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Holley bog

3K views 20 replies 13 participants last post by  Hafrod 
#1 ·
I got my 55 runnin' yesterday. When I hit the throttle in park or driving it bogs pretty bad, then goes. It seems like it's in the primaries if I can get it to do it in PARK. It's a BRAND NEW Holley 750 3310 vac secondary. After the bog, this thing feels pretty strong!! Even driving in my neighborhood it acts like it's surging. I set the needles out 1&1/2 turns, On the vac. gauge I have 16 lb of vac., so I put in an 8.5 power valve. I advanced the timing and retarded the timing but still have the studder. I have a 355 dish, 305 H.O. heads ported, Crane springs matched to a 465-488 cam, dual plane intake, patriot headers, Flowmasters, 350 turbo trans, shift kit, 3500 stall.brand new Mallory HEI and 8mm wires, AC R43TS plugs gapped at 40, 125 shot NOS, stock rear(rebuilt) 370 gears, aluminum radiator with black majic electric fan. I CANNOT REMEMBER IF I PUT THE TIMING CHAIN IN 4 DEGREES ADVANCE OR STRAIGHT UP!!! This bogging-studder thing has me going nuts!!!
 
#5 ·
I just unhooked the vac advance and plugged the port on the jet plate. I then BARELY give it some timing and now it will squeal the tire!!! No more bog BUT just drove it around my block around 25MPH and it acts like its cutting out! It's very light but you can hear it. I had to MAKE the plug wires( universal Mallory Sprints) and I'm beginning to wonder if I just DIDN'T get one together right! :confused: Wonder why it runs better off idle without the vac advance?
 
#8 ·
Set your total timming at 38 degrees, doesnt matter where your initial
timming is at. Sounds like your vac is at 16 inches, so I would try a 6.5 power valve, Sounds like per data, you have enough motor for the 750 holley carb, You need to tune carb with vac gauge, so you can set front's at highest vac,Hope fully you installed cam straight up? as cam already has 2 to 4 degrees ground in cam already.you want cam@ straight up.
If still having issues, retune carb, using vac gauge, keep us posted.
 
#9 ·
Have you "read" the plugs to see if it's rich???? Sounds like a lot of carb. for 305 heads and low compression ash trey pistons!!! Just my thoughts....wouldn't be the first time I was wrong!! I would also make sure the cam was installed straight up and not advanced!!!Have never had any luck with advancing one that way!!
 
#10 ·
I pulled ALL the plugs and 5 look NEW and 3 look lightly black on ceramic-the strap looks new! WEIRD! If I nail this sucker, it blows the heck out of the right rear tire!!!! Cruising around it misses!
 
#18 ·
Here's a place to start..



looking at the plugs. It's a race plug type bit of info, but should help in getting started.
http://cochise.uia.net/pkelley2/sparkplugreading.html
I use whats called an "otoscope", to look down in the plugs. An otoscope is what the ear dr uses to "scope out" your ears, when you use the excuse, "sorry dear, I didn't hear you".:D
LOTS of them on the bag... not expensive.
Any large difference in plug readings would be a red flag...
5 "new"?? Obvious they are not firing, or if they are, not getting fuel. I'd bet that the "no fire" situation is most likely with the "homebuilt" wires.
As for a carb backfire... that sucker went dead lean when you whacked it. Have you checked the float levels, and the fuel pressure?
I'd lose the vac advance, and recurve the dist to perform as you want it to. I put total timing in by 22-2500 rpm.

just my $.02.
Back under my rock!:)

My $.02 on the vac carb...don't use it. A mech sec carb will serve you better in a hi po application.
 
#11 ·
HOWDY HAFROD; THAT IS A LOT OF CARB TO BE DUMPING FROM LOW RPM'S. YOU MIGHT WANT TO MAKE SURE THAT THE PUMP STTING ON THAT HOLLEY IS CORRECT. IS THAT A VACUME OPERATED SECONDARY CARB. DEPENDING ON THE MANIFOLD YOU MAY NEED A SPACER AS WELL AS A LARGE AIR BREATHER. HOPE THIS HELPS STEVEN
 
#14 ·
Spec sheet on the 3110 says 70 primary jet, 21 secondary metering plate (equivalent to 75 jet), 6.5 power valve, #31 pump discharge nozzle, and Black secondary diaphragm spring...
 
#19 ·
Tooooo much carb!!!

Still think it's to much carb!!!!!!! Borrow a 600 carb from someone and see if it makes a difference!!! I also agree to see the total timing between 34-36 degrees.. It's a common mistake to run to much carb, my mildly built 461" bbc runs perfect with a 750 Dominator; and your running a 750 with 305 heads and low compression pistons and a small camshaft??? Don't think it's gonna work correctly!!
 
#20 ·
I have to agree and disagree.

While a 750 carb may or may not be ideal for a mild setup, if it is in good working order and hasn't been in the hands of a moron (and they are out there), the carb will have driveability on all but the most radical setups, provided the timing is right, there are no vacuum leaks, and the engine is running on all 8.

I have put a 750 double pumper, stock out of the box, on a mild 283, and it ran fine. Gas mileage sucked, but it had no bogs or other glaring problems.

Too much is made about little carbs and big carbs as far as basic problems. And too many guys start modifying things and get even further off base.

Just my opinion.
 
#21 ·
I have run MANY 750's on 350's. 2 years ago I had a 650 D.P on a fairly healthy 355. I bolted on a buddys 750 D.P. and gained 2 tenths! I think my biggest problem with the carb right now is my bad heads creating the miss.
 
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