Build engine
07-03-2022 | 07:09 AM
#71
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From: Croatia
Well….I guess you could be correct.
Floats set too low or needle and seats too small could do this also. Ie: keeping good pressure but not enough volume. One would think it would happen faster than a minute, but that’s just thinking.
Be careful running it the way you have (wot rpms falling after a bit) as this can cook things fast.
Floats set too low or needle and seats too small could do this also. Ie: keeping good pressure but not enough volume. One would think it would happen faster than a minute, but that’s just thinking.
Be careful running it the way you have (wot rpms falling after a bit) as this can cook things fast.
07-03-2022 | 07:17 AM
#72
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From: On A Dirt Floor
Thick one ? Don’t know what that means. What is the size ? Or part # ?
I’m working on boats all day, docks and boats yesterday, so won’t be around much.
Here in the states it’s July 4th weekend. Ie: Independence Day week end. Biggest boating and barbecuing days of the year. Reason Why many won’t be around on the forums.
I’m working on boats all day, docks and boats yesterday, so won’t be around much.
Here in the states it’s July 4th weekend. Ie: Independence Day week end. Biggest boating and barbecuing days of the year. Reason Why many won’t be around on the forums.
07-03-2022 | 07:36 AM
#73
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From: Croatia
Thick one ? Don’t know what that means. What is the size ? Or part # ?
I’m working on boats all day, docks and boats yesterday, so won’t be around much.
Here in the states it’s July 4th weekend. Ie: Independence Day week end. Biggest boating and barbecuing days of the year. Reason Why many won’t be around on the forums.
I’m working on boats all day, docks and boats yesterday, so won’t be around much.
Here in the states it’s July 4th weekend. Ie: Independence Day week end. Biggest boating and barbecuing days of the year. Reason Why many won’t be around on the forums.
needle and seats...i know you are a working man like i am...time diferenc makes problems..im very grateful for your time you spend on me...wonted to surprize you on 4 of july be the first one to wish you and ewerybody else all the best..only if you could take a quick look at my fuel pump and tell me is it a 40gph or smaller...if it is to small what should i order..a 80gph pump(wich brand)..tnx
07-04-2022 | 12:16 AM
#74
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Posts: 5,769
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From: tn
The ONLY way you are seeing fuel starvation with 12 to 14 psi of fuel line pressure (assuming 6 psi of WOT boost) is if your needle/seats size is too small.
Holley needle/seats are typically .110" size and the front and rear combined will flow 58 gph with fuel line pressure 7 psi higher than box pressure. If you are making 625 hp and jetted on the rich side, there is a chance you are POSSIBLY maxing out the needle/seat flow.
If you run the high-flow needle/seat (.120") those will flow (Front and rear combined) 71 gph at the same 7 psi delta.
If you install the high-flow units you should not have to worry about draining the float bowls unless you observe a drop in fuel pressure. At $35 per carb, it's cheap enough to install them to rule out the possibility.
Holley needle/seats are typically .110" size and the front and rear combined will flow 58 gph with fuel line pressure 7 psi higher than box pressure. If you are making 625 hp and jetted on the rich side, there is a chance you are POSSIBLY maxing out the needle/seat flow.
If you run the high-flow needle/seat (.120") those will flow (Front and rear combined) 71 gph at the same 7 psi delta.
If you install the high-flow units you should not have to worry about draining the float bowls unless you observe a drop in fuel pressure. At $35 per carb, it's cheap enough to install them to rule out the possibility.
07-04-2022 | 01:15 AM
#75
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From: Croatia
The ONLY way you are seeing fuel starvation with 12 to 14 psi of fuel line pressure (assuming 6 psi of WOT boost) is if your needle/seats size is too small.
Holley needle/seats are typically .110" size and the front and rear combined will flow 58 gph with fuel line pressure 7 psi higher than box pressure. If you are making 625 hp and jetted on the rich side, there is a chance you are POSSIBLY maxing out the needle/seat flow.
If you run the high-flow needle/seat (.120") those will flow (Front and rear combined) 71 gph at the same 7 psi delta.
If you install the high-flow units you should not have to worry about draining the float bowls unless you observe a drop in fuel pressure. At $35 per carb, it's cheap enough to install them to rule out the possibility.
Holley needle/seats are typically .110" size and the front and rear combined will flow 58 gph with fuel line pressure 7 psi higher than box pressure. If you are making 625 hp and jetted on the rich side, there is a chance you are POSSIBLY maxing out the needle/seat flow.
If you run the high-flow needle/seat (.120") those will flow (Front and rear combined) 71 gph at the same 7 psi delta.
If you install the high-flow units you should not have to worry about draining the float bowls unless you observe a drop in fuel pressure. At $35 per carb, it's cheap enough to install them to rule out the possibility.
07-04-2022 | 10:17 PM
#77
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Joined: Sep 2001
Posts: 5,769
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From: tn
If -
- you are running .120 needles and seats.
- you have 6 psi of boost (manifold pressure) at wide open throttle.
- you have (AND MAINTAIN WITHOUT IT CREEPING DOWNWARDS) 12 psi of fuel line pressure at wide open throttle.
Then - you are not experiencing fuel starvation at wide open throttle.
You HAVE to be certain that your fuel line pressure remains constant while at wide open throttle, without dropping after a few seconds or so.
If your pressure DOES drop as time passes at wide open throttle, then you should look at TWO places - fuel pump volume AND fuel pickup flow. If your fuel pickup in the tank is too small, you can starve. Sometimes, the springloaded anti-siphon valve on the pickup is a restriction that impedes flow - BUT IN ALL OF THESE CASES, you still would SEE the line pressure dropping.
- you are running .120 needles and seats.
- you have 6 psi of boost (manifold pressure) at wide open throttle.
- you have (AND MAINTAIN WITHOUT IT CREEPING DOWNWARDS) 12 psi of fuel line pressure at wide open throttle.
Then - you are not experiencing fuel starvation at wide open throttle.
You HAVE to be certain that your fuel line pressure remains constant while at wide open throttle, without dropping after a few seconds or so.
If your pressure DOES drop as time passes at wide open throttle, then you should look at TWO places - fuel pump volume AND fuel pickup flow. If your fuel pickup in the tank is too small, you can starve. Sometimes, the springloaded anti-siphon valve on the pickup is a restriction that impedes flow - BUT IN ALL OF THESE CASES, you still would SEE the line pressure dropping.
07-04-2022 | 11:00 PM
#78
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Posts: 258
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From: Croatia
If -
- you are running .120 needles and seats.
- you have 6 psi of boost (manifold pressure) at wide open throttle.
- you have (AND MAINTAIN WITHOUT IT CREEPING DOWNWARDS) 12 psi of fuel line pressure at wide open throttle.
Then - you are not experiencing fuel starvation at wide open throttle.
You HAVE to be certain that your fuel line pressure remains constant while at wide open throttle, without dropping after a few seconds or so.
If your pressure DOES drop as time passes at wide open throttle, then you should look at TWO places - fuel pump volume AND fuel pickup flow. If your fuel pickup in the tank is too small, you can starve. Sometimes, the springloaded anti-siphon valve on the pickup is a restriction that impedes flow - BUT IN ALL OF THESE CASES, you still would SEE the line pressure dropping.
- you are running .120 needles and seats.
- you have 6 psi of boost (manifold pressure) at wide open throttle.
- you have (AND MAINTAIN WITHOUT IT CREEPING DOWNWARDS) 12 psi of fuel line pressure at wide open throttle.
Then - you are not experiencing fuel starvation at wide open throttle.
You HAVE to be certain that your fuel line pressure remains constant while at wide open throttle, without dropping after a few seconds or so.
If your pressure DOES drop as time passes at wide open throttle, then you should look at TWO places - fuel pump volume AND fuel pickup flow. If your fuel pickup in the tank is too small, you can starve. Sometimes, the springloaded anti-siphon valve on the pickup is a restriction that impedes flow - BUT IN ALL OF THESE CASES, you still would SEE the line pressure dropping.
07-10-2022 | 03:51 AM
#79
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From: Croatia
Hy guys hope you are doing well...Tomorow im goin to try to solve my fuel problem on my 502 but before that i want to ask you guys can i use the distributer from a mercruzer 7.4 on my 502 to get rid of my car distributer...is it compatible..than you
07-10-2022 | 07:04 PM
#80
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Joined: Sep 2001
Posts: 5,769
Likes: 151
From: tn
There honestly is no reason to chase ghosts here. Don't throw parts at a problem until you have isolated the problem.
It has been established that your needles and seats are .120", so there is no reason to point at those as a restriction
You have told us that your WOT fuel line pressure (measured before the fuel line enters the box) is 12 psi and your WOT boost pressure (measured in the intake manifold) is around 6 psi.
As long as your fuel pressure STAYS above (boost psi + 6 psi) then you are NOT experiencing fuel system inadequacies.
Run WOT. Constantly watch the boost pressure and fuel pressure. Whenever the motor feels like it is starving for fuel, TAKE NOTE of those pressures AT THAT TIME.
If the fuel pressure remains steady and doesn't drop as you experience the "starving" issue, then you DO NOT have a problem with fuel supply.
You MUST get this test out of the way and behind you before you know where to focus next.
It may not be a fuel starvation problem at all.
You could have heat-soak which may be triggering ignition detonation. You may have a weak coil or ignition module which loses output when it heats up (under boost at prolonged max revs).
It has been established that your needles and seats are .120", so there is no reason to point at those as a restriction
You have told us that your WOT fuel line pressure (measured before the fuel line enters the box) is 12 psi and your WOT boost pressure (measured in the intake manifold) is around 6 psi.
As long as your fuel pressure STAYS above (boost psi + 6 psi) then you are NOT experiencing fuel system inadequacies.
Run WOT. Constantly watch the boost pressure and fuel pressure. Whenever the motor feels like it is starving for fuel, TAKE NOTE of those pressures AT THAT TIME.
If the fuel pressure remains steady and doesn't drop as you experience the "starving" issue, then you DO NOT have a problem with fuel supply.
You MUST get this test out of the way and behind you before you know where to focus next.
It may not be a fuel starvation problem at all.
You could have heat-soak which may be triggering ignition detonation. You may have a weak coil or ignition module which loses output when it heats up (under boost at prolonged max revs).
