My Problem is both cruise and WOT. I just got it running with the new heads a couple weeks ago. I had to drill the IFR to get it to idle. I went .046 on the prim and sec. metering blocks IFR. Now im thinking maybe i shouldn't have drilled the sec. metering block, being i only have idle mixture screws on the pri block. It idles at 13.5:1, but crusies at 10.5:1 and quickly goes lean to 15:1 under WOT before i let off at 8 lbs of boost. My Combo is:
'85 351W block
Vic Jr heads
MP T70 .96 A/R
Performer intake & k&n carb hat ( I started this project under the influence of the old toohighpsi.com days. hence the intake and carb hat
crane cam .510/.520, 230 duration, and 112 lsa
Mallory maxfire 15 deg int, ramping to 35 deg by 2800rpms with a 1 deg/psi retard
E85
A1000, 13202, -10 feed and return
homebrewed 650dp carb
82/96 jets,
IFR .046 front and back
PVCR .090
P/V 2.5
Air bleeds untouched so far
Any ideas on where to go. Previously I was using the factory iron heads and tried to run too much boost/timing with pump gas and blew a head gasket. however I had the A/F holding steady at 11.5-12:1 @ WOT on 91 octane with this combo minus the these heads and distributor. Im thinking about blocking off the high speed air bleeds to help WOT lean condition. Maybe open up the idle air bleeds to help lean out part throttle and cruise. Does this sound good? or should i aim elsewhere. thanks. Keith

 

Here are a couple pics I took with my phone. I'll get some better ones up soon.

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plug the rear high speed bleeds and put .025 high speeds in the front and see what ya get. And put in an earlier opening power valve like and 6.5 or 8.5.

Make sure the T-slot is only showing about .040 on the primary side. If its way more than this it can cause your cruise to be rich.

I think the carb hat is hurting you some.

 

I was thinking something along those lines, my t slots were about equal squares before i fiddled with the idle screw. I got some 8/32 cap screws and im going to drill and tap my air bleeds so i can adjust them. probably tomarrow. I should know more friday when i attempt to drive it 30 miles to work. I will try the power valve also. I wonder if opening up my IAB's or closing up my IFR, or just reducing main size would be the best start on leaning out my cruise and part throttle. Thanks for the advice tbird

 

What rpm are you cruising at? Most times crusing has activated the main system at least a little if not all the way. You have a large front jet so you may need to drill the body and restrict the transition circuit some, but you have to be careful not to restrict it too much cause it can affect how it takes the fuel before the mains kick in.

 

I cruise 60 mph at 2500 i believe, I have 26 inch tires, 2.73:1 gears and a C4 so its not too high. I think that would be right on the edge of the main circuit

 

what kind of power you looking to make outta this thing? you should be able to get the carb to work but it'd be better to see a 750 on there with a better hat. also trying vent tube ext. wouldnt hurt either. should help cruise a bit. i would strongly advise keeping a eye on your backpressure as i made 632/700 on 15lbs with my 351/70mm same heads but diff other parts and it was all out by 4900 and then it was dead

 

500 rwhp is my goal. I tried a few mods on the carb and it is getting better. I set the secondary butterfly to expose .020 transfer slot, none was showing. Then moved the primary to .020 slot showing, about .120 was showing. Closed sec IAB with wire from .042 to .025. Closed sec HSAB with wire from .022 to .005. changed jets from 82/96 to 77/99. First 2nd gear pull it blew the hose off the wastegate and boost went to 18psi before i noticed, i was watching the wide band. It held at about 12.5:1 and the tires went up in smoke and very quickly hit the 6200 rev limiter about the same time i saw the boost. After watching the log it started at 11.5:1 and went to 12.8:1 at 6150 @ WOT. I don't think it hurt anything. It now cruises at about 12.5:1 also. A new problem though is it wants to go really lean and die when i pull up to a stop, unless i pump the throttle a couple times. other than that it runs pretty good.
I was thinking about changing the main jets to 72 and maybe open up the pvcr to .105 from .090. Maybe that will drop my cruise A/R and richen up the WOT to where i can jet it down a little. Or should i try some more air bleed mods? Maybe some vent tube ext. will help it maintain the A/F more steady.
Also i was wondering if others are having trouble with oil coming out the valve cover breathers. I guess i may need to look into a separate tank and plumb over to it from the valvecovers. Thanks for the help. I am going to try and see the potential of this bonnet and intake. I hope to get it on a dyno here within a month or so, once i get all the bugs worked out. Keith
EDIT... I just used the handy search button and found a million threads on the valvecover issue, so forgot i mentioned it.

 

Well i switched the mains to 70, opened up the pvcr to .125, and changed to a 4.5 PV. The good news. it now cruises at about 13.7, but with a nasty lean spike at part throttle and starts to miss. I did a 2nd gear pull from 2000, it pauses for a sec the took off, spinning the tires. the A/f is leaner now at 13.1 at WOT. maybe i cant flow anymore through the main wells. or should i modify the secondary metering block for a PV. :hmm: I got some better pics, once i figure out how to resize them

 

have you tried vent tube extensions yet? kind of crude but they do work pretty well

 

Here are some more pics. I haven't tried the vent ext. yet, but i probably will and see what happens, i read a lot guys putting them on and some taking them back off

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i had put them on mine and they had worked good for me. some people only need one for front or rear but its worth a shot cause its cheap

 

If you didn't modify the main well, cross-channel or booster that is probably your problem. If you keep going bigger on the secondary main jet and the PVCR and it won't fatten up any more at WOT that is probably your issue. Especially if it leans out at higher RPM.

 

Well i closed the sec throttle back down cause there was a large gap when i opened it up enough to show the transfer slot. I think that was the worst part of my lean spike at part throttle. its still goes lean, but now only until about 16:1 or so opposed to off the scale and missing. Then i opened up a set of 99 jets from .125 to .140 along with the jet extensions and put them in the sec. metering block. That brought my wot A/F down to 12.5:1 so that was in the right direction. Neither of these mods have effected my good 14:1 cruise ratio. Also the closing of the sec throttle blade down also fixed my problem of it wanting to die at stop signs. Now if i could just get my part/mid throttle around 13:1. I'd be getting real close. I think if i raise the main jets if will richen my cruise. Part/mid throttle brings my vacuum to 2-8 inches, cruise is about 12-15. Any ideas? Also i think my C4 is about to go tits up I'm switching to a th400 but thats a whole other set of headaches probably. so i hope to have the carb firgured out before then.
The primary main well i think is maxed out, because my wot A/F didn't change when i raised the pvcr's from .090 to .125. I'm guessing the secondary main well is probably close with those .140 jets. Does anyone know the factory diameter of the main wells? i still plan on trying the vent extensions, and a BRPV.
Anyone having any luck with a manifold referenced BRPV on E85 or does it work better referenced to the hat? Thanks for all the help

 

Factory main wells can be as small as about .140 . . . I suspect they are typically closer to .160 for a gas carb and should be .180" for E85.

Before you get into the main well too much, try a 4 window power valve and see if that helps get some response back with the large PVCR sizes. The power valve starts to become more of a restriction when the PVCR gets up over about .080. PVCR size increases above .080 - .090 will still add more fuel, just not as much fuel as you think the change would cause. (IOW diminishing returns)

 

The internal restriction in power valves is in the passage through the threaded part, the clearance between the stem and the ID and 'guide ribs' if there are any, like in the standard Holley valves. The genuine Holley high-flow valve has a larger hole and no guide ribs.

The 4-window valves have guide ribs and a smaller hole through them and do not have as much flow as a genuine Holley high-flow valve.

Check all the different valves for the radial clearance around the valve stem and the inside of the hole through the threaded portion of the valves, you will see for yourself.

In addition, a low number valve, which has a soft spring, may not open fully if the pressure difference between the manifold and bowl is not great enough due to throttle or venturi restriction. With PVCR's as large as you need with alcohols that can't be tolerated.

Of course, that depends on the plumbing of your particular carb bowl vents and PV pressure reference, boost-referenced, etc.

http://www.innovatemotorsports.com/forums/attachment.php?attachmentid=3338&d=1236148714 picture of PV internal passages


The genuine Holley high-flow units are gold colored on the die-cast threaded body and have much more clearance around the valve stem through the body. The inside of the body doesn't have the four guide ribs or vanes inside the threaded section. Compare them by moving the spring retainer laterally and the difference will be obvious.

 

I will see if i can find a actual hi flo power valve in the area. All the ones i have are the standard flow. See if that makes a difference, then try drilling some if the passages one by one and see what makes a difference. If this dang transmission will keep the car moving, right now its only acting up after it heats up, like 5 miles or so.

 

Tuner, i read some posts you made on the innovative motorsports website, in regards to eris68's lean at part throttle. Im at about 16:1 now at part to mid-throttle, w/o a missfire. so i guess this would be ok as long as im not getting a missfire...
Eric68 that 7 page write up on innovative motorsport site is VERY informative. Thanks for taking the time to log all that.
I found a hi-flo holley 6.5 pv and plan to try it if it quits raining around here. Right now i have a "prototype" carb an old guy at my work modified and wants me to try. Its a 750, vacuum sec, however, he built a little piston and cylinder to make the sec open with boost pressure, instead of lack of vacuum. i'll take some pics of it here. Im using my metering blocks and bowls, but his IAB are TINY, compared to mine and it smokes and hardly idles at the moment. I dont really want to drill on his mainbody, so maybe i could just reduce the size of the IFR's to compensate. right now i can completely screw in my idle mix screws and it still barely idles at 10:1 A/F.

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The secondary IAB in most vacuum carbs, like a 3310 or 1850, may be .028' or so. It's because they originally have no curb idle adjusting screws on the secondary. The carb in the picture looks normal for a 3310. If the secondary is open a little too far, so it is feeding from the T-slots, it will be very rich, so you might check that. If the primary IAB is smaller than about .060' or 070' it might be pretty rich, but it depends on the particular Idle Jet. Maybe it's rich because the power valve diaphragm is leaking?

Eric's thread is full of good information for tuning E-85 or gas. The calibration specifics are important, but more importantly, his attitude and perseverance exemplify what it takes to reach the goal of a good running carb.

On the other hand, '˜on the internet' you can buy carbs 'guaranteed to run perfect right out of the box'. (I think that was an example Barney Frank used to justify legalizing on-line gambling.)

The carb that opens the secondary with boost, what closes the secondary? What prevents it from staying open as long as there is boost, which there would be as long as a throttle is open?

It sounds like your 'old guy' (I'll bet he's just a pup, probably in his 50's, you kids are funny.) has read Hugh MacInnes bok, 'Turbochargers'

 

I dont think its the power valve diaphram because it worked fine with my 650 mainbody and i didn't have any intake backfires since installing his 750 mainbody. My IFR are .046, and my IAB's are about .090. his IAB's are .025 which i think is the problem. I tried putting .017 wire in my IFR to drop them to .029, but that didn't help. still 10:1 with idle mix screws all the in. Also his is a 750, but i didnt think that would cause a change in idle properties. The secondary is open to show maybe .010 T.slot I could try and close it down alittle more. Im thinking that unless he lets me open his IAB I dont think i will be able to get it too work.

The secondary's wont open unless the primaries are open and will close with primaries and the return spring. Hopefully that is enough to overcome boost pressure under the little piston. I assumed that since im currently using the manifold to reference it, i sholdn't have any residual boost trying to hold the secondaries open after i close the throttle like i would referencing it to the bonnet. we did adjust the tension on the return spring for the little piston so it starts to open at about 2 psi with a regulator.

Now that i think about it, it might get a little funny at say 1/2 primary opening, when you might get alittle boost under the plates and then the secondaries try and open alittle unexpectedly :hmm: