matthon
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Tunnel ram try out
- Thread starter aaronk785
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aaronk785
Well-Known Member
What about 1:1 linkage?
j par
Well-hung Member
It's not one to one?..
yellow rose
Overnight Sensation
I like to do it. I use the adjustable linkage, not that cheap link you have to bend.
Of course, that won’t get it on the booster any quicker.
aaronk785
Well-Known Member
YR. How do I get the boosters to come in earlier. Bigger MAB? Now that I've richened up the mains could I be getting to much shot. Did I go with to much to try to cover up the lean condition at launch.
yellow rose
Overnight Sensation
I’d get as close as you can on the main jets without trying to crutch transition with a big pump shot, and then open up the MAB .004 at a time and that will bring it on the booster quicker AND lean out WOT, so use caution so you don’t end up lean up there.
aaronk785
Well-Known Member
OK. Will try at next test and tune. Should have AFR gauge by then also.
aaronk785
Well-Known Member
New best with tunnel ram. 10.48 at 130. 1/8 mile and 60 ft. still off a ways. Best 60 of the day was 1.57 and best 1/8 mile was 6.73. With single 4bbl 60 was in the 1.44 to 1.46 range and 1/8 mile was 6.50 to 6.60 range. Best e.t. in 1/4 was 10.51 at 128. So this thing really picked up the second half. Now I have to work on the 1st half.
What would you recommend for a transfer slot restriction on a pair of 1850s? I have a similar 440 with an oxygen sensor and am fat under cruise. I believe the transfer slot is dumping in excess fuel. I tried closing my primary butterflies and cracking the secondaries, no change as when I'm just tipped in cruising down the street it's at 12.5. A little throttle goes to 14.5 then leaner until I open the power valve. I think I need to restrict the transfer slot in the main body. Not sure where to start. .075 ?
I'll throw a lot of info here so I'll try to break it up:
A. @yellow rose was banned from FABO, apparently permanently.
While I'll try to answer you, be aware that I'm not even looking in much, never mind signing in. Too much politics and BS. However when I do check in, Racers forum is one of the ones I do check.
B. I beleive YR was suggesting TS restrictors because of the proform bodies. Just a guess here. Check out hte links in post 15 that discuss when and why TS slot restrictions are needed in some situations.
C. Hopefully helpful responses to your observations posted above.
I have a similar 440 with an oxygen sensor and am fat under cruise.
It's typical for many hot rods and race engines the AFR to be richer than stoich under low throttle cruising.
That alone should not be a concern.
I believe the transfer slot is dumping in excess fuel. I tried closing my primary butterflies and cracking the secondaries, no change as when I'm just tipped in cruising down the street it's at 12.5.
12.5 just above idle and at very low speeds (like 25-30 mph) may be a little richer than it needs, especially fully warmed up.
I'd experiment with idle air bleed and idle air bleed- idle feed restriction first.
With two carbs, there's double the fuel supplied for a given manifold vacuum.
Similar problem exists with single 4 corner idle carb on an engine with relatively strong vacuum at idle.
A little throttle goes to 14.5 then leaner until I open the power valve.
This is exactly what it should do. The AFR should get leaner with more throttle (for more power) until at least half power and sometimes not until close to 90% power is needed.
Let me repost this here so you can see. Where the AFR line goes richer again approaching maximum power is where something like a power valve opens.
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"The [relationship] is rich idle, lean cruise, leaner (leanest, actually) part-throttle acceleration and rich WOT. The leanest is at mid-load, half-throttle or" somewhat more. Cruising, especially at lower speeds, requires little throttle and puts relatively little load on the engine. Half throttle or mid-load would be going up hills or part throttle acceleration. "The thing to understand is most engines respond to being leaner...at part-throttle..."
In summary "at moderate to mid load, engines will run lean and like it, and burn much less gas while doing so. They must be rich at idle and very low load, lean in the middle, and rich at WOT." The load where richer is needed varies with engine, gearing and vehicle. It may be 60-70% as shown here, or as high as 90%. Load relates to manifold vacuum, and therefore vacuum is used to signal when enrichment is needed.
F is Fuel/Air ratio for gasoline. Invert the numbers to convert to Air/Fuel ratio.
0.08 = 12.5 AFR
0.667 = 14.7 AFR
0.06 = 16.6 AFR
Constant power is any steady throttle condition.
Steady 15% might be something like driving 40 mph on a flat.
Steady 25% might be cruising 60 mph on flat or steady 40 mph up a long grade.
Steady 100 % might be something like towing or dragging max load up up a really steep long grade, foot to the floor, without losing or gaining speed.
The acceleration loop shows that maximum acceleration (full throttle) has about the the same fuel-air needs as constant 100 % power.
"This ... graph is from Walter B. Larew, Carburetors and Carburetion. At the time he wrote his book on carburetors he was a retired Brigadier General who taught Military Science at Cornell, among his other accomplishments. He published this carb book in 1967. He didn't specify an engine type for this graph but his information is in the context of engines in general. His sources were most likely military aviation research. The math in his book is from NACA TR-49 and similar publications.
This graph is representative of a richer part-throttle that may be necessary to tolerate with an engine that has radical valve timing and perhaps not so good A/F distribution at part-throttle."
quotes and graph from Tuner on Innovate Motorsports Forum and full text now reposted at RFS
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My suggestion is to tune for performance.
Use the WBO2 to observe what, if any, effect changes on carb setting have on particular conditions.
Whether your particlar engine will 30 mph cruise at 13.4 or 12.9 AFR or somehting else you'll have to establish by experimentation.
Idle and off-idle (low throttle). Best performance is defined by pulling strong (least drop in rpm when going into gear) and no hesitation when slowly opening throttles above idle. Do the best you can with throttle positions, IAB and IFR before starting to restrict the transfer slots. Remember the t-slot is a variable airbleed as well as a restriction. It is also located downstream from both the IFR and IAB. Trying to restrict fuel at this point is not the same as controling it when its just liquid fuel from bowl.
Wide Open throttle. Strongest pull in high gear (3rd or 4th), MPH in the quarter or hp on a dyno. Jets and PVCR together. You can trim the shape with the MAB if you see it drifting rich or lean as it goes through the rpms.
Crusing at interstate speed. Go as lean withthe main jets as it will tolerate without surging, then a jet richer. It will be on primaries only. Exacty what mph before its mostly on the primaries I don't know with the tunnel ram. Gearing offf course makes a differnece too. But somewhere above 55 mph the wind resistance and friction is high enough generally the throttles have to be opened enough thee main circuits are taking over from the low speed circuits.
Once you get those conditions worked out, then come back to the trickier conditions if needed. Trickier to work out is anything that is changing rapidly (like pump shot) or using several circuits (like overlap betwqeen low speed circuit and main circuit).
Sometimes you have to jump tuning order, but that's the concept.
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Wow. Thanks for the info. I need to start by drilling out and tapping all the fixed bleeds on my 1850-3 carbs. This will probably be a winter project. I've complicated things a bit by adding Quick fuel metering blocks and secondary plates. The primary blocks have 3 emulsion. 028 bleeds, a fat .059 pcvr and I believe a 35 idle bleed. BTW car weighs 3980, 4 speed 410 28 inch tires. Most of my cruising to work is 40 mph or less 2700 rpms or so. Comp 280 solid. Ran 115 mph last time I took it to the track.
By the way this is a street only car. My Valiant ran a 10.23 at 132 yesterday at Epping!
The quick cheat on the air bleeds is stick wires in them. Same can be done on the others but a little trickier to install securely.
Plug the middle e-hole.
.035 is the idle feed feed restriction (IFR) also known as idle jet. A better description would be low speed circuit jet.
We were just discussing the effects of too much emulsion in cudafever's thread. Proform 850 dialing it in closer
A race car and street car. Nice!
Yea that's quick!
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