I'm tinkering with this double pumper, and I'm in the process of setting the throttle blades. Theres 2 different schools of thought regarding rear throttle blade position: slightly cracked open, or transfer slot opened enough to be "squared" (along w/the primary).

Here's my problem, If I square the rear blades, they are opened much more than the front. I took the baseplate off and noticed that the transfer slot is longer on the primary side than the secondary, so no matter what I do they can't be squared or the car idles very high. I'm thinking just cracking the throttles an even amount (measured w/a feeler guage). The mixture screws are extremely sensitive to throttle position.

Before you guys tell me the rear just needs to be cracked, let me just tell you that the mixture screws become ineffective on the rear, and I have to really open the primaries. I think this results in too much tranfer slot in the front and a very very rich idle.

Carb is a worked over DP (which may be part if not all of the problem), it has 172 and 173 blades.

Help....

Hello Vince,

When I tweaked my 850 and HP 1000 double pumpers, I removed the secondary stop screw from the bottom of the baseplate and reinstalled it from the top to be able to get to it without removing the carb during tuning.

I never compared secondary blade positioning to the primary blades after I got done tuning. What I went after was the best adjustment I could get out of the primary air fuel mixture screws on the 850, and all 4 corner mixture screws on the 1000.

My car likes the secondary blades open a little. It helps get more air into the engine at idle. Car idles at 1000 RPM (stick, in neutral). 850 had no holes in blades. 1000 comes with all 4 blades drilled (probably unnecessary on my ehgine as the 850 did not need the holes)

Tough to put this adjustment into words. My goal is to get the car to idle at 1000, with solid response from the air fuel mixture screws. Then I know the carb is doing it's job at idle.

Another way to look at it is......if the primary blades are open too far to keep the car idling, then the air fuel mixture screws will not adjust / do anything when you turn them. So.....tweak open the secondary blades open a bit which will allow you to close the primaries a bit. Keep closing the primaries & tweaking open the secondaries until the air fuel mixture screws begin to work. Then you know you are close to optimum setting for the blades.

I will say that my 850 was touchy if the secondary blades were to closed. The car would occasionally cough / spit at low speed, low RPM parking lot type driving. Tweaking them open a bit cured that problem. Maybe drilling holes in the blades would have done the same thing (let more air in at idle).

Good luck, Joe

Hey Joe,

I actually bought the seconday idle adjustment lever which is really nice http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=5843&prmenbr=361, but the dam thing hit the choke mechanism. Nothing that a little grinding couldn't fix.

I guess I'll just try to keep both blades even. Did you ever notice the different transfer slot lengths?

dont try to keep both blades even, with a 2 corner idle. Set the primary up to be less then .040" transition showing, then on the secondaries open them up until you acheive the idle speed you're looking for.

Hi Vince,

Thanks for posting link to adjuster lever. Trick item. Would be very helpful during the primary / secondary balacing act.

Sorry, I never did look at / measure where the blades are positioned to get my idle correct.

Put it this way.......when I started the process on the 850 (2 corner primaries only)...........I set the primaries all the way closed using the Idle Stop screw. Then I set the secondary blades to reveal about .040 of the transfer slot using their stop screw (which I flip from bottom screw in to top of base plate.). Start the car and try to get idle at 1000RPM (my engines' idle speed may not be same for other engines) using the Primary Idle Stop screw. Then make sure the Air Fuel mixture screws work. If the engine would not idle unless primaries were open "too much" (killing the Air Fuel mixture screws)................then I back off the primary a little and open the secondaries a little. Trial and error until engine idles and Air Fuel mixture screws work.

So.....if you start with secondary blades revealing about .040 of transfer slot and the primaries closed / slightly open.....you should be in the neighborhood to do start some tuing.

Might you hit Jackson NJ Outlet Stores for last Friday of month Cruise Night? It is Exit 16 off 195. About 40 minute straight run on 95 to 295 to 195 from Philly I guess. I have seen 1000+ cars with ease. Friday 5/27 looks like first one this year.

....Joe.

i've been to that show before, i used to go every month. Dont think i will bring the camaro this year if i go, i cant stand the bald guy who runs it.

they let too many stock late model cars in, then people with classics, who have to work during the day, are stuck driving around for an hour looking for a parking spot.

think i would rather have this at a car show then a late model corvette

http://hobbystage.net/camaro/camaroracer/1116630743-006480.jpg