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![]() Colbat, I cannot thank you enough for putting in all this time and effort in making this information available, and in such a straight forward and easy to understand format. This is going to help me and anyone else who refers to this thread tremendously. ![]()
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Something else comes to mind in this area- and that's to tighten the carb to the thick insulator-type gasket evenly but not too tightly. Because the gasket of that type has a lot of give to it, it can cause the base plate to warp- sometimes enough to cause the throttle shafts/blades to bind. Quote:
How much is too much? If you get an erratic idle or if it's obviously worn out. There will be play in ALL of them, though and that's where determining how much is too much is tricky. But if it idles good, it's good to go, IMO. Quote:
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Another thing that is a stop-gap measure at best for a leaky well, is those black, 1/4"-3/16" thick foam rubber pieces that most carb kits include. They will work for a while, but are not permanent. Quote:
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Like you said, hopefully this will help someone doing a search, and because of your descriptive title, I was more inclined to add to your thread, so good job w/that. All too often, threads will get a title like, "Need Help". Or "Problem With My Engine". ![]() |
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So, for now, I'll be ordering a new accelerator pump as well as the power piston retainer. I am considering new jets but don't know how to tell what size they are. In any case, the originals seem to have cleaned up well. I will also be buying the bit mentioned in the earlier post to clean out the two orifices. In the mean time, if you feel that something else requires attention, please do point it out! ![]() |
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I don't want to rain on your parade but I think you are being penny wise and pound foolish by not investing in Cliff's book. There are some very simple and cost effective modifications he recommends for even a stock rebuild which will enhance the performance and reliability of the carb and greatly increase the chance of a successful rebuild. The lean idle qualities and accelerator pump circuit of the emissions era quadrajets specifically need to be addressed.
BTW he recommends Devcon Marine-Tex epoxy as the only permanent well plug sealing material he has found. He is a great source for parts and has a forum where you can get advice and feedback on your rebuild. His rebuild kits are a little pricey but would have addressed some of the parts issues you have described. Just my 2 cents. Take it for what its worth. |
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The jet and rod sizes are stamped into them. The jets have the number on the top surface as you look down at them orientated as if they were installed.
The rods (primary and secondary) have the size stamped onto the rod, you'll need to look for it, possibly use magnification (I do, but my eyes are old). Earlier carbs used a jet that was about 30 numbers larger than the rod number. Later carbs the spread was less. This depends on the air bleed type, etc. and isn't anything you need be overly concerned with at this point- I would reassemble the carb w/the stock primary jets and rods first before changing anything. Then after the engine has run long enough for you to get ahold of the traits and plug readings you see, changes can be made if needed. I have heard the Ruggles and Roe books are good. Most guys seem to say they like the Ruggles book better- it spells out "recipes" for different engine scenarios that can be followed. People like to be told: "do this and then do that", rather than having to figure things out for themselves. This is fine, but leaves me wondering if that method actually helps anyone to actually understand the "cause and effect" of why a change does this or that. But I digress- the book has had good reviews (that I assume also equates to successful carb builds), and I suppose that's what matters most. |
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Hey TommyK,
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![]() I have read nothing but good reviews on Cliff Ruggle's "How to Rebuild and Modify Rochester Quadrajet Carburetors". Its true, I did try to cheap out by not buying the book and resorted to look for online articles and help instead. I actually tried to borrow one but that never worked out. However, now it only seems wise to buy a copy and read it thoroughly. (I'm working on a part timer's budget). I never knew that there was an online shop/forum run by Cliff (Cliff's High Performance Quadrajets). Reading the previous posts, I noticed that cobalt327 did mention Ruggles as a good place for plugs but I never got a chance to look into what it was. Frankly, I am rather amazed that his website never came up when I was researching online. I like the fact that they can custom build a customer's rebuild kit and the starting price is the same as what I paid for my kit plus a new float. I did see the Devcon Marine-Tex epoxy. $20 plus shipping seems bit much but if it gets the job done then, I'll fork it out. I'm going to try and purchase everything I need from Cliff's site, but I must say I couldn't find the power piston retainer anywhere on the site so I will inquire about that. Since I have been picking everyone's brains on this forum, and several members have taken the time and energy to contribute tons of useful information on this rebuild, I will continue documenting it here. It is actually a part of another project which the forum members have been helping me with. However, I will now also use Cliff's forum to obtain any other necessary information and feedback. I am going to be away for a week so I'll probably do some reading then. (As of this writing, it seems that the big man has been out due to surgery and is still recovering). TommyK, your two cents are worth alot more than that. Thank you for sharing this information. It has already helped me out and it will help someone in the future. ![]() -------------------------- Good morning cobalt327! Quote:
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Final shopping list (until something else comes up ![]() By the way, cobalt327 and the rest of the forum members, I do wanna say that, due to circumstances in life, you guys are the closest thing to a shop teacher I may ever have, with this forum as the classroom and textbook. I really look forward to reading everything you guys have to say and teach. ![]() |
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Post #22 has a link to the split retainer for the PP if Ruggles doesn't carry them. Gessler also has most- if not all- of the hard to find small parts you could ever need.
Have you seen "Lars'" info on the Q-jet? If not, google "lars q-jet". If the well plugs aren't leaking- leave them alone! The carb you have usually does NOT have this problem. |
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Just wanted to give an update on a few things (aka, a late night rant about nothing
![]() I went ahead and ordered Cliff Ruggle's "How to Rebuild and Modify Rochester Quadrajet Carburetors", which should arrive this week. Since I am going to be away for a week, I'll go ahead and read up on it, along with Lars Grimsrud's "How to Tune a Q-Jet". I went to Quadrajetparts.com, Carburetion.com, and Cliff's High Performance to price out my order for an accelerator pump, a power piston retainer bushing and a primary metering rod retaining spring for the power piston (mine seems a bit funky when compared to the way the new ones look). While shopping for these parts, I noticed that sometimes the year application for certain parts didn't match up to what my carburetor currently has. For example, when searching for the primary metering rod retaining spring, I noticed on Quadrajetparts.com, the website says the spring I currently have (it is the oval-shaped one) is used in 1974 an earlier models (mine is a '77). For 1975 and up, the website shows this one. An inconsistency I noticed between the three sellers is the correct choke pull-off (I'm not buying one, but was merely curious to see how much a replacement is). By matching up what I have with the pictures on the website (which can always be incorrect), I determined that I have what Cliff's refers to as the Chevrolet Straight-Inlet. However, while Cliff's website says it is applicable for years 1971-74, both Quadrajetparts.com says it for 19737-78 and Carburetion.com says it is for 1972-78. Of course, this is nothing that can't be clarified by contacting the sellers but just wanted to mention this for anyone else who does a price comparison with the three sellers. All this prompted me to look up C & J Engineering, the local performance shop which at some point worked on my carb (they placed a small sticker for their company on the front of the carb that has since come off due to the dip). If something doesn't make sense, I figure I can always try and ask them about it as well. So for now, I have decided to hold off on buying any replacement parts until I've read through the book and at least cleared up on the primary metering rod retaining spring. I should be getting back to completing this in about a week and a half. As always, thanks for the continued help! ![]() |
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I most often see the 'squared' primary rod retainer clip (below) used on the APT equipped carbs ('75-up). It is what is on the '86 non-feedback 4.3L Q-jet I have- that also has the larger 800 CFM casting, oddly enough.
![]() I went back and looked at your PP. Your carb doesn't have APT by the looks of things, the PP would have a pin coming out of it near the top. So despite what the numbers say (you're sure of them?), it seems this is an earlier-type carb. If you were ever interested in finding or needing a 800 CFM Q-jet, the easiest way by far is to source one from a late model truck, including the 5.7 and 5.0 V8's and the 4.3L V6 up to '86 they can be found as non-feedback w/"good" HEI distributors, too (w/o feedback; w/vacuum and mechanical advance). About the PP retainer- I seem to remember some older carbs ('74-'75 and older?) using the metal clip retainer for the PP rather than the plastic clip. The years I cite may be off, but I'd want to look into your PP to be sure it ever used the plastic bushing/retainer in the first place- especially now that it appears the carb is an earlier design. In any event, the numbers can be different than the published info. The 1705xxxx does usually mean '76-'79, though. |
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Hey cobalt!
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![]() I decoded the numbers using Holistic Page's carburetor page. And according to Recarbo's website, apparently "it is a documented fact that Rochester didn't follow these rules 100%". When I disassembled the carburetor, I did not see a APT screw in there. Maybe I missed it? Quote:
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You should use something to carefully measure the length of the primary rods from tip to tip. The later carbs ('68-up) used a rod that is 2.4" long. The earlier carbs use a rod that's slightly longer. There were cases of the longer 703xxxx-style primary rods being used in marine-type 170xxxxx stamped carbs. But these carbs also often used the earlier pivot float- which your carb doesn't have (which is a good thing, the earlier pivot/large float carbs were touchier re fuel pressure). Quote:
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But there is no real advantage to the 800 casting, IMO- unless you have an engine that actually NEEDS the extra flow. The downside to the 800 CFM casting is the primary venturi is larger. This give slightly less response, although it is still better than most every other carb design due to the multiple booster arrangement. The difference in airflow between the 750 and 800 carb: Primary Flow for the Q-jet 175 to 185 CFM for 750CFM Q-jets 210 CFM to 225 CFM for 800 CFM Q-jets. The 225 CFM figure is only for the one-year-only '71 Pontiac 455 HO 4M Q-jet. It lacked the outer booster rings found in the other carbs. Quote:
So basically, "feedback" equals computer controlled. Quote:
Last edited by cobalt327; 02-09-2011 at 03:46 PM. |
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You have a picture in post 24 that looks like it shows the PP with the retainer on it. It is not uncommon for the retainer to fail to positively secure the PP in its hole in and of itself. The solution is to take a chisel and gently stake the edge of the hole in one or two spots against the retainer.
Its in the book!LOL! ![]() |
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Cobalt327, you are on a roll! ![]() ----------------------------- Hey TommyK, Quote:
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![]() Last edited by lt1silverhawk; 02-09-2011 at 08:07 PM. |
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Tommy has good eyes!
The retainer collar IS on the PP (below). It has become loose over time, and if too loose, staking it into position might not be a good idea (but it IS an option for a slightly loose retainer), unless a replacement couldn't be found. But Gessler has the split collar type for a couple bucks, so... At least there's no more wondering on my part whether it used the steel retainer or what. Mystery solved. ![]() AFA "on a roll", w/the good title, hopefully this thread will get used, and early on dinger (a mod) asked about putting it in the knowledge base- so all the more reason to put a little effort into it. |
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4mv, carburetor, quadrajet, rebuild, rochester |
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