Ok guys here is what I have, 355 chevy edelbrock C3B, crane cam 110 551 3:70 gears and a manual shift PG I have a 4778-1 700 double pumper, rebuilt with holley trick kit, I want to run. Orange cams for primary and secondary, stock jets, and stock squirter #'s. Manual choke. 6.5 power valve. I have a 600 vac secondary on it now, and being that I have to tinker, I want to see what it drives like with the double pumper. When I had it on before ( the DP) I had the bogs worked out, but I had a low RPM hesitation, and upon spraying carb cleaner into the carb it would speed up RPMs... I plan on re-checking the pv and all gaskets, but what would cause the low RPM miss, and the carb cleaner thing. On my 600 spraying carb cleaner irt wants to choke the engine out and I have to work the throttle... Also on the 600 I had to set the secondary with the set screw on the bottom of the throttle plate, is there a way to set the secodnaries on a DP other than the manual linkage? Thanks
what's the duration on that crane cam? and what stall speed is the torque converter in that PG? Sounds like there could be a mismatch there that the DP carb can't make up for, but the vac secondary carb does not have a problem with? (edit: since the vac sec carb is the right one for the application?)
That sounds like a pretty big cam, the power valve is definatly mismatched, you could try a 4.5 but if economy isn't a primary issue, block off the power valve and jet up to match the secondaries #78 (that seem too large to me, but that is from holley) and test it. You didn't describe if it bogged on start or throttle stab in the p***ing lane, the powervalve would affect both. But you might also have issue with accelerator pump, i'd get rid of the orange cams and pump the pink (most aggressive) cams in there. The secondaries may be adjusted by a set screw that you get to by turning the carb upside down, it makes contact with the linkage plate that you have the orange cam fixed to, they are usually a ***** to get loose. I set them so that the lower edge of the plate is just above the transfer slot - just a bit higher that stock holley spec. If you feel you need to adjust this often there is a replacement plate from holley or others that has a screw on top, or you take take the existing screw out and replace it with an allen screw with the hex hole facing up and adjust it from top - can't have motor running becaus eyou have to open the throttle blades all the way.
Adv Duration is 284 Stall is 2800-3200 Now, I have a 4.5 PV in the 600 and the 6.5 in the DP I cannot find the set screw on the throttle plate that opens the secondaries like I have on the 600 vac sec. I had the pink cam on and had a bog when opening the throttle by hand, kinda like a lag, so I used an orange cam and it cleared up, but I have new cams with my kit and can try different ones.
OK I found the screw for the secondary transfer slot adjustment, and they we not open enough for the slots to show at all, so I fixed that as oj described. That may be part of the problem.
I had a similar problem with my Demon carb. Turned out a few turns of the idle mixture screws and a timing adjustment cured any bog or hesitation.
Dude, I have a similar combo, you need to do it right from the get go otherwise you'll be chasing your tail.. Your cam should be around 240 @.050"....not too radical in a decent 355: chevy. Here's what I do to dial in the DP : i. Warm up engine to op temp ii. Makes sure timing is right on. iii. Add a vac*** gauge to the vac port on the baseplate (not the one on the metering block) and adjust idle mixture screws to give MAX idle speed vac in PARK. Then recheck it in gear. iv. The vac needle on the gauge will be boucning around....wherever it "bounces" at the lowest point should be how you choose your Power Valve. ie: if it drops to a lowest reading of 5" inHg, Id run a 4.5 PV. v. Once all that is done set you idle speed again then go for a long drive to but a "burn" on the plugs...ie: 20-30 mins on the freeway. Cut it clean 9do not let it idle) and coast to the roadside. Pull plugs for a dark tan/light chcoclate colour. If its too light - its lean. If ists too dark - its too rich. vi. Rejet the primaries for 60 ft accelration - rejet the secondaries for MPH/Top end.
Well I got it running/idling The secondaries were of due to the wrong adjustment for the transfer slot. I played with the idle with my vac guage, and it seems ok, but it's raining so I can't drive it. No hesitation, no missing no bog either... But I need to test drive it to see what's up... thanks for all the help
I think too,that you have to open the throttle blades too much in idle.Pretty common on cammed up motors.This way the idle transition cuicit is exposed in idle,which is way to early and making it useless.That only richens idle too much. What i always do is to drill little 1/8 holes in the primary blades and drill the idle transition slots (the ones above the idle holes) to double size. This cures almost every light throttle stumble. Ollie
Ollie, opening the secondaries just a "little" with the stop screw mentioned in the above posts achieves the same thing as drilling the holes in the primary blades.. With the added benefit of being reversable/adjustable ! Kinda hard to undrill a hole or make it smaller.... Also, this Adjustment REALLY wakes up the throttle response on carbs with 4 corner idle screws..It helps with primary only idle carbs, just not as much. Dave
Yea, looking back part of my problem was that the transfer slots were not exposed at all the first time. For now until I can drive it, I am keeping the jets and squirters the stock #s but I did add the squirters with the extensions/nozzles that were in the kit. The orange cams seem to work at without much load, so once i drive it I can really start to dial it in.
Geez, we actually fixed something! I'm impressed. You probably have #28 squirters on it too, messing around one day try #31's or so. Let us know, thanks oj
I do have #28 squirter on the primary and 31 on the secondary. What would be the benefit of going to the 31 on the primary?
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