350 holley help

**drtlvr** · 07-22-2013, 06:05 AM

I've been having a unique problem with heating all this year. This is a 2300 5.7 rods, wisecos, head cut to intake bolt holes, 500 lift solid cam, 350 holley and tri-y header. I've been running the same carb for years and has been running flawless. All this year it's been running lean and the motor gets 240 at the end of the race. The carb is a 7448 with a good metering block with power valve restrictors. Usualy ran 64 jets, now I'm at 68 and it loads up some off idle where I went up on jets. 4.5 power valve. The carb runs perfect other than lean. The tailpipe comes out the door. For the past few years it's been blacking the side of the car and no overheating. Now it's chalky white and gets hot. It ran cool last year and nothings changed that I know of.

**7uptruckracer** · 07-22-2013, 08:40 AM

I wouldn't lean towards carb. I've always run alot more jet like 74 with that setup, 25 squirters, white pump cam, 7psi. 3.5 power valve. I'd lead towards timing, or some kind of cylinder wall crack or head crack, or radiator problem.

**drtlvr** · 08-05-2013, 04:16 PM

OK...so I've went up to 74 jets and when the power valve opens it'll barely run until I get wide open on the track and my rpms have came back up to 8500 where it was leveling out at 7500. Should I just block the power valve and go up on the jets? What happens to a carb when it runs rich with 64 jets 4 years and all of a sudden it goes lean and end up going 10 sizes bigger on the jets? Everything is the same as the past years. Cam, head, new springs, bottom end. It runs perfect just too lean.

**return to dirt** · 08-05-2013, 10:25 PM

i would look for a problem some place else. i run about 64 jets on my 350. 74 or 75 is too big for a 350. that's what i run in my 500s. recheck your ign timing and cam timing.

olin

**drtlvr** · 08-06-2013, 05:58 AM

I'm thinking something's happened in the metering block. We freshened up an old Earl Parker 500 we used to run. If it runs good I know it's the carb. I agree with you on the jets, I've never had to go that high. We've checked all over this car for vacuum leaks, timing (cam and ign), fuel, etc....

**FlaviaBlackwelder** · 08-07-2013, 02:07 AM

But i think it is great..

**millerlt3** · 08-08-2013, 10:03 PM

It may be fuel delivery problem check the float level at idle but make sure there is not a problem with the float, needle and seat if its sticking as the fuel is being used it wont draw fuel into the carb also try a different fuel pump to see if that fixes it

**drtlvr** · 08-09-2013, 10:38 PM

Well I tried a 500 and didn't like it so went back to the 350 for the feature. 2.5 powervalve, 69 jets, still lean. New fuel pump going on it before next week.

**drtlvr** · 08-17-2013, 07:22 AM

New fuel pump fixed my problem. Thanks for the help

**checkeredflag2006** · 09-04-2013, 03:08 AM

Its little late on this post but on my 350 we run a 35pv 76-78 jets

**checkeredflag2006** · 09-04-2013, 11:20 AM

What fuel pump are you running kinda having same problem

**drtlvr** · 09-04-2013, 12:05 PM

stock ranger. Changed it and went back to original jets. I had 75 jets in it at one time and could barely get through the pits where it was loading up. She's right now

**Aden8100** · 09-11-2013, 11:42 AM

I am also facing the same problem with my car. I read out interesting and informative ideas. This will be sure helpful for me. thanks everyone...

**checkeredflag2006** · 09-23-2013, 01:38 AM

New pump fixed mine to!!

**dave41** · 09-24-2013, 06:35 PM

Originally Posted by checkeredflag2006

Its little late on this post but on my 350 we run a 35pv 76-78 jets

how can you get that much air and fuel mixture out of 350 cfm's

**let-r-eat** · 09-25-2013, 03:19 PM

OK gentlemen, let's think this out a little so people understand a little about jetting and what is actually happening. When the velocity through the carburetor is LESS you need MORE jet. That's right, an engine that isn't moving any air will need MORE jetting. Let's think about it some more. The air goes through the venturi and creates a depression that pulls the fuel through the booster. Withl less PULL from LESS velocity we will need a LARGER jet. With higher velocity air we will use a SMALLER jet. I want to run a SMALLER jet to achieve stoichiometric within reason.Carburetors are designed to use within a range of jetting. The style of booster used is the biggest contributor. Just think of your carburetor as one of those air blowers that has a hose running into a bucket to draw out parts cleaner or a paint gun that draws from a cup. The velocity of the air/size of venturi/placement of booster in the venturi are what contributes to the jet size. The emulsion metering inside the carburetor adjusts this to the varying velocities/such as WOT verses idle/part throttle.For instance: A very large cam at idle has a bunch of reversion happening that creates a LOW amount of velocity through the venturi with a large carburetor. Downleg boosters create more draw on the circuits than straight leg style booster requiring LESS jet than the straight leg booster would in a similar carb.Hope that helps.

**Big E tech** · 09-26-2013, 03:37 PM

Originally Posted by let-r-eat

OK gentlemen, let's think this out a little so people understand a little about jetting and what is actually happening. When the velocity through the carburetor is LESS you need MORE jet. That's right, an engine that isn't moving any air will need MORE jetting. Let's think about it some more. The air goes through the venturi and creates a depression that pulls the fuel through the booster. Withl less PULL from LESS velocity we will need a LARGER jet. With higher velocity air we will use a SMALLER jet. I want to run a SMALLER jet to achieve stoichiometric within reason.Carburetors are designed to use within a range of jetting. The style of booster used is the biggest contributor. Just think of your carburetor as one of those air blowers that has a hose running into a bucket to draw out parts cleaner or a paint gun that draws from a cup. The velocity of the air/size of venturi/placement of booster in the venturi are what contributes to the jet size. The emulsion metering inside the carburetor adjusts this to the varying velocities/such as WOT verses idle/part throttle.For instance: A very large cam at idle has a bunch of reversion happening that creates a LOW amount of velocity through the venturi with a large carburetor. Downleg boosters create more draw on the circuits than straight leg style booster requiring LESS jet than the straight leg booster would in a similar carb.Hope that helps.

Well said! The fact that a carburetor works off of depression is OFTEN overlooked...