Fine Tuning the Holley 350CFM carb after DuraSpark Conversion

[clcooper]

1985 Ford Ranger, 4wd, 2.8L (cologne)
Engine Rebuild; bore +.003 standard / standard
Duraspark Conversion successful

Need some good pointers on fine - tuning the holley 350 cfm carb that I decided to use, instead of the AL / MC 2150A

I am going to look into the jet size on Monday (going to speak to the company that I purchased the Holley from); but still need to pointers on dast idle, warm idle, bog during gear engagement or slow - stop, etc.

Any help would be greatly appreciated

 

[kimcrwbr1]

If you purchased the carb already set up for a 2.8 as far as jet sizes make sure you dont have any vacuum leaks and adjust the idle air for the highest vacuum pressure or RPM. I found for mine the timing is critical also and mine runs best at 5 DBTDC and I have the advance on the manifold vacuum tree with the ported vacuum nipples on the carb plugged. Finding the balance between timing and fuel delivery. The 2.8 you cant hear the engine ping like you can on a 302 and the best way to time the 302 is on the upper end or total advance and the engine almost pings with the skinny pedal down. My theory is the 2.8 harmonic balancer gives you a false TDC from years of time and pressure and the only way to fine true TDC is to have the damper rebuilt. I have searched for over a month for a new or rebuilt one and the best I have found is send mine in or get one from the bone yard and have new rubber put in it. I plan on doing that this summer just to test my theory. It runs real good right now at 5 degrees or 15 dbtdc with the advance plugged in. It starts quick has the upper end power and dont studder when I shut it down.

 

[clcooper]

Good advice

Well, the good news is that timing is rock solid 10 TDC.

Thank you so much for your feedback.=)

 

[ammocj]

Check this.
http://www.bob2000.com/carb.htm

I never could get my Holley working correctly so it sits in a box. Al

 

[speedysprocket]

You want your vacuum advance on the distributor to go to the small fitting on the carb, not the manifold. Manifold vacuum decreases as load increases, while the carbs fitting's vacuum increases with load, and the whole point of vacuum advance is to increase advance as load increases...

 

[kimcrwbr1]

Mine runs best on manifold vacuum the 2.8 dont idle very well on base timing. So try putting the advance on the vacuum tree giving you about 20 degrees at an idle then adjust the idle air screws for either high vacuum or rpm. So base timing 10 degrees plug the advance on the vacuum tree giving you 20 degrees adjust the idle air then you can set the high idle and choke where you want it after it cools down. Make sure the engine is up to temp and the choke is fully open before adjusting the carb .

 

[kimcrwbr1]

Your jets may be ok, make sure the float level is good and you plug the vacuum ports on the carb your not using. At least try using the manifold vacuum for the advance and always adjust the idle air when you adjust the timing. Turn the idle air screws out for the highest rpm then adjust the idle speed screw then adjust the idle air again until you get a nice smooth idle around 750 rpm. Let us know what you find out. I found out why mine ran best at 5 degrees when I did the water pump I found out the pointer on the block was bent back 5 degrees I bent it strait and it is sitting right on 10 degrees also.

 

[Big Jim M]

Sorry

You want your vacuum advance on the distributor to go to the small fitting on the carb, not the manifold. Manifold vacuum decreases as load increases, while the carbs fitting's vacuum increases with load, and the whole point of vacuum advance is to increase advance as load increases...

Sorry speedy, but you are totally incorrect. The ONLY reason to use the outlet on the carb is to retard the timing at idle. This makes a bit less smog at idle than if the timing is advanced where it SHOULD be at idle.
As far as less or more vac here or there... nope! It is all, more or less, the same all over the intake system..
It is just that ONE OUTLET that has no vac at idle!
Big JIm

 

[85_Ranger4x4]

Sorry speedy, but you are totally incorrect. The ONLY reason to use the outlet on the carb is to retard the timing at idle. This makes a bit less smog at idle than if the timing is advanced where it SHOULD be at idle.
As far as less or more vac here or there... nope! It is all, more or less, the same all over the intake system..
It is just that ONE OUTLET that has no vac at idle!
Big JIm

He wasn't totally incorrect, generally you do want ported vacuum not manifold vacuum. I will let you guys bicker back and forth about what is better for a 2.8, ported works great on my 302. Less smog at idle is fine with me (maybe it will help keep the treehuggers off our backs a little), and since the 2.8 has to wind up to make any power anyway I wouldn't think it should really hurt low end much either. Dunno anything about a Holley, but my Edelbrock has a port for each on the front. Manifold vacuum is lower (closer to the intake) on my carb than ported.

 

[kimcrwbr1]

He wasn't totally incorrect, generally you do want ported vacuum not manifold vacuum. I will let you guys bicker back and forth about what is better for a 2.8, ported works great on my 302. Less smog at idle is fine with me (maybe it will help keep the treehuggers off our backs a little), and since the 2.8 has to wind up to make any power anyway I wouldn't think it should really hurt low end much either. Dunno anything about a Holley, but my Edelbrock has a port for each on the front. Manifold vacuum is lower (closer to the intake) on my carb than ported.

The 2.8 is not a 302 I was just stateing what works best for my 2.8 and suggest he try manifold vacuum. When you have the skinny pedal down ported and manifold vac is the same and with the stock TFI the advance is well above 20 degrees at an idle with the spout wire connected and you get better vacuum with the timing at 20 degrees at an idle. 10 degrees base and the vacuum adds 10 degrees. I was researching The MSD ignition and dizzy and for the 302 you dont even worry about base timing your performance comes from total timing around 38 degrees at 3000 rpm or just before you get engine ping especially with mods. You cant hear the ping on a 2.8 from the cab. It is all in finding the sweet spot between timing and fuel delivery.

 

[85_Ranger4x4]

The 2.8 is not a 302 I was just stateing what works best for my 2.8 and suggest he try manifold vacuum. When you have the skinny pedal down ported and manifold vac is the same and with the stock TFI the advance is well above 20 degrees at an idle with the spout wire connected and you get better vacuum with the timing at 20 degrees at an idle. 10 degrees base and the vacuum adds 10 degrees. I was researching The MSD ignition and dizzy and for the 302 you dont even worry about base timing your performance comes from total timing around 38 degrees at 3000 rpm or just before you get engine ping especially with mods. You cant hear the ping on a 2.8 from the cab. It is all in finding the sweet spot between timing and fuel delivery.

I was mainly just saying there can be more than one port on the carb, and you guys can dicker about which one is better for the 2.8. Just saying "don't use the port on the carb" isn't always a correct statement no matter what kind of vacuum you seek.

 

[The_Dealer]

http://www.jeepforum.com/forum/f8/holley-500-cfm-adjustment-advice-needed-550345/

3rd or 4th post down, best writeup on tuning holley 2bbl carbs