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Discussion Starter #1 (Edited)
I bought a new 650 DP for the 406. Had a 750 with a single plane and the low end was, well, not. It's not a strong build, with pretty much all stock stuff (76cc heads and dished pistons to keep the compression down). The cam is .228 @ .050 with .480 lift, so not overkill.

Anyway... the 650 is from AED. It's the HO series DP and it's essentially a reworked Holley. Right out of the box it didn't work very well. The needle and seat on the rear bowl was stuck and gas shot out of the vent tube (what a pleasant sight!). I pulled that out and cleaned it (couldn't see any trash though), and got the float levels adjusted properly. Tweaked the 4-corner idle and off I went.

First impression - lot's more throttle response, and don't think I'm losing a ton off the top end, so it appears that the 650 will work, even though the majority was recommending a 750 (except Barry Grant, they said 650). It was a hard decision!

Worst impression - damned thing has slight hesitation at cruise speeds. Need larger primaries? It has a 66/78 combo. Next, the motor wants to bog and almost die on hard braking or hard turns when off the gas. Maybe the float issue again? Next, there's a slight starting stumble with moderate throttle. Has 31 shooters. Help!

The power valve is a 4.5. I have lots of vacuum, pulling 15" at idle, 19.5" at no load cruising at 2500 rpms, 10" with a moderate load, and 0" at WOT. I'm thinking an 8.5 valve is about right. I need some advice here as well.

So where's the best place to start? Jet's/shooter's/pump cam/valve? Take it back and get one that works?

:huh:
 

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I've been using an Edelbrock 600 cfm. Right now I'm investigating a Holley 4011. That's a 650 cfm spread bore with vac secondaries.

My guesstimates from your description are:

Cruise hestiation is lean.

Bogging on braking + turns is leaks past the needles.

Starting stumle is a combo of idle adjustment and accelerator pump.

What fuel pressure do you have? If more than 6, you need to reduce it. I'm using a Holley 804 regulator which allows me to send excess fuel back in the return line.
 

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change the PV to a #65 as the ones you have open too late causing you hesitation. if it is a HP you may need to increase the size of the PVR and go to smaller jets.
 

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Discussion Starter #5
Thanks for the input! Keep 'em coming...

Here's an excerpt from the other Forum...

Got on the phone a couple times with AED today.
They said their 650HO DP flows much more fuel than a stock 750 with Vac secondaries (tidbit since that's what I replaced).

They said the hard braking and foot off gas hard turning bog can be somewhat corrected by lowering the floats just below the sight glass, or to a point where it doesn't run out of gas. They said the Holley mechanical carbs have that inherent problem and usually just drops a couple hundred rpm's, then it comes back up. Said the vacuum Holley's don't have that problem.

....I tried the above and it seemed to help. Still a little bog, but not as serious....

Next is the hesitation at cruise speeds. They said that most always, the problem is from too little timing. I told them mine was 14 initial and 38 total by 2500 rpm's. They said that's most likely the problem. They recommend 26 degrees initial and 36 total, all to come in by 1500 rpm's. When they setup MSD distributors that they sell, it's always with a 10 degree timing spread. Said their carbs are only happy with this kind of timing. Well, If I'm cruising at 2500 rpms, and all the timing is in...what's the difference?

....no resolution for the above 'cause they've got me all confused with this one....

Where I was thinking lean, evidently things are too rich. Jets are 66/78. They said I could send it to them and they'll put their mod in the transition circuit which should help with hesitation (or something like that was deciphered from the techno-babble).

....I'm confused here as well. My thinking is that it feels like a lean hesitation like AlwaysWave mentioned. I'm also wondering why the 4.5 PV. Guess if these things are built for 'real' racer types, they'll have much less vacuum....

-----

They also mentioned that the back idle adjust corners should be in 1/2 turn more than the front. Huh? I told them I adjusted for max vacuum. They said wrong way to do it. At max vacuum, all corners were out 1.25 turns. I tried their recommendation of .75 rear and 1.25 front. Ran like crap! I'm back to 1.25 all around.

I'm thinking I got the wrong kinda carb, but I won't throw it on eBay just yet. It feels like there's some real live 'go' potential compared to the 3310 I replaced, so want to make this thing work.
 

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Discussion Starter #6 (Edited)
C'mon, Norval... jump on in here.. You must have had to work today!! :) :laughing:


Motorman... I bought some 6.5 PV's. I don't really want to fiddle with the restrictor holes... yet. Going to try the basics first (jets, shooters, pump cam)

AlwaysWave... the fuel pressure is about 4.5. Pumps are 30cc and the shooter's are 31.
 

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Chris I have really been busy the last few days. I am putting a machine shop in my shop and spent the last few days moving a mill and all it's accessories.

I run 2 850 double pumper 4 corner idle holleys and with the blown 454 get 14.4 miles to the gallon around town anytime.

I buy new carbs and pull then apart immediately and start from scratch modifying them.
I remove the choke horn and polish the venturies.
I drill about .100 holes , one each in all the throttle blades but the location of the hole is important,
I install .015 wires in each of the idle circuits.
I would install a 8.5 power valve in your case. Stock jetting seems to work with the leaned out idle circuit.
Set the front floats so that with the motor idleing the fuel just seeps out past the threads with the sight plug removed. That is the correct setting. Make the back just a tad more so the fuel just starts to run out.
Set the idle screws at 1 1/2 turns out, holleys are designed to run in this range.
Make sure the accelerator pump has no clearance between the arm and the lever on the pump itself.
If you notice off idle stumbling richen up the squirter. I end up drilling a few thousand bigger, give it a try and keep on going up until the off idle stumble is gone. Make sure to stuff rags in the ventura when removing the squirters to prevent it from falling into the motor.
All timing sould be in by 3000 with initial in the 15 range and the rest comming in with the distributor by 3000. I just set the total by reving the motor past 3000 and setting the max I want.
Sometimes the squirters get too large and the screw becomes the limiting factor so it needs to have a hole drilled in it too.

The motor under light cruising doesn't run on the power valve but in passing and going up hills it should kick in, then out again at the crest of the hilll.
The power valve should be just about 2 points below the cruising vacuum.
LIke is said before I don't like holleys but I know them and can get them to work very well. Out of the last 3 new ones I had 2 had major problems right out of the box and could never be used as is but after reworking they worked fine.
Get the idle leaned out and the cruising rpm will take care of itself.
I have an oxygen sensor and run 15-1 on the highway and the power valve drops it to 13-1.
Good luck
 

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Discussion Starter #8 (Edited)
Norval... Tnx for the info!

I'm still confused as to why cruising hesitation will take care of itself once the idle circuit is right (leaned, or maybe I misunderstood something). My first impression was larger primary jets since that seems to be the only thing added to the other circuits when steady cruising. If I'm sounding like I need to read "Holley for dummies", it's only because it's true. :laughing:

Off idle I understand how the cam, pump and shooters come into play, and also understand the PV boost issue, but remain stumped on the slight hesitation at no-load cruising (see " " above). Feels like lean hesitation, and the plugs aren't black, so I'm stumped...

So how do you get the .015 wire to stay in the idle circuits? L-bend to have the gasket hold them in place? I think I will go up on the PV as well, but want to try one thing at a time to learn more about what's happening. What's the best order of things to do, if there is such a thing...?

Here's the cool part of this... if the design works best at 1.5 turns on the mixture, and the transfer slot shouldn't exceed .040, how do you adjust anything! :huh: :laughing:

Oh, one other thing... Would using jet extensions help out the hard braking or off-the-gas hard turn bogs? Seems like I also read where that bog can be from gas coming out of the rear vent tube. Things did improve a bunch when I lowered the float levels. Also saw where Holley recommends trying 1/8" below the sight plug as a possible fix.

Oh, #2 one other thing... When I installed the Holley, I had to reroute the fuel line over the top of the heater hose, so there's a loop going up from the filter, over the hose, and back down to the carb feed lines. No idea is this can be an issue of any kind, but thought I'd toss that into the hat.

:smokin:
 

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Hesitation does not take care of itself, you have to fine tune the squirters. If off idle is a problem then slowing increase the squirer size after making sure the pump cam is in the richest setting, 1 or 2 I don't remember.
I slowing drill out the squirters until of off idle is smooth. If you exceed I think about .040 on each squirter the screw holding the squirter needs help also.
The holes drilled in the throttle plates allow the idle to be backed right off closing the transfer slots and allowing the car to idle striclty on the idle circuit. Having the idle set too high with the idle screw opens up the transfer slots, a no no.
I drill .100 hole in each throttle plate to start.
As for the .015 wire take the float bowl off and the metering block. Carefully take the large gasket off and there is a machined "Vee" groove. At the bottom of this "V" groove is 2 holes , one running straight in and one on an angle. The straight is the idle circuit and the angle is the power valve.
Take a 3/4 inch long piece of approx. .015 wire bend and L with equal length arms and insert one end in the hole and play the other branch on the metering block gasket surface, do this for each hole and replace the gasket, it holds the wires in place.
This leans out the idle circuit and makes the idle screws more sensitive.
These mondifications are also recommended by holley.
 

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If you are worried about fuel sloshing out of the breather tube you could try a hose inserted over both breather tube, that's one hose with one end on each of the breather hoses and a hole up out of the very top of the hose for breathing and hide it all under the air cleaner. I have seen this before to help with that problem.
 

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Discussion Starter #11
Ok, tried some basics today. Upped the PV from 4.5 to 6.5 and went from 66 to 68 jets in the primaries. Most of the time was spent getting that damned red coated gasket crap off the carb!! Who's the genius that came up with that brainchild!! :whip: Now using the blue non-stick gaskets.

Test drive resulted in no off-line or cruising hesitation. Perhaps a touch of initial hesitation accelerating up a hill, so will try a 7.5 or 8.5 PV and will also try messing with the cam and squirters. I don't think it needs much more. Will also try the wire trick to see if I can get the idle down a bit (at 850 now). The primary plates already have holes drilled in them, courtesy of AED. Haven't measured them, but they're not tiny. I probably don't need them.

Anyone have a link showing cam colors and effect? I'm using pink at the moment. The squirters are 31.

Thanks!
:buhbye:
 

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i will scan you a list of the pump cams and the CC volume each one produces
 
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