bhaas

I went to the track the other day. Car ran like total ****. Bogged worse than before, all the way down the track in all gears. The mods I did from the last time I was there were: New distributor and regapped my plugs to .045 from .035. Went to a lighter spring in my carb, switched from 87 to 92 octane and timing was at 6 deg BTDC and moved the vac advance hose to ported vacuum so the vac adv was coming in till over 1000 rpm. I did manage a 13.95, but I red lighted and still had a RT of .719. What's up with that? Wouldn't I have no RT if I red light? Well any way, my timslips were much more consistent last time then this time. I know there is low 13's in this car. I see I still have some work to do. I am # 4126 on the timeslips.

Brad...

F-BIRD'88

Well at least ya got a 13 sec time slip.

When you are setting the timing at 6 deg BTC @ idle
what is your total timing at high rpm with vac adv disconnected?

Al-though they vary by origional aplication, most HEI's
are set up with 20 degrees advance built in.

6+20=26 at high rpm

should be 32 to 36 deg at high rpm , that would be 12 to 16 at idle

If your car detonates when set like that, either you don't have 92
octane gas in the tank ( could be mixture of left over 87)
or your carb jetting is too lean (a constant wot bog could mean lean too) , or the motor is overheating.
Or wrong heat range spark plugs.

what jetting/rods is in your carb now and what spark plugs are in now?

bhaas

My timing is at 26 deg at high RPM's, when I hook up the vac advance and rev it to high RPM's I get about 50 deg adv. I have all 92 octane in it. I was on my second tank of 92 when I went to the track. My car was almost out of gas when I put the first tank of 92 in. My carb is totally stock. Edelbrock 1412 800 CFM. I put the stock metering rod spring back in. I'm also using the Autolite 103 plugs. My car seems to run great on these cool mornings. No bogging at all. It was quite hot at the track. About 80 deg. Do I need to readjust the carb depending on how hot it is maybe? If so how? Could I do it with a vacuum gauge? I'm pulling 14" of vacuum last time I checked it. Thanks.

Brad...

F-BIRD'88

Ok your timing should be 32 to 36 deg total at high rpm
with vacuum advance disconnected so you have some work to do.
When you get that sorted out. The amount of vaccuum advance
added is/will be too much.
Should add about 10 to 15 degrees vaccuum advance
under high vaccuum cruise conditions.
Look on the vacuum canister linkage plate
Factory gm vacuum canisters are stamped with a number
that relates to the amount of advance that that caister causes.
Some aftermarket vaccuum cans are adjustable
you adjust them with an allen key in the vacuum port
to adjust the rate, and you limit the travel of the rod to adjust
the amount of advance.
Try this, reset your timing to 32 degrees @ high rpm and leave the vaccuum
advance disconnected temperairly.
Road test the car with vac adv disconnected and see if it still detonates at full throttle.
If it is ok now at 32 with no vaccuum advance
then your problem is/was too much vaccuum advance.
If your vaccuum advance canister is not the adjustable type,
you can try using the one off your old distributor. Or get one from another old distributor. The number if degrees of advance is stamped on the mounting plate. look for a 10 or 15.
20 may or may not be too much but 25 is too much.
Check the jetting in your carb. Jetting should be .113 pri
.107 sec and a .071x .047 metering rod.
You can go to edelbrocks internet site to see how to tune your carb or get the edelbrock tuning manual for your carb (owner manual). There is a tuning kit specific to your carb that has a relevent selection of jets and rods to fine tune your carb.
You can bet that your carb is set up rich "out of the box"
because this is a safe way to sell universal carbs.
Being a little rich won't hurt a motor but too lean will burn one up real quick.
You can probably lean down the primary side with jet and rod combinations and get some performance and mileage gains.
Generally a carb needs to be richer on cool clear weather
days and leaner on hot muggy days.
Bogging is usually and indicatation of lean mixture. Either lean jetting, not enough accelorator pump or lack of fuel flow.
Some times a car will have a rich bog caused in hot weather
(fuel perkulation) Fuel boiling in the cab bowls or in the fuel lines.
usually after sitting hot and restarting or while idleing
for a long time in hot weather.
Gasohol... gasoline withn 10% ethanal tends to do this in hot weather. It is more volotile. Many brands of 92 octane gasoline use 10 % ethanol to raise octane.
Just raise the idle speed for a short time after a hot start to clear the hot gas from your fuel system before racing will avoid this hot stumble.
Let me know how you make out with this. Takes a lot of patience to get a car dialed in sometimes.

bhaas

The other day at work I checked my vacuum advance and it looks like it adds another 24 deg. That seems a bit excessive. So that could be a prob right there. I haven't had too much time to mess with it too much. It's too hot for one. This heat is killing me. I might be able to do some testing this weekend. I do appreciate the help. Building the motor is the easy part. Dialing it in is kinda tough. At least until I figure it all out. Thanks.

Brad...

ATOMonkey

Definately run w/o vac advance hooked up. That will only cause problems. Run a heavier spring if it is bogging. A lighter spring opens the secondaries early and if you don't have the fuel or air velocity it fall right on it's face. On muggy hot days you want to use an even heavier spring because the air is so bad. I doubt it's a metering issue in the carb. The timing is all fubar. You need to be able to see total advance around 3000 RPM. If not then you need a new dist spring. Total advance should be 30 w/ the vac off. Car should run much more better.

F-BIRD'88

I hear ya about working in the hot weather.
Summer has finally arrived here in Ontario with a bang.

I picked up a used Edelbrock 750 performer carb today.
Gonna install it and experiment as soon as I pick up some fuel fittings.

I've had the same Holley 715vs carb (Ford) on numberous cars for 25+ yrs and got to know it pretty good. The Edelbrock should be interesting, might even pick up 10th or so.

bhaas

I set my timing to 32 deg BTDC with the Vac adv. off and drove the car. Ran awsome. Didn't think it had it in it. I loved it. I'm gettin there. Now, when I hook up the vac adv to non ported vac to see what it is,it goes from 12 init to about 35 deg. That is way too much. I know as soon as I drive on that it'll ping/knock like right now. I tried the allen wrench in the dist. to see if I could adjust it. Seemed like it kinda grabbed on something in there sort of but I wasn't able to adjust it that way. Anyone know what size the allen wrench is that I need? And which way do I turn it to lower it? I have a CSI distributor that I bought at National Auto Parts. It may not be adjustable. But I want to make sure. I'm gonna call them and see if they can tell me. Also, will it hurt to drive around with no vac adv? Ok, I just called them and they said it probably wasn't adjustable but I can run without it if my car runs fine and doesn't ping or knock it'll be fine. I'd like a second opinion on this. Do I need vac adv? What purpose does that serve? I think I might have it dialed in. Just need to go to the track and see. That ain't gonna happen till the 19th probably. Thanks.

Brad...

ATOMonkey

All vac advance does is help the car idle and drive at part throttle. If it already does those things well then it's not a problem. I ran mine w/o advance all the time. Mostly because my engine doesn't hardly make enough vac to work it. Anyway, just leave it off. The worst it's going to do is give you a hit on fuel economy. Let's see those time slips.

bhaas

Coool. Fuel economy is the least of my concerns. I do wanna try and run 87 octane again though. I can now that I don't have that vacuum advance screwing me. I won't get to the track till the 19th probably. Just called the track about a minute ago to see if they had racing this Wed. (They usually do on Weds.) But not this week. Bummer. I hate waiting. And I have to work the next Wed.
Oh well.

Brad...

F-BIRD'88

I drove my car to the Track last night with my new (to me)Edelbrock carb.
I got a little pinging at hi cruise too like you did. (with your vac advance hooked up)
I seems that the Edelbrock carb's timed vacuum port sends a healthy signal to the distributor vacuum advance.
Now my 20 deg advance canister is too much. I'm going to cut it back to 12. I'm going to go one step richer on the primary cruise curcuit by changing the metering rods from .071x.047 to .
068x.047,, as full throttle was ok. This carb gets better mileage than my holley.

F-BIRD'88

Your bogging could have been caused by vapour locked fuel lines.
This happened to me at the track last night.
My fuel line comes up and over the valve cover to the regulator
on top of the manifold and along the manifold to the carb fuel fitting. The fuel line and regulator were too close to the hot manifold and valve cover. And my car bogged miseriably
the first time down the track. I tie wrapped a strip of wood under the fuel line and regulator to keep it off of and insulate it from the hot manifold and valve cover. Presto...No more vapour lock bog.
Wood is about the best cheap insulator/ isulator from heat that there is. If something like that is why your car bogged at the track, try this.

bhaas

I have a rubber fuel line running from the drivers side snaking inbetween the power steering and through the water pump down to the mech. pump then up to the carb. It does get a bit hot. But since I got my timing set right and not running any vacuum advance the car runs killer. I was getting down on it hard on the way home this morning from work. Blew my top radiator hose. My cooling system has been killing me lately. Just bought a new radiator then the T-stat goes out 3 days later now the top hose is gone. At least all this hasn't stranded me anywhere (yet). Might get to the track this Wed. if I'm lucky, but on the 19th for sure. Can't wait. Thanks.

Brad...

F-BIRD'88

I would replace all that rubber hose, especially on the suctionside of the fuel pump. When it gets hot and soft (just like your rad hose) it will collape, shutting off the fuel. or worse it will burst causing a fire.
I'm suprised they let you run at the track with the fuel system plumbed like that. It's is a true fire hazard and it will let you down
sooner rather than later. You want no more than a few inches
of unsupported rubber hose in your fuel system.
Not a good idea to drive without the vacuum advance hooked up.
It makes your cylinder walls and valves run cooler
and increases gas mileage. replace the vacuum canister with the right one with a lesser vac rating, as soon as you can.

my heat soak problem didn't show up till I drove to the track
50minutes then idled all through tech inspection.
By the time I got to make my first pass, my car was nice and heat soaked. So thats why it vapour locked half way down the track.

But the wood strapped to the fuel line fixed 'er up.

AlkyIROC

I agree with the rubber fuel line. Get rid of it. Run a hard line or a reinforced steel braided line. I used #8 Aeroquip 3000 psi hydraulic type hose for fuel line.

My distributor has no mechanical or vacuum advance. It's set to full advance and it stays there all the time. My ignition drops the timing back up to 20 degrees for starting. I don't recommend having a locked out distributor for street use but it wouldn't take much to swap distributors and reset the timing at the track.

If you're using the older large cap HEI distributor you should pull it and and have a look at it any way. Sometimes the weights get worn out on the pins and bind or seize up. I've seen cars in the junkyard like this and wondered if the owner always complained about a lack of power. You'll need to pull the weights off to inspect them and the pins.