HARRISONMIRAGE

At what throttle setting should my power valve come into play.I have a 9022 carb and it is on a 10:1 comp.502.The engine has a 224/234,112lsa roller cam installed on a 110 ilcl.It has aluminum heads with 2.25 intake valves,110cc chambers and 290 cc runners.The intake manifold is a RPM air gap and doesn't match the heads perfectly as it is large oval and the heads are roval.The way this is now I can cruise up 3900 RPM on the primaries and I still have 11" of vacuum.The power valve that came with this carb is 6.5".My primary jets are 90 and secondaries are 98.I don't get a vacuum drop to 6.5" until about 4700 RPM.Should the power valve come into play on the primary circuit.My idle vacuum is around 10"(it's a bit jumpy)so if I up the power valve I would imagine I would have an enrichment problem at idle.So to sum it up from idle to 3900 I am on the primary circuit,from 3900 to4700 I am on the primary and secondary circuits,and from 4700 to 5500 I am on all three circuits.It is a new motor and I seem tobe having a problem getting coulor on the plugs.I am mostly concerned about a lean situation from 3900 down on the primaries.

jspeeddemon

It would depend on how the intake distributes the fuel from back to front or front to back with primary and secondary sides staggered. Some open plenum intakes seem to be better at equally distributing the fuel to 1 and 7 as well as 5 and 7. Try the different throttle positions and see if you can get the ceramic to turn tan. Try not to run back thru the fuel curve slowing down, shut off at a safe speed and check the plugs. You can get different power valves and stagger them differently in the front and back, depending how you intake is moving the fuel being that you have a dual plenum with air gap. I think I would try a 7.5 in the back and a 8.5 in the front to see what happens. As well it takes a little while to color the plugs, won't happen instantaneously. Remember lean is mean, will cost you, not much harm for being rich unless excessive.

TURB02256

My guess is that the intake you are using on I presume aftermarket heads just woun't flow the air the heads are capable of. The RPM Air Gap and the standard Preformer RPM manifolds are set up from Edelebrock to not step on the flow of basicly stock factory porting.

TURB02256

I used a set of Edelbrock oval port heads on my 7.4 Seabold. They were ported to flow 290 CFM at .5 lift.
With no other changes stock cam etc. I tested three intakes the Performer RPM, the RPM Air Gap and the Torker. I felt no difference in performance between the dual plane manifolds (the air gap wasn't worth the price or modification of the 40 dollar supply hose). The Torker definitely did. It was much quicker out of the hole practically eliminated bow rise increased midrange power way quicker on acceleration to 5200 RPM (rpm limiter setting). Could have used a bigger prop for sure. The Torker probably stepped on the air flow a bit to and if I had my air flow bench then would have checked it. I have done a lot of port work since then and manifolds with some maxed out heads have I rarely found an intake manifold that wouldn't't step on air flow. Your vacuum readings just seem a bit high to me for the RPMs your turning possibly a manifold restriction. Just my gut feeling after reading your post.

TURB02256

You might even be running my heads I think a guy from Canada bought them.

PatriYacht

Holley doesn't list a 9022 carb on their website. Can you give a better description of your carb?

Liberator21

It sounds to me like you need to get your jetting straight. The power valve is designed for enrichment during heavy load open throttle (low vacuum) situations.
It is essentially a dump valve to give you enrichment when you need it. Cruising on the primaries, the power valve shouldn't come into play. Don't try to compensate for lean jetting with the power valve. It sounds like you have some other intake issues as well (previous posts). After you get things straight, find someone who knows Holleys to help you tune it.

HARRISONMIRAGE

The 9022 is a 4150 marine series holley 800cfm double pumper 30cc prim/50cc sec,primary power valve only.I am new to holleys and I guess what threw me off a bit is the power valve is in the primary bowl but in actuality it has nothing to do with the primary circuit.Turbo what are the negative effects of high vacuum due to manifold restriction other than lack of maximum performance.I only have about 1 hour on this motor right now.The heads are GM performance made by Edellbrock but I think the roval intake port might be special to GM.I know that GM lists a cnc ported manifold that matches these heads.The mismatch is minamal and is the right way small to big.My plan is to run it to the top of the primary circuit and jet for color,then run it up to the point just before the power valve opens and jet for color,the run her full open and if lean play with the pvcr size.I hope I don't have to get into drilling the pvcr.I gues I'll come back to my original question,at what point should I be shooting to have the power valve open.I have a consistant drop in vaccum from 4000rpm and up so it would be quite easy to pick the rpm the power valve kicks in at with the corresponding power valve.Right now it is at about 4900.My primaries seem rich to me from what others seem to be using but it runs good.I need more run time to get proper color I think.
Thanks fellow OSO members

TURB02256

Lets start with your cam. What are the lift numbers? I see a listing for GM aluminum heads 292cc, 112cc combustion chambers, 2.25/1.88 valves which look to be roval ports which are an Edelbrock design. Next what is your intended purpose for this engine and max RPM usually 5200 RPM for a Brovo drive. What boat are you using it in? If an intake is too restrictive it can really screw up the circuitry in a carb. I start my carb tuning with the idle curcuit then the accelerator pump circuit then the set the jetting for max RPM. After this is accomplished I start in on optimizing the ignition curve recheck all the previous carb settings then work on the power valve vacuum settings, power valve feed restrictions and final main jetting. I suggest getting one of the Holly timing books such as HP has and begin by reading it several times. The whole book to get a better understanding of carb circuits.

HARRISONMIRAGE

Turbo it is a zz502 cam that I advanced the intake lobe by 2* dergees to give me a 112 lsa.This also retards the ilca from104 to 108.I did a sprocket mod to instal it at 110.The profile on the lobe is the same.This gives me an intake closing at 42* after bdc witch is about the norm for this compression level.