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Author
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Topic: Baseline jetting?
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Butch Jennings
Gearhead Posts: 624
From: No. California
Registered: Apr 2000
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posted 06-07-2002 02:19 AM
   
I was wondering where I should jet this alky carb when I switch it over. It's a 1050 Dominator list# 80586. I run my 1050 gas carb (list# 9375) at 88 square or 86/88, so where should I baseline this alky carb so it's close? I'm gonna run the car next week on gas just to run in the new rings and make sure everything is ok before I throw another wrench in the works. I plan on making the switch to alky later this month or early next month, I'd just like to have it close enough to not wash it down or burn it up before I can get it right. Also, what's a good petroleum oil to run with Alky? I'll probably switch it over to Royal Purple, but again, I don't want to throw too many changes at it at once. I've always used Kendall GT but I heard that it's been changed and sucks now since Sunoco bought them. Thanks all. ------------------
Butch
460 powered 1967 Comet Cyclone
10.271 @ 130.231
Butcher's Home Page
"Friends don't let friends drive Chevys" [This message has been edited by Butch Jennings (edited 06-07-2002).]
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Moneymaker
Administrator Posts: 25883
From: Lyons, IL, USA
Registered: May 99
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posted 06-07-2002 10:10 AM
Butch, KV can probably clarify this better, but as a rule 20-25 % increase in jet size when switching to alky.
I have always liked Castrol or Kendall petroleum produts. Anything BUT Penzoil really. Start with a 20-50 until you break it in with 3-6 passes then switch to a 10-30 or 10-40.  ------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator NHRA/IHRA/SRA member
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The Barry of BarrysGrrl
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Dad Vishus
Gearhead Posts: 836
From: Moscow, Iowa, USA
Registered: Dec 2001
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posted 06-07-2002 12:17 PM
Number 11 RP has worked well for us on alchohol. Its pretty thin, 5-15(?) but the best part is they leave out the additive that suspends water in the oil. Run it for the week-end, let it sit a while, then crack the drain plug and drain out the water.Alky does draw moisture. We also open the breathers on the valve covers and it doesn't hurt to prop open the butterflies while the motor cools off to let any moisture out. We have run oil several weeks doing this and have seen no ill effects. Kid could give you a better idea than I could about jetting, but it takes alot more alky than gas to run a motor. Probably close to double. Good luck. Methanol makes lots of power and keeps things running cool. 
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kid vishus
Gearhead Posts: 6098
From: middle of NC
Registered: Oct 2000
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posted 06-07-2002 07:13 PM
I'm not sure about the jetting on a carb that big. I do know that the alcohol jets I have are numbered based on the diameter of the hole in them. The carb I have has no powervalves in it at all, and they are removed completely and the enrichment circuit is plugged off (it uses the big open hoel for more volume). Also on the primary side there is a small hole drilled right over top of each jet to richen it up even more. That all being said, I have .136 jets in the front, and .180 in the back. My carb does use .150 needle and seats, and has the bowl extensions for even more capacity. Any good petroleum oil should be ok so long as you keep heat in the motor. On your last pass of the day, get the water temp up to around 190* before shutting it off and then leave it there, the helps the moisture to evaporate out when you are done. Also, when you are in the water box and not WOT, it's not going to sound real good, that's normal for an alchy carb, so dont worry about it. Mine sounds terrible in the water unless it's "on the mat", but it runs fine down the track. Hope I helped some.
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kid vishus
Gearhead Posts: 6098
From: middle of NC
Registered: Oct 2000
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posted 06-07-2002 07:56 PM
Something else I just th0ought of, once ou get the jetting figured out, you shouldnt have to touchit ever. On my car, it didnt seem to matter how big the motor was under it, or what intake it had, or camshaft or compression, it always ran best with the jets in it that BG sent (.136 front, and .180s rear). I tried leaning it down whit the smaller motor and it made it inconsistent, I tried fattening it up with the big motr, and it became inconsistent and slowwed terribley when the humidity went up. Now, the humidity is about the only thing that affects it. Once the humidity starts to go up, it starts to slow a little regardless of what the temp and barometer are doing. Same thing duriong the day, the temp can go up 10*, but if the humidity comes down 5%, I'm going to pick up a couple.
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Butch Jennings
Gearhead Posts: 624
From: No. California
Registered: Apr 2000
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posted 06-07-2002 08:22 PM
Thanks for the help guys. I was thinking about buying a set of alcohol jets for $75.00 that has everything from around .130 to over .190, but it sounds like a waste of money once I get it right . This carb has no power valves and it's got .154 in the front and .188 in the rear, both front and rear have what looks like an enrichment jet/bleed (brass) next to the jets. Maybe I'll just buy 4 pair of jets to go a step higher or lower on either end and hope I've got enough tuneability to get by for a while. One more question, how many numbers should I change per "step"? 4 numbers? It seems that 1 or 2 numbers wouldn't be much of a change considering how much fuel it's passing. Sorry for all the seemingly simple questions, I'd just like to be somewhat close when I run this thing for the first time on alky....I don't want to get out there and be worlds away from where it wants to be. Thanks again ------------------
Butch
460 powered 1967 Comet Cyclone
10.271 @ 130.231
Butcher's Home Page
"Friends don't let friends drive Chevys"
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kid vishus
Gearhead Posts: 6098
From: middle of NC
Registered: Oct 2000
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posted 06-07-2002 09:00 PM
Dont quote me on this, but I believe my jets go in increments like, .118,.120, .124, .128, .132, .136, .140... etc. I think they come in steps of .04. I would try that carb thge way it is. It might be a little fat, but its better to be a little rich than a little lean. Just ofr a reference point, my motor picks up about 10* water temp in an 1/8 mile pass, and around 15* qrtr. Just treat it like any other carb on the first pass, if it starts to lay over, lift, alchy will melt stuff down quick if it's too lean. I burned the electrodes off 2 plugs last year on one pass when I was trying to slow my car down to run 10.90 (I unhooked the secondaries and was running off just the primaries and they were closed part way [side note, it didnt work] ).
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Butch Jennings
Gearhead Posts: 624
From: No. California
Registered: Apr 2000
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posted 06-07-2002 10:56 PM
Thanks Kid, That's exactly the type of info I'm after. ------------------
Butch
460 powered 1967 Comet Cyclone
10.271 @ 130.231
Butcher's Home Page
"Friends don't let friends drive Chevys"
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jsracingbbf
Gearhead Posts: 2751
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 06-08-2002 01:04 AM
Butch, back when I ran the 351C in my car and beefore i went to the toliet ( ron's racing injection ), I ran a C & S specialties holley 950. I don't remember the jet sizes but I do remember that I tried to move them up a couple and then down a couple and finally wound up with what the carb was sent with. I never messed with the jets after that. I think alky is a forgiving fuel as far as that goes. I know you can get injection so rich that it slobbers out the collectors, because I accidently did it once. I think your gonna like it. Everything KV posted held true for my car also.
Jerry
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