Too much fuel?

[alfred e numan]

Still running the F-270 on the XB. It has the jet-pro rear mount, 990, ada manafold, dt-1 filter, the tall velocity stack. On flat ground, it sounds as though its getting too much fuel at some rpm-s, lean in other places, Gas filters clean, vented tank, the carb is pulling up plenty of fuel. Its apart with a thread tap in one of the manafold bolt holes-- other things came up to do yesterday. So, later today i will install the torque velocity stack- no taper, just a hole. the 270 is just a little engine- could be the tall velocity stack is forcing too much fuel into the little engine?- only one way to know--

 

[Guest]

I've always wondered if those intakes make any difference. I've tried the short and tall stacks, but can't tell a difference. Maybe it's just me.?

I'm curious to hear if you notice any performance changes.

 

[alfred e numan]

Yes, I am starting to wonder the same thing about the stacks. The carbs all ready have a velocity stack. When either the 3/4" or the 1" stacks are bolted on - just running a finger down the throat of this setup you can feel and see that there is no longer a smooth transition into the carbs bore. Gitzmotors site, he says a few things about the modded carbs- the 771 comes to mind-, something about a boundary layer that keeps the flow on the walls of the carbs bore- something like that anyways-- Yea, the cars assembled, back flushed the vent- gas line inlet filters- I use the Du-Bro "final filter". Just need to let the red, yes, red loktite cure. It never becomes loose no mater what abuse i dish out-- Use t-27 torx bolts -- hexes are iffy with red --. nex day or 2 we will give the car a good wringing out and post opinion- results.

 

[Guest]

Sound good. Good luck.

 

[alfred e numan]

Its 5:30 am-- overslept today! I ran the xb the other day around the back yard. little long rod F-270 engine990-jet-pro rear mount-dt-1 two stage filter.I removed the velocity stack and bolted up ddm-s " Torquer Stack". My guess was correct as far as idle to 3/4 throttle. The tall velocity stack evedently forces too much into the engine. the 990 does meter quite a bit of fuel to begin with. Its supposed to pour rain today- this will give high traction conditions- put a greater load on the car @ wide open throttle. Lots of varabiles on this topic- a bigger engine with dental work on the jug will be able to pull more fuel than a stocker. also, on the above statement about the stack forcing too much fuel- i could install a carb that meters less fuel with the 1" velocity stack and see what happens-- lets see- time to nurse another cup of coffee- gotta reach my target heart rate before daylight-- lol!

 

[alfred e numan]

O.K. folks, I said the he#@ with everything for a while and ran the xb. wfo. held it pegged for 20-30 seconds @ a time except for some sidehilling. The jury is in about the velocity stack- at least the 1" vresion. Its proper place is in a little corner of the roll away. The DDM "torquer" stack, actually, it is not a velocity stack @ all- simply a means to mount a air filter- anyways-- this stack wins- hands down. smoother off idle to midrange transition- more power from mid to where the engine simply will not rev any higher. I did the run on a old school track- loose on top- wet under the fine gravel. Then repestly flogged the mighty xb from one end of a football field to the other- approx 2" tall wet fescue grass. a good load on the car and engine. Reved higher than it ever did before. --- your results may vary-- The jury is still out -unknown how the 3/4" stack versis the "torquer" on a full mod gitzmotor on a tb2 come out-Thing is folks- the carbs we use allready have a velocity stack -

 

[phreerider]

nice tweaking on the stack options. may i inject a few concepts that may further confuse or possibly enlighten. ...not fuel but air ..the resistance to change in pressure across the carb intake is where the velocity stack plays the role. the air flowing into the carb is fastest at the center and slowest at the edge of the intake. the stack gives the carb the effect of being larger so the air entering the carb is more uniform flow rather than laminar...hence the actual air speed at the meter points sees HIGHER VELOCITY air speed.

so it may draw more fuel at the jet at the same settings. basic concept . anything to smooth out the turbulence at the mouth of the intake.

some units already come with flow stack on the carb body any rigid filer is all it really needs. well balanced pipe pressure from behind and maximum air intake speed is gonna make peak rpm band really stand out. stroker set ups will have sweet spots higher in the rpm power band.

it is difficult to judge performance when not on track/dyno with varying conditions...but hey when it rips up the hill differently its hard to deny!

very nice comparison numan. temp, humidity, ...got elevation? definitely will help! relative conditions count.

 

[alfred e numan]

Thanks for your post. The temp that day was 48 tp 50 degrees. 95% moisture. 1,780 feet up. Running 91 octane non-ethanol - Vp-110 c non oxygenated race gas - 75% pump gas - 25% race gas. Klotz super technaplate @ 32-1. Use a 2 stage DT-1 filter. Oiled with no-toil filter oil. This oil is a highly modified animal fat. Gitzmotors has a 2nd generation of Walbro 778? with a modded ventura. Claims the new taper makes the air consontrate better on the walls of the carbs bore. May spring for one of these in the future. I have to wonder if a Baja style air filter would operate better than the small filter - it has a much larger filter area and would also have a greater volume of dead air space.- just a random alfred thought--

 

[alfred e numan]

Should also say- The F-270 has the factory porting. I wet sand the edges of the ports with silicon cabide paper- 1000 grit. Open crank, Nachi mains, zen seals, non stuffer crank. Ported piston. The piston gives the engine about 20% more power From approx idle to 10,000 - 10% more from 10,000 to max rpm.- just a guess. One of Alfreds next of kin came by for a frendly visit sundsy- showed up in a beater Buick Roadmaster. Still cannot understand a damm thing he says- so Spanky the dog translated.- Sorta like how only za za and Mr.Drucker were the only ones that could understand what Arnold Ziffle would say--- LOL!!1!

 

[phreerider]

F270 comes with a piston like that! G. gazoo...flow go kit fo sho!. 32;1 always livens it up. even better below 60% hum..the built in taper is all the velocity stack u need, esp. when family is around.

how do the 270 compare to 29 with head kit ? both of these are pretty hot out the box..

can u get 27 rpm peak like 23? squeeze'em hi and tight like my african strangler!

 

[Ildy666]

Alfred ur too much...lol....after seeing a picture of ur cousin i couldn't stop laughing....haha i'm still crackin up....

 

[alfred e numan]

Always do my best! Even on a Monday.

 

[alfred e numan]

F270 comes with a piston like that! G. gazoo...flow go kit fo sho!. 32;1 always livens it up. even better below 60% hum..the built in taper is all the velocity stack u need, esp. when family is around. how do the 270 compare to 29 with head kit ? both of these are pretty hot out the box..

can u get 27 rpm peak like 23? squeeze'em hi and tight like my african strangler!

No. That is not the stock F-270 piston. The piston was shipped from Asia to me this spring. The Cy 29 is a great basher engine, Lots of torque off the bottom. Have one sitting on the shelf.

 

[Guest]

LMAO Too Funny!