NCross

iTrader: (18)

I'm working on a friends car. 85 GS 12A stock port, MSD coils, RB Holley 465 kit, Mallory 6 PSI fuel pump. All stock otherwise.

I rebuilt the engine and found that after sitting for years the poor Nikki was beyond repair so he ordered a brand new Holley RB kit and Mallory pump.

After some slight adjusting of the float bowls, idle screw, and accelerator pump It is finally drivable, but there is a a periodic flat spot (notorious on Holleys?) under load in 4th or 5th gear. Usually uphill. Starts fine, idles fine, cruises fine, accelerates through the gears fine, top end is fine. Just an annoying periodic bog under heavy load in low gear.

Suggestions? should I really remove the float bowl screw to check levels while running as Ive heard? Also I can only get it to idle under 1200 RPM 50% of the time. Its either t 850RPM or 1200RPM.

Thanks!

wankel=awesome

Nah, they run perfect out of the box 100% of the time, the problem is your car, blah blah blah, RB has been in business for 30 years, blah blah blah, etc.

Seriously though, those things are junk. They are a power valve enrichment based setup, but the problem comes from the recent Holley castings only "read' vac drops from ONE of the primary barrels. With an individual style runner manifold like RB makes, the vac for the 1 rotor its reading doesnt stay smooth under load or even at idle. The flat spot you feel is the power valve popping open then closing repeatedly as it rises and dips below 8.5 inches of vac in the manifold.


Block it off, jet up to 53 or 54 main jet and for the love of god invest in a pump cam kit. Try your Rb factory white cam in the #1 position on the linkage. I still have no idea why they come delivered with it in the #2 slot. #1 is earlier shot, #2 is later.


Good luck with it man...

NCross

iTrader: (18)

I was really hoping for an easy fix. Like a regulator and larger primary jets. Im used to tuning nikkis. Is there a place or someone we could mail it off to for tuning?

NCross

iTrader: (18)

Thing is too... it runs great one time, shut it off and come back tomorrow... it runs like **** and needs adjusting. So erratic and it never keeps its setting. The fast idle cam jams or doesnt even come on sometimes too

wankel=awesome

100% perfect out of the box











Anyways, heres the deal. Rb "tunes" the 465 kinda stupidly. They overcome the problem of not having transfer slots exposed by boring the idle feed restriction out really huge. It doesnt fix the off idle drag, but it helps heaps to do this.

The problem with that "fix" is that the larger your idle feed is, the more impact changes in flow and conditions have on the low speed circuit.

Ever notice how sensitive the idle screws are when adjusting? 1 turn from "perfect" in either direction will almost kill the engine. That's plain wrong. So if you think of it like this: if the idle mixture screws are affected this badly by manual flow changes, how badly do atmospheric and conditional changes in flow or fuel density affect that mix?

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Because the circuit is performing this way, its hard to establish a set AFR at idle just because conditions are rarely exactly the same the next day or even hour as they were when you set them before. The larger this IFR is, the more that it becomes apparent.

The "correct" fix has been kicked around here on the forums by me and others for some time.

After getting your idle speed set on your carb, take it off the engine and use a coping saw blade to extend your transfer slots about .020 inch beyond the butterfly, as holley intended in the first place.

Once you've done this, youll notice its off idle conditions are perfect, but very rich. You will have to secure an unmodified metering block at this point, that has a normal .026 or .028 idle feed restriction in place. (down from the .113 RB IFR.) You can copy the RB emulsions tune pretty easily, but I wont go into how to do that here.

After you cut all of the excess fuel out of the low rpm circuit, your idle mixture screws will work properly and allow you to make minute changes to the AFR with "normal" ranges of screw turns, and thus control the impact changes in flow and density have on the idle circuit.

Once you have done all of this, youll need smaller IAB's (idle air bleeds, around 0.055) to allow your idle circuit to be more responsive and keep you in the correct ratio to run properly at low RPM's. You will also need to go to smaller HAB's (High speed bleeds, around .045) to allow your primary circuit to come online earlier and help transition from the newly lean cruise circuit.

Of course, now you are seeing why it is bad to pay extra money for a "pretuned" carb. I dont care how well someone is established or how experienced they may be. Every engine is different, and every application throws even more variables in that to make it so.

You should finish off your install with either the black, or orange pump cam set to the #1 position to address a much needed rework of the crappy pump profile that comes with those things.

Good luck, have fun lol. Post your results.


PS: the fast idle cam thing is super common, just have a look at the arm that rides the cam and youll probably see it is bent or not centered and binding on the side of the cam.

NCross

iTrader: (18)

Well weve thrown in the towel. were giving it to a puertrican in florida to tune. If he cant tune it no one can!

placd1

iTrader: (3)

Just once I'd like to see someone who's really dialed in the tuning on a Holley 650 double pumper! Everyone has a different take on what size idle and high jets to use, ranging opinions on what color cam to use in different positions and don't even get me started on the whole debate about AFRs at low speed vs high speed. Hollers are so damn affordable but require so much in depth tuning.

Jeff20B

iTrader: (13)

It just might be Nikki time. Good luck.

NCross

iTrader: (18)

Im a Nikki fan, but his Nikki even after a rebuild was toast. Accelerator pump circuit was unclogable. We felt it would be more reliable to just to buy a Holley. Oh well lesson learned.

wankel=awesome

The 650 is too large for me to ***** with. I have 12A's and 6 port 13b's. 650 DP would be overkill for any of them.

Jeff20B

iTrader: (13)

There's a way to unclog an accel pump circuit. If the little metal ball is stuck at the bottom of the accel pump section of the main body, you can flip it over, drill through the tiny brass or aluminum plug, tap out the stuck ball, then machine a small piece of brass or aluminum rod and tap it into the hole. Then stake it in so it can't leak, kinda like factory. This fix worked for me. I used a spare thin brass weight from a parts carb for this, and replaced the nasty ball with a healthy one from the same parts carb. It helps to have spare parts.

This fix won't work if the ball is stuck under the accel pump nozzle. I can sometimes tap on those with a small tool and little brake cleaner sprayed down into it, and they usually free up.