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Old 06-12-2010, 12:53 AM
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carburaetor psi

what is the maximum psi an edelbrock model 1314 800cfm can run.
today I was at the track and my Z28 was comng to life then nose diving,time after time ,its a 355 11:1 comp xe 268 cam a carter gm6624 120 gph fuel pump 041 fully ported heads an msd streefire hei ignition 1.6 roller rockers 1 5/8 headers i had the regulator set to 5.5 psi as the calibration book stated,a gentlmen with an 8 second nova overheard me talking to my friend about this problem,by the way my best time was 15.84 @94 mph with an M21 and 3:42 gears,he recommended I increse the fuel pressure by 1 psi, which i did,voila I ran a 14.43@98.6mph now how can that be if edelbrock recommends a maximum of 6.0psi but prefers 5.5psi if 6.5 did that would 7psi be even better.I'm lost on this one.

Any thoughts on this one I like the reliability of the 1412 its a daily driver so for now I am not interested in Holleys.
PS it only does this at the track. On the street she goe sideways down the the street in the first 2 gears regardless of the rpm even @ 5.5 psi.of fuel pressure.

Anyone I'm all ears.

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Old 06-12-2010, 01:11 AM
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My first thought would be that maybe the regulator is off by 1 psi.
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Old 06-12-2010, 05:16 AM
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Sounds like you've got some tuning to do.

The '68 elcamino I had with a non-original stock-bore 350, 186-camels (un-touched), HEI, Performer manifold, 0-1850 Holley, Isky 256 supercam (small...), mechanical fuel pump, Saginaw 4-speed/3.08 open 10-bolt...clocked high-14's/low-15's with one-legged tire-spin.

800cfm is a little on the big side, in my opinion.
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Old 06-12-2010, 11:58 AM
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carb psi

Fair enough but why in the daytodady driving does she she perform flawlessly street highway having alittle fun on the back roads?
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Old 06-12-2010, 12:22 PM
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Sounds like a lack of fuel volume to me. Lines, filter or pump(or a combination of the three) are not big enough. Works fine when you are blowing the tires off on the street( not much real load on the engine) as compared to less spin (and more engine load) on the traction prepped track surface. More load = more fuel used.

Raising pressure is just a band-aid and diagnostic move, not a solution to the problem.

Is the pump mechanical or electric?? What size lines??

How do you know your fuel pressure gauge is accurate?? Check it against anything else to verify??
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Old 06-12-2010, 08:55 PM
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Quote:
Originally Posted by ericnova72
Sounds like a lack of fuel volume to me.
I think Eric has nailed it.
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Old 06-13-2010, 08:45 PM
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carb PSI

I have 3/8 lines tank to carb, summit 140 gph billet fuel filter, carter 120 gph freeflow mechanical pump when I pulled the k&N xtreme flow 3 inch filterassembly off it did th the 14 secoond run, next time around put the filer assembly back on went 15.68@88mph could the secondary butterflys be playing open close due to an air restriction or air guidance problem,the linkage is mechanical on the carb but for the air to be drawn into the scondarys the weighted flaps/butterflys might not be opening for the whole run.I dont know would trying a holley /street demon for an experiment help, either in DP or VAC secoodary,650-750 in size, Eric you seem to think logically what do you think.
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Old 06-13-2010, 09:10 PM
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I have no experience with the extreme K&N lid, but it has lots of reviews by real professionals with real dynos that all show a power loss with this lid. Lots of theories as to why but no conclusions.

I have personally seen just a dirty K&N filter slow a car that much and it did not look dirty to the naked eye at all, if we hadn't bought a new filter to be able to rotate use and cleaning of them we would not have suspected it.

If it has been to a body shop you can gaurantee it is dirty beyond how it looks.
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Old 06-13-2010, 09:30 PM
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carb psi

You think a straight 3 inch fram paper filter will work best
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Old 06-13-2010, 09:37 PM
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Quote:
Originally Posted by sapsz28
You think a straight 3 inch fram paper filter will work best
Just wash the K&N and recharge with the correct oil.

Take a look at your fuel filter size and all internal sizes of the fittings in the fuel system. You may still have a delivery issue. Get a pressure reading at load, tape a temporary fuel pressure test guage to the windshield so you can see it. Just setting it at idle doesn't ensure it is right under load.
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Old 06-13-2010, 10:09 PM
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You will never see a Fram filter of any kind on anything I drive.
They're cheaper for a reason.

See for yourself. Buy a Wix filter and do some comparisons.
--No I don't work for Wix.
--Yes, there are lots of people on this site that will tell you the same thing.
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Old 06-13-2010, 10:17 PM
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In regards to the fuel pressure, it was recently suggested to have a fuel pressure guage temporarily mounted externally, but visible ... in order to see if the pressure is maintained or not at WOT under load.

Low profile air cleaners can also be quite restrictive. I'd recommend one of those Moroso (big) air cleaners ... if you have room for one.
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Old 06-14-2010, 05:04 AM
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carb psi

Dont carry wix air filters up here in Pickering Canada but we do have a Napa parts store as for oil filters I use a 2qt Moroso or K&N.
Eric I'll take my fuel system apart after the pump an look for any restrictions.

Thanks Guys.


Anyone else got a theory.

Last edited by sapsz28; 06-14-2010 at 06:22 AM. Reason: grammar
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Old 06-14-2010, 05:36 AM
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NAPA filters are Wix filters.
They just drop the first digit of the part number.

i.e.
Wix 51061 = NAPA 1061
Wix 42098 = NAPA 2098

etc.
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Old 06-14-2010, 01:06 PM
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Quote:
Originally Posted by sapsz28
Dont carry wix air filters up here in Pickering Canada but we do have a Napa parts store as for oil filters I use a 2qt Moroso or K&N.
Eric I'll take my fuel system apart after the pump an look for any restrictions.

Thanks Guys.


Anyone else got a theory.
My theory is a too low float setting. This is allowing the engine to effectively drain enough fuel to cause the porpoising as the pump refills and the engine subsequently uses the fuel from the too-low float bowl.

Along w/the low level sloshing back and forth- causing the jets to cover then uncover- would cause it as well.

The raising of the pressure effectively caused the fuel level to behave as if it were higher.
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