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Old 02-14-2017, 10:21 AM
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There are a lot of NHRA class cars making big power with carbs smaller than 650.

I run a 625 Carter on my low compression 355 most of the time, as well as a single Holley 150 gerotor style pump. It has a large alcohol style stainless screen prefilter, no filter after that, a single inlet, and a bypass style regulator. The carb does have bigger needle/seats, but close to original inside. Still has the choke horn, but no choke.

Here's a graph from a 625 Carter test with the nitrous window switch set to 5000-6000 1st gear only. It has a FAST dual wideband w/ rpm module as well, but that doesn't record to the Racepak.



7800 on the 355 is like a 383 at 7200. It leans a little at high rpm, due to pulling enough hi-speed vacuum to suck the needles back down in the jets (kind of a built-in hi-speed leanout), would likely be a problem on a 383. Problem could also be a piece of fuel cell foam sticking a bypass open (had that happen on a Holley black pump long ago). Bigger needle/seats may help as well.

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Old 02-14-2017, 02:45 PM
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Nitrous being a two parts air it's not really the same thing as N/A stuff. No where did Voodoonova say anything about N20 nor does the the picture he/she posted show N20 lines. I don't think that style carb hat would likely be very good for air entry in the carb either so that makes me suspect. Feeding air/fuel to an honest 600hp is a bit different that feeding an honest 375hp and that would change my opinion of what might be the problem. I don't want to say it can't be making 600hp but in my experience it would need a custom Carb at least and that's going to cost $12-1500ish for a good one. All I can say say is check the pump valves and lines and filters cause the cell foam makes a huge mess when it breaks down and comes apart. I don't use it for that reason. I use cut and drilled PVC piping on square cells and wedge or tear drop cells when fuel burn off and slosh is an issue.
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Old 02-14-2017, 05:24 PM
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Quote:
Originally Posted by johnsongrass1 View Post
Nitrous being a two parts air it's not really the same thing as N/A stuff. No where did Voodoonova say anything about N20 nor does the the picture he/she posted show N20 lines. I don't think that style carb hat would likely be very good for air entry in the carb either so that makes me suspect. Feeding air/fuel to an honest 600hp is a bit different that feeding an honest 375hp and that would change my opinion of what might be the problem.
Maybe i didn't explain my graph well enough. The nitrous was only flowing for that brief period between 5000 and 6000 rpm, less than 2 tenths of a second. The only reason i mentioned it was to explain that what might look like a bit of wheelspin on the graph is actually a 225 shot. After it settled down, from 6500 on up was all NA thru the little 625 Carter/Edelbrock. A 355 spinning at 7800 only has to make 404ft/lbs to produce 600hp, the reason i posted the graph was to show power didn't fall off a cliff above 6500 because of the small carb.

The car is a little quicker with an 850, but it's still pretty quick and much easier to get races with the 625. I don't even bother with the 850 anymore.
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Old 02-15-2017, 08:21 AM
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I hear what you saying but is that carb on off the shelf Edelbrock/Carter? My guess is it's not.

1.69hp/cube is no easy feat for sure.
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Old 02-15-2017, 09:20 AM
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Quote:
Originally Posted by johnsongrass1 View Post
I hear what you saying but is that carb on off the shelf Edelbrock/Carter? My guess is it's not.

1.69hp/cube is no easy feat for sure.
It started off as an off the shelf Carter 9635. Melted booster skirts and throttle blades have been replaced due to a couple N2O backfires over the years, so it's got a combination of Carter/Weber/Edelbrock parts in it. I could buy a core off craigslist and most parts would swap right over, a few with minor modification. Nothing has been done to gain airflow beyond removing the choke and trimming the excess material from the throttle blade screws. Weights on the secondary air valve are stock Edelbrock with no trimming or added weight. Overall calibration is surprising close to stock with this cam.

Grant

Wanted to add, i'm running exactly the same Holley 150 fuel pump as the OP.

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Old 02-15-2017, 11:13 AM
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Quote:
Originally Posted by VooDooNova View Post
Hi,
I have a fairly new build carbureted 383 stroker that's pushing close to 600 hp on 93 octane, .that is starting to flutter/sputter at WOT and will actually shut down due to lack of fuel and I have to wait until the pump pressurizes and I pump the throttle and then starts right back up. does this hot or cold.
Its like the engine demand is sucking the carb. dry!???

I am running an Edelbrock 650 single line with a Holley 150 fuel pump and regulator that is brand new and is holding 8lbs of pressure at switch on and then maintains 4lbs at engine idle to 3000 rpms.

I recently cleaned all fuel lines and changed both fuel filters and their seems to be great flow.
I did find some fuel cell sponge residue in the fuel and then pulled and replaced the cell sponge after flushing the fuel lines.

air flow mixture is relatively stable sustaining 12.2 - 13.4 ratio.

it appears that all the vacuum hoses are fitted properly and not leaking and the timing appears to advance etc.. while accelerating.

I know this is a long post, but we are now totally lost as where to find the problem. Any Ideas???
Any help or recommendations would be appreciated

A 600 hundred horsepower 383 sucking through a 650 cfm carb? Let me in the trick!


Bogie
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Old 02-15-2017, 11:30 AM
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Quote:
Originally Posted by VooDooNova View Post
hi,
it is a Holley 150 electric fuel pump and regulator, (brand new)
I am running 3/8 steel braided fuel line front to rear.
the fuel pressure guage is at the carb, but on throttle rap test the pressure stays at a consistant 3 lbs.
I cannot duplicate the problem in the garage, only under a load while driving.
I can start out on a roll and rotate into the throttle to full and 1st gear is okay then quick shift into 2nd then act like no more fuel at about 38-4000 rpms and the car will shut off. I set and wait for the fuel line to re-prime and pump the throttle while starting and will come back, coughing and spitting until I clear it out.
the car runs ok at idle and as long as I don't ask much of it, like interstate driving. (no quick throttle oscillation)

filters, I cant remember what holley prescribed but whatever holley they said is, that is how it was set up. I think 100 pre-pump and 40 after pump
thanks
This sounds like hydraulic lifter pump up or valve float to me. If you have at least 2 lb fuel pressure at WOT, you don't have a fuel delivery problem.

Conventual hydraulic lifters are not suitable for high performance camshafts. You can get much better performance from a high performance hydraulic lifter camshaft with limited travel hydraulic lifters. Those are called "cheater" hydraulic lifters because the lifter preload is limited to .005" and the total plunger travel is limited to .050" by design. The limited travel hydraulic lifters cannot pump up and float the valves because there is nowhere for the lifters to pump up to.

I quit usin conventual hydraulic lifters in 1975.
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Old 02-15-2017, 06:33 PM
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Quote:
Originally Posted by MouseFink View Post
This sounds like hydraulic lifter pump up or valve float to me. If you have at least 2 lb fuel pressure at WOT, you don't have a fuel delivery problem.

Conventual hydraulic lifters are not suitable for high performance camshafts. You can get much better performance from a high performance hydraulic lifter camshaft with limited travel hydraulic lifters. Those are called "cheater" hydraulic lifters because the lifter preload is limited to .005" and the total plunger travel is limited to .050" by design. The limited travel hydraulic lifters cannot pump up and float the valves because there is nowhere for the lifters to pump up to.

I quit usin conventual hydraulic lifters in 1975.
Valve float die to lifter pump up is going to cause the engine to actually stall, then be hard to start?? What are you smoking, cause I want some too.

Lifter pump-up is not the primary problem here....it might be happening and be a secondary problem the OP will need to deal with later on down the road, but it ain't what is making the engine stall.
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Old 02-17-2017, 10:44 PM
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383 stroker acts like fuel starvation at wot

SO...
we have removed both filters and screens and recleaned them, adjusted and re-adjusted the floats, double checked that the holley hp 150 is actually producing fuel pressure at or above 5-6 lbs at idle and full throttle and still have a fuel starvation like issue at WOT.
We bring the engine up to temp, between 160-170 degrees and will do a rolling 1st gear run up, hit 2nd at full throttle and by the time I get to the 4800-5000 shift point to 3rd, I'm out of fuel and have to pump the throttle to get fuel enough to keep it from stalling.

I have a new 800 thunder avs that will be here tomorrow and we will see if the problem persists.

other than that, could it be ignition?

I had a V8choppers trike that had a 400ci dart racing engine with 575hp, running an edelbrock 650 as well, that had a similar issue and we chased it for months and then after the manufacturer purchased it back from me, they called me a couple of months later and said that the battery was shorting out under hard acceleration???? I have never heard of that before ever.
So, I hope that new carb corrects the issue.

I will keep you informed, and thanks for the ideas and advice.

regards
VooDooNova
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Old 02-18-2017, 05:32 AM
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I have had week ignition coils/CDI boxes act very similar to what you are describing.
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Old 02-18-2017, 07:04 AM
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Post a video. I want to hear and see it do w/e?
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Old 02-18-2017, 01:02 PM
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Hydraulic Lifters can pump up and stall the engine at high RPM. When the lifters pump up, the valves will not seat and your entire engine loses compression and stalls until the lifters bleed off. It is just like you switched off the ignition key. That was common before the factory first introduced the so-called "anti-pump up" lifters in 1966. Some GM vehicles were equipped with the pre-1966 standard lifters through 1969, before the factory inventory was depleted.

I have floated the valve with lifter pump-up several times until I got tired of losing and installed a solid flat tappet camshaft. I now would not use any lifters except the edge oriface solid lifters or the limited travel hydraulic lifters. Edge orifice solid lifters were introduced in 1964 for the Chevrolet 30-30 fuel injection cam. The limited travel hydraulic lifters were introduced by GM in 1969 for the Pontiac Ram Air 4 cam. The limited travel hydraulic lifters set at .005" preload and do not have anywhere to pump up to. The GM and aftermarket so-called "anti-pump up" lifters only adds 500 RPM to the effective RPM range before they pump up and float the valves.

When using edge orifice lifters, or restricted pushrods, it is a good idea to enlarge the small upper main bearing feed hole in the three center main bearings to match the 5/16" oil holes in the block three center main bearing saddles. That will increase pressurized oil volume to the main and rod bearings. Your engine will love it.

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Old 02-18-2017, 04:52 PM
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383 stroker acts like fuel starvation at wot

O.K.

just got the brand new edelbrock 800 cfm thunder series carb installed and fired right up.

tweeked it a little and adjusted idle and took off.

drove for about 10 minutes til engine temp came up about 160 and did the same scenario.

1st gear run up to 4500 the hit 2nd gear full throttle and drifted right into third.

it felt so good that I did the same thing again and the when I made it to the 3rd gear shift point, started fluttering again like fuel starvation.

i'm lost!!!

can anyone recommend a tuner in North Carolina?

I'm in Asheville, but will take it to Charlotte, Statesville, Bristol

regards

VooDooNova
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Old 02-18-2017, 04:59 PM
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Sometimes when carbs are too small the engine begins pulling a vacuum that seats the springs/needles/jets.
A vacuum gauge could probably help diagnose this.

It may very well be the carb floats bowls are too small as the needle and seats may be to small to feed the fuel demands.

Try lowering the pressure on the dead head style regulators. They don't equate fuel pressure to fuel volume.
They work by making the passage smaller to increase pressure but it passes less liquid.
Lowering the pressure(opening the regulator) might be the answer.
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Old 02-18-2017, 05:15 PM
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To add to what Johnsongrass1 said, there are larger hi-flow needle and seat assemblies for the Carter/Edelbrock carbs.

If you haven't rigged a temporary fuel pressure gauge and taped it to the windshield where you can see exactly what the fuel pressure is doing while at WOT and at the time the car starts blubbering ....then you are still kind of shooting in the dark, you can't differentiate between fuel starvation because the needle/seat won't flow enough OR whether the pump/line/filter/cell outlet could be the problem.

WOT testing in the garage tells you nothing, it has to be when the motor is under a high load and is really using fuel at a high rate.

If you have good pressure on the gauge at WOT 3rd gear when the motor starts blubbering, then it is a carb related problem....but if pressure isn't there to put fuel in the bowl then the problem is something before the carb.

You've got to get the info to nail one or the other down....or you can just keep throwing parts at it.

AutoZone will rent you a vacuum/fuel pressure gauge, just buy enough vacuum hose to "T" it in after the regulator, or right off the regulator itself.
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