, but it will do. Tell us more about the engine?? After this, you need to move onto the vacuum advance and the springs in the distributor (to allow the mechanical advance to come on sooner).

Get the timing curve set before you try any carb tuning. Any timing tweaks will affect the carb tuning!

 

it is an hei dist. po put the 77 350 bored 355 with holley avenger carb. says he put an aftermarket cam in but i dont have specs. so im working somewhat blind here.

 

also i put a "timing tape" on the 8" balancer so i can set timing wherever.. so i should get it up to 2500 rpm and set at 34?????

 

Warm the car up and then turn the idle down as low as it will go without stalling. You should be able to get down to 700RPM or so. Now, set your initial at 12* (just to be safe). Next, rev the engine a few time to see if it is advancing. Where does it stop and at what RPM? Work your way up slowly. If, for some reason, the distributor allows a ton of mechanical, you don't want to go much over 36* total.

You need to do all of this with the vacuum advance UNPLUGGED and the port at the engine covered (no vacuum leak at the engine). Don't just start your engine and set the timing at 34* at 2500RPM. That tells you nothing about your curve.

 

Not just that, you need to make sure that the distributor is fully advanced at that speed. This will require replacing the weights and springs in a stock distributor.

 

ok got it pretty close. when i put in gear and hit gas slight hesitation......

 

when you tune that holley use the vacumn gauge. Go all the way in untill each idle screw LIGHTLY bottoms out, then go out 2 FULL TURNS. Start the car, set the idle to were it wont stall, with the vacumn gauge hooked up, turn1 idle mix screw in or out untill you get the highest vacumn reading (take note of how many times you turned it) do the same to the other side,(We are looking for the highest vacumn reading) each idle screw MUST be turned the same ammount (ie 1 turn each or how ever many you did on one side you have to do on the other in or out) Whan you hit the highest vaumn reset you idle to were you want it. Recheck your timing and reste as needed and your done. This has worked for me for years and is how holley says to do it.

 

Check you acclerator pump you might be off a little. Looking down into the carb with the engine off, you should see fuel as soon as you move the throttle, if not the pump arm is off and thats were it hesitates.

 

Need more description...is this when it is just idling and you tap the gas? Or, is it when cruising and you floor it? There are many things that could cause hesitation or a stumble.

Two of your best friends will be a vacuum gauge inside the car (and hooked to manifold vacuum source) and an O2 gauge in the car. I have a narrow band (wish I could afford a wide band with data logging!).

 

at idle. put car in gear. hit gas. hesitation......

just found a new 02 sensor sitting around from my last camaro. at some point im going to get fitting welded into exhaust then hook this one up to an aftermarket gauge. just using external vac gauge right now.

 

i see the fuel coming into the carb (looking from top down)

 

Whats you initial timing at right now? The hesitation problem may be in the carb, but your timing can cause it too. I just delt with this myself on my car after swaping intakes.

 

had it at 8 then about 34 at 2500

 

Did you have the vacuum advance hooked up? If not, try adding that to the mix. 8* initial is still pretty low. 34* total means your HEI is adding 26* mechanical. If vacuum advance doesn't fix your problem, bump up your base timing to 12* (38* total). See if that makes it better or worse. If none of this helps, we'll move onto pump cam and squirter tuning.

 

Did you fix the advance rate yet? Is it fully advanced at 2500?

 

let me reword this i set intial at 8. then got rpms up to 2500 and set it at about 32/34

 

Can't do that...you don't know how much mechanical advance is left above 2500RPM...it could be 10 more degrees! Set your initial back to 8* (at 700 RPM) and rev the crap out of the engine to see where it maxes out at.

 

alright just went back outside. i have the vac advance from the the dist detached and plugged. plug where the advance went into carb. set timing at 8 and curb idle to 700 this all correct?????

 

Sounds good. Now rev it up to at least 4000RPM to see where the total mechanical advance goes to.

 

If this is a stock HEI distributor, start here below "THE ADVANCE SETUP". https://www.thirdgen.org/hei

 

And you see the gas spray the exact second you hit it? there should be NO DELAY at all. If there is then the acc pump is out of adjustment. If not let me know and I will go to step 2.

 

so ill have to get someone to bring car up to 4000 rpm and check timing at 4000

 

You should be able to do it yourself. You only have to bump it quickly (not rev and hold). We just want to see the max it will go to. From 8* to XX*. Once we know the max, we can adjust the initial so we don't go too high at max. Then, you set the rate at which max comes in (around 2500RPM is probably close).

 

as soon as i pull on accelerator it comes out and rpms go up. only does it in gear

 

i can do that but cant see the tach. will that matter?

 

it is an aftermarket hei dist . mallory i believe

 

This can be made simple. Warn the car up, shut it off, unplug the vacumn advance from the dist. Hook up a vacumn gauge to the intake, start the car, adjust the timing to the highest vacumn reading you can get(could be as high as 19-25, tighten the bolt,then check with the timing light to see what you have without the vacumn advance hooked up.Timing should be set at the normal foot off the gas idle no higher, the vacumn and mechanical advance take care of that. All these timing numbers being told may not make a difference, because IF there is a mild cam base numbers mean nothing because you dont know what cam is in it, and therefore the base timing will be different than stock. The idea again is to set the timing to the highest vacumn reading you can get with the gauge, then put the light to it and see what it is. You have to take the unknown cam size into account here.

 

No not yet it doesnt. Set the low speed idle to were you want it and were it will not stall. Worry about RPM after the timing is set. Base idle will be around 700 or so.

 

If that is the case then the vacumn advance can be adjusted also. Dont worry about that yet, get the base timing set first.

 

As one of the other people here said, lets make sure the timing is as dead on as we can get it. If the timing is off then the normal advance will be off and that will cause hesatation also. We can worry about that a little later. Hell getting the timing right may fix everything. The carb should be the last thing checked. So for the time being lets stick to the timing untill you/we get it set dead ***** on.

 

check your Privit messages. I just replied to you.

 

i got 45 degrees at 16 on vac gauge at 750 rpm idle.

 

You mean at idle with the vacuum advance you are getting 45* advance? That is fairly normal. My car idles at 52* advance and 13" of vacuum (1100 RPM idle speed).

 

im going to say 50 and about 13.5 vac 800 rpm idle right now

 

just hit the gas a few times back and forth in driveway. no hesitation so far. need to take it out on the street and see i guess

 

thats the test see how it runs in the street. Its all about the basics when tuning a car. I hope the pms helped.

 

runs great. launches from dead stop. thanks to all. now i guess ill tune the carb now that timing seems to be set.

 

You shouldnt have to now. At best just set the idle and leave it alone.

 

Shouldn't have to tune the carb?

 

No not at all. the problem was with the timing he set it and the hesitation went away. he said as much in the post. so no need to adjust anything but the base idle speed.