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#21
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Had a very similar issue that smaller primary jets cured
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Chris D 69 GTO Liberty Blue/dark blue 467, 850 Holley, T2, Edelbrock Dport 310cfm w Ram Air manifolds, HFT 245/251D .561/.594L, T400, 9" w 3.50s 3905lbs 11.59@ 114, 1.57/ 60' |
#22
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Main Jets do not effect the idle air to fuel ratio in any way shape or form, but the idle air bleed jets outside the fuel bowl do!!
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#23
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Is the carb new? If not, take it all down and clean all the main body, metering block and baseplate holes out. Mine was working fine on my old 455. Took it off for 6 mos. Had a red shop rag over it. Put it on the new motor. Running rich. Blew out the air bleeds. They had trash in the body.
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#24
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Put the Idle Feed Restrictions back down in the lower position on the metering blocks.
I have fixed many many 950 HP carbs (as was said, not a true 950 cfm carb by any stretch). They all run poorly until you fix the idle circuits properly. Lots of info in my Holley Carb Sticky. 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. |
#25
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Update
Closed idle screws all the way and idle increased.
Removed carb, bowls, bleeders, idle screws (cork seals were disintegrating) power valve and primary and secondary jets. Flushed everything I could see with carb cleaner. Going to replace cork seals and gaskets. Secondary plates had holes that were epoxyed over. Should I leave those alone? Lowered primary plates using idle adjuster to where I could see the top of the transition slot. I think too much transition slot was showing. Wish me luck waiting for seals to be shipped. Damian |
#26
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I hope you were doing this with the carb turned over:
Quote: "Lowered primary plates using idle adjuster to where I could see the top of the transition slot." With the carb turned over, (air cleaner stud pointing down), You should have a small square "window" above the throttle blade edge. The Transfer Slot is about .100" wide so the height would also be about .100" high. Go by the width of the transfer slot, easy to gage the right distance that way without measuring. 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. |
#27
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"Secondary plates had holes that were epoxyed over. Should I leave those alone?"
Someone likely needed (or thought they did) additional idle bypass air at one time. Having epoxy on an area that could break off into the engine makes me a little nervous. Should be fine if the epoxy was applied on both sides of the hole, so less chance of peeling off the throttle blade. Probably leave it alone for now, get the carb running well, then replace the blades or braze/solder the plates for a more secure fix. Sent from my SM-G965U using Tapatalk
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68 Firebird-- Street/Strip - 400/461 Eagle Forged Bottom End & Ross Flat top pistons. KRE 325 CFM D port, Ultradyne 263/271 @.050, .4267 lift. Crower Solid roller lifters and 1.65 stainless rockers. Quickfuel 1000 on Torker2 intake and 2" open spacer. Hedman 1.75" headers. TH400 w/brake. Ford 9" w/3.80 gears & 28x9 Hoosier pro bracket drag radial. Best ET: 1.35 60ft, 6.29 @ 107.20 mph, 9.99 @132.33 mph. 3,300 race weight |
#28
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Quote:
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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 |
#29
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Glad I helped you out on that deal. BUT I learned that trick from Richard "Dick" Harroun,
who was the "on site" Holley Carb Technical Expert located at Ford's Dearborn Research Center. RIP Dick, you knew about 10,000 times as much about carbs as I ever will. Tom V. Google link for Dick's Dad (Ray Harroun) who won the very first Indy 500 Race. https://en.wikipedia.org/wiki/Ray_Ha...dianapolis_500
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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. |
The Following User Says Thank You to Tom Vaught For This Useful Post: | ||
#30
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Also there are two HP 950 configurations. The "classic" with 750 venturis and 850 throttle blades and another that is identical to a 850/1000HP in venturi and throttle blade size.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#31
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While I wait for the gaskets, is there a cleaning solution I can submerge the carb in to clean it?
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#32
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Quote:
i think somebody started rating their carbs differently and holley responded for marketing reasons? i thought i heard that somewhere. so the hp or street avenger carbs are rated differently than the old double pumpers, 1850, 3310 and so on? |
#33
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Quote:
- 750 and 750HP CFM 1.375" venturi x 1.688" butterfly - 800 CFM 1.375/1.438" venturi x 1.688" butterfly - 830 CFM 1.562" venturi x 1.688" butterfly - 850 CFM 1.562" venturi x 1.750" butterfly - 950HP CFM Classic 0-80496-1 1.375" venturi x 1.750" butterfly - 950 CFM Street HP 0-82951 1.563" venturi x 1.750" butterfly - 1000HP CFM 1.561" venturi x 1.750" butterfly QF1000, has a 1.50 venturi x 1.750" butterfly As for soaking, I know the old Berrymen Chem Dip (apparently before they changed the formula to be EPA friendly) was good for cleaning. Might still be. I use regular carburetor cleaner and compressed air.
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Only a pawn in game of life. |
#34
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When I hear about exhaust that stinks and burns eyes, my first thought is not "rich" but "engine misfire".
"Rich" mixture results in heaps and piles of carbon monoxide (CO). CO is deadly but it's odorless and colorless. Doesn't burn your eyes, doesn't stink. Silent killer. Getting a stinky, eye-burning exhaust requires unburned hydrocarbons (HC). HC is merely "fuel" that didn't combine with oxygen. In other words, a cylinder's load of fuel/air went out the exhaust valve without burning. A "rich" mixture has to be REALLY rich to go beyond excess CO to result in massive HC. I would be looking for the misfire. Even a lean misfire will produce eye-burning "rich" exhaust. Are the plugs black from excess fuel, or from excess oil? If fuel, is the mixture too rich all the time, or only at idle, or only at cruise, or only at heavy throttle? |
#35
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Quote:
Comparing the first two carbs posted: - 750 and 750HP CFM 1.375" venturi x 1.688" butterfly - 800 CFM 1.375/1.438" venturi x 1.688" butterfly Both carbs have exactly the same Primary Venturis & Throttle Plates with the 800 cfm carb gaining 50 cfm with the slightly larger 1.438 secondary Venturis. The next two carbs: - 830 CFM 1.562" venturi x 1.688" butterfly - 850 CFM 1.562" venturi x 1.750" butterfly Both carbs have the same size Venturi 1.562" but Holley put the smaller Butterfly Throttle Plate baseplate on the carb. By doing this they lost 20 cfm so now a 830 cfm carb. So going back to the old 850 cfm throttle blade diameter baseplate you get the true 850 cfm airflow numbers. Next two carbs (with Marketing Modifications). - 950HP CFM Classic 0-80496-1 1.375" venturi x 1.750" butterfly - 950 CFM Street HP 0-82951 1.563" venturi x 1.750" butterfly We already saw that the 830 cfm carb was using the smaller throttle blades vs the 850 carb and lost 20 cfm. So the supposed 950 cfm 80496 carb (actually a 770 cfm carb) had the same 750 cfm venturis and the better 850 cfm throttle base. So 750 plus 20 more cfm for the 850 sized baseplate or 770 cfm in reality. The 950 cfm rated carb 0-82951 has exactly the same specs as the original 850 cfm carb but now they call it a 950 cfm carb. (100 cfm overrated for marketing purposes). The only change being the choke tower removed vs the older 850 cfm double pumper 4781 carb. But they want you to believe that smoothing out the air horn area got you 100 extra cfm or the 950 cfm rating. Same logic applied to the 1000 cfm carb I guess except there the air horn removal got the 150 cfm extra flow. Sorry I do not believe that marketing hype in the least little bit. Do a test on a 1/4" radiused entry part on a flow bench with a carb and a test with a large bell-mouth entry, you will get the same flow. The radius is what makes the flow change not the bell-mouth expansion. So that is my take on the carbs. I haven't even mentioned the raised test pressure on the flow stand from the industry standard 20.4 inches of water test pressure to the inflated 28 inches of water Always have to smile at that testing method. ADVERTISING HYPE 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. Last edited by Tom Vaught; 06-24-2020 at 08:29 AM. |
#36
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Would an issue with exhaust valves also be a factor, did the paper test on the tailpipe and it was flapping, like it was getting blown out and sucked back in. Think I might be removing heads over the summer.
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#37
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Quote:
a compression or leakdown test right now isn't necessarily a bad idea, but if you are a busy person just trying to get your car on the road and the car runs well otherwise, just focus on the idle circuit and forget everything else until that is figured out. |
#38
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Good advice, Steve, thank you everyone!
Damian |
#39
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Quote:
I recently took the 950HP off dad's engine to replace with a 4150 Sniper Stealth. Here are some measurements I took. The 950HP bore size right under the booster was 1.460" The bottom of the bore was 1.710" The blades are #325's which are 1.750" and come with air bypass holes pre drilled in all for blades, .093" This carb has the high flow shafts and screws in the base plate. And while the entrance of the bore at the booster seems small, this carb was able to support 724hp on a 571 ci Pontiac. I doubt it flows anywhere near 950 cfm. The sniper stealth 4150 for interesting comparison is only rated at 870 cfm. Yet it has no boosters in the flow path. The bore also isn't tapered, as the top measures much larger than the 950HP at 1.768", more than .300" larger. The bottom of the bore is around 1.685" and the blades are 172's which are 1 11/16" While the blades on the Sniper are only .063" smaller than the 950HP, it has the added benefit of no boosters in the way, and much larger entry at the top (no need for venturi affect with EFI). Yet it's only rated at 870 cfm. Go figure. |
#40
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If you design the Carb correctly the "High Signal" boosters remove a small amount of airflow vs a Open Bore Tube as the flow is determined by the throttle blades.
A Proper Entry to the booster section and a proper transition back to the throttle blades caused very low flow losses. Example provided below: Look at picture on the lower right of the patent. EGR mixer for high-boost engine systems Patent number: 8056340 is an example. https://pdfpiw.uspto.gov/.piw?Docid=...iew+first+page What I did was design a bore that had a slight venturi (like Holley did some of the 650 cfm 2 BBL carbs years ago) and instead of pulling fuel thru the "venturi" it pulled EGR Gas thru the discharge holes under high boost conditions. I know a little bit about how venturi and flow passages work. Tom Vaught
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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. Last edited by Tom Vaught; 06-24-2020 at 02:47 PM. |
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