Tunnel ram or no tunnel ram...

[Miszny]

Here is a short movie that shows what’s going on. As you can see, over 3000 rpm cruise is where it needs to be(14-14.5), same with WOT at 12.9 but I can’t show that one handed recording from my phone. It’s cold outside so probably it will be .2 lower in summer.
I had to give it gas because it wanted to die.
All the bad stuff happens below 3000.
T-slot restriction change didn’t do much, I will remove them completely and try to test again.
As for MABs, there were 39s in with 78 jets. Now I have 74 front and 75 back with 28s square.
From 3000 to 7000 the car picked up a bunch. I can light the tires in 3rd at 60mph.
Fixing what’s going on in lower rpm range will make it a total win.
Don’t mind the whistle, it’s my vacuum pump valve, easily addressed, I’m just focused on carbs now so I don’t care about anything else.

 

[Miszny]

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.

View attachment 1716009927

Would you be able to list how many of which set screws do I need?
Is t 6x 6-32 for emulsion and, 2x 8-32 for idle feed restrictors and 2x 10-32 for power valve?

Would suck if I didnt get enough ;-)

 

[MomsDuster]

I get mine in packs of 100

 

[Miszny]

This is full spec of my carbs now.

 

[MomsDuster]

I’m no expert but, the idle air bleeds seem large to me.

 

[Miszny]

I’m no expert but, the idle air bleeds seem large to me.

My reasoning was that I have more turns out on idle mixture screws. I was asked by the builder to check .004" bigger than he put therer which were 76 size. I didnt have .080 drill so I made a set of .082". I can come back to smaller size.
I have just over one full turn on the screws now.

 

[MomsDuster]

Again, I’m no expert. I would put the bigger IAB’s in and see what the changes are. Anything over 1/2 turn on the idle mixture screws (up to 1 1/2) is acceptable as I understand it. I’m curious as to what the guru’s here will say.

 

[Miszny]

Again, I’m no expert. I would put the bigger IAB’s in and see what the changes are. Anything over 1/2 turn on the idle mixture screws (up to 1 1/2) is acceptable as I understand it. I’m curious as to what the guru’s here will say.

I tried as big as .090" and also tested with .060". The only difference I see is amount of turns on the screws. I am guessing my IFR is too small? I will remove T-slot restrictors completely, this should show dramatic change if they are too small.

 

[Miszny]

If that’s the case drill them out to as big as you can so it’s no longer a restriction and just leave them in there.

Then I would drill out some 6-32 set screws (you’ll need 8) to .026 and get the idle air bleeds at .068 to start. If the idle is rich or lean you can adjust it by changing the IAB either smaller or larger depending on what you need. It‘s way easier to get to the IAB’s.


Thats AWESOME that you don’t have the 3rd circuit. That makes it way cheaper and way easier to fix.

Ok, looking at the pictures…someone should be slapped for blocking the emulsion holes like that. They should be tapped and blank jets or screws screwed in there. That’s crazy.

You need one emulsion hole of .028 at or slightly above the float level and one of .028 at maximum float drop.

I‘d probably use 2 and 5 and block 4 because 1 and 3 are already blocked.

Im scared to drill IFRs out not having any parts on the table so I'm waiting with that move.
What size of IFR would you say will make a visible difference? I think its either IFR or T-slot restriction at this point.

 

[MomsDuster]

What ever you do, learn from my mistakes and make one change at a time, (ask me how I know) LOL and document the change and the results. Be sure to test the changes in the same fashion. Need to have true comparisons or as close to it as possible.

 

[Rat Bastid]

This is full spec of my carbs now.

View attachment 1716010802

From the top to the bottom of your emulsion stack (1 being the top) this is where I would start but first let me say that there is enough wrong (compared to the way I do it) that you just need to start over so for your emulsion stack I would use:

1. Blank
2. .026
3. Blank
4. .026
5. Blank

Thats all you need for emulsion.

Your Idle Feed Restricters need to go in the lower hole and I’d start at .026 and start with .066-.068 Idle Air Bleeds. You need to get some fuel out of the idle circuit or you need to add air. As you’ve already seen, it takes a TON of air to change the ratio. Think AFR. It takes way more air to make a move than fuel, whether you are trying to go leaner or richer. So get some fuel out of it and then when it’s close enough you can use the IAB to dial it in.

With your boosters you should be somewhere around a 76-78 main jet and a Power Valve Channel Restricter of .062-.066 and your secondary main jets should be somewhere around 84-88. I’d start at your .028 MAB and see what that looks like.

I think you’ll need a power valve opening of 8.5-9.5. I don’t think it will need to open it any later than that.

 

[Miszny]

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.

My car normally runs between 185 and 190 F because its half filled block. I never tried to run it cooler for that reason.
Please have a look at the movie I posted in HQ. There is vacuum gauge next to AFR. You can see that it leans out and vacuum holds at atound 6 inHG or above. It drops only when engine almost dies. It also happened at higher vacuum situation in ths movie.

 

[Miszny]

From the top to the bottom of your emulsion stack (1 being the top) this is where I would start but first let me say that there is enough wrong (compared to the way I do it) that you just need to start over so for your emulsion stack I would use:

1. Blank
2. .026
3. Blank
4. .026
5. Blank

Thats all you need for emulsion.

Your Idle Feed Restricters need to go in the lower hole and I’d start at .026 and start with .066-.068 Idle Air Bleeds. You need to get some fuel out of the idle circuit or you need to add air. As you’ve already seen, it takes a TON of air to change the ratio. Think AFR. It takes way more air to make a move than fuel, whether you are trying to go leaner or richer. So get some fuel out of it and then when it’s close enough you can use the IAB to dial it in.

With your boosters you should be somewhere around a 76-78 main jet and a Power Valve Channel Restricter of .062-.066 and your secondary main jets should be somewhere around 84-88. I’d start at your .028 MAB and see what that looks like.

I think you’ll need a power valve opening of 8.5-9.5. I don’t think it will need to open it any later than that.

So you would use even smaller IFR than I already have? Why is that? I'm pretty sure Im in the transfer slot when my problems occur.
I can plug the lowest hole easily as a temporary sollution. What will this cause for me? I'm trying to understand the way this works...

 

[71GSSDemon]

I am having the exact issue with my 660 center squirters. I am following along

 

[Rat Bastid]

So you would use even smaller IFR than I already have? Why is that? I'm pretty sure Im in the transfer slot when my problems occur.
I can plug the lowest hole easily as a temporary sollution. What will this cause for me? I'm trying to understand the way this works...

Yes, smaller IFR’s. When you use 2 four barrel carbs with four corner idle you are effectively doubling the IFR area. You just don’t need it. And a .003-.004 change in IFR is like making an .008-.010 change on the MAB. And like I said, once you get close at idle then you can fine tune it with MAB.

I always always start with the idle circuit and work my way up so to speak. If the idle circuit is screwed up, every tuning change you make after that will be wonky because these circuits over lap each other. So cleaning up the idle should be first.

Then I go to cruise which is what the primary main jets do. You get to your cruise speed/RPM/load and then take main jet away until you get a lean surge. Once you get that lean, you go up 1-2 sizes and leave it alone. You don’t touch the primary main jets again UNLESS and that’s big unless you get to the drag strip and you get a bit lean. Then you can add some primary main jet BUT you need to go back to your cruise main jets when are done.

Why is that? Because at the track it’s much quicker and easier to change out a main jet than it is to pull the power valve and change out the PVCR’s. If you need to add primary main jet quickly then you need to go back to what you had so your cruise tune up is where it needs to be.

Once the idle and cruise circuits tuned up, then I move on to WOT. That’s a change of PVCR’s on the primary side and main jets on the secondary side. Again, once your cruise tune up is spot on, you don’t change the primary main jets to get your WOT tune up right or you screw up your cruise tune up.


When all of that is done you can work on your transition circuit. Thats the T slots and T slot restricters. That includes getting your power valve opening time correct. An early opening PV will cause a rich condition in transition and a late open PV will cause a flat spot in transition.

The T slot restricter size changes the cruise AFR only when you are cruising on the T slot. This is when a data logger is worth 10 times its weight in gold. You can measure MAP, throttle position, AFR and graph them together and see exactly where you are in the throttle so you can easily determine exactly what circuit you are on and how far into that circuit you are.

Either way (data logger or not) the T slot restricters change the amount of fuel at cruise on the T slots.

Thats a quick run down on how I do it and why.

 

[Miszny]

OK everyone, we have a win! I removed the T slot restrictors which Gary Williams said he never used and its a different car now. Stumbling is gone completely. It cruises between 14 and 15 afr steady as a rock. This also affected idle. Now I have 13.5 afr in park and 14.5 in gear with 150 rpm change. I put back the 76 IAB and stayed with 28 MAB.
WOT is 12.8-13.0 which is on the high side but its almost freezing temp here so probably this leans things out a bit, same with cruising. I have no air cleaner on it yet also.
Weather to drive is almost over so not much tuning can be dune further but I'm impressed on how it runs. I will have a 50 miles trip to storage tomorrow so I will report on how it works in more detail. I will work on it but only on some weekends. I got all the stuff for metering blocks mods, so we will probably come back to this as well.
I need to make a movie from driving so you can see where I'm at for yourself. I will try tomorrow on longer drive.
I can now put in in 3rd and accelerate from stand still without any acting up.

The builder used 76 IAB and 36 MAB in these carbs.
I am at 75 square jets now and will go up to 77 but this day was a total win.
This thread is not over, I will update for sure.

Thank you, this forum is great place to be.

 

[71GSSDemon]

OK everyone, we have a win! I removed the T slot restrictors which Gary Williams said he never used and its a different car now. Stumbling is gone completely. It cruises between 14 and 15 afr steady as a rock. This also affected idle. Now I have 13.5 afr in park and 14.5 in gear with 150 rpm change. I put back the 76 IAB and stayed with 28 MAB.
WOT is 12.8-13.0 which is on the high side but its almost freezing temp here so probably this leans things out a bit, same with cruising. I have no air cleaner on it yet also.
Weather to drive is almost over so not much tuning can be dune further but I'm impressed on how it runs. I will have a 50 miles trip to storage tomorrow so I will report on how it works in more detail. I will work on it but only on some weekends. I got all the stuff for metering blocks mods, so we will probably come back to this as well.
I need to make a movie from driving so you can see where I'm at for yourself. I will try tomorrow on longer drive.
I can now put in in 3rd and accelerate from stand still without any acting up.

The builder used 76 IAB and 36 MAB in these carbs.
I am at 75 square jets now and will go up to 77 but this day was a total win.
This thread is not over, I will update for sure.

Thank you, this forum is great place to be.

That's great. I hope to be able to sort mine out to fix the same issues. Can't wait to hear more

 

[Rat Bastid]

OK everyone, we have a win! I removed the T slot restrictors which Gary Williams said he never used and its a different car now. Stumbling is gone completely. It cruises between 14 and 15 afr steady as a rock. This also affected idle. Now I have 13.5 afr in park and 14.5 in gear with 150 rpm change. I put back the 76 IAB and stayed with 28 MAB.
WOT is 12.8-13.0 which is on the high side but its almost freezing temp here so probably this leans things out a bit, same with cruising. I have no air cleaner on it yet also.
Weather to drive is almost over so not much tuning can be dune further but I'm impressed on how it runs. I will have a 50 miles trip to storage tomorrow so I will report on how it works in more detail. I will work on it but only on some weekends. I got all the stuff for metering blocks mods, so we will probably come back to this as well.
I need to make a movie from driving so you can see where I'm at for yourself. I will try tomorrow on longer drive.
I can now put in in 3rd and accelerate from stand still without any acting up.

The builder used 76 IAB and 36 MAB in these carbs.
I am at 75 square jets now and will go up to 77 but this day was a total win.
This thread is not over, I will update for sure.

Thank you, this forum is great place to be.

Read post 290. IMO, and this is just my opinion your tune up is far enough off that taking the T slot restricters out is a band aid to cover up other issues.

 

[Miszny]

That's great. I hope to be able to sort mine out to fix the same issues. Can't wait to hear more

Because of lack of any parts I was worried about drilling anything as I would not be able to come back easily. After I heard over the phone that these restrictors should not be there + suggestions to get rid of them by 68 HEMI GTS + Rat Bastid it took 10 minutes to get them out and drive again and wow.
I wonder why previous owner put them there. Also the fact that my idle in park was affected by this change. Time to learn about this stuff.

I have one more question. Is emulsion adding air or gas? More or bigger holes is leaner or richer?

 

[Miszny]

Read post 290. IMO, and this is just my opinion your tune up is far enough off that taking the T slot restricters out is a band aid to cover up other issues.

That’s why it’s good I have all the stuff to make it work better. Now at least I can drive the car to storage instead of renting flat bed which is great. This will also show me where I’m at better.
I will report further.

 

[MomsDuster]

My head is spinning! I don’t want to highjack this thread but @Rat Bastid how much if any does IFR size affect the transfer slot?

 

[Miszny]

My head is spinning! I don’t want to highjack this thread but @Rat Bastid how much if any does IFR size affect the transfer slot?

FYI I talked to BIGs also and after sharing my fulll spec, including engine and all car combo he suggested staring from .080” t slot restrictor and said that he’d use .090” restrictor in my car if I ordered carbs from him. I also gave him full carbs spec as they were before restrictors removal. He straight out said that my t slot size is way too small.

I was talking to him about dual dominators for 605 race hemi I’m slowly putting together for a friend of mine.

 

[Miszny]

My head is spinning! I don’t want to highjack this thread but @Rat Bastid how much if any does IFR size affect the transfer slot?

In case of IFR my understanding is that these restrictors deliver only gas so they can be rather small. In my case t-slot restrictor was not allowing the engine to pull right amount of gas in the transition slot which resulted in very lean condition.

 

[MomsDuster]

In case of IFR my understanding is that these restrictors deliver only gas so they can be rather small. In my case t-slot restrictor was not allowing the engine to pull right amount of gas in the transition slot which resulted in very lean condition.

I get that. I guess what I’m asking is do the transfer slots get their fuel directly from the main well? And in my case whenever I’ve gone down in IFR, my transition has leaned out a bit also. Is that simply from there being less fuel in the idle circuit? Or is there a direct relationship between the IFR and transition? It’s my understanding that the engine pulls from both the idle and transition until the mains come in.

Edit: Found info I was looking for on an old “SpeedTalk” page. IFR/IAB supplies fuel for both.

 

[Miszny]

I get that. I guess what I’m asking is do the transfer slots get their fuel directly from the main well? And in my case whenever I’ve gone down in IFR, my transition has leaned out a bit also. Is that simply from there being less fuel in the idle circuit? Or is there a direct relationship between the IFR and transition? It’s my understanding that the engine pulls from both the idle and transition until the mains come in.

Edit: Found info I was looking for on an old “SpeedTalk” page. IFR/IAB supplies fuel for both.

This should help you out visualize things.