Hello every one,
This is my first post here. I try not to ask until I can't figure it out on my own. But this is a little different. I am tring to get into bracket racing. I just finished my first serious engine. I have some questions about my carb, and am scared I may run it too lean and do some damage, so I need some opinions before I run the car any more. The engine is a 400 sbc. I have a 6 in. rod, 12.5 to 1 comp. brodix track 1 227 cnc'd at M2. Isky solid roller, Int. 290 seat 260 .050 .650 lift. Ext. 298 seat 264 .050 .645 lift. 108 lsa, in at 104, with 1.6 rockers. Untouched vic. jr. and a 850 cfm 4150. 1 5/8 pimary tubes, 3in.x10in. collectors. I litteraly went broke putting this together. Question is, I set the carb up with 83's to be safe. Anything over 3000 was a mess. I pulled jetting out of it until I was at 78s. I still seems rich. I can't read the plugs, they have a slight bluish tint. They don't seem to color.? I am scared of going too lean. I this was your engine where would you start? Jets, power valve, squirter, cams. And how would you guys tune this car. I have bad traction problems. Should I use mph or just go lean till det. and then fatten up a couple sizes? Thanks alot for any help. As you guys can tell I am new to this, 21 yrs. old, and broke . Also please critique my combo. I had to use some parts I al ready had. Thanks alot.
Alex
-what was the original carburetor number?
-are all the carburetor components stock for that carburetor?
-have these float bowls, meter blocks or the main body ever been messed with by humans?
-what are you using for fuel? how much fuel pressure?
-what do you have for an air filter?
-do you have a choke horn on the carburetor?
-What do you have for a torque convertor stall?
-what transmission?
-do you have a trans brake?
-what does the ignition system consist of?
-what altitude are you at?
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-Have you replaced the O-rings that surround the needle seat housing?
-how do you set the float levels?
-Are you using brass floats or nitrophyll (black) floats or white plastic floats?
-Do the float bowls have the captured checkballs in the pumps diaphragm well or do they use the orange rubber flapper checks?
-how large are the power valve fuel restrictions?
-What number power valves are you using?
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-What do you mean when you state "anything over 3000 was a mess"?
-Have you tried to get the carburetor right just on the primary side, by disconnecting and disabling the secondaries?
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-I would start with 80 jets in all 4 corners if you have approximately .060 to .070" power valve fuel restrictions.
-I'd set the floats with the bowls off and inverted to where you can slide a 7/16" bolt between the float and the ceiling of the bowls as that high level and a 1/2" bolt as a starting point.
-I'd have the fuel pressure regulated and adjusted down to 5 pounds max until you start getting things sorted out.
-Check the diameter of the needle seat hole and start with stock .110" viton needle and seat assemblies.
-For power valves I'd install a 4.5 in the primary as the high and a 3.5 as the low---and I'd definetly use a 2.5 in the secondary.
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-make sure the check needles are in there under the pump nozzle screws.
-try to locate the idle orifices and get the diameter of them, should be about .036" to .040".
-how far open is the primary blades up onto the transfer slot?
-if it's more than .025" then you need to get more air into the engine at idle so that you can close down the blades on the slots---and that may take more a lot more idle ignition timing than you have if you have a slow advance curve.
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-if you happen to remove the bowls and meter blocks look at the imprint on the gaskets to make sure they show positively the imprints of the main body.
-make sure the air bleeds are all open especially the little ones closest to the bowl vent tubes.
I did not get to the garage to day, so I will anwser what I can for now.
-what was the original carburetor number?
-are all the carburetor components stock for that carburetor?
YES
-have these float bowls, meter blocks or the main body ever been messed with by humans?
NO
-what are you using for fuel? how much fuel pressure?
110 TORCO, 6.5 LB.S
-what do you have for an air filter?
5 IN. TALL K&N
-do you have a choke horn on the carburetor?
NO
-What do you have for a torque convertor stall?
3000 IWOULD LIKE A 4500-5000
-what transmission?
TH-350
-do you have a trans brake?
NO
-what does the ignition system consist of?
MSD PRO BILLET, 6A BOX, 8.8 MM WIRES, 34* IN AT 3000
-what altitude are you at?
S.W. MICHIGAN ?
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-Have you replaced the O-rings that surround the needle seat housing?
NO
-how do you set the float levels?
RAISE IT UNTILL FUEL SPILLS OUT THE SIDE HOLES ONE THE BOWLS
-Are you using brass floats or nitrophyll (black) floats or white plastic floats?
WHITE PLASTIC
-Do the float bowls have the captured checkballs in the pumps diaphragm well or do they use the orange rubber flapper checks?
-how large are the power valve fuel restrictions?
-What number power valves are you using?
5.0 FRONT AND REAR, ENGINE MAKES 7 IN. AT IDLE
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-What do you mean when you state "anything over 3000 was a mess"?
MISSING BAD, SMALLER JETS HELPED ALOT
-Have you tried to get the carburetor right just on the primary side, by disconnecting and disabling the secondaries?
NO, BECAUSE MOST OF MY PROBLEM IS IN THE MID TO HIGH RPM
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-I would start with 80 jets in all 4 corners if you have approximately .060 to .070" power valve fuel restrictions.
-I'd set the floats with the bowls off and inverted to where you can slide a 7/16" bolt between the float and the ceiling of the bowls as that high level and a 1/2" bolt as a starting point.
-I'd have the fuel pressure regulated and adjusted down to 5 pounds max until you start getting things sorted out.
-Check the diameter of the needle seat hole and start with stock .110" viton needle and seat assemblies.
-For power valves I'd install a 4.5 in the primary as the high and a 3.5 as the low---and I'd definetly use a 2.5 in the secondary.
---------------------------------------------------
-make sure the check needles are in there under the pump nozzle screws.
-try to locate the idle orifices and get the diameter of them, should be about .036" to .040".
-how far open is the primary blades up onto the transfer slot?
-if it's more than .025" then you need to get more air into the engine at idle so that you can close down the blades on the slots---and that may take more a lot more idle ignition timing than you have if you have a slow advance curve.
-------------------------------
-if you happen to remove the bowls and meter blocks look at the imprint on the gaskets to make sure they show positively the imprints of the main body.
-make sure the air bleeds are all open especially the little ones closest to the bowl vent tubes.
-Personally I don't like and never use the white plastic floats and I think you have to drop the float level when using them.
-You have to get the fuel level under control inside the bowls first and that requires:
-A: new O-rings on the needle seat housings so that fuel isn't leaking past the housings.
-B: understand that the sight plugs are not always the same height so I would rather use dial calipers to set the float levels and if you pay attention to the adjustment nut you'll find that each 1/6th of turn or one wrench flat of the adjustment nut is worth right close to .025" of float level.
-So if you set the float levels at say .500" and later on you want to raise the floats .050" you rotate the nut CCW 2 flats to raise the float that .050".
-C:the diameter of the hole within the needle seat assembly is stock at .110" and for most every application is plenty adequate up to about 800 hp.
-if you have bad traction problems then you can't possibly be making anywhere close to what you think the engine will make for horsepower and at 3000rpm the engine is way down on total fuel flow requirement so you can be flooding the engine by having 6.5psi fuel pressure when you only need about 5 (at max power).
-Then if the floats/fuel level are too high, the boosters can suck the fuel way too easy and make the engine rich---so you could drop the float levels 2 flats at time until something bad or worse happens but I prefer to know the float level numbers using dial calipers.
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-12.5 compression ratio and wide open throttle at 3000rpm is not real good because the airspeed virtually stops when you open all 4 barrels at once at that low an rpm---and this causes the fuel to stay wet or unvaporized because there is no air speed or vacuum or heat to vaporize the fuel---so the fuel can't burn because it's wet so the engine acts like it's way rich which it is.
-Fuel has to be vaporized or evaporated into a vapor to burn so you have to work on "driving the carburetor" by not going quite to wide open throttle until the rpm gets up a ways.
-If you had a 5500 convertor with a trans brake it'd be an entire different deal and the engine would run good.
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-If the secondary ignition wiring has ANY places where the spark can jump to metal it will when you go to wide open throttle and this is fairly easy to find in total darkness doing a fairly hard stall test.
-if the spark is jumping off to the headers or out thru the boots to ground---or if the sparkplug gaps are too wide and the "spark dies on the vine"---those cylinders will not fire and that makes the engine act rich because it is.
-Personally I don't like and never use the white plastic floats and I think you have to drop the float level when using them.
WHICH ONES DO YOU RECOMEND?
-You have to get the fuel level under control inside the bowls first and that requires:
-A: new O-rings on the needle seat housings so that fuel isn't leaking past the housings. I WILL REPLACE THOSE
-B: understand that the sight plugs are not always the same height so I would rather use dial calipers to set the float levels and if you pay attention to the adjustment nut you'll find that each 1/6th of turn or one wrench flat of the adjustment nut is worth right close to .025" of float level.
-So if you set the float levels at say .500" and later on you want to raise the floats .050" you rotate the nut CCW 2 flats to raise the float that .050".
-C:the diameter of the hole within the needle seat assembly is stock at .110" and for most every application is plenty adequate up to about 800 hp.
-if you have bad traction problems then you can't possibly be making anywhere close to what you think the engine will make for horsepower and at 3000rpm the engine is way down on total fuel flow requirement so you can be flooding the engine by having 6.5psi fuel pressure when you only need about 5 (at max power).
-Then if the floats/fuel level are too high, the boosters can suck the fuel way too easy and make the engine rich---so you could drop the float levels 2 flats at time until something bad or worse happens but I prefer to know the float level numbers using dial calipers. I SET THE FLOATS AT 7/16. I SEE WHAT YOU MEAN WITH SIGHT PLUGS. ONE WAS HIGH AND THE OTHER WAS LOW. I WILL ALSO DROP FUEL PRESSURE TO 5 LBS.
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-12.5 compression ratio and wide open throttle at 3000rpm is not real good because the airspeed virtually stops when you open all 4 barrels at once at that low an rpm---and this causes the fuel to stay wet or unvaporized because there is no air speed or vacuum or heat to vaporize the fuel---so the fuel can't burn because it's wet so the engine acts like it's way rich which it is.
-Fuel has to be vaporized or evaporated into a vapor to burn so you have to work on "driving the carburetor" by not going quite to wide open throttle until the rpm gets up a ways.
-If you had a 5500 convertor with a trans brake it'd be an entire different deal and the engine would run good. A 5500 WAS IN THE ORIGINAL PLAN. BUT THE MONEY ALL RAN OUT.
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-If the secondary ignition wiring has ANY places where the spark can jump to metal it will when you go to wide open throttle and this is fairly easy to find in total darkness doing a fairly hard stall test.
-if the spark is jumping off to the headers or out thru the boots to ground---or if the sparkplug gaps are too wide and the "spark dies on the vine"---those cylinders will not fire and that makes the engine act rich because it is. EVERHING IS IN PRETTY GOOD SHAPE, BUT I AM GOING TO REPLACE THE WIRES ANYHOW.
Thanks alot, I am going to run the car some to day and will try this. I have 3.5 p.v.'s. Would they be better to use than 5.0's for now? I have anothe question. I would like to lock out my timing, for more consistancy. Do I need to wait untill I get my new converter? How will low speed drivability be affected? I am at 34 total by 3000 now, am I in the ballpark?
Thanks,
Alex
. Also please critique my combo. I had to use some parts I al ready had. Thanks alot.