Tuning HP 1000 main circuit for street

[CDN]

Need some guidance on tuning for street use only now Holley HP 1000 BLP billet baseplate and metering blocks Have the idle and cruise afr ALOT cleaner dual sensor set to Average AFR with dual plane intake 475ci bbc 250@.050 cam 9.8 cr manual 5 spd trans 4.30 rear

Idle @ 1050rpm 7hg AFR 13.9 -14.0
Cruise up tp 2100 14.2 -14.7

As soon as I get into the mains it goes into 12's pretty much 12,5 what can I do to to make the curve more gradual ??

IFR .033 IAB .070 ( when it warms up may try .073 ) MAB .028

Thanks

[rgalajda]

Smaller main jets

[rgalajda]

If it goes rich when you get into the mains the main jets are too large . Air bleeds won't help yet. You need too reduce main jets until you are at least 14:1 AFR.

For typical non oxygenated gasoline 14.6 to 14.8:1 stoichiometric fuel , naturally aspirated engine.

Rich at idle 12.5 to 14:1 , lean at cruise 14.5 to 16:1 ,( leanest mixture which the engine will tolerate without missing or surging in level road cruise and moderate to intermediate acceleration). Leaner or leanest at part throttle acceleration until the power valve opens and rich at WOT , 12.5 to 13.4:1 AFR.

Idle AFR will be dependant on camshaft specs. More duration equals less vacuum requires richer idle.

Minimum fuel consumption at idle usually requires the vacuum advance adding about 20 degrees more timing . ( this was done away with in light of emissions )

Lean cruise of say 60 mph will be dependant on vacuum advance adding timing to as far advanced as 45 to 55 degrees.
A typical performance Holley carb should be able to achieve 15:1 AFR at cruise.
A Quadrajet or Cater carb can acheive 16:1 AFR at cruise.

[CDN]

Tks yes I guess Now to jetting down more
Ive already jetted primary down 3 sizes from original when jetted for best power on dyno

AFR numbers are the average of the 2 sides dual plane intake it is never equal at idle /low rpm so now just check the average ???

Car is idling and cruising very good and I can cruise easily in low 14 "s or better One thing Ive noticed and it makes sense as I lean it out its more sensitive to engine temp actually intake/ carb temp

Currently at IFR .033 .070 IAB .025 Mab mains dont start til about 2200 very happy with that

The engine can be at 160/ 170 cool here still
but it does not run real nice and or the afr is solid until intake has been fully heated Having an air gap intake it does take longer engine at 170 intake is still cooler when I ck with gun

I now dont adjust mixture screws until after a good heat soak that definitely makes screws more sensitive

I have primary screws out 2 turns Sec screws out 1 1/4 It is what is seems to like
I know the internet says all should be the same but thats what it likes so maybe something is not quite right yet ?????

I have adjustable Wagner PCV
adjusted it 1/4 turn in from recommended to reduce flow and that picked up idle vacuum and helped the idle mix sensitivity so far no issues from reduced flow

Yes more timing at light load high vacuum would help currently still running locked at 38* no VA plan to change to a mech curve with a VA at some point

Overall very happy with how it runs on street idle and cruise way cleaner now Starts fine you need to feather throttle when cold more now that tells me pbly too rich before

IDLE AFR is now 14.2 at 1050 rpm 8-9hg when fully warmed up

I dont really believe the idle AFR is truly 14.2 because of the overlap on my cam I think its about 40* 250 ish @.050 109lsa

Question : How much does cam Overlap at approx. 40* during dilute idle AFR numbers ????

Thanks for all the input been a learning experiencing taking a strong running carb at track to run nice on street

[rgalajda]

Is that the annular booster 80514 carb or the down leg booster 80513 carb ?

What size jets are you at now ?

What temp thermostat are you running ? Did you test the thermostat for accuracy ?

If they are down leg boosters , are they stepped ?

Idle mixture screws on 4 corner idle should be around 1 turn out if IFR is sized right.
What is the secondary idle throttle opening set at ?

Question : How much does cam Overlap at approx. 40* during dilute idle AFR numbers ????

Hard to put a number on it. Too many variables .If your gauge reads 14.2 at idle , I would assume it may actually be 12.2-13.2 ? Don't worry about idle AFR reading
That's a lot of cam for a true street car, but oh well.

I run a 180 thermostat , and in the spring and fall run a partial rad air flow blocker. But I am in southern Ontario, Canada. Where are you?

I must say that you have made good progress.

[CDN]

The t stat is good I checked it Robertshaw I have a very robust cooling system the clutch fan engages about 170F
Im in Arizona for winter with car it has been unusually cool here so hard to get it warmed up on short drives esp on cool days

Anyway its the 80513 stepped downleg booster carb
jetting was 83/91 best power on dyno
now 80/89 PVCR is .070 IFR .033 IAB ,070
I know the internet says out 2 turns says IFR too small but when IFR was .035 plugs were sooty at idle /cruise at track WOT was 12 5 which IMO was a bit rich but safe

The IFR now at .033 plugs look way better in street driving actually top thread is still alittle sooty

it idles great wont stall even when cold just chugs away at 7-800 then when fully up to temp idles at 1050

Yes a lot of duration for 475ci street car but in current tune it cruises real nice 1800-2000 rpm in 5 th on highway can lug it down to 1650-1700 although have light flywheel still so not the best below 1700 in 4th or 5th
Its a custom designed HR cam with hybrid lobes currently running .903 solid roller lifters lash very tight so have lost some actual duration with the lash

Be nice to get idle mix screws in more but it dont like it primaries any less than 2 turns is not smooth loose vacuum the sec are out 1 1/4 ish so assume it idling more on prim

Not sure how to get idle mix screws more sensitive and in more Have not restricted the transition slot size its a BLP billet baseplate the slots appear more precise / smaller then orig holley baseplate

All 4 throttle blades are drilled P trans slot is squared off sec blades is just cracked open well below trans slot both blades open same amount

More curious then anything what the idle AFR really is I realize with alot of overlap at 1000 rpm the shown 14.2 is not reality the cruise rpm 1500-2200 rpm is always in the 14's will get to 15,s in 5th under very light load at highway speeds

One thing before I turned in the sec idle mix screws to 1 1/4 AND reduced flow of my PCV it idled at 13.8/9 after the pcv and sec idle mix adjust it went to 14.2 ( again these are average numbers of the 2 banks so told me its leaner

Im more curious how much the overlap skews the idle AFR it dont make sense to me that this motor witht this size cam / idle vacuum about 9-10 will idle nice at 14.2
I would expect mid 13's at best
Right now Im tuning by the plugs and performance ........... no stumble pulls hard once in the mains although have not got on it hard alot down here 91 pump gas not great here in Phoenix compared to home

Ive never had a problem getting a carb to make power and not stumble on hard acceleration etcetc but this street tuning with a big a dbl pumper Holley is chalenging for sure