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enough carburetor |
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7555 |
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HA! step 1: TURBO! step 2: BLOWN HEADGASKET lol. i await someone else turboing this engine, ala the Dick Datson books. i'm already out on a couple of limbs. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7555 |
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4000 rpm, 90% VE. this engine has substantial head and valve work, forged pistons, and balanced. see, the sports car folk use different criteria with Weber carbs, for sizing. a lot of american car stuff assumes V8s and drag race. and Webers go by "venturi" (choke) size and not "CFM". so by those methods two 44m bores is correct for this displacement. there's some weber "calculators" that try to use math to justify what seem to be anecdotal decisions. i forget which one i used but most of them came up with 48mm (times 2) so i dropped a size down. also i can install a narrower choke (aka venturi), it's a fantasticallty tunable carb (you can change the main jet from OUTSIDE the carb! |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7555 |
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absolutely night vs. day, 32/36 vs 38/38. no comparison. same engine, changed only carb. right after bolt-on huge mid-range power increase under foot. then in the past year, back and forth with jets and spark timing, since they interact, and after that, the decision for the IDF 44. 16,000 miles on it this year alone. "CFM" is an american car drag race thing. over-carbed is a real thing, but i'm incrementing up in carb size with sports car type logic and it's paying off. we'll see if dual 44m is too large. i dont think it is. if it's too large, i can replace the venturis. this winter (now) is: IDF 44, fuel cell, roll bar. its now fast enough to need the roll bar and four-point belts. the build, the light weight, gearing and tires, the car is actually fairly fast. like a sports car, not a drag car. it's a 17-second quarter mile car, but on mountain roads and tight stuff, the car is faster than i am. i'm following results of experimentation and measurement and research, and trying to ignore lore and "what everyone knows". i'm finding that's wrong as often as it's right. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7555 |
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with the work done to it, yes. this was not a rebuild. it was an endurance modest race build. substantial head, port, valve seat work, undercut and otherwise fancy valves, forged pistons. and critically important, oiling and cooling to support it all. not having a performance background, i'm pushing things in a nerdly manner. i used to sweat when i revved it past 3200. i'm running up to 4000 rpm now and it seems happy. so then i tune it for mid 3000's and of course it breathes gets up the HP curve, .... lather rinse repeat. i do not know what the limit is. that's what i'm working at. it's just metal. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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InRogue
AMC Nut Joined: Aug/20/2018 Location: Florida Status: Offline Points: 362 |
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I would believe a 40 would work better, but yes there's always smaller vents.....I used to run the SU carbs with turbo with great success. I used the HS series from 1 1/2" to 2", but always found the 1 3/4" was the best all around size for what I needed. If you want something different....
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Always roll with the correct damper crown, a generous helping of flex tandems and a pocket full of brass fitting nickel slits.
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19692 |
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So the venturii on the IDF and IDA are changeable, the DG series is fixed. With the height of the IDF/IDA maybe you should have used a side draft DCOE and a curved adapter. The extra length and curve would add some flow resistance though. How close is an air cleaner going to be to the hood? I'd always thought a turbo with 3-5 psi would be great, but with the rather small sealing surfaces I wouldn't put more than 6 psi to it, and even then I think I'd want to copper o-ring the cylinders or use a solid copper head gasket (the later probably the easiest). Actually, I just looked up some info about copper head gaskets and they recommend a copper wire o-ring WITH the gasket! I've seen copper wire o-rings used with normal gaskets though. 4 psi would theoretically add about 50% in power over the base power, so should be adequate.
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Frank Swygert
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InRogue
AMC Nut Joined: Aug/20/2018 Location: Florida Status: Offline Points: 362 |
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I always ran low boost, never over 10 psi with the vw's, never had to do a thing and they don't have a gasket. I would think he could get away with 8 psi okay.
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Always roll with the correct damper crown, a generous helping of flex tandems and a pocket full of brass fitting nickel slits.
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Jmerican
AMC Addicted Joined: Mar/29/2016 Location: Seattle, Wa Status: Offline Points: 585 |
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there are many other important factors in matching carburetion than cfm. Those caught up in that are missing the whole picture.
Keep going.
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Ken_Parkman
AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1814 |
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The biggest problem is that calculation everyone uses for carb sizing was written by someone who does not know what an engine looks like, what it does, or how it works. It is woefully incorrect.
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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I'd add to that that an engine is MORE than just an air pump! IF it's tuned correctly, you actually will flow MORE air than the engine would normally pump if it was operating strictly as an air compressor sort of situation. There's scavanging, the inertia of the air, tuning the exhaust (to aid scavanging - pulling air in while the valves are open even just a little) Small valves and ports are only part of it - add velocity - push the air harder, faster, even without boost it can flow more than a mere CID calculation would lead you to believe. I also seem to recall area expert, Ken, posted about how carbs rated the same may flow far differently - and it's not just flow, what about venturi design? I seem to recall also that the Motorcraft 4300 had a better design than some of the carbs people swear are performance carbs. (I still want to yank and toss that bloody Edelbrock that's on my 70 now and put a properly restored 4300 on it) As far as carbs - Now this is V8 info, but hey, I'm running dual quad on my 360, two crappy edelbrocks (why do I seem to get cursed with those?) and if my memory serves - they are 600s, and that means I'm running 1200 WOT on a 360 bored to 37X They are linked directly meaning one to one - so when I mash it both primaries open and it's fine with torque - in fact, too much for the street until I get the cal-tracs on...... finally. Anyway, good luck! Go by real life and skip the simplistic calculations if your engine is not stock and you have good pipes, good scavanging and so on. Once that air starts moving it has inertia....... and will wish to keep moving unless something slows or stops it and good flow will "suck" more in than you'd expect. I know, this guy so picky with terms and being proper used the word suck. Air isn't sucked in, it's pushed in and good output creates lower pressure on the out-going end, causing the 14.xx psi air pressure to push air in more easily and intertia makes it want to keep moving even when the pressure difference is relaxed a bit. Anywho, that's my take - I'm not a professional race car driver nor do I play one on TV. My racing and autocross was largely illegal at the time. Shhhhh......
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