SickSilverado

Hey guys. I seem to have a pretty rich cruise circuit. I can get idle fine- around 13-14:1. Haven't done WOT yet. But my cruise seems to always be around 11:1 or richer. I'm pretty sure my WOT will be close, so I don't want to change these jets yet. Will a lower power valve to come in later? Sorry I don't have a vacuum gauge or MAP...lost both in a recent storm. I think my problem is the 6000 stall since I have to give it so much gas to get down pit road(race only vehicle). I have a 4.5 PV in my bag but can order something else if needed.

Combo
LY6 with ported heads and 230's cam
6000 stall, TH400, 4.56 gears
29" tires

Carb
Holley 750HP
6.5 PV
72 Primary 84 Secondary jets
Fuel pressure 6.5

speedtigger

iTrader: (16)

The lower the number, he more throttle it will take to open the power valve. So, if you are shooting for leaner part throttle readings, run a lower number. If that doesn't fix it come back and let us know. There are other strategies that will.

Pop N Wood

iTrader: (1)

Temporarily borrow a map sensor from another vehicle. They are pretty generic.

Are you shooting for 11:1 at WOT? Seems awfully rich to me.

Here is a pretty good article about wideband tuning.

http://www.innovatemotorsports.com/r...FI_mileage.php

speedtigger

iTrader: (16)

Not a fan of that article and their "jumbo high speed bleed" strategy. What they fail to account for is what running their "jumbo high speed bleeds" will do the the WOT fuel curve. They would have done better to lean out the main jet and increased the PVCR. This is the most common and accepted way to lean out the cruise without upsetting the WOT fuel curve.

dogsballs

exactly what i did. had the primary jet up, but then opened up my PVCR's and jetted down primary heaps. thing drinks a heaps less fuel now as well.

SickSilverado

I found my MAP sensor. Not sure if it's still good, but I'll throw it on there. I only have 'til Saturday to get it decently driveable, so probably can't mess with bleeds/IFRs yet.

I guess it came out wrong, but what I meant is that I think WOT will be close to where I want it(12.5-13:1). I just hate that on the way to the starting line it goes stupid rich like 9,10,11 rich. With this stall it pretty much seems like I'm almost going WOT when I'm just doing maybe 20-30mph. I got a 4.5 PV in there now, so gonna try it in the morning. I also bought a 2.5 and 3.5 just in case.

Pop N Wood

iTrader: (1)

The good thing about that article is they give you a nice, methodical approach to the problem and some guidelines as to where you want the AFR's to end up.

The Holley book I have, the one you didn't like either, discusses how double pumpers are notorious for having overly rich main jets and undersized PVCR channels. He said they did this purposely because it is better for performance. But it was also his opinion why double pumpers have a reputation for being gas hogs. Open up the PVCR and lean out the mains for better economy. Basically turn it into a street avenger. A full race machine might want to go the other way.

To the OP, at some point your power valve has to open, and if you are running that flipping rich you definitely need to back off on something. I keep thinking I run a 750 DP with a 71 primary jet and 6.5 power valve and the AFRs seem near perfect. You have an HP and a lot more cam, but you seem to be getting a bunch more fuel. Weird.

SickSilverado

Maybe I get so much fuel because I'm cruising at 3000+rpm? Or maybe I have a really strong signal with the Mast intake and HVH super sucker spacer on top of that? I got my timing set to 32* from 700rpms up. I idle at around 1000(I dont't remember why I wanted it that high).
I did check out that article...good info. Are the PVCRs any better in the Quickfuel billet blocks compared to the stock 1990's Holley blocks?

speedtigger

iTrader: (16)

The quick fuel billet metering blocks are better because the PVCRs are replaceable jets. So, it makes tuning much easier.

SickSilverado

Ok, I have those blocks, but they're in a annular 850 Demon. I'd love to just run my Demon, but this badboy gets straight up blubbery at my cruise rpm. I should have those other 2 powervalves tonight. You think that might make the Demon OK for my combo?

SickSilverado

Well I tried the 4.5 power valve and it seemed ok on the short drive. If I watch my speed it'll stay around 11.5-12.5:1 (15mph max). If I get into the pedal any more than that, it goes 10/9:1. Haven't got to go WOT, State trooper lives a block away from me...so you know. My 3.5 and 2.5 are on there way.

SickSilverado

Is there a rule of thumb when enlarging the PVCRs and lowering the main jets? Like if you go this big then reduce this many jet sizes?

dogsballs

not sure, i opened mine up ~%10 and dropped 10 jet sizes (i run e85, so have monster jets).

i personally think changing to smaller PV isn't the answer, lots of people run the 6.5

Pop N Wood

iTrader: (1)

+1. Probably the second to last thing you want to be screwing with right now.

Your jets are way too big if you are running this rich.