Optimal HIF needles for a B20F?

[spock345]

Is anyone here running a B20F with HIF carbs? I swapped my HS6s for HIF6s because the HS6s need the little throttle linkage ears on the shafts replaced (one is badly worn).

I was originally running DX needles in the HS carbs per planetman's suggestion. The current carbs have BBB needles (for a B20B) and I am wondering if that is quite right for the motor. Am I just overthinking this?

[AndrewNance]

When I swapped the worn out b18 for a lightly-modified b20f, I assumed I’d need to change the needles but I don’t think it ever made a bit of difference. I tried two or three different pairs and nothing seemed to change at all so I just put the originals back in and left them alone.

[spock345]

Originally Posted by AndrewNance

When I swapped the worn out b18 for a lightly-modified b20f, I assumed I’d need to change the needles but I don’t think it ever made a bit of difference. I tried two or three different pairs and nothing seemed to change at all so I just put the originals back in and left them alone.

Ok, I've just had this nagging feeling ever since I swapped the carbs and actually had to richen the mixture from the base setting instead of leaning it out, which seemed contrary to what most tuning guides describe.

It is annoying though to remove the whole carburetor when crap gets in the needle valve. At least it is a bit easier to get to all the mounting nuts thanks to its more compact form factor.

The biggest boon for me has been the hot start device. Much easier to get through those fuel vapors that build up when it sits warm. With the HS6s I've had to give it some choke and really lay into the throttle to get it to clear.

[FrankBooth]

When I was running my HIF6's I put BBZ needles in them. I was switching back and forth between those and HS6's w/ KD needles and couldn't really tell the difference. I have since put DX needles in the HS6's and did notice they ran leaner which helped bed in the new piston rings on my engine.
Not very helpful, I know. With all the work I've done, my engine is not what I'd hoped-- later carb head (same as f head but without injector holes), B18 distributor (no vacuum port), k cam.

[spock345]

Originally Posted by FrankBooth

When I was running my HIF6's I put BBZ needles in them. I was switching back and forth between those and HS6's w/ KD needles and couldn't really tell the difference. I have since put DX needles in the HS6's and did notice they ran leaner which helped bed in the new piston rings on my engine.
Not very helpful, I know. With all the work I've done, my engine is not what I'd hoped-- later carb head (same as f head but without injector holes), B18 distributor (no vacuum port), k cam.

Seems to be the normal story with B20s. The way out seems to me to be higher compression but I am not sure. I plan to figure that out. DCOEs maybe but I don't quite want to pull the trigger on those given current gas prices. The SUs have a pretty good fun to efficiency ratio.

As far as I can tell the other sprung needle options Volvo used in the later HS6 and HIF carbs are BAL and KN. The difference in profile seems marginal. All following the same rough taper. Some a bit richer or leaner on either the high or low end.