How big r your jets, holley 2 barrel?

[ammocj]

I got my truck all together and I think I cured the oil pan leak.
Now the tuning.
I'm up to #67 jets and it still seems to be running lean.
I checked for vacuum leaks and don't seem to have any.
I've rebuilt the carb twice and made sure all passages were clear.
I'm running headers and a 10" air filter.

Just seems like a lot of jet for this little motor.
Is anyone running bigger than #67 jets in their 2.8 with a 2 barrel holley?
Al

 

[skippy]

dang?i'm using #57 jets,i started at the #61 that came with the holley 350cfm carb and it ran rich until stepping down.are you setting the idle speed richness by ear or with a vacuum guage?

my plugs were sooting up with #61 and#59 jets,they went clean at #57 jets.

 

[ammocj]

I'm setting the idle richness by ear but that shouldn't effect how it runs at speed, would it?
My plugs are coming out spotless.
I found I had a set of 68s, I put em in and will drive it with those tomorrow.
It seems to be getting better as I go richer.

I forget to mention, I'm at 3400 feet elevation. I know that used to make a big difference jetting my RZ350 Yamaha. I never could get it perfect here.
Al

 

[skippy]

I'm setting the idle richness by ear but that shouldn't effect how it runs at speed, would it?
My plugs are coming out spotless.
I found I had a set of 68s, I put em in and will drive it with those tomorrow.
It seems to be getting better as I go richer.

I forget to mention, I'm at 3400 feet elevation. I know that used to make a big difference jetting my RZ350 Yamaha. I never could get it perfect here.
Al

the manual that came with my new holley says decrease the jet size one number for every 2000 ft increase in altitude.something wrong here,we are somewhere around 1047 ft above sea level.but that is what i've done to get it running decent.

been using the holley tuning site too.i may go up to #58 for the hell of it,see what happens.got a pair on the bench.

 

[289-tiger-]

3400 ft elevation? Trim for level flight.

 

[skippy]

manual also says they are calibrated for 70 degrees at sea level,we are more like 80 to 96 this time of year.

 

[ammocj]

I may have figured it out.
Seemed to be an obvious vacuum leak.
Well, I found there is a hole under a plate the choke mechanism is mounted to on the carb.
That hole runs right to the base of the carb.
I imagine it is for some sort of automatic choke so I plugged the hole.
More to come once I run it.
Hopefully it will be running very rich now.
Al

 

[skippy]

I may have figured it out.
Seemed to be an obvious vacuum leak.
Well, I found there is a hole under a plate the choke mechanism is mounted to on the carb.
That hole runs right to the base of the carb.
I imagine it is for some sort of automatic choke so I plugged the hole.
More to come once I run it.
Hopefully it will be running very rich now.
Al

don't know if you are using or not,but some usefull info here.http://www.bob2000.com/carb.htm

good luck!

 

[ammocj]

Yeah,
that's been a lot of help.
After finding that hole I checked that and he mentions converting from auto choke to manual you need to plug that hole.
I didn't convert it. Bought carb used as a manual choke carb

Still runs like crap at full throttle.
more stuff to check.

 

[skippy]

Yeah,
that's been a lot of help.
After finding that hole I checked that and he mentions converting from auto choke to manual you need to plug that hole.
I didn't convert it. Bought carb used as a manual choke carb

Still runs like crap at full throttle.
more stuff to check.

anything new to report?have you figured it out?

 

[ammocj]

No,
I checked everything;
Compression is between 124.5 and 125 all cylinders (motor just rebuilt)
Vacuum is high (I forget the numbers)
Vacuum advance from carb and advancing timing is working
New cap, rotor and plugs
I finally bought new spark plug wires (they usually are a waste of money as is the case this time, runs the same)

I'm pretty sure it's the carb as it's still running lean with #70 Jets.
I will try an old stock carb to see if it'll run full throttle with that.
If that doesn't seem to do it I'm going to try an old electronic box that used to work in my Jeep. Hopefully this weekend.

Any other ideas? Al

 

[skippy]

i'm out of ideas at this time.mine is starving for fuel,put new pump on,new hoses to tank(that was fun) and still trickles fuel to carb.have a clear in line filter just before carb.

guess it's time to look at the fuel pickup in the tank.

drop that guy a line at the tuning site maybe?

 

[skippy]

fixed!wrong gasket under carb,removed holley gasket and installed the 2150 gasket and fuel filter filled up and truck runs great.retuned idle mixture and it's off to the races.vacuum leak caused by wrong gasket?

 

[Big Jim M]

Skippy don't forget to put a set pf 59/60's in there before you start screaming bout the milage.
Big JIm

 

[Will]

It's too big of a carb for that motor so the out-of-the-box jets aren't going to be very good. A 200CFM 6224 Holley Bug Spray would be sized almost perfectly for these and would run well right out of the box. As it is, it's going to have a weaker signal than Holley designed it to have at low rpms. Things like the main air bleeds and booster venturies are expecting to see a 250cid motor drawing on them. Nothing is going to work properly in a 170cid motor.

But check your manifold vacuum at WOT while you are trying to make it work. And see what powervalve you have installed. Manifold vacuum holds the power valve closed. When the signal drops below the number stamped in the valve, the valve opens richening the mixture. If you have a 60 (6.0") power valve and your vacuum is always below 60 the valve will be open all the time. This could happen since your response with that large of a carb will cause you to have your foot in it all the time. In that case, try a 70 maybe. Or, if you find you are never even using the powervalve because your manifold vacuum never drops below whatever the power valve is, it will be running lean.

A 350 cfm carb could work well on a pretty radical 170cid motor. Like a 7,000rpm monster that never sees heavy throttle below 3000rpm. It's like having a 750 double pumper with all four throttle plates wired to open simultaneously on a 350cid motor.