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Posted by: bigjim Mar 6 2004, 01:30 PM

okay i give up, i want to go to carbuertor here is the question which one to do duals or SINGLE PROGRESSIVE 32/36 i like the idea about one carb any thoughts 1976 2.0l d-jet 914
jim

Posted by: 7391420 Mar 6 2004, 01:34 PM

Give us some more info on your car, IE- what engine, what year, is it FI now, etc.

generally for the 2.0 liter cars dual webber 40's or 44' are the way to go, but there is some more work involved than just ripping out the FI and poping in the carbs, especially if you want it to run well!

-adam

Posted by: SirAndy Mar 6 2004, 01:35 PM

single carbs are crap. go dual webbers.
BUT, if you do so, get a more agressive cam in there so you actually get some punch, otherwise you just spend top $$$ on carbs that won't do you any better than FI.

big questions is: WHY???

i am quite happy with my D-Jet FI
Andy

Posted by: McMark Mar 6 2004, 01:58 PM

Please don't throw on carbs expecting your car to idle perfectly and pull hard. It won't happen.

<_<

Posted by: SirAndy Mar 6 2004, 02:09 PM

- check the engine wire harness first. take it out, check out all wires for cracks. they get old and brittle. also check all the connectors for corrosion and clean the ground contacts (on the engine).
if that doesn't work out, Jeff Bowlsby offers new and rebuild engine harnesses.

- make sure you have enough fuel pressure. ~34 lb

- check fuel-filter, replace if suspicious

- check/clean injectors

- check FI trigger points

- check head-temp sensor

- check MPS, contact Bleyseng about a good used MPS. he rebuilds them.

- check vacuum hoses, replace if needed

- check ignition system (coil, cap, rotor, points, plug wires & plugs)

i probably forgot a few things, hopefully others will chime in ...

hope this helps a bit,
Andy

Posted by: steve@ottosvenice.com Mar 6 2004, 02:13 PM

I have gotten them to work but it not really worth all that is involed: Insulate the runners by coating them in Dip it Drenched Ace bandage .
Use a 1983 2.8 v-6 Blazer Carb base heating element.
Get a Ford pinto Air cleaner and mod it to take hot air off the hot air outlet in cylinder tin fitted to a 74 Bus.
Take the intake base that the carb bolt to put a good coating od Dipit on the outside but not at the tab on the bottom of the casting. The peice that connects the Carb base casting to the block needs to be steel not Aluminum.
I used a manual choke carb .
I had a switch on the dash for the Carb hearter and installed a Icing gauge .. Good luck it can be done. Steve


Attached image(s)

Posted by: synthesisdv Mar 6 2004, 03:09 PM

we live down here in miami, why do you need all the heat in the carb? Do you have to do the same thing with dual carbs?

dr

Posted by: Bleyseng Mar 6 2004, 03:26 PM

Keep the Djet as it will run better than any carb setup.
What is wrong with the car to make you want to change over to pos carbs?

Geoff

Posted by: kdfoust Mar 6 2004, 03:56 PM

Hey Jim;

If I make your location correctly you're in SoCal. Do you think that your '76 will pass smog with carbs(s)?

Regards,
Kevin

Posted by: 914ghost Mar 6 2004, 04:53 PM

Dont do it..
unless it's your only option.
I have carbs I LOVE carbs....and I know carbs in general. If you have most of the F/I and it ever worked correctly then learn it and fix it.
It will be better for what its worth.
If you have only pieces of the F/I and its all tore up anyway and you KNOW carbs well (which I cant assume since you're considering a single progressive!!) then go with the carbs.
my .02 is get the 44 webers or 40 Dellorto's and the correct tech book for the carbs.
www.cbperformance.com has it all.
I know the progressive carbs are cheap...but you wanna guess why?
They're crap compared to F/I OR Dual Carbs.
-Bob O

Posted by: sunfloweryellow914 Mar 6 2004, 06:47 PM

I've also been thinking about a single carb, in a theoretical sense. To start with, the size of the intake maniforld is only 36mm. I measured it today. First thought: What is the point of having a carb which is bigger than the intake manifold? Next thought: If you have a carb feeding each cylinder, then the air flow gets interupted with each revolution. Therefor the air pulses or "hammers" in the intake manifold. This must be why it is necessary to raise the carb several inches above the head, and also why it is also necessary to put the short pipe above the carb, but if you think of the acoustics of such a system, there must be a particular frequency (read revs) at which the acoustic system works perfectly. At other rpms it wouldn"t work as well.
On the other hand if you had a PROPERLY DESIGNED MANIFOLD, then the air would be pulled through the carb more or less continuously, and voila! Everything works evenly at all rpms. Notice that most American cars were built with single carbs before fuel injection became possible. Almost none had a carb for each cylinder. At any rate if you had a single carb, you wouldn't have to worry about linkage and syncing etc. This is all theoretical. I must be wrong, because everyone agrees that the progressive single carb system sucks. Someone tell me what I am missing in this.

Posted by: DNHunt Mar 6 2004, 07:29 PM

Some of what you say is correct, however keep in mind, with carbs you have the gas and air mixed in the intake manifold. If you have a single carb you have the long runners similar to FI which provides ample opportunity for fuel to condense on runners. If there is any compression in the intake manifold of the AF mix, condensation can and probably will occur and air fuel mix is screwed up. Also, during cold opperation, condensation will occur. Carbs, keep the runners short (webers or duel Dels). If you can keep the injection.

Dave

PS I love MS

Posted by: Bleyseng Mar 6 2004, 07:34 PM

What you are missing is the fuel condenses on the long steel runners and causes poor running.
This is why the FI is best as it sprays the gas right at the intake valve, perfect mixture.
Dual carbs have the short manifolds which works pretty well went the engine is hot but crappie when cold as the fuel doesnt mix well.
For the best running, use FI Djet or Megasquirt or Whatever....

Truely, the single carbs just dont work very well. Ok the car will run but not as it was designed.

The duals take work to get and keep running.

I have had 4 years now of perfect running with the Djet I reinstalled on my car. Yep it was a pain in the butt, but I did learn alot about Djet in the process.

Posted by: sunfloweryellow914 Mar 6 2004, 07:53 PM

Aha! Condensation! So you have to heat up the runners.

Posted by: Mueller Mar 6 2004, 07:56 PM

and they came out with some of the higher HP cars had dual 4 barrels or a "six-pack" to try and get around the poorly located single 4 barrel carb.....a

but if you noticed, most of the good European cars had a carb (or venturi) for each cylinder...

look at the design of the flat 4...there is no possible way to make a single carb manifold "correctly" PERIOD....

anything can be made to work, but that does not mean it's a good idea.....

Posted by: steve@ottosvenice.com Mar 6 2004, 08:04 PM

That why you need to insulate the runners and heat the base of the Carb plus pull in hot air other wise you will get Icing. steve

Posted by: rhodyguy Mar 6 2004, 08:34 PM

fucked up fuel injection runs just as bad as a fucked up set of carbs. my 73 with 40's and the mystery motor pulls real hard. cobras with 4 carbs and a throat for each cylinder pulled REAL hard. farraris and porsches too.

kevin

Posted by: Mueller Mar 7 2004, 10:13 AM

having an A&P License, I know all about single carbs used on aircraft

yes, anything can be done, but there are better alternatives.....

I guess if this guy got the single carb for free along with all the heaters/insulators that would be fine, but if he planned on spending a few hundred bucks to do a half-a$$ repair, he'd be better off investing his money to do it properly,either with dual carbs or fuel injection (factory or aftermarket)

Posted by: 914ghost Mar 7 2004, 11:25 AM

About the Carb vs Manifold size too-
Having a Larger carb diameter than manifold is sort of like the venturi effect.
When you get carbs you can make them "run" with just about any vent/jet setup BUT larger is not always better- Matching the intake manifold to the head is purely for airflow.
But you want a constriction somewhere in the circuit to increase air velocity.
Thats a venruri. Some people think a larger venturi = more air + more gas = more power.
Not really, the engine should create the same amount of negative pressure on each intake stoke so a smaller venturi will make the air passing though it move faster. So there's less chance of the fuel condensing out of the mixture. Also, the smaller venturi has the effect of more 'vacuum' at lower RPM for the carb and can cause the carb to run on a richer or power ciruit sooner- counteracting the leaning effect of a smaller venturi.
Same idea about a smaller diameter runner- the learger the diameter the intake runner the slower the mixture will travel thru it and the greater the chances the fuel will de-atomize.
Thats just for starters...it gets waaay more complicated.
-Bob O

Posted by: garyh Mar 7 2004, 12:48 PM

Dig around in the archives. There's a comment from a racer about carbs on a 914 that's worth repeating:

"After 5 years of adjusting, I'm almost as fast as a stock FI setup." (slight paraphrase)

And this is from someone who appearantly has the time/energy/skill to do carbs right.

YMMV.

Posted by: Bleyseng Mar 7 2004, 01:57 PM

Fact: There is no way that carbs provide the same accurate fuel metering as FI. They are a compromise, feeding fuel across the rpm range going rich to lean.
Check the more modern EFI with its computer realtime readouts. You can adjust the fuel mix at every stage of the rpm range.
The only time carbs are great is on a car that runs at WOT (race car) then you can feed more air and fuel in than a EFI.

Name one car that is produced now with carbs.

Geoff

Posted by: morphenspectra Mar 7 2004, 02:20 PM

I'm not sure, I'll have to check, but I think that ferrari and lamborgini still use carbs on some of their production cars.

Posted by: rhodyguy Mar 7 2004, 02:28 PM

new cars? moot point. so you get better mileage than i do geoff? the " bad carb, good fi" is a debate that will last forever. didn't both the 4 and the 6 have carbs in the beginning?

kevin

Posted by: Bleyseng Mar 7 2004, 04:45 PM

No, the 4 always had FI except for the Euro 1.8 which had dual 40 Solexes.
The six had the carbs but that was to futher separate it from the more expensive 911's.
Carbs are fine if you like em, I think its just keeping your feet back in the '50's.
If and when I go to a six it will be with FI. I love starting my car up even when its cold with a touch of the key and driving off.
Last I checked Ferraris had Throttle body injection.
914's that have a modified cam in them in the past had to have carbs, now we can go to modern EFI like the Megasquirt or Kits set up.Maybe 140hp 2.0l is possible.
Geoff

Posted by: Eric Taylor Mar 7 2004, 08:12 PM

For me personally I would never switch a stock build engine over to carbs, because it will not run nearly as well as d-jet, However if you put in a carb cam won't the car run just as well as with FI, except for the milage? I know that if I do a rebuild on a 4 i'm deffinatly gona put a carb cam in and run dual weber's.
Eric

P.S.
What's the cost on a total Megasquirt system?

Posted by: Bleyseng Mar 7 2004, 08:14 PM

I think maybe $500 excluding dyno time which you should do on a carbed engine too.

Geoff

Posted by: vsg914 Mar 7 2004, 08:53 PM

Posted by: dinomium Mar 7 2004, 11:26 PM

I am going back to Fuel Injection on my 74 2.0. But do I have to buy the mega dollar tri nipple fuel pump or can I use a less exspensive pump for the 75/76 modle years?
Why or why not?
One more reason to go back to FI, production classes at PCA or SCCA autocrosses

Posted by: Bleyseng Mar 7 2004, 11:29 PM

you can use the 75-76 pump and locate it under the tank so you wont suffer from vapor lock. I have an extra pump too laying around

Posted by: dinomium Mar 7 2004, 11:40 PM

[QUOTE]I have an extra pump too laying around
Are you thinkin you might sell it?
I have two that are the later model, but no gas comes out of them... I am not "priming" them correctly? They have been sitting for gawd knows how long and were storred dry

Posted by: Bleyseng Mar 7 2004, 11:43 PM

yeah I'll sell it

Posted by: dinomium Mar 8 2004, 12:11 AM

thanks, I think I might go with a new one form the bird this time... The sun is out and I am running out of time!

Posted by: Bleyseng Mar 8 2004, 12:16 AM

Where are you located anyway?

Posted by: bigjim Mar 8 2004, 12:25 AM

okay you all talked me into it and i think i got it down now i got the d-jet write up by kjell nelin and with this i think i found what was worng Pressure Senor does any one know a good place to get one under $1,000
jim

Posted by: dinomium Mar 8 2004, 12:25 AM

skyscraper free mid town Bremerton WA!!
I saw the sun three times this weekend, that means it is time to drive! I was out at the raceway (spectating) on Saturday, the Alfa club had a skills day. I counted only three Alfs, the rest were a hodge podge...

Posted by: rhodyguy Mar 8 2004, 08:29 AM

they all had fi except the euro 1.8s? then ALL of them didn't have fi.

kevin

Posted by: Bleyseng Mar 8 2004, 09:20 AM

you couldn't buy it here and the Euro 1.8 wasnt in the beginning. I am sure it drove like the 1.7 bus I had with dual Solexes, crappy.

Geoff

Posted by: John Jentz Mar 8 2004, 10:21 AM

Get Brad Anders D-Jet theory and troubleshooting from:

http://members.rennlist.com/pbanders/index.html

This is the absolute best stuff you will find period.

Posted by: Bleyseng Mar 8 2004, 11:08 AM

Yes, Brad Anders wrote the bible on Djet. His garage is full of all these djet gizmos and testers. He is a great guy too! Must be working too much cuz I havent seen him post in awhile.
Geoff

Posted by: dinomium Mar 8 2004, 11:30 AM

that has all the stuff you need to know, thanks for the link!!

Posted by: 7391420 Mar 8 2004, 02:42 PM

OK,,

-I have dual webbers, and the car runs great. I havent had to tune it at all, once it was set up it has been fine for around 7 k miles.

-I agree that FI is better because it's more precise, its smoother, and the car will run better and more evenly up the RPM's...

But,

Answer this,

-What about vapor lock, vac leaks, electrical failures-from PO wiring f-ups, 30+ year old electrical issues, and safety issue of a very old fuel system running at 34psi?


I would say that if your FI is working right, or if you can put the big$$ into fixing it than it's better.

But,

if not, carbs are less problematic, easier to fix, and still run pretty good....IE-they are a comprimise, but when set up correctly, they dont comprimise much.

Posted by: Scott Schroeder Mar 8 2004, 03:48 PM

I posted this on a different thread. I barely did more than lift my car cover since before Thanksgiving. Got in this weekend, turned on the key, pumped the gas once and it fired up and stayed at a nice idle without touching a thing. 30 seconds later I drove away up a hill (under load) without any hesitation or popping/hissing. Over 4 monthes and a ton of climate changes. I am pretty pleased.
My car came with carbs and the PO removed everything relating to the FI. There is no way I would invest money into putting it back on. I will throw that toward a six conversion - that will also most likely be carbed.
It can be done right - regardless of how old the technology. Besides, part of me likes the car to feel a bit rough around the edges... it's part of the fun of owning an old car. If I wanted it to drive like a new honda, I would buy a new honda!
I still really want to build the 250 Gt California replica used in the Ferris Bueler movie. I plan on using a hipo 289 ford - with 4 webers!

Posted by: Dave_Darling Mar 8 2004, 05:31 PM

The only one of those issues that a carb setup cannot have is the 29-36 PSI fuel leaks. Instead, they can leak at 3.5 PSI. Which still means fuel can drip onto the exhaust--which leads to Bad Things regardless of the pressure.

--DD

Posted by: Mark Henry Mar 8 2004, 06:06 PM

I've seen it happen, I've seen the aftermath and I've almost been a victim.

Posted by: garyh Mar 8 2004, 10:42 PM

Rebuilt/Recalibrated by a list member is $150. (Geoff has stock right now IIRC; correct me if I got the price wrong.)

I have one NOS 1.7 MPS.

G.

Posted by: Bleyseng Mar 8 2004, 11:07 PM

Hmm Kevin, I thought you had vapor lock when we went to JP's.

I do have a couple of rebuilt (by me) MPS's but its hard to replenish them. These are recalibrated to the factory spec's of 2.0l's. I think I have one 1.7l one too. Usually I rob these for parts. (good factory diaphrams)

Geoff

Posted by: SirAndy Mar 8 2004, 11:12 PM

i hate carbs ...

Posted by: 914ghost Mar 8 2004, 11:43 PM

Given the choice of which system to have, Carbs or F/I ALREADY installed and in good condition we'd all probably take the F/I. But given a budget of money AND time, and a 30 year old car with a foggy history AND the responsibility of installing and maintaining either one of these.. . .? No contest. Carbs.
I can take just about ANY carb set you give me and piece it together with minimal $ and time and make it work well (maybe not perfect) enough. ANY CARB, rusty, seized, dirty. The parts are available and affordable. Give me an average condition carb and I can make it near perfect. I'd put a street value of an average carb set at $300. And I KNOW when the problem is with the carbs or otherwise.
You know its a friggen crapshoot when you go buy F/I stuff. Its either un-obtainium or used and who knows the REAL condition.
And go into the database and see how many F/I "help wanted" issues there are compared to carbs. Wait...maybe dont go that far...I dont want to know!
Its also a personality thing, carbs are old school cool.
I can adjust em' and I can drive 4000 miles and what's gonna break?
Not the MPS or the AAR or the CHT or anyof the 57 connections or the various relays... ..
yay for Me!!
-Bob O

Posted by: rhodyguy Mar 9 2004, 07:01 AM

no geoff. it was a starter issue on the way to jp's. or rather a generator/alternator indicator bulb and a low battery. with new fuel lines and the rotary pump mounted at about the same elevation as the stock one i've never experienced any hint of vapor lock. YET .

kevin

Posted by: Jake Raby Mar 9 2004, 08:26 AM

some people hate carbs, I hate FI.....

The parts gods preach it because the mark up on a set iof webers is less than 80 bucks.....

Posted by: Bleyseng Mar 9 2004, 09:36 AM

If I am a parts god look out!

I put it back on my 914 ripping out the 40 Dells (still have em) cuz I remember how well my 69 fastback ran for 5 years.
There was no Djet Bilble website when I did it.
It wasnt that hard to find a complete setup at the local junkyard, installed it and it ran pretty well.
The tuning to get the hp and performance is what took time cuz there wasnt shit for info anywhere on it!
"You can't tune Djet"- Bullshit! I worked at it taking things apart and playing with stuff to understand how it worked. Then I took it to a dyno shop and adjusted the MPS to get the right A/F mix and hidden HP.
Then I found Brad Anders and started talking to him, wow the light really went off then. Otherthan the ECU, Djet is sooo simple to understand, no VooDoo.

If you like carbs great, they work pretty well. I still prefer FI.

Geoff

Posted by: 7391420 Mar 9 2004, 10:23 AM

Yeah-What Bob-O said,

-Just like I said, only he's more articulate.

Posted by: dinomium Mar 9 2004, 11:43 AM

Webers do look kewl with the velocity stacks, but with all the other projects I have going, I want something binary.
Works=drive
not works=Mo $$