Inliners International Forums General Discussion Hi Performance 292 with Offy 3x1 = .080 Jets Still Too Lean??

I've been chasing what I believe to be a lean mis-fire at higher (4,000) RPM and would like some input.

I'm up to .080 jet in all 3 carbs and plugs show it wants more which surprises me so I'm curious what others might be running.

Some Details:
Lumped 194 head w/ 1.94's & 1.5's
Clay Smith Cam - .560 Lift, .231 duration @.050",
Mallory Dual Point, stock coil.
Offenhauser 3x1 , Truck Model B Rochesters non-progressive
5/16" Fuel Line
Stock Manual Pump

Things I've checked/tried fuel related:
Ensured Correct Carb Base Gasket for Power Valve Operation
Float Levels
New Fuel Filter
New Fuel Pump
Vacuum Leaks (none and idles great)
Carbs are synced
Pulled Air Cleaners (thinking restriction)
Isolated Carbs from one another
Fuel Pressure (hard to read with manual pump)

Things I've checked/tried ignition related:
2 other distributors
Different and New Plug Wires
Points
Condenser

The engine acts like it's hitting a rev limiter. Can be going down the road at 3500 and easily throttle it up starts to miss at 4k. Valve springs are good. Recently checked seat and open pressure on two springs (130# seat, 280# open).

Next Steps and your thoughts:

Yet Bigger Jets??
3/8 Fuel Line??
Different Induction?? - I seem to recall these Model B's each being just shy of 200 cfm - should be enough I'd think.

Thanks for your time/input.

You may not have enough fuel Pressure Or Vol. to keep the carb Bowls full. Try and take the linkage off one carb and Test drive to see if it will now go over the 4k issue If so That is your issue not enough fuel to the carbs.

Thanks Larry. Yeah I've unhooked each one individually and also unhooked the 2 outboard ones just running on the center. Results in all cases was way down on power but still did it.

You never mentioned timing, either baseline or total advance. So verify the advance in the distributor is working properly and returns to the correct settings at idle and when running through the RPM's.

Good point on timing and I should have included that. 12 degrees initial with 36 degrees total. The second distributor I tried was set up on a distributor machine and looked/behaved good.
I forgot to include that voltage to the coil looks good and I tried a new coil. Also unhooked my tach thinking the tach might be grounded out the ignition or something - it's got me kind of stumped.
I have a stock HEI (external coil) kicking around I could try but it's pretty crusty and would take some parts ($) to get it ready.

Go get an AEM wideband O2 gage - it'll make your tuning a lot easier - instead of guessing - you will have real data to work with.

If your running dual exhaust get an extra bung do you can try the sensor in each pipe.

At WOT you should be aiming for 12.6 to 12.8:1 AFR.

What are the plugs gapped at?

Good thought Tom. Plugs are gapped at .035 and the look lean. Not white lean but lean enough to want more fuel.
I just can't imagine going to bigger jets hence the question asking what others may be running.

efi-diy - good idea and I' might look into that. I'm just used to using my old Sun 1120 but obviously that doesn't have CO or Hydrocarbon readings which would certainly help.

AEM

summit

You might do well to upgrade the ignition coil say to a MSD blaster and a pertronix kit.

I set up a offy 3x1 a number of years back and did not have your exact issue, just really poor drivabilty and over rich problems (giant jets which caused awful idle and off idle issues). A few years ago, Inliner K. Patrick Smith wrote a pair of articles on dialing in multiple Rochester carbs. Pat was the longtime crew chief for Dyson racing and one of the best engine minds I know. His method is a bit of a pain but I did it and got a 261 motor that ran like dog doo to run pretty good. His articles are on the Stovebolt Engine Company website. You might consider starting there. I assume you are running some kind of heat to the bottom of the manifold correct?

If it turns out that you are running the carbs out of fuel, just changing to 3/8 line will not solve the issue. You have to change the fuel tank pick up to a 3/8 pick up (using an adapter fitting defeats the purpose of the larger line as you are still restricted by the 5/16 pick up.) The next problem area will be the mechanical fuel pump. You need to find one that uses a real 3/8 inverted flare fitting, or you will have to carefully modify the pump (if the casting is thick enough) to drill and tap for a 3/8 fitting. Also, those carbs do not like a ton of pressure, like 6 max, a little bit lower would be better.

When you had the dist set-up/dialed in on the machine Did they change the module in it. Because the stock ones are only good for about 4000-4500rpm then they start to fall off. But I have had many go good to around 5000. But I still think you have a fuel issue If the plugs are as lean as you say.

Good call on the module Larry - both distributors that I have tried are both dual points. I know HEI is the way to go but I'm still in the dark ages I guess.
I think it's fuel related too but what's odd is I can be driving down the highway at like 3500 and just barely open the throttle and it will go up to 4,000 and start missing....it's the darnedest thing. Does it from a dead start too...runs up to 4k and starts popping.
I was thinking about keep increasing jet size until I get some decent color in the plugs then go back to ignition but again that distributor looked good on the machine so hell I don't know.

Thanks mdonohue for sharing your experience. I read Pat's article awhile back and I do not have heat to the bottom of the manifold. Thanks for the reminder and I've added that to the list.
A couple of weekends ago at the track we had a track temp of 112 degrees. I accidentally touched the intake and it was pretty dang hot. Not sure how hot but burned me pretty good. I raced the car all day with it popping and missing not going over 4 grand.
Good call on fully changing 3/8" line the whole way. When I built this car I thought 5/16" would be fine but maybe not.

Our dyno rule-of-thumb was one 3/8 line is good for 600 hp.

That's a great data point Flyer and thank you for sharing that. I don't know if fuel line size is linear or not but I'm way below 200 hp if I had to guess.

Thanks efi-diy. Yeah I've thought about going to Petronix. Last set of Echlin points I had to have shipped from VA ( to CO) and I was like dang....time marches on and here I am still using points.

Maybe you are struggling with a fuel issue. My 261 runs a pair of weber 38mm carbs on a Clifford manifold. This set up was new to me last year. I previously ran 32/36 weber pinto carbs. Did not have a problem when I ran the motor up. 5/16 lines. When I ran the 57 at last year's trifive nationals, ran the carbs out of fuel every run. The video is my first run with the new set up.

You can hear the miss and popping as I pulled into second gear. Is this what yours sounds like? Even though this motor is not making all that much power, probably 200 or less, I still ran it out of fuel with the mechanical pump and 5/16 lines. So maybe you start there and upgrade the lines, pickup and pump, install an electric pump like a carter 4070 and eliminate the fuel supply as an issue.

www.youtube.com/watch?v=1xJbck9QQH8

Can you verify the float levels are at their correct height, if they are too low or inconsistent on all 3 carbs, it can starve the engine for fuel as well.

Thanks mdonohue05 - great insight and interesting that the mechanical pump and 5/16" lines didn't have enough on your new pair of Webers.
That's a great looking '57 and look at that 261 spin those tires - very cool and thank you for sharing that.
I think the biggest thing for increasing delivery would be increasing the size of the pickup tube out of the tank - it's 5/16".

Good call CNC-Dude and I have. Matter of fact when I put the .080" jets in, the front carb was maybe a tad too high as when I pulled the air horn the fuel was way up in the bowl...like to the top.
The other thing I checked was making sure the power valve assemblies weren't jammed or stuck like they can sometimes get. I guess my "checking" them all I did was push the plunger with a small screw driver to make sure they sprung back. Not sure if there is a better, more precise way to check that assembly.

Many thanks for the complement. Just as an fyi, I sold a couple of rare intakes and other parts to fund the purchase of the Clifford set up. Best decision I could have made. the clifford set up made a huge difference from my old set up which was a weiand 2x1 with adapters and two holly/weber 32/36 (and that set up ran pretty good). The dual 38's can go though some fuel but oh my heaven, what a difference. I have owned that car for 40 years (I took my driver's test in it when I was 16) and it sits pretty much they way I built it in high school. That is decades old lacquer paint, all the speed equipment is either from the late 70s or older (I bought the traction bars used in 78 and they were who knows how old when I got them, lol.). Still has my velour seat covers from 1980 (my boys wont let me replace them.) If you have any 12 port news issues from the early 90s, you may find one reporting a little inliners gathering at Englishtown, NJ Raceway park during one of the nostalgia drag shows they use to put on there. You will see that the car has not changed a bit, lol. I was the Northeast Chapter President for a short time before an illness kicked the daylights out of me.

It will be more then just replacing the pick up. Take one of the brass fittings off of your fuel pump and compare it to a 3/8 fitting. It is a real difference. Also, the bowl capacity of the pump is smaller so while a larger pick up and lines to the pump is a good start, the backup will be at the pump. Couple that with the fact that I know of no 235 or 261 fuel pumps, or any other mechanical fuel pump that can be retrofitted to a 235/261, that takes a 3/8 fitting. Believe me, I am in the middle of changing over all of my stuff to 3/8 which I would rather not have to do but there is no other way. I had the fuel issue on every run I made except for one where I shifted well below 4000 rpm. the more I think of your problem the more I am convinced that you need to eliminate the fuel supply as the potential problem. You could really get yourself down a rabbit hole without knowing for certain.

Mike

A fuel pressure gage tied into the lines feeding the carb's (mounted outside the cab for safety) - will quickly reveal a fuel supply issue.

I have not worked on a B carb for a long time .. is the needle and set big enough to keep up with a big main jet?

.080 dia. jets are HUGE--never heard of anyone running them that big especially on multiple Model B's...problem must be of a delivery nature, maybe trash in fuel line, packed up filter, restricted/crimped fuel line--off the wall vacuum leak
problem

Approx. 200cfm in two bbl talk (measured at 3.0 hg. suck)! when measured at 1.5 hg. suck (like four bbls) its only about 140 cfm in common four bbl talk...thus three would be good for approx 420 total cfm in more commonly heard four bbl talk....The famous 500 cfm holley two bbl is only 350 cfm when spoken in four bbl talk...so no danger of over carburation--heated or not isn't too big a problem with a carb above each intake port- hardly any port length...does this happen in all gears?....could tank be crudded over from disuse or a shop rag sucked into tank?

Thanks Mike - so I've had a fuel pressure gauge on this a couple of times tied in right before the fuel block and it pulses or bounces from 2-5 lbs.
I assume this is because it's a manual pump and it's reading the pulses?? Both pumps I've had on it showed the same pressure.The action on the gauge stays the same running up to 4,000 rpm and then when starts missing.
Good thought on the needle and seat assembly - I would think it would be fine.

I hear ya preacher. .080's are huge and it doesn't make any sense. Tank was new 4 years ago and a new filter and fuel pump had no affect. Yeah thinking I need to go back to the tank, start there to make sure nothing is odd and see about going to 3/8" line.

Great Information and Thank You!! It does happen in all gears and 420 cfm or so doesn't sound like much.
Tank is fairly new and although I don't think there is a shop rag in there I am trying to remember what I did for fittings coming out of the tank. Maybe I have some restriction there.

Guys THANK YOU for all your input and advice - I really appreciate everyones help and involvement with this.

Pulled the tank out of the car and tank looks clean with no restrictions. I had just a 5/16" outlet on it so starting there and redoing the fuel line with 3/8".