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Old 05-30-2009, 02:23 PM
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383 bog

I have a pro-built 383 stroker with the following parts: 350 4 bolt mains .060 over, block completely balanced & bluprinted. Forged crank, pistons, and keith black forged pistons-10-1 comp. Pro-comp alum.heads, cnc ported w/ 2.05/160 ss valves & 1.6 roller rockers Cam has 540 lift. not sure of the rest of the specs. MSD pro-billet Digital E-Curve #8394. This dist. has an electric vac,not an actual vac.advance. This is Chinese to me, but the builder installed it when it was built. Edelbrock rpm manifold,Quick Fuel 830 cfm dbl pumper carb. ( this probably over carbed- I talked with Quick fuel and they said the body is a 750 cfm) It came with 78/86 jets- changed to 73/81.,changed power valve from 6.5 to 4. My car makes 8 lbs. of vac. in gear at idle of 850 rpm. 1-1/2 headers; 2 1/2 exhaust w/electric cut-outs.350 turbo w/2000 (this is probably another one of my problems,not enough stall) Gears are 4.10 w/ 25" tires. ---When I try to take off from a dead stop the tires go up in smoke. If I floor it from a roll at around 1500 rpm the tires will start to break loose for 1/2 a second , has a small bog for another 1/2 sec. and when the tach hits around 2200 rpm the tires will go up in smoke all the way to third gear shift. I know this motor is not going to perform great at such a low rpm ( max torque is 485 @4200-max hp is 493@5900) but if I could just a consistent acceleration without a bog-even if it meant less hp.) Also it has a habit running on when warm. I've changed the inital up and down; currently it has 15 deg. initial have even tried pulling of the power wire to the dist. with no success.Could I get a back feed from te Auto-Meter 5" tach ? The car is a 65 rambler wagon ( close to a chey 2 , w/ a mustang 2 front susp. Car also has a high flow water-pump and a 1-wire alt.Any ideas.

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Old 05-30-2009, 02:33 PM
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Why the drastic change in jet sizes? 5 steps down on both the front and the rear is a ton, it should have been very close the way it came from Quick Fuel. What was your reason for the jet change?
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Old 05-30-2009, 02:43 PM
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It sounds like the carb needs more pump shot- I'd try a cam w/more pump duration first, if no (or not enough) help, go w/a bigger shooter and drop back on the duration. Increase duration again, if needed.

Have you adjusted the "vacuum" advance to see if that changed the run-on? It sounds something like a pre ignition-type thing, whether from a hot-spot in a cylinder, too hot plugs, but I'm thinking that the plugs you would have already checked.

I've not heard of that tach feeding back voltage, but a simple check would be to remove power to it and see if the run-on persists.
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Old 05-30-2009, 03:31 PM
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In response to the jetting I felt that since the carb. was bigger than necessary I would back it down. The carb has 4-corner idle adjustments and they are turned out 1/2 turn for best vac. The engine always smell rich, but thats probably an idle adjustment A friend brought me an 0 2 sensor & bung so I will install it and adjust from there. The squirters pump so much gas that I'm sure their not lean. I'm open to any ideas. I'm not a rocket scientist.
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Old 05-30-2009, 04:28 PM
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[QUOTE=stanjr41]In response to the jetting I felt that since the carb. was bigger than necessary I would back it down. [QUOTE]

This is incorrect thinking. A large carb does not become smaller because you jetted it down.

A carb works off of pressure differential, i.e. pressure flows from high to low.

Take your 830 carb for example and the jetting it was supplied with, and this is a hypothetical situation being used as an example. On your 383 it may provide a perfect fuel curve, put it on a smaller engine like a 302 and it will be lean. Reason? -- the 302 moves less air, and therefore "pulls" less hard on the jets and draws less fuel through them. The same carb on a 454 may end up pig rich because it "pulls" on the jets much harder and pulls more fuel through the same size jets. Understood?

Specific to your example, it sounds like you have created a lean hole in the fuel curve when you went so lean with the jets. Car will blow the tires off from a dead stop and the lean hole doesn't show itself because this doesn't put a real good load on the motor. Going from a roll, the accelerator pump shot "covers" the lean hole until the shot runs out and then the fuel curve goes lean because it is jetted too lean, and the engine struggles until it reaches a high enough rpm to pull hard enough on the jet to get enough fuel and start making good power again.

The 830 carb is by no means too big for your 383. We are running an 825 Demon on our 383, and because it is the Race version with removable airflow venturi sizing sleeves, we are going to change it to a 950 as we feel it is too small. This is a street/strip engine we race every other weekend.

I always tune the mixture screws for best vacuum, then richen each one 1/8 to 1/4 turn from this point to improve throttle tip-in from a low rpm rolling cruise, otherwise it will be too lean.

Last edited by ericnova72; 05-30-2009 at 04:46 PM. Reason: more info
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Old 05-30-2009, 04:45 PM
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I am running a holley 830HP on my 408 and have never done anything to it straight out of the box. bolt on GO. Dont know if these people are correct or not cant remember who it was but anyway they told me i could go up to 1000 cfm on my engine . Cole
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Old 05-30-2009, 11:01 PM
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383 bog

I agree with both of you concerning my jetting reduction. The car ran better with it as sent. I talked with a tech at Quick Flow and he thought I might need to lower the jet size, but I picked the size,not him- my fault. As for the power valve; he told me to check the vac. at idle in gear(900 rpm) which was 8 #. he said to change it to a 4#; so I assume that is right.The car still smell awful rich at idle and while driving. I know that carb has adjusable everything and what you can't adjust you can replace with a different size. I have been building cars since 1969 (probably at least 50 street rods and modified 60s era cars) I think I know just enough to get me trouble;and I have a bad habit of overthinking and overcorrecting my problems. I can be a danger to myself. But that's why I have you guys here to save me from myself. I have another problem that just surfaced a few hrs. ago. I started the car to go to a car show and the motor kicked backed off the starter. This happened 3 times in a row, and then the same going home. Sounds like too much advance. It's 10:00 here so I won't check it out till tomorrow.Initial is still 15 deg. Once starts it runs great. Thanks to ericnova72 and eloc431962 and cobalt 327.
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Old 05-31-2009, 10:43 AM
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Quote:
Originally Posted by stanjr41
I started the car to go to a car show and the motor kicked backed off the starter. This happened 3 times in a row, and then the same going home. Sounds like too much advance.
I'd agree- unless the starter is dragging or the battery's unable to spin the motor over with authority.

But most likely too much initial timing, like you think.
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Old 05-31-2009, 11:26 AM
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You are right. Somehow the timing had been bumped up to 20 deg. initial. I even rechecked it after I tightened the dist. down. The cap on this thing can move a little when you are turning it to set timing. It does have an option to replace the spring type over to a screw.which definately won't move. Only problem is that you have rotate the wires one spot or pull the dist. and rotate it- that's what I'll do when it's running right. Any ideas on initial-elect. vac and total timing? Thanks for your input. This dist. has two small dials to adjust the timings. My son watched me and said I may not have had it in the exact spot. I put my timing light on it and had a total of 8 deg. in the dist. for a total of 20 deg-not good. Will try resetting the dials I'm not sure ;but this getting to be a PITA. I readjusted the floats because they were a shade high. Maybe I should stick to one problem at a time; what do you suggest ?
FYI= I e-mailed my problem to MSD a week ago- no answer. On their forums there are a few people that have that problem of little or no responce.
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Old 05-31-2009, 01:32 PM
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Quote:
Originally Posted by stanjr41
Any ideas on initial-elect. vac and total timing?
Well, not other than the oft repeated (and correct) assumption that most SBC's w/o "fast burn" combustion chambers run well w/timing at about 34-36 degrees total (w/o vacuum advance) and an additional 10-15 degrees of vacuum advance.

Vortec and "fast burn"-type combustion chambers require less timing- somewhere in the area of 32 degrees, give or take.

As to how fast to bring the mechanical advance in, this will vary AFA variables like CR, gasoline quality, weight, gear ratio, usage- you know the list.

I have no empirical knowledge of your Pro Comp heads or their particular requirements for timing. I have read nothing but conflicting reports regarding the heads in general, so that leaves me w/o enough info that I consider valid, to comment on them one way or the other.

Quote:
This dist. has two small dials to adjust the timings. *snip* Will try resetting the dials I'm not sure ;but this getting to be a PITA.
If you have just started tuning this set-up, hang in there- those dials will become more "user-friendly" the more you work w/them.

They're a whole lot easier to deal w/than having to change weights and springs and likely more accurate to boot.

Quote:
I readjusted the floats because they were a shade high. Maybe I should stick to one problem at a time; what do you suggest ?
If it were me, I would return the jetting to what came originally.

Then, w/the floats adjusted correctly, adjust the idle mixture screws for best vacuum or best idle speed. During this you will probably need to also adjust the curb idle along with the idle mixture screws- just don't turn the curb idle up too much and cause the transfer slots to be over-exposed. You will know you've opened the blades too far w/the curb idle adjustment screw if you get an off-idle stumble that won't go away.

From there, I'd suggest setting the initial timing at a point where you get no starter kick-back and the engine will start and idle cleanly. Then you can begin working w/the dials that control the timing curve and lastly the vacuum advance.

If these dials came w/a baseline setting, begin from there and work forward.

Too much vacuum advance will cause a "surge" at cruise, too much initial can cause hard starting/starter kick back, too much total or timing in too quickly will cause the engine to "ping" or go into detonation. Obviously, this is to be avoided- and even if you don't hear it, it can be happening to a smaller degree. This is why total advance (again, w/o vacuum advance added in) is kept at or below 36 degrees for the "average" SBC.
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Old 05-31-2009, 02:24 PM
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383 bog

cobalt327 your'e exactly right. I am guilty rodding biggest mistake; IF BIG IS GOOD, THEN BIGGER IS BETTER. I am trying to make a high rpm motor work at low rpm. The car is light and has 4.10 gears,a 2500-3000 stall was reccomended, but around town I don't see much more than 2000 rpm. I was afraid to put the converter stall right in the middle of my cruising speed. I was afraid it would get too hot from the slippage. I am more concerned with a quick start than a top speed. (I can't afford a ticket, but taking off to fast isn't smart either). After NASCAR is over I will change the carb back to original. THANKS
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Old 05-31-2009, 04:52 PM
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Quote:
Originally Posted by stanjr41
The car is light and has 4.10 gears,a 2500-3000 stall was reccomended, but around town I don't see much more than 2000 rpm. I was afraid to put the converter stall right in the middle of my cruising speed. I was afraid it would get too hot from the slippage.
You want the TC to hit right at the torque peak RPM for the hardest launch. Considering your light weight and steep gears, the choice to run a 2K stall TC isn't quite so bad as it might first seem. It sure wouldn't have hurt to have followed the recommendations, though.

The heat build-up isn't seen as much w/a loose TC until you "work" the converter, either by hard launches or high speed cruising. Putting around town can be done w/a 2.5-3K TC w/o too much undue heat build up.

That said, you always want to use a good tranny cooler, plumbed either as a stand-alone unit (as is recommended by a well known tranny parts company) or as I prefer to do it- run the ATF through the radiator's cooler followed by the auxiliary cooler.

Quote:
After NASCAR is over I will change the carb back to original.
I was watching that and the drags that were on at the same time! lol

Good luck!
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Old 05-31-2009, 05:48 PM
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383 bog

I was watching NASCAR & IRL. Will change jets and see what happens
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Old 05-31-2009, 09:28 PM
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383 bog

I re-jetted the engine, set timing at 14 initial & 16 in (mech ?) electronic advance, reset idle screws. Now my bog is the worst it's ever been and runs on a shade when shut down. Once it reaches around 2500 rpm it runs great like it always has. I'm at a loss now. It seems like it's in the carb. I will call Quick fuel tomorrow.
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Old 06-11-2009, 08:13 PM
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383 bog

It's been a while since I updated my car. I installed a 3000 converter and I must be blowing by that bog since I can't feel it now-that's the miracle of a converter. Now the bad news. While working on my car, I revved it up to 3000 to check total advance. I did what I always have done and had a screw-driver setting on the radiator. When it hit 3000 the driver fell into my fan and came out and hit me in the left eye. I got 9 stiches, broken blood vessels in my eye, a detached retina, and a pupil that won't dialate. That was June 5. The Dr. grounded me; and today is the first day I can use the comp. So much for my mechanicing. Will have further on my car when I can work on it. Stan
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