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#21
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Put the blue cam on it.
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-Jeremy 1968 GTO 4-spd convertible, console, factory gauges, hidden headlights, 3.90:1 posi, AM/FM radio. 1962 Catalina convertible, Starlight black w maroon interior & white top. |
The Following User Says Thank You to webfoot For This Useful Post: | ||
#22
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Sometimes it backfires thru the carb but not everytime
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468/TKO600 Ford thru bolt equipped 64 Tempest Custom. Custom Nocturne Blue with black interior. |
#23
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I'm guessing from the hints you've provided it's a holley style carb.
Pink cam should be just fine. I find that I use those the most out of the cam kits on many different types of applications, and install it in the #1 hole. What I'd like to know is what holley style carb specifically, what is the jet spread front to back and what power valve are you using. I tend to get that part dialed in first before worrying about pump shot. From there I'd leave the pink cam and start playing with the squirter. Lots of these carbs come with pretty small .025-.028 front squirters that likely won't cover up the big hole you create whacking the throttle on a 455. But getting the front jetting correct, and a power valve that opens at the correct time helping the transition is the first thing to do. Then you might find you don't need to touch the squirter. You're going to have to open it up and see what's inside for any of us to get you going in the right direction. Backfire through the carb when whacking the throttle is classic lean. Sometimes it's just a big hesitation. If it's doing that when free revving the engine, it's going to do it with a load too. |
The Following User Says Thank You to Formulajones For This Useful Post: | ||
#24
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Formulajones, X2.
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#25
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Alot of the holley carbs Ive had were small on the squirter size and would have a lean stumble if floored from a idle. Like was said .028 or so squirters probably would be too small. Usually my carbs had to have a .031 at the least. It would take 2 seconds to pull the squirters and see what size they are and try up from there.
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72 lemans,455 e-head, UD 255/263 solid flat,3.73 gears,,,10" 4400 converter,, 6.68 at 101.8 mph,,1.44 60 ft.2007 (cam 271/278 roller)9"CC.4.11gear 6.41 at 106.32 mph 1.42 60 ft.(2009) SOLD,SOLD 1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.64 @ 87.3 mph on slippery street tires.Bad 2.25 60ft.Owned since 86' |
#26
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Make sure the basics are covered. Square up the transition slot, make sure the acc pump lever is adjusted properly and proper idle mixture. Then work on your shooter size and or acc pump size.
And what carb is this???
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466 Mike Voycey shortblock, 310cfm SD KRE heads, SD "OF 2.0 cam", torker 2 373 gears 3200 Continental Convertor best et 10.679/127.5/1.533 60ft 308 gears best et 10.76/125.64/1.5471 |
#27
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It’s a Quick Fuel Brawler 750 mechanical secondary
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468/TKO600 Ford thru bolt equipped 64 Tempest Custom. Custom Nocturne Blue with black interior. |
#28
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There are different versions but if that's the more common street series it should have 72 front jets and a 6.5 power valve.
Since you're in the Carolinas you're near sea level. I'd like to know what vacuum your engine produces at idle to be sure, but if I had to guess you should be making 12-13 inches at idle easily enough when tuned properly. So the power valve in my opinion opens a bit too late. I'd like to have an 8.5 in there so it's getting into the power circuit a bit sooner and helping the transition. From there, being a 455 and at sea level, I'd also bet the 72 front jets are probably a tad lean. Considering I run that size jet in SBC's here at 5000 feet elevation, I think a 455 might be a pinch thirstier than that. I'd likely bump that to a pair of 74's and try it. Rear jet should be 80's, I'd leave that alone for now. Squirter should be a .031 in that carb, probably okay for the time being. Getting the power circuit working sooner may be enough to cover the big hole you're creating when whacking the throttle and you may not have to touch the squirters. The calibration I'm seeing on that carb is more suited for a 350 out of the box, you're going to have to change some things for optimal performance and good drivability. Start with the power valve and front jet and report back. |
#29
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Quote:
Larger trucks with Holley cars used LARGER NUMBER POWER VALVES because they wanted ADDITIONAL FUEL to the engine SOONER, not later. So a 10.5" Power Valve in a truck was installed for a reason. Same deal for the recommendation to use a 8.5" Primary Power Valve in the carb. More fuel SOONER when you WOT the throttle at lower speeds. As posted the carb is lean. 74s or even 76 jets is more common on 455 sized engines on the Primary side. It would be nice to have the actual "List # off the airhorn of the carb and the build date code. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#30
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First thing I would like to know from the OP is what the transition slot looks like? This could be the cause of the dead spot..no amount of jet changes or PV changes will help if this isn't correct. Cover the basics first.
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466 Mike Voycey shortblock, 310cfm SD KRE heads, SD "OF 2.0 cam", torker 2 373 gears 3200 Continental Convertor best et 10.679/127.5/1.533 60ft 308 gears best et 10.76/125.64/1.5471 |
#31
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Dead Spot At Idle
What ignition system are you running on your engine? If you are running a vacuum advance HEI distributor you may be having an intermittent open in the pickup coil when vacuum immediately drops when the throttle is opened. Also, along the same condition you may have a ground wire problem with the point plate if you are running a point style distributor. If you are running a vacuum advance style distributor, disconnect and plug the vacuum line and see if your condition decreases. Also make sure that your initial timing is adjusted. I would recommend 10 to 12 degrees advance as a starting point.
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#32
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I am in the Carolina mountains. Way above sea level. My transition slots are not uncovered, in fact the idle screw is barely turned in. My idle is a loping idle between 900-1100. I am using the Summit RTR distributor that I stepped down to the 18 degree bushing in to cure the overheating. Now it stays dead between 176-183. Initial is 14 degrees. 15 pounds of vacuum.
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468/TKO600 Ford thru bolt equipped 64 Tempest Custom. Custom Nocturne Blue with black interior. |
#33
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If I am reading you right and your saying that your primary throttle blades are barely open, then that is a good part of your issue.
This means you must be idling more off of the secondary’s then the primary’s. Can you pull the carb off and post up a picture of how your primary throttle blades look in relation to the transfer slots in the base plate? PS. Vacuum is stated in inch’s, not lbs.
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I do stuff for reasons. |
#34
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The Transfer Slot position should be exposing about a .040" square window below the throttle blades on the Primary Side of the carb.
Post up what you think the amount of Transfer Slot exposure should be in your OPINION on the Primary side of the carb. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#35
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Quote:
I'd bump up the front jets too. 2 sizes to start, but as mentioned, it might take 3 or 4 sizes. This will most likely take care of your WOT stumble. |
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#36
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I will post some pictures as soon as I’m able. It’s not idling on the secondaries. Maybe “barely” was the wrong word. I can adjust it easily with the throttle screw it just isn’t turned in but about 1 to 1 1/2 turns
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468/TKO600 Ford thru bolt equipped 64 Tempest Custom. Custom Nocturne Blue with black interior. |
#37
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Good info. learned a lot about Holly Carbs, as far as my Tri-Powers are concerned on my 428 ci, I need to ease into the accelerator, "not" stomping on the accelerator as your explaining, you don't want to spin the tires any way on acceleration or you lose traction. My Carbs work as they are designed, if you want motorcycle response get Webbers or SU carbs or so I have learned. IMO, this does not mean you can't tweak in your Holly Carb. better though! GOOD LUCK. |
#38
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I found this today, might help in your case, good Luck. https://help.summitracing.com/app/an...4730/related/1 |
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