[harry k]

they been around for a while but never heard of them in here
their main website is down,
>>http://www.rockcrawler.com/features/...99dialajet.htm

[shaker455]

Hey that's really slick but your Holley already has a dial-a-jet feature called a Powervalve.

[carbking]

Haven't used their product, but their description of how a carburetor works is erroneous.

Jon.

[Tom Vaught]

Harry, Kind of hard to beat Holley Engineering.

A LOT of gimics out there but Shaker455 is correct. Basically just another way of adding another fuel circuit to the carb. You want another fuel circuit on your 850 carb call Braswell and he can do a three circuit 850 cfm carb. I have done several of them over the years.

Tom V.

[Half-Inch Stud]

Rockcrawler site usually has supurb information, and how-to.

The dial-a-jet may be useful for re-jet on the fly without cracking the fuel bowel gaskets (what a crappy design). Rock-crawl Jeep folks may find that sort of adjustment to be superior than pulling bowels and "dialing-in" the performance.
They care about snappy low-end torque with buko gearing more than full-RPM HP.
Some of them folks prefer the Inline-6 running radical gearing before considering a small chevy.

Dial-a-jip not looking like our kind of tuning handle for 1/4mile Perf.
Suprised to have responded, I'm so biased to using Q-Jets. :ranger :HIS

[rattus]

Bit of a hijack but...does the 4500 style intermediate circuit have any advantage over the 4150 power valve circuit?

[shaker455]

The int circurt is really not related to the PV circurt as some 4500's have a powervalve as well.

It's my belief that the int circurt was created for race engine that have little to no vacuum and it mask the transition to WOT.

[Cliff R]

Many factory Q-jets used a similiar system on the primary side to provide additional fuel for quick/heavy throttle openings, POE or Pull Over Enrichment. The system, if used, allows for slightly leaner jetting for light throttle cruising (at least that's the theory), then adds additional fuel via the POE for heavier throttle openings. The system works to some extent, and we can outfit most later castings for it as the passages are in place but not drilled and not tubes extend into the fuel bowl to pick up fuel.

I have the system in place and operational on one of my test carburetors, it shows little if any noticable benefits, at least nothing that I can measure?.....Cliff

[Half-Inch Stud]

Cliff, YESH!

I use the 68-70 Q-Jets with Part-Throttle Enrichment System so I can run the Primaries a tad leaner for MPG. Wish I understood what Plunger spring to use, and wish I could control the Pri-Plunger depth from the Dash during Highway cruise. HIS

[Cliff R]

HIS, all of the later carburetors have the holes on the air horn to add POE. Dig through a pile of later airhorns and many will have POE (6 brass tubes instead of 4). Much better in design than the early POE, as those carburetors robbed fuel from the supply passages to the secondary fuel nozzles, later POE pulls fuel from the main fuel bowl. I DO NOT like or use the early POE carbs for serious high performance applications. The POE works against you. It becomes more difficult to dial in the correct secondary metering rods as we have no control over the airbleed size and the huge brass tubes take up a LOT of room in the fuel supply passages.

The power piston spring used really has little if any effect on fuel economy. Use the strongest spring that will stay down at idle, this provides best throttle response and power on a well set-up carb. If you move up to a post 75 carburetor with APT for the power piston, you can dial the A/F in exactly for your combination. This is much easier and more precise than changing jets/rods in the early units. You also get the later float arrangement, which is superior in every respect than early units.....Cliff

[Geoff]

Looking at the picture on the r/crawler website, it appears that the bottom float bowl screws are hollow & this where the additional fuel is drawn from, & then up through tubing to the enrichment device. Looking at the long fuel flow path, it hardly seems that response would be 'instant'.