CRG Discussion Forum
Camaro Research Group Discussion => Maintenance => Topic started by: 69302DZ on September 12, 2020, 07:08:38 PM
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Stock DZ302, Holley 4053 - While I've had numerous SBCs over the years, I've never owned a solid lifter motor / car until now. I am interested in checking the valve clearance as it seems a tad noisy to me. I read from the Chassis Service manual that the clearance should be 0.030" (intake and exhaust) while hot. I understand the manual to say that they should be adjusted with the motor idling (?). I've adjusted newly assembled hydraulic lifter motors running numerous times but am not clear how this would go with feeler gauges and the solid lifter motor running. Please advise on what the preferred method is - statically with the motor warm? Other? I don't know for a fact that the cam, etc is stock but believe it to be.
Also the car doesn't want to idle warm less than about 1200 rpm. I know the spark plugs were replaced before I purchased it. I need to verify other basics like the points, timing, etc. but am interested in other's thoughts regarding purchasing a rebuild kit for the Holley 4053 if other basic parameters check OK. The external portions of the carb look great but have no idea how old the internal parts are. The inability to lower the idle and have it maintain a normal idle is something I want to correct. Thank you!
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Here's the preferred method of mechanical lifter adjustment.
http://www.camaros.org/302valves.shtml
If that is an original carb, it may have mis-matched components or just be worn out. Best to have someone with extensive Holley carb experience examine and rebuild it.
www.z28camaro.com
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Welcome! Let me just say that the carb will be or has the potential to be more complex a problem. Most advice given in this forum will be based on the assumption that the stock equivalent cam is installed. But a larger duration cam could cause more carb problems. If idle is that high, the idle slots by the throttle plates could be uncovered causing the main circuit to render the idle circuit ineffective. Also the power valve can be dumping fuel if the vacuum is low. There are carb mods to overcome these conditions, but hard to say how to proceed without knowing what cam you have?
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Thanks so much for the feedback and advice!
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I'd use the adjusting routine suggested in the thread rather than adjusting at idle - I've done that myself many times in the past; even with Erson rocker arm clips to restrict the oil coming out of the pushrods (and blowing all over the place), you really have to be quick and accurate to get it right and keep from scalding yourself with a bunch of hot oil. Never one of my favorite chores, but it was the way I learned to do it. Nigh unto impossible if you have poly locks instead of factory thread locking nuts. You said stock, are you positive the motor has never been "upgraded" ?
Holleys are easier than Quadrajets in my opinion to kit/rebuild. Make sure and use the later ethanol resistant gaskets and needles unless you have the car on a steady diet of non-ethanol gas. Common problems with the 4053's are blown power valves and overtly small accelerator pump squirters, which manifests as an off-idle bog. Easy fix -
Regards,
Steve
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If it is a 50 year old Holley you might want to get a pro to rebuild it. Warped parts, worn throttle shafts, and such need special tools and expertise. Most have "restore" new coloring and rebuild options if you don,t want to spend the bucks for "like new" looks.
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imho one of the most overlooked adjustments on a Holley is the Secondary Idle Speed Screw.
Yes, the SECONDARY. It is on the passenger side and goes up from the bottom through the aluminum baseplate. It is a pita, but it can remedy a number of tuning woes. It is a very small flat blade screwdriver 'set screw' with a 'played locking action' is one way to put it. it is recessed into the #10 iirc threaded hole in the baseplate. Here is an image from a Holley document about it.
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Very good post here by Eric of Vintage Muscle Car Parts regarding confirmation of correct parts and possible modification before rebuilding carb.
https://www.yenko.net/forum/showthread.php?t=84742 (https://www.yenko.net/forum/showthread.php?t=84742)
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The carb baseplate changed from the one without the boss to the one with the boss mid 1971 model year... my July built 1971 Lt1 has the Boss, earlier 71's do not have the boss.
I need to check the March 1971 LT1 we just bought.
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Or flip that screw over so that you can make idle adjustments without taking the carb off
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Or flip that screw over so that you can make idle adjustments without taking the carb off
BINGO!!!
This is what I do.
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Even with the Holley Secondary Idle Speed Black flat-blade Set Screw "Flipped Over" you still can not access & use it to adjust the idle speed on-the-fly with the engine running as the secondary throttle shaft end piece tang is resting on the top of the set screw & in the way... Using a bench grinder and a couple 1/8" or 5/32" Allen Wrenches to make a pair of .120" wide flat blade screwdrivers nicely does the trick with the carburetor in place, on the engine, from underneath, while running... 8)