I didn't want to highjack another thread, but the 750 DP I am working on (with the 4-corner idle adjustement) has a plug screwed into the secondary power valve opening...

Since this is a mild street cruiser (absolutely NO racing, and probably never even floored all the way (I am not driving), and somebody mentioned in that other post that the PV should be called an "economizer' valve.

Should I remove the plug and install a PV (the rebuild kit has 2 PV, both 6.5)?

If so, should I also jet the secondaries down 6-8 sizes? I think they are currently 80s...


I know this isn't ideal, but I want the best drivability/mileage I can from THIS carb.

thanks,

Tony


As a side note my buddy, the cars owner, was complaining that the car felt wierdand it seemed to have a lack of power... So we took it for a test-drive, with ME driving...

I stopped, dropped the shifter into low, and hammered the throttle (only about 3/4 really), smoked the tires and launched pretty hard (for spinning street tires...)
From the look on his face, my buddy had never even come close to full-throttle...

He just wanted a nice car to take to cruises and car shows, and he used to own a 66 SS Chevelle that he sold in the early 70's (traded in on a new VW bug during the gas crisis).

Tony

80 jets are stock in the rear of that carb. with a blocked rear PV the jetting should be 88s or so, sounds like someone blocked the PV and didnt jet up.

which may explain your buddies comment about it feeling "weird".

I concure... 71 on the pri's and 80 on the sec's. Holley does not show a sec power valve on the List 4779-6 carb though. The 6.5 PV on the pri side is correct. http://www.holley.com/HiOctn/ProdLine/CarbList.pdf

Tony - the kit you got covers several different 4150 style carbs so not all the parts in the kit are used...

Thanks,

Cennis, yeah, I know the kits usually have extra stuff, but when I was reading that other post, I thought "Hmmm. Why wouldn't Holley use a metering block without a PV opening if thats the way they meant it to be?"

I was also thinking that maybe since there was the secondary idle mixture screws that maybe I should also use the secondary PV for the enrichment...

I have fooled with quite a few Holleys over the years, but not much in the past 3-4 years, and I never tuned one with the rear idle mixture screws, so I just didn't know what was best...

Thanks again...


Dennis, the good news about all this! When I bought the rebuild kit from Kragens (saw it on display actually), I noticed it has the teflon ribbon bearings for "bushing" the throttle shafts. I previously bought a complete rebuild kit from Summit for $85, because I needed those seals AND the Holley tech said they were NOT included in the inexpensive rebuild kit (liar!)... Thankfully I haven't opened the kit yet, and so it is going back to Summit for a credit (this will be for that 4346 carb I bought at Goodguys last March). That basic kit was like $27 (maybe less from Summit, I'll have to check)...