Jet offers three stages of modifications for your carburetor, depending on your application, budget, and desires. What we like about their service is that the mods can be done to your existing carb for reasonable prices, rather than shelling out for a new carb which still won't be dialed in for your specific engine. Jet does sell their own line of new Holley carbs with the modifications below, ranging from $400 to $625 for typical Holley 650 and 750 double pumpers, check their website www.jetchip.com, or call them for more details. We've outlined some of the key modifications for each Stage below:

(~$185)	This stage is basically blueprinting the carburator, and is a good choice if you have a carb you want rebuilt and revived for a stock to mild engine. Jet's experience shows that Holley carbs can have a wide range of manufacturing irregularities which can affect air flow and fuel atomization through the carb. Jet disassembles and cleans the carb. The carb is inspected and adjusted for proper sizing of the idle, transition, acceleration and main metering circuits. Boosters are aligned in the venturi and the throttle bores are aligned for proper seating. All the mating surfaces are milled true, and the floats and gaskets are upgraded. The carb is coated with dichromate to prevent fuel pitting and corrosion, which can affect the metering. The carb is installed and adjusted on a test engine before being shipped back.
(~$225)	At this level the carb receives all of the modifications outlined in Stage 1, plus the fuel metering circuits are inspected, blueprinted and calibrated to match any modifications done to the engine. The choke horn is also milled off, unless the customer specifies they need a choke. This is an ideal level of modifications for street/strip engines with intake, heads, and cam modifications.
(~$325)	Jet performs all of the tweeks found in Stage 1 and 2 carbs, plus modified venturis for greatly increased airflow, modified discharge boosters for increased signal strength and atomization, machines throttle shafts, four corner idle circuits, fully modified metering blocks, and high flow needle and seats. This is the choice level if you've got a strip engine like ours, which may have some finicky characteristics (low compression and displacement, high power band, large duration cam, etc. )

Results:
The first thing we noticed when we got the 750 back was that the jetting and the shooters were no where near the sizes we had been running. On the stock 750 we had set primary and secondary jet sizes to 73 and 78 respectively, with "40" shooters for both front and rear. Jet replaced the jets with 67's in the primary and 76 in the secondary. The shooters were seemingly way too low at 31 squared. Our initial reaction was, "great, we'll need to dial in the jetting and shooters all over again." Wrong! Road testing the car was an awesome experience, every throttle position felt smooth and crisp. Previously I'd cringe and hesitate while accelerating from part throttle because the engine would sputter as if it was about to backfire out the carb. Well this problem was completely gone, the engine can now cruise around at 2500 rpm in 5th gear and not skip a beat. Crack the throttle gradually and it accelerates like it should. It seems as if the fuel curve is tailored perfectly to the engines requirements throughout the rpm range, whereas previously we'd encounter a "dead spot" in the carb from 1800 to around 3000 rpm. We're still experiencing some backfiring upon quick deceleration which is probably timing related.

But the real test of course came at the strip. We brought along a jet kit and bigger shooters expecting to go larger after the first run, but instead we were pleasantly surprised. The car launched hard off the line without bogging, indicating the 31 shooters were perfect, and that the carb was metering much more efficiently requiring less of a pump shot. Less pump shot is beneficial in many ways -it saves fuel, and also prolongs engine life by reducing the amount of raw fuel in the cylinders, which washes and dilutes the oil off the rings. We decided to leave the jetting alone and run the carb as Jet set it up. For most of the night it seemed we were slightly rich for the 80 deg. balmy night. After the sun went down the jetting seemed to catch up with the cooler air, posting our best ever ET at 11.96 @ 115.7 mph, on a 1.69 60ft. Two runs later the car knocked of its best ever 60ft (1.62) and shattered the best 1/8 ET, but apparently Victor got too excited and missed 3rd gear! The 1/8th ET on that run was an outstanding 7.57 seconds, compare that with the 7.69 on the 11.96 run, indicates we were certainly on our way to a mid 11.8 pass. In comparison, our previous best ET with the stock 750 was 12.05 (7.73 - 1/8th). With a Barry Grant Silver Claw 750 the car has run 11.98 (7.69 - 1/8th).

We're very pleased with the results. Our primary purpose was to solve the driveability problems, which we can say has been accomplished. But what really impresses us, and proves that the Jet modified carb meters so much more efficiently, is the reduction in jet and shooter sizes. The carb also performed very well at the track, posting better 60fts and ET's than the stock 750 and Barry Grant Silver Claw, both of which had to be jetted over five jet sizes higher to get optimum ET's. We even estimate the Jet carb to be one or two jet sizes on the rich side, so leaning it out next time out should get the ET's slightly lower. All in all, if you've got an ailing carb, it is definitely worth the money to have Jet modify it exactly to your engines needs.