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| Best Build of my 58 3B Engine; Need better carb for altitude | |
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| Tweet Topic Started: Aug 1 2011, 09:17 AM (1,292 Views) | |
| dcook | Aug 1 2011, 09:17 AM Post #1 |
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I need to do something different for a carb. The YF Carter apparently only has metering rods that work up to about 6000 or 7000 ft. I want mine to run at lower altitude, but be able to run well up to 11,000 ft as well. My 3B has so much going for it with all matching numbers, that Id like to keep it that way. I have been building engines for 40 years, but am interested in any Good Carb Solutions from any of you with experience with the 134 F-Head, especially at altitude. My engine is going to a good machine shop in a couple of weeks for a freshen-up, balance, crank grind, valve job etc. My dilemma is carburation and air flow above 9000 ft altitude. It ran ok up to there, with the YF carter. I have a couple of carbs, and have tried the leanest metering rod made. It still loads up. I contacted several custom carb shops, but all they can do is fabricate custom "Experimental" metering rods, and charge hundreds of dollars for them. I checked on the Weber conversion carb, but it will not work with my engine because the dipstick tube is too close. Please let me know your thoughts, and Ideas on this - Thanks! |
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| oldtime | Aug 1 2011, 10:21 AM Post #2 |
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What specific model of YF are you using ? Lean YF 938 SD metering rods are available. The various lean sizes are intended to be used with specific heads. # 800572 Head, cylinder assembly (Ratio 6.9 to 1) for use under 5000' altitude # 649172 Head, cylinder assembly (Ratio 7.4 to 1) for use over 5000' altitude # 800569 Head, cylinder assembly (Ratio 7.8 to 1) for use over 10,000' altitude # 911689 Head, cylinder assembly (Ratio 6.48 to 1) (Export only) |
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Currently building my final F-134 powered 3B . Rock Crawler using factory parts from the Willys Motors era (1953-1963) http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new | |
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| dcook | Aug 1 2011, 01:08 PM Post #3 |
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Thanks - Good Info! I'll confirm my carb, and head numbers tonight when I get home. |
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| P8106jr | Aug 1 2011, 02:13 PM Post #4 |
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I wil tell you what mime will do next week. Head to Colorado Thursday. Base camp at 8000 ft. U am using a Petronix and a hotter coil |
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Jamie Powers 1963 CJ3B 1947 Bantam Trailer 1973 CJ5 Houston TX | |
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| dcook | Aug 2 2011, 09:43 AM Post #5 |
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OK - I confirmed that both of my YF carter carbs are 938SA. I dug up some information I printed off this 3B site a year ago with a lot of info on the carter carb. Where is the best place to buy a 938SD carb kit & get the metering rod & jet for altitude? According to this information, I need a 75-1504U Unitized Package to convert the 938SA to a 938SD. Then purchase a 75-1571 metering rod which is 2 sizes lean? I'm assuming this will lean it down to run to 10,000 ft? I want to be sure the kit I buy, has the full complement of items to work together as a 938SD. Next is my cylinder head. I can not find numbers on it that identify it according to the numbers you provided above. How do I know which compression ratio I have? There are casting numbers in several places on the top of the head, but no longer numbers like those above. |
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| oldtime | Aug 2 2011, 10:24 AM Post #6 |
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The earlier Carter 938's can all be upgraded to 938 SD. I'll have to dig up the specifics but it mainly entails re-drilling of the pump discharge air bleed. Also changing over from a pump discharge check ball to a pump discharge check valve. A new pump discharge check valve is available in all good quality rebuild kits. There are only a few places to look for quality kits. And due to your intended high altitude useage . You should only consider the highest quality parts. For your stringent requirements I suggest only genuine Kaiser NOS or Carter OEM parts. For NOS kits contact eBays "Bluemoonscooter" from Vietnam Or contact the guy in Europe selling Carter OEM 938 SD's. He also had some correct NOS kits. Doug Hoffman, should remember his name. Familiaize yourself with the YF 938 issues covered here: http://www.film.queensu.ca/CJ3B/Tech/Carter.html Know how to properly perform what I call the pump discharge "one minute test". The standard metering rod for the 938 SD is the 75-1500. You will need your metering to be two sizes lean for 10'000 ft. elevation. I believe I have the one size lean specifications listed here on the B.B. Use the SEARCH function (upper one only) and type in "metering rod step". I'll see if I can dig up the 10'000 " metering rod specsifications. You will likely need to make a 2 lean rod. Jon Hardgrove can do that if you can't. For head identification see: http://z4.invisionfree.com/CJ3B_Bulletin_Board/ar/t705.htm |
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Currently building my final F-134 powered 3B . Rock Crawler using factory parts from the Willys Motors era (1953-1963) http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new | |
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| oldtime | Aug 2 2011, 06:55 PM Post #7 |
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It is not mandatory that your YF 938SA be upgraded to a YF 938SD. However the internal components MUST be synchronous. Meaning you must match metering rods to main jets and also these both must be mated to the specified pump discharge air bleed for the given model. 1] Please verify the pump discharge air bleed diameter. The pump discharge air bleed for all S, SA, SC models is .025" diameter. This passage enters the carburetor throat at a diagonal from the side of the check ball or check valve bore. If upgrading any earlier 938 to become an SD one must drill out the brass pump discharge air bleed with a #68 drill to .031". 2] Please verify the main metering jet. Most all are stamped but some may not be so I also am also posting the orfice diameters. 938 S...........#120-160.......096" dia. 938 SA.........#120-155.......091" dia. 938 SC/SD...#120-166.......0935" dia. 3] Please verify your metering rod number if its stamped. Otherwise you will need precision measurements in order to identify the rod. Remember the main metering jet must be associated with a correct metering rod for a specified model. 938S...........75-806 (standard) 938S...........75-808 (1 size lean) 938S...........75-913 (1 size rich) 938SA.........75-996 (standard) 938SA.........75-1114 (1 size lean) 938SA.........75-1400 (2 size lean) 938SC.........75-1436 (standard) 938SC.........75-14xx (1 size lean) 938SC.........75-14xx (2 size lean) 938SD.........75-1500 (standard) 938SD.........75-1570 (1 size lean) 938SD.........75-1571 (2 size lean) |
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Currently building my final F-134 powered 3B . Rock Crawler using factory parts from the Willys Motors era (1953-1963) http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new | |
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| dcook | Aug 3 2011, 09:12 AM Post #8 |
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Excellent Info - Thanks! I will not be able to get further into my Carbs until next week, but will continue to follow up with you on this then. I very much appriciate your help and attention to my search for information! I was able to inspect both cylinder heads I have. The one on the engine ( which is disassembled now ) has the normal reported embossed numbers and letters. I'll call them casting numbers. It has no stamping at location #2 ( as referenced in the 2009 info you provided ) Location #3 has 086 stamped there. My other head is the same with no #2 stamping, but a 084 stamped at #3 location. I do not remember which head was originally on this engine. I used the best parts from both to build it. Unfortunately the crank profile was not good enough to live with the low oil pressure encountered when the engine was loading up at altitude last summer. Now it will get a complete 100% "Only the Best, First Class Rebuild". I also see no stampings indicating that either head, or the block has been surfaced. Is there a finished machine dimension for the heads? Surfacing the head, or block will affect compression ratio, but how much is too much? |
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| Doug | Aug 3 2011, 09:41 AM Post #9 |
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If you check out eBay, search this number: 110721333257 Seller is "nos4jeeps" from Turkey. That is the same Carter Kit that I purchased to rebuild my carb. If you want to get a better idea what is in the kit, you can see more detailed photos HERE Just scroll down. |
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1963 CJ3B - F134 Hurricane, T-90C, D-18, 5.38s, Overdrive, 938YF, 12V alternator 1969 CJ5 - Dauntless V6, T-14, D-18 2004 TW 200 | |
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| oldtime | Aug 5 2011, 03:55 PM Post #10 |
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To my knowledge F head blueprints may no longer exist. They quite possibly were all destroyed when the Toledo factory was torn down just a few years ago. CC'ing the F- head is the only other way to determine the compression ratio on unmarked heads. I have not found the time to properly CC any F-head chambers but do plan to do so for my next build. With old Vic Hickey or Brian Chachua heads the L-134 could benefit from a compression ratio of 8.1 without detonation. As you know increasing the compression ratio will increase the burn temperature. |
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Currently building my final F-134 powered 3B . Rock Crawler using factory parts from the Willys Motors era (1953-1963) http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new | |
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| yjcanibul | Aug 5 2011, 05:13 PM Post #11 |
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the current willys overland parts and body supplier claims to have all the original tub engineering schematics, maybe they got all of it |
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57 3B : big speedo / Hurricane / YF 938 SD / IAY-4012 / T90 / D18 / 5.375 final drive / open diffs / Firestone 6ply Military NDCC / 12v Delco SI alt / Kayline Top / venting windshield / tub patched / "still fixing leaks one at a time" 89 wrangler : h/duty axles + 5spd / 200+hp 4.2L / arb locked / multiport fuel inj / warn hubs+winch / 1/4 mil km / fishing+trail riding / gets me to work | |
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7:41 PM Jul 10