About that Holley carb ...

After exhausting every avenue locally , today I ordered one on eBay .
I have one already , but everybody says that a 750CFM 4160 is just too
much carb for a 305 small block GM motor even with the mods I've made .
The one I ordered is a 600 CFM 4160 , and it has some differences . The
biggest one is the fuel bowls on the 750 have center pivot floats and
dual inlets vs the 600 has side pivot floats and a tube to feed the rear
bowl . Both have metering plates on the secondaries and in all other
respects as far as I can tell are identical . Is there anything
inherently better about either center vs side pivot floats ? I have a
full rebuild kit that fits both , so it will be torn down as far as they
recommend .
The stock quadrajet has problems , and I'm tired of trying to tune it
. Everybody always told me Holleys are a lot easier , and I've always
wanted to try one so here we go !
Reply to
Snag
Loading thread data ...
Don't have much to add directly, but we ran a Holley 650 with vacuum secondaries on a 351W in a full size 2 door Bronco. (a little bigger engine) and it was plenty.
Reply to
Bob La Londe
Unless you have a huge cam in that 305 a 500cfm carb would be adequate, and the 600 will be as big as you want to go. As for the floats? if you are going off-road or severe off-camber driving the center-hung carb will make you a LOT happier. Can you put the center hung bowls on the 600???
Reply to
Clare Snyder
I was wondering about switching the bowls ... which would also mean switching to the dual fuel inlet setup . I'll see what will fit when the "new" carb arrives . As far as the cam , the mfr classes it as a "stage 3 RV cam" (Elgin E-922-P) , whatever that means . I think it's pretty close to what we used to call a "3/4 race cam" . Specs are .444 lift intake and .466 exhaust , with 214° and 224° duration @ .050 lift (288° and 298°) . Lobe separation is 112° . I don't think it's all that radical ... I expected a reasonably decent idle around 800-900 , but I can't get the quad to run right below about 1500 or so (haven't hooked up the new tach yet) . Idle speed screw is almost all the way in and the idle mix needles are making no difference at all . I just totally rebuilt that carb , everything is spot on the specs and I sealed the metering needle wells with JB weld . This carb has had a history of long cranking to start if it's been sitting more than a few hours , like the bowl is emptying while it sits . I'm just tired of trying to figure this one out , I usually have no problems with getting a quad to run well .
Reply to
Snag
Put a good heat insulator between the carb and manifold to help prevent the bowls boiling dry on a hot shut-down (makng the engine over rich after a short shutdown - and slow to start after a long soak. The "stage 3 RV cam" WILL be lumpy below 1200RPM but unlike the "3/4 race" will be biased twards low end "grunt", not high RPM performance. Good from 2000 to 4600 RPM. The 922 runs from 2200 to 5400 RPM - more of the "3/4 race" grind. - close to the factory z28 cam of the late sixties. The 921 is basically the L82 cam. Whar CR are you running? Hopefully better than 9:1
Reply to
Clare Snyder
Original C/R was 9:1 , we replaced the .080 dished pistons with .060 over flat tops . The machinist that did all the work figured that I should be right around 9.5 or a bit more . This guy is known regionally for his excellent motor work . The motor came with what are supposed to be the best flowing stock 305 heads , I forget which casting number (816 ?) they are . I did a little port matching on them to match the Edelbrock Performer intake manifold . As far as the carb , I did use the thick spacer supplied in the carb kit . The truck has done this from the day I drove it home . I thought the well plugs might be leaking from researching that problem , so I coated the bottom of all 4 with some JB Weld - the machine shop guy also suggested I do that just as a preventive measure . If it's leaking , it ain't from the plugs . I really wanted to run that original carb , nothing in the world sounds like that quadrajet moan when you dump the throttle , and IMO the balance between performance and economy is very hard to beat .
Reply to
Snag
Oh, I should have said that was two different CAMs. First time was somthing called a 1/4 race CAM. Second rebuild was with an RV (long duration) CAM. The same carb worked great for both applications. Never felt like it was leaning out.
Reply to
Bob La Londe

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.