Tunnel ram or no tunnel ram...

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Where the blue circles are is where your ifr’s are now. If you can’t get them out, drill them as big as you can so they aren’t a restriction any more.

Then drill the holes circled in red (if you have to, they may be to size already…I just don’t remember if they are or aren’t) and tap them 6-32 and then drill your brass set screws to .026 and screw them in those holes.

That way the ifr’s always have a head over them.

351BE189-A2B0-44B8-BC69-555B1DAACBB9.jpeg
 
This is what main body looks like.
Screw in restrictors ale 0.049” or very close to it.

A821FDCF-EC13-4695-B145-89C29A4ED0FC.jpeg
 
This is what main body looks like.
Screw in restrictors ale 0.049” or very close to it.
That’s your lean cruise. Normaly those are in the .070’s range on a 4150. I’d start .078 as a starting point but, you could remove them initial pay for a drive to see how it acts.Where’s the hole going in your angle channel in the pic I posted? That main body doesn’t even appear to be drilled for a 3rd circuit. So I don’t see it in your blocks or main body. 3 circuit blocks normally look way different. Those are ringers for a 2 circ.
 
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I discovered major vacuum leak today. I will report on this very soon.
It may be a source of my problems.
It behaves very bad and was not like that on my 1st drive. Perhaps silicone I used to glue it is not gasoline resistant. I will make a gasket for it today.
I feel like an *** quite frankly. I will report tomorrow. Will work on it tonight.
 
With any luck that’s real good news. Sure, it smacks the ego square in the nose but that’ll heal. Had a similar experience when I forgot to hook the vac advance hose back in. Chased my tail on that for a bit. Keep at it, it’s going to be worth it!
:thumbsup:
 
I discovered major vacuum leak today. I will report on this very soon.
It may be a source of my problems.
It behaves very bad and was not like that on my 1st drive. Perhaps silicone I used to glue it is not gasoline resistant. I will make a gasket for it today.
I feel like an *** quite frankly. I will report tomorrow. Will work on it tonight.
This is an easy fix, don’t feel like an ***, feel hopeful. We have all been there, hopefully you found your issue.
 
In my genius I decided to use silicone to glue top on the intake. Silicone literally melted from gas. After getting bolts out I just lifted it up, it was not held by wrinkled and detached silicone. I made a gasket this time and will use light coat of proper sealant. Will wrench on it tonight and report tomorrow.

BEE92F07-229D-4453-B903-5F889F8C23F6.jpeg
 
With any luck that’s real good news. Sure, it smacks the ego square in the nose but that’ll heal. Had a similar experience when I forgot to hook the vac advance hose back in. Chased my tail on that for a bit. Keep at it, it’s going to be worth it!
:thumbsup:
I often rush things because I hate waiting ;-) I post all my stuff from start to finish so hopefully people learn and avoid my frustrations.
Fortunately I only screw up on my stuff. When I do things for people I’m slow and check after myself, write stuff down etc.
 
OK vacuum leak was there for sure.
Now I can drive the car almost normal but lean spot is still there. If I slowly accelerate there is a point when it starts running rough because it’s very lean. The same thing happens when I try to cruise in 3rd gear, at low rpm. I get 15-16 afr. I tried smaller iab and it does nothing.
I had to remove power valves and small jets because it was extremely lean.
It’s now back to 78 square jets, I need to try 77 all round because its bit too rich.
Idle is better but I noticed that fuel level fluctuates. I set it right with car standing. I get great idle and then when I start moving, drive and go over some turns and fuel level is almost max which causes rich idle. What would cause that??
Overall I have the same impression as at the very beginning, which is a lot of power but not much consistency and unstable cruising.
 
OK vacuum leak was there for sure.
Now I can drive the car almost normal but lean spot is still there. If I slowly accelerate there is a point when it starts running rough because it’s very lean. The same thing happens when I try to cruise in 3rd gear, at low rpm. I get 15-16 afr. I tried smaller iab and it does nothing.
I had to remove power valves and small jets because it was extremely lean.
It’s now back to 78 square jets, I need to try 77 all round because its bit too rich.
Idle is better but I noticed that fuel level fluctuates. I set it right with car standing. I get great idle and then when I start moving, drive and go over some turns and fuel level is almost max which causes rich idle. What would cause that??
Overall I have the same impression as at the very beginning, which is a lot of power but not much consistency and unstable cruising.

Ok, I’m not sure you are understanding how the power valve works.

It should have been called an “economizer” valve because that’s actually what it does.

Depending on the size of the holes behind the power valve (power valve restricter channel), you can reduce the primary main jet size. And that’s what you want.

You set your cruise AFR with the primary main jets and then you leave them alone forever. You don’t touch them. Once you have the primary main jets sized correctly for cruise (a nice, clean, crisp, lean cruise if you have enough ignition) you can move on to other areas of the fuel curve.

For WOT tuning you now have to add fuel (or remove fuel) from the primary side with the power valve channel restricters. Not the primary main jets. And you control when you get the added fuel from the power valve circuit by changing the timing of when it opens relative to manifold vacuum. The higher the number the sooner you add the fuel through the power valve circuit.

This means you can get a very nice, clean cruise with the smaller primary main jets and still get your WOT AFR correct with the primary PVCR’s and the secondary main jets.

One other thing. I thin you said your T slot restricters measured .049 or close to that. That’s much smaller than anything I’ve ever needed. I’m usually in the mid .060’s to the mid .070’s. You may want to drill out the T slot restricters to .0625 (1/16 inch or 1.5 mm) and see what that does for your tip in lean spot.

You still have 3 emulsion holes open. You have a bit if tuning to do, but once you get it all cleaned up you’ll be surprised at how well a tunnel ram drives and how much more power they make.
 
That’s your lean cruise. Normaly those are in the .070’s range on a 4150. I’d start .078 as a starting point but, you could remove them initial pay for a drive to see how it acts.Where’s the hole going in your angle channel in the pic I posted? That main body doesn’t even appear to be drilled for a 3rd circuit. So I don’t see it in your blocks or main body. 3 circuit blocks normally look way different. Those are ringers for a 2 circ.

Ok, I’m not sure you are understanding how the power valve works.

It should have been called an “economizer” valve because that’s actually what it does.

Depending on the size of the holes behind the power valve (power valve restricter channel), you can reduce the primary main jet size. And that’s what you want.

You set your cruise AFR with the primary main jets and then you leave them alone forever. You don’t touch them. Once you have the primary main jets sized correctly for cruise (a nice, clean, crisp, lean cruise if you have enough ignition) you can move on to other areas of the fuel curve.

For WOT tuning you now have to add fuel (or remove fuel) from the primary side with the power valve channel restricters. Not the primary main jets. And you control when you get the added fuel from the power valve circuit by changing the timing of when it opens relative to manifold vacuum. The higher the number the sooner you add the fuel through the power valve circuit.

This means you can get a very nice, clean cruise with the smaller primary main jets and still get your WOT AFR correct with the primary PVCR’s and the secondary main jets.

One other thing. I thin you said your T slot restricters measured .049 or close to that. That’s much smaller than anything I’ve ever needed. I’m usually in the mid .060’s to the mid .070’s. You may want to drill out the T slot restricters to .0625 (1/16 inch or 1.5 mm) and see what that does for your tip in lean spot.

You still have 3 emulsion holes open. You have a bit if tuning to do, but once you get it all cleaned up you’ll be surprised at how well a tunnel ram drives and how much more power they make.
My understanding is that PV alows extra fuel when vaccum drops below certain value.
I think I dont have right PV size, only 4.5s and probably need 2.5. My engine idles at 4inHg in gear.
For now it runs smoother with no power valves and bigger jets. I will come back to this for sure.
I bought 6-32, 8-32 and 10-32 taps today. Will need blank restrictors, cant find anything I can use to make them locally. I was thinking to buy brass screws, cut the threaded part, file them for flat screwdriwer and drill them in needed sizes but all I see is steel screws that small.

Before all that I'd like to address the very lean cruise problem. I will verify the size of t-slot restrictors today. My dominator had 0.055" and I had to enlarge them with 1.5mm drill to make it cruise at 14.5:1 afr. I think it was 0.060" hole? It was still very lean but no surging so I left it alone. Plan was to go to 0.065" and it never happened.

My ignition is locked at 34, well its actually locked at 44 but I have programmable box and map sensor to make it work as vacuum advance for crusing. So now its set to 34 flat, I will play with map sensor again ince things run well again.
 
The whole size your pv from idle vacuum is false. There’s a lot of times I run a higher PV number than what an engine idles at. You adjust that too where you need the enrichment from a cruise state. You can’t compare the TSR to your dominator. Dominators typically require a smaller TSR due to huge transfer slots.

My order of operation.

Make it idle good, neutral and in gear
Make it cruise and take off like it should.
Then I start worrying about WOT and WOT transition.

Looks like RB and I think and tune very similar.

And for the record as someone always says this. THE PV HAS NO EFFECT ON IDLE A/F RATIO UNLESS ITS LEAKING OR BLOWN.
 
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The whole size your pv from idle vacuum is false. There’s a lot of times I run a higher PV number than what an engine idles at. You adjust that too where you need the enrichment from a cruise state. You can’t compare the TSR to your dominator. Dominators typically require a smaller TSR due to huge transfer slots.

My Oder of operation.

Make it idle good, neutral and in gear
Make it cruise
Then I start worrying about WOT and WOT transition.

And for the record as someone always says this. THE PV HAS NO EFFECT ON IDLE A/F RATIO UNLESS ITS LEAKING OR BLOWN.
With PV in I had hesitation when car was rolling slow and i gave it some gas, it was leaning out for a moment and then going forward. I came back to no PV because I remembered I didnt have this behavior without PV. I think I just dont have right size jets for front. I guess 73 would work but I dont have them. Will buy more jets soon, just need some baseline.
 
You need to open up your TSR first. Tune for cruise, then work on part throttle enrichment (accelerating from cruise) with the PV.
 
I talked to the builder of these carbs and have exact numbers now: IFRs are 0.033" and main body restrictors are 0.052"
He suggested to put smaller MABs, there are 39s in the carbs. He says I have a weak booster signal problem so no fuel is drawn thru. I really dont know what to say. I think I have 32 and 34 MABs to try...
 
That’s big for MAB’s. Starting to explain why this this is why it is. Personally I’d bump those right down to around .028 myself.

Kind of like been mentioned several times. Lay out all your bleed and orifice on a sheet of paper. Personally if it were mine I’d scrap the whole tune up and completely start from a different starting point as the whole thing is out of whack. I feel like you’re going to be chasing your tail for a while. Trying to get this thing straightened out. It needs a couple big moves off the bat, then you can work out the small details.
 
I talked to the builder of these carbs and have exact numbers now: IFRs are 0.033" and main body restrictors are 0.052"
He suggested to put smaller MABs, there are 39s in the carbs. He says I have a weak booster signal problem so no fuel is drawn thru. I really dont know what to say. I think I have 32 and 34 MABs to try...


LOL…that’s why I said at the beginning you need annular boosters. I understand that’s probably not poss so you may have to do some things I try and not do because if everything’s correct you‘ll lose power. Without annular boosters we need to think differently.

As 68 HEMI pointed out above, you don’t not set your power valve opening by idle vacuum. That’s never been right and to this day, Holley and the whole internet and everyone else still teaches that.

At cruise RPM you want to see what your vacuum is and then go down two numbers as a starting point and tune from there.

For example, if you cruise at 12 inches (that would be pretty low but this is just an example) then I’d start at a 9.5 power valve. That’s 2.5 inches below cruise vacuum. So that’s a good start.

I agree with dropping the Main Air Bleed down some. It will start it on the boosters sooner and it will make it richer at WOT so you may have to reduce main jet/PVCR to your WOT back in shape.

Because you have a tunnel ram (cold air intake) and because you have a pretty big venturi and a down leg booster and because the booster is a long way from the valve you may have to run your engine coolant temperature higher than I normally would. I don’t remember your compression ratio or what you have for an ignition or timing curve, but normally I try and run between 160-170 degrees F.

Contrary to popular belief, you can run higher compression ratios on pump gas and make more power if you can keep coolant temperature in that area.

One issue when you have lower coolant temperatures like above is getting the fuel (most of it anyway) vaporized before it gets to the chamber. Of course, you can have too much vaporization and those expanded gases will displace air and drop horsepower. So it’s a balancing act.

With your induction system and down leg boosters I suspect you are having a vaporization issue. The manifold is cold and your boosters don’t atomize the fuel enough and you end up with wet (solid) fuel getting in the chambers. When you have that, it takes heat from compression to vaporize the last of the fuel and it causes a power los. Plus, you end up running more jet and most of the fuel that gets vaporized in the chamber is just wasted.

So you need the booster (emulsion adds some to this and lots of carb builders use extra emulsion to try and help but IMO that’s not the best way to do it) to atomize the fuel. Once it’s atomized then the fuel gets vaporized on its way to the chamber by manifold heat. That also pulls some heat out of the intake charges and makes power.

So you have to have atomization and then vaporization to make power and it needs to be done correctly to get the most power out of the fuel.

Soooooo…thats why you may have to run 190-195 degree F coolant temps. That will help the vaporize the fuel that wasn’t finely atomized by the booster.

I know it sounds a bit daunting to straighten this out but it’s not that bad once you get the hang of it.

If you can make your own set screws that will work.
 
If you are tapping holes, you may need bottoming taps to get the thread depth you need in a shallow hole.
 
I just realized I only have 26 and 27 air bleeds 4 each. How many jets do I need to drop when I go 10 sizes down with MABs?
 
That’s your lean cruise. Normaly those are in the .070’s range on a 4150. I’d start .078 as a starting point but, you could remove them initial pay for a drive to see how it acts.Where’s the hole going in your angle channel in the pic I posted? That main body doesn’t even appear to be drilled for a 3rd circuit. So I don’t see it in your blocks or main body. 3 circuit blocks normally look way different. Those are ringers for a 2 circ.
I enlarged them to 0.060" to test tomorrow before noon. In the afternoon I will get more drill bits but I assume change by 0.005" here should be visble.
 
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