this is regarding the "project 145". Over the weekend, I pulled one of the jets for replacement, as it was a jet for a rear carb, and installed on the front carb. I know, I know....

I also adjusted the rich/lean appropriately, and got 'em synced just right. Only problem now is that the car just does't have the upper end power it used to. Feels a bit starved for fuel. However, this didn't feel to be the case in the mountains.

Upon furthur inspection, I noticed that the jet I removed had a larger hole in it. So, the question is, could it be that I need to go with oversized jets? Or would I be better off trying narrower needles? Both? Would an elevation gain of about 2000 reveal that, or am I off my rocker again? Or is there something else I should be looking into? Of course, I could keep riching it out more, but I figure the venturi would have to be dropped well below the surface of the carb intake, which couldn't be ideal.


Keep in mind this is the "mystery engine" which is an overbored, biggie valve, high lift cam '74 B20... The fella I spoke with when ordering the new jets seemed to think that stock jets would be fine at my (5000 foot) elevation, but now the car runs right only when at about 2000 feet higher..

Thanks for any insights...
-Matt

If one of your jets has a larger hole than the other, it's worn out. Replace it.

DX needles work quite well on "bigger than normal" Volvo OHV motors, and are commonly available (RPR, for instance).

SU carbs make great barometers... you can expect to retune the mixture for every few thousand feet of elevation -- but the right needles will pretty much be the right needles for any particular motor. You just need to raise or lower them as needed.

Usually all the jets are the same - its the needles which are specially tuned to adapt the carb to the engine.

Rhys Kent (posts more at the SwedishClassics website) know lots about them - he suggested a new set of needles for my 544 (I was using the B18 carbs on a 2.2 liter B20) and was able to supply a used set for me for a very modest fee. The mid and upper RPM power increased nicely - prior to that the power would feel a bit strangled.

http://members.shaw.ca/islandautomotion/home.html

Of course, having gotten it nicely sorted on the SU's, now I've jumped into some deeper water with a pair of DCOE's. I'm thinking off getting together some parts and assembling a wide band O2 sensor to aid in their tuning.

Yea, that sounds about just like what mine is doing... I too am currently running HS6 carbs off a '65 B18. I'll look into some...thinner, more tapered?.. needles. That would keep it proper at idle I suppose, and only offer up more fuel when it is needed.

My big thing was that it really does run well at 7000+ or so altitude now, but feels...like you said....strangled here in town at about 4500 feet. It used to run strong all the time with that one oversized jet, but it never idled right. Now it idles about as good as I can expect the the R-sport spec cam....

I really do want to stick with the SUs...because I like 'em. And they are fairly easy to work on...

I'll look into needles first.

Thanks,
Matt

Which SUs do you have?
Sure there are no vacuum leax?
Far as I know the jets should be the same size and I'd think you should
be able to adjust them to work OK unless you are at REALLY high altitude.
My 164 was fine at 12,000 feet in Costa Rica. (I wasn't!)
If I were you I'd get a (or a pair of) Colortunes and see what is really
going on. Their rep is:
Sample Inc
2800 Palmwood Terrace P-222
Boca Raton
Florida 33431

Tel: 561 417 7571
Fax: 561 417 7572

Contact: Michael Hayes
(This address is from Dec 1999 so it may be out of date.)

On my 164 I put them in 2 and 5 to adjust front and rear carbs.

BTW do you have the same needles in both carbs?

--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma