# carb conversion problems/questions



## Antikrist~86CGT~ (Mar 24, 2009)

I had a few questions for everyone running carbs, I've converted my 86 Audi coupe GT from CIS to a weber 38 and I'm having some problems. here's whats been done to it so far. the coil is an MSD blaster 2, Bosch+4 spark plugs, 8mm wires, all other ignition stuff is stock. I've had the head decked to raise the compression a bit, 5 angle job and a mild port/polish with a 272 cam. Audi 5-2-1 "header", high flow cat, 2.5" all the way, and a Magnaflow muffler. now, I got her started and running, she sounds BEAUTIFUL! but she keeps boiling over coolant from the overflow. I've been told this sounds like a timing issue, but all my timing marks are dead on TDC. would this factor in? the boiling over stops once the fan kicks on but returns shortly after it stops running is there a secret to running these engines with carbs? I know it's a 5 cylinder but its essentially the old 8V VW motor with an extra cylinder and 2 more valves
is there any trick to the timing? anything to look for? where to start? I've been working on this swap for over a year and I really need this thing on the road ANY help ANYONE could offer would be GREATLY appreciated! TIA all.
I'll post some pics up of the setup tomorrow.
Joey


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## Antikrist~86CGT~ (Mar 24, 2009)

*update on my situation for any who might care....*

so, after putting the crank and cam timing back to TDC, I started her up, cold and lumpy at first but she sounds sooo nice once she's warmed up!







I got the boiling over issue sorted, I'm guessing it was the timing and lack of a thermostat, because I let her run for a good bit, revving her up and no boil over







now immediately off throttle I'm getting some popping/burping/backfiring from the carb when I romp it hard, I'm thinking the timing may still be off on the distributor because when I threw the timing light on it the crank timing was off(?!?) would the distributor timing throw the crank timing off like that? I thought my lil bro had put the distributor back to TDC but I'm thinking he didn't now and he's MIA at the moment so I can't strangle him >.< lol. so I'm gonna go back out in the ridiculous heat and reset all the timing AGAIN :\ and give it another shot. gonna have to get the carb back to baseline specs again too which is gonna annoy me I'm sure but hopefully it's just a matter of tuning the carb to get it finished. *just ran out checked and reset the timing, the distributor was off slightly so I reset it to TDC as well. didn't try to start it yet because I haven't gotten the carb back to "from the factory" specs yet. hopefully I can lure my horribly pu$$y-whipped older brother over to play with the carb seeing as he's the only person I know who has formal experience and knowledge with carbs. anyone here have any experience with the 38/38? any tips for me? I'm hoping that by Sunday she'll be drivable and I can get her to the DMV on Monday. but that probably won't happen. 








Joey
a pic for you all, I know I need some nice lines and a better FPR, but the budget is a bit tight at the moment.

















_Modified by Antikrist~86CGT~ at 7:54 PM 7-2-2009_


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## B4S (Apr 16, 2003)

*FV-QR*

Damn, that's a nice setup. Never knew they made 5cyl carb manifolds. When exactly does the burping and popping start? When you are on the throttle, or immediately after you stomp on it and remove your foot from the pedal? Burping and popping means a lean condition, usually, but if it's only when there is no load on the motor, it's not the end of the world. It's how it drives that's important. If it stumbles while driving, then you'll definitely need to jet a bit richer. A lean pop off throttle without load could also point to the idle mixture screw needing a bit more turning-out to richen up the idle.


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (B4S)*

thanks!







yea, it took alot to get ahold of the manifold, I started tossing around the idea about 2 years ago, when I bought the CGT the CIS system was in HORRENDOUS shape, vacuum lines rotting, everything neglected and filthy, I expressed my interest in converting to a carb and was ridiculed for not wanting to stay with CIS. people telling me to just learn it and love it, etc. but someone on audiworld(before it changed and everyone moved to quattroworld) directed me to a guy in new york who had run a carb after his CIS lines caught fire. he went back to CIS and sold me the manifold







said he got it off ebay europe/uk or something. I don't know of anyone else (in the states at least) running a carb'd 5 cylinder, makes getting info on it a bit of a problem







lol. now the popping,etc. starts as soon as I stomp on it with no load. so should I get it moving, give it some stomps and whatnot and then adjust? I absolutely LOVE the sound, and the response when I had her moving was amazing!







now by "jet a bit richer" you mean adjust the jets themselves correct? not just the mixture screws? thanks so much for the info and kind words, hopefully I'll get a chance to take her for a spin today and see how she's doing, I'll post more pics, and a video of her running soon.







http://****************.com/smile/emthup.gif 








Joey


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## B4S (Apr 16, 2003)

*FV-QR*

With no load on it, the only real tuning you can reliably do is tweak the mixture screw(s). Get it to idle well, with the proper timing, and start the tuning once you start to drive it. Here's a little diagram that may help with exactly what jet/tube to tune with for varying conditions:








You probably won't have much tuning to do in regards to emulsion tubes, they're pretty much the last thing that you should touch. It's very much a black art now







. Start with the basic jets, idle, main, and air correctors. I'm not too familiar with the 38/38, but if it's similar to the 32/36, then the idle air correctors are not adjustable, so they're out of the picture. The air correctors will move the fuel curve of the main jet up or down in the RPM range, so a larger air corrector will start the main early, and lean it out up top. A smaller one will do the opposite. Once you get the basics down, you'll see it all starts to become second nature...or you'll have the towing company's # memorized







.


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (B4S)*

ok so I did very little fiddling today, but let me get a few things correct,
I should return the carb to baseline specs, make sure timing is all at TDC, start it and let it warm up, once the choke lets off fiddle with the mixture screws til it's nice and stable then adjust the idle screw to smooth and stabilize it correct so far?
now with regards to tuning the jets, should I go by 1/4 turns identical on both due to it being synchronous to "road tune" her? also I stumbled across this page http://www.racetep.com/webfuelspark.html#webfuel would this be a good investment? it says not to exceed 3.5psi in all the weber stuff but these guys swear 4psi is perfect. I got a poopy mr.gasket pump and regulator(*braces for the ridicule) on it now..any recommendations? its KILLIN me that I'm not out on the road yet















Joey


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## B4S (Apr 16, 2003)

*FV-QR*

I run 3.5-4psi, as long as the needle valve isn't oversized, you'll be fine with a bit of fluctuation. I've never tuned a synchronous carb like the 38/38, so I'm not certain if you turn both or just one screw. The idle screw itself doesn't really help much with the cruise mixture, it's the size of the jet itself. The cruise mixture is fed from the idle jet through the progression holes as the throttle plate crosses over them. Having a rich idle will help with the throttle response at tip-in, although you shouldn't have to go very rich to take advantage of that. Don't waste any time with the mixture screws for cruise, just get the idle set where you want it, and size the idle jet itself for your cruise mixture, making appropriate changes to the idle mixture screw if you go bigger or smaller on the jet itself.


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (B4S)*

ok so I started her, let her warm up, moved the FPR up to 4PSI, fiddled with the mixture screws and idle screw til it sounded nice, fiddled with the air corrector jets slightly, no real popping except from the exhaust at very high RPM(4500-6000RPM) with NO load. so I back her out and take her for a spin, a lil sluggish in the low RPM range of 1st gear(idle-about 2800/3000 RPMs) then rather nice







so I swing a left to get her on the straight-away of the parking lot to run her through more then one gear, and at the end of the turn, boom. she dies.







is this sounding like a fuel pump issue? its getting the proper PSI but I'm not sure if its flowing enough. I'm about to buy the Carter4070 to replace this Mr.gasket piece of poop fuel pump. it apparently only flows like 30-35GPH http://****************.com/smile/emthdown.gif any advice? thanks so much for all your input! http://****************.com/smile/emthup.gif















Joey


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## B4S (Apr 16, 2003)

*FV-QR*

My guess is that the float bowl is emptying out. When it dies, pull the cover off and see if there is any fuel there.


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (B4S)*

ok will do http://****************.com/smile/emthup.gif so would that point to a pump issue? I'm gonna order the Carter from summit regardless, this pump is a POS!








Joey


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## B4S (Apr 16, 2003)

*FV-QR*

It might not be completely pump related, it could also be a half clogged fuel filter (been there, walked home from that), or a stuck needle valve. That regulator is pretty much junk, it restricts volume as well as pressure. I'm running a Facet 40105 pump and no regulator, works great. The carter 4070 NEEDS a regulator, so when you order it, also get a cheap holley 1-4psi reg http://****************.com/smile/emthup.gif.


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (B4S)*

now I'm a lil confused







which would be the best bet? I see lotsa people with the carter with a regulator down the line, one site says it(the carter) only flows 4psi another says 6psi one says no regulator needed the other says I do. and the facet 40105's I'm finding on the net are all saying it flows to 4.5psi







the facet is looking appealing because of my rather tight budget at the moment, but I'm afraid of damaging the carb







I'm gonna go get a new fuel filter screen tomorrow, and start there. now another question, I have the fuel line coming up from the passenger side of the engine bay(rubber line all the way to the tank) fuel pump in stock location behind passenger rear wheel area, filter after the pump in the engine bay before the regulator, then the line runs around the front passenger fender side of the engine bay around behind the headlight, u turning to the inlet. could the distance be a problem? the bends? should I just straight shot it from the PS bullkhead over the intake mani to the inlet for a direct flow? should I run a pre-pump filter as well as an aft? sorry to throw so much at you, I REALLY appreciate all the help you've been giving me







your the only one who's been giving me any kind of help with my carb questions. and for that I couldn't thank you enough. http://****************.com/smile/emthup.gif








Joey


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## B4S (Apr 16, 2003)

*FV-QR*

No probs dude, just trying to ensure that you don't swap back to EFI and dump that super cool setup





















http://****************.com/smile/emthup.gif
The run isn't an issue at all, no worries there. The facet pump is a 2-4.5psi model, usually pumping around 4 according to my gauge. It's perfectly fine to run 4psi on that carb, I have run one myself with this same pump and no regulator. There actually is nothing to break inside the carb, so you're safe. If you were to run 6psi on it, then it would overflow the needle valve and you'd have leaks from every hole. If the float height is set properly, then you've got some leeway in pressure, which is what makes the facet just right







. Now, for the fueling needs of a 5cyl, perhaps a larger pump is better, or at least one that flows a bit more than 30-35gph. It's been fine for me so far, but I'm only at 105whp (dynoed).
No matter what anything says, ESPECIALLY the vortex, the carter needs an FPR. There have been a few threads here that state that, after the owners have had nothing but issues with pressure. Some guys get away with it somehow, but I'm willing to bet there are other factors that are just being ignored. I don't run a pre-pump filter, but all my fuel lines (and tank) are brand new, so I simplified my setup by omitting it.
Long story short: 2.5-4.5psi is fine, pre-pump filter is optional (IMO), and the run of lines is not an issue







.


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## 75injectedSB (Feb 6, 2006)

*Re: FV-QR (B4S)*

I had some of your same problems on a rabbit running a 32/36 and carter 4070. I was running that same FPR that you are and it was garbage. The car would not run, take it out and stomp on it and it would die or bog really hard. I would jump out, turn the dial on the FPR for more pressure and it would run fine for a little while, start the same problems again, jump out and turn the knob again. Vicious cycle. I switched it out for a Holley 1-4 and set it at 3 psi and the car ran so much better.


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (75injectedSB)*

hmmm could that be a contributing culprit to the popping on immediate no load throttle mashing? lol. I bit the bullet and just ordered the 4070 and the Holley 1-4 from summit, should have em in about 2-3 days http://****************.com/smile/emthup.gif 








Joey


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (Antikrist~86CGT~)*

well...I got the Carter4070 and the Holley FPR on, took some bracket making but it looks nice http://****************.com/smile/emthup.gif and of course I'm still having some problems..







I didn't change much in regard to the carburetor settings, but turned her over, she was cold slow and lumpy, set the FPR to 3.5psi my brother played with the idle mixture screws slightly, she stabilized a little and we allowed her to warm up. now when I would give it a little gas while it was warming up, she would stumble immediately but if I coaxed her above the stumbling, she smoothed out until I let off the pedal at which point the RPM dropped ridiculously low(2-400) or just die completely. after it warmed up, we tried to get the idle to just stabilize around 1000(where I would like it) and EVERY time we thought we had it, I'd blip the throttle and the idle would change itself







sometimes to 600 sometimes to 2000







also when I would blip the throttle she was still popping occasionally bumped it to 4psi and it seemed to smooth out a bit more. when we thought we had it stable enough I took it for a drive round the parking lot, a lil sluggish of a start but woke up after about 2200, but as soon as I let off the throttle the idle jumped up and stayed pretty high(1800) and when I was taking off to get back to the driveway she sputtered a little, but no dying in the turns http://****************.com/smile/emthup.gif we did this about 6 times with it popping,dying whatever before I gave up, thought the return spring might be binding where it was so we moved it, same ****.







oh and for some reason my fuel filter after the Carter was filling with fuel, draining almost completely, and then refilling at what seemed like the last minute. UNLESS the throttle was opened up, at which point it would fill the filter rapidly and constantly....???!!!WTF ???!!! I know I need to return the carb settings to BASE-LINE and try again before getting too upset and setting this fecking pig on fire but I don't know WTF to do. I don't wanna go back to FI but if I can't get this thing on the road and to the DMV soon I won't have much of a choice.








I'll post a pic of the setup as it is now tomorrow. http://****************.com/smile/emthup.gif 
Joey


_Modified by Antikrist~86CGT~ at 8:57 PM 7-10-2009_


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## chickenfriend (Jan 31, 2005)

*Re: FV-QR (Antikrist~86CGT~)*

Your throttle plates might be binding in their bores. 
Back-off the idle speed screw, take the carb off when warm, turn it upside down, and watch the action of the plates as you work the throttle cam by hand.
Having the throttle shaft nut too tight, or having the plates off-center, can cause sticking of the plates, resulting in erratic idle.
Good luck.


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (chickenfriend)*

I loosened the throttle shaft nut ever so slightly, not too much of a change, I fiddled with my distributor timing ever so slightly and it seems to have stopped the popping from the carb, and smooth her out a bit, but its popping slightly from the exhaust now with no load around 4000rpm. I took her out and the response is FANTASTIC! http://****************.com/smile/emthup.gif







but the idle is still a lil jumpy, I'm beginning to think its the throttle cable and the ungodly way it's set up because after the first blast down the parking lot when I let off throttle and slowed down to turn around the idle sat at like 2000! but when I tapped the accelerator pedal up the idle returned to where it should be (1000) so its seeming like I'm gonna have to figure out WTF to do about the cable







before I can go any further. I mounted the carter in the engine bay as you can see in the pic








should I have mounted it in the stock location in front of the passenger rear wheel? the filter after the pump is not constantly full, and for this thing supposedly being able to flow high GPH it's seeming like bull**** because wouldn't that mean my fuel filter (after the carter) should be always full? do I need a pre-pump pump to get the gas to the carter? should I put my poopy Mr.Gasket one back in the stock location to help out? I'm running out of patience and have already ran out of time. if I cant get this thing drivable in the next 2 weeks I'm giving up. I simply can't put anymore time or money into this ****ing project. it's my daily driver (which it hasn't been for OVER a year!) and if it can't be that again soon I'm going back to the horrid CIS because at least that ran. I don't know, I think I just bit off more then I could chew and should have just left well enough alone








Joey


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## chickenfriend (Jan 31, 2005)

*Re: FV-QR (Antikrist~86CGT~)*

Get your idle around 900 rpm and do timing. What is the timing spec for your engine? I doubt that it is TDC.
Your pump might be sucking air between it and the tank. Old hoses from the tank or a loose connection back there would be culprits. Air in the lines will cause pressure fluctuations and vapor lock. That's why some prefer to place electric pumps in the back, next to the tank, so the gas is driven forward, not sucked to the front. Do this: Unhook your filter and put a long hose on the pump outlet. Turn the pump on and drain the gas in a bucket. Judge your pump output by that test.
I would use a longer throttle cable and hook the cable end fitting directly to the throttle cam ball stud, to elimimate the linkage pivot adapter gizmo. Fabricate a holding bracket for the cable as close to the carb as possible.
The coolant boiling-over problem you had is not a carburetor-related.
Last but not least,







find an attachment point for your throttle cam return spring that is on the engine and isolated from the bay. From your first picture, it looks like the spring is attached off the engine, to something in the bay. Every rock of the engine on its mounts is going to move the throttle!







You don't want that. 
Good Luck.


_Modified by chickenfriend at 4:56 PM 7-11-2009_


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (chickenfriend)*

my timing was set right, with a timing light, (well, since I have no bentley I've relied on the input of other CGT owners for the correct marks to use) but no matter what adjustments I made to the carb to get the idle right it wouldn't go above 600rpm and still pop and try to die off low throttle with no load. I fiddled with the dizzy to get it to just idle smoothly. and surprise, no pops.







all the lines are rubber from tank to carb and all fairly new, with new clamps all over. I'm gonna run the throttle cable directly to the cam and see if that helps with the idle. this gizmo worked well on the holley 5200 but the throttle cam moved opposite of what the 38 does (it was a push the weber's a pull) and I was just using it to make up for the distance needed :stupid: the return line is plugged and deleted really well but my "vent" line is just hanging should that be capped/plugged as well? should I just say feck it and put the pump in the back?








Joey 


_Modified by Antikrist~86CGT~ at 3:52 PM 7-11-2009_


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## chickenfriend (Jan 31, 2005)

*Re: FV-QR (Antikrist~86CGT~)*

Ok, but you need to change the return spring location, as I mentioned above. That's the biggest problem I see visually in the set-up.
Pops and backfires suggest a timing problem. If your spec positions are not working for you, then I suspect the cam could be off a notch or more on the belt.
Keep trying to get it, but don't rule out getting some help from local enthusiast, like an older air-cooled guy.


_Modified by chickenfriend at 5:45 PM 7-11-2009_


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (chickenfriend)*

sorry for the goofy response, I read your reply in an email which doesn't give all the text of your post







I'm working on the return spring bracket now because I definitely see what your saying! not good at all! lol, for the throttle cable holder thingy, is it okay if the cable angles up from the loop holding it? I'm trying to get the cable from the loop/holder to the throttle cam in as straight and even a line as I can, but after that its gotta go up to clear the head/valve cover. will that be okay? and as far as finding another enthusiast around here







no such luck. its all mustangs and domestic, the only imports are the horrible hondas andother assorted ricers and all the VAG guys around here don't like anything that isn't turbo or FI







there IS a place about 20 mins. from me that specializes in older porsches and german stuff, so if I absolutely MU$T I'll take it to them but they're WAY expensive.







I'm gonna head back out in a second to continue raising my hairline a few millimeters







and btw, THANKS a bunch for the input! http://****************.com/smile/emthup.gif


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## chickenfriend (Jan 31, 2005)

*Re: FV-QR (Antikrist~86CGT~)*

Good. I am glad you see what I am saying about the return spring! I had to chuckle when I realized the problem there!
On the throttle cable, I was just thinking you could drill a hole in that blue plate thing sticking up from the carb side of the valve cover, and start it from there. Looks like you might need a few inches more of cable length, however, and it looks like what you already have was not cheap!


_Modified by chickenfriend at 9:32 PM 7-11-2009_


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (chickenfriend)*

yea, I chuckled myself!







and I did exactly what you were thinking and drilled a hole in the blue plate thing (







) should line up perfect I have some bicycle brake cable that's nice and long that I'll feed through and hook up tomorrow, but with the return spring hooked up and the cable unhooked she started and warmed up nice, with no popping when I blipped the throttle after warm-up and the idle stayed and returned steady http://****************.com/smile/emthup.gif so should I move the pump? would it be bad to put the old pump back where it was as an assist? I'll be taking, and putting up more pics tomorrow and maybe a vid of it running








Joey


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## chickenfriend (Jan 31, 2005)

*Re: FV-QR (Antikrist~86CGT~)*

Right on! http://****************.com/smile/emthup.gif 
I'd leave the pump where it is, for now, if things seem to be working ok. It looks like a durable unit. You can always move it later if you have to.



_Modified by chickenfriend at 10:21 PM 7-11-2009_


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## ejg3855 (Sep 23, 2004)

*FV-QR*

very interested and want that manifold.


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (ejg3855)*

man it took me ALOT of scrounging around to find this thing! I was lucky enough to find an enthusiast in the states who got it from europe(the UK I believe) I thought about getting a few copies of mine made as well as getting a fab shop to make a couple of side-draft manifolds (single and dual) but figuring out how to split the 5th intake runner on a dual may be a bit tricky lol.
Joey


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## ejg3855 (Sep 23, 2004)

*FV-QR*

do you have a part number for it ?


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## Antikrist~86CGT~ (Mar 24, 2009)

*Re: FV-QR (ejg3855)*

no, no part numbers ever located on the mani







and believe me I looked! I'll get some part#'s for you though off vagcat for some carb manifolds if your really interested http://****************.com/smile/emthup.gif
Joey


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