switching to carbs

[JasonM914]

does anyone have advice about switching to carbs in a 1.7? Is there any real performance gains? What are the negatives? Any info would be great.

[Conrad W Peden]

You will need to change the cam and the distributor.

Get an 050 dist. and then choose the type of cam based on the type of perormance you are looking for.

After that you may want to look at head work(porting/polishing) then compression ratio.

Its all depending on why you are going to carbs.

If you are looking for real horsepower then this isn't a multiple choice question. The anwer is all of the above. Except maybe increasing the compression ratio.

After this type of work is done then you will need a way to get all this extra exhaust out of the engine too.

If it is just a case of an FI system that is too costly to fix then I would say a set of 36mm or 40mm carbs and the 050 dist. will get you around town respectablely.

------------------
CWP/VIR
72 914 L20E in rusto.
73 914 L20E 2.0L in resto.
http://members.rennlist.com/a914lover

[Dave at Pelican Parts]

If the motor is completely stock, you will hurt the performance by slapping on a set of carbs. After you tune and re-jet them, you'll have about the same performance as a properly-functioning FI system. You might get a little bit at the top end, but if so it will be at the expense of the nice mid-range that the 914 motors have.

You do not have to replace the stock distributor. Nor do you have to replace the cam. However, you can actually get some real power gains if you do replace the cam. Swapping to the 050 or to the stock 1.8 distributor would help some as well.

There are significant downsides. First of all, there are a number of issues you'll have to figure out. Things like the crankcase and head vent system, the fuel vapor system, how to power the fuel pump, and so on. Second, you'll wind up with lousy cold running behavior. Third, you'll have the wrong fuel mixture when air conditions (humidity, temperature, pressure, etc.) change significantly. And so on. In general, carb setups offer worse overall driveability.

--DD

[TimW]

Quick answer: Don't do it.

Soap Box Answer: Speaking first hand, way back when, after an engine fire that completely destroyed the 1.7L FI, I swapped the FI for dual-Delortos without changing anything internal. I never could get the engine running smoothly. Same conditions Dave described, probably for the same reason.

But...I have heard of people getting carbs running well on FI engines w/o internal modifications. That may just be an urban legend? (By FI engine internals I mean [primarily] a new cam designed for carbs.)

There is also a political side to this. It's generally accepted that the FI system, when properly maintained, will give excellent performance. So many will ask, why switch?

Rather than simply swapping FI for carbs, I might suggest you keep your FI motor original, and find a different one you can build up with all the carb related goodies.

That's my, how do you say?, $.02.

[Conrad W Peden]

I stand modified (rather than corrected)

(didn't say it wouldn't work)

[JasonM914]

Thanks for the input . I have a poorly functioning FI system, and thought maybe carbs would be a cheaper/easier fix, but it sounds like its worth it to put the money into figuring out the problems. Thanks again!

[TimW]

I don’t disagree the suggestions above wouldn’t work, in fact they would. They have been proved time and time again. I guess I’ve just become one of those who hates to see a good F.I. converted.

If you have a poorly functioning FI system, I can think of a few next steps:

1. Check the posts here and see if someone has had the same problems you have – see what they did.
2. Post your specific questions here, see what the group comes up with.
3. Take you car to a shop and have them look it over. (Put a cap on what your willing too spend beforehand.)
4. Your in CA right? Maybe someone local would be willing to check it out?
5. Maybe someone could suggests some good books on 914 F.I. (I’d like to know that one for myself hint hint hint).

Also check out the Ignition Systems & Fuel Injection tech articles here at: http://www.pelicanparts.com/914/914tech_articles.htm

But if it turns out you need 4 new injectors, a new fuel pump, etc., etc. etc., then just make sure that when you compare the cost of fixing the FI with the cost of carbs that you include the cost of everything above: the carbs themselves, new fuel pump, new cam [which required cracking the case apart which will introduce it’s own set of problems and expenses], new gasket kit, etc., etc. etc.

Oh, and don’t forget the fun stuff you’ll also be temped too do since the engine will be apart anyway, like porting & polishing, balancing, etc.

Don’t let me talk you out of carbs, just make sure you think it through.



[This message has been edited by TimW (edited 01-22-2001).]

[DDS]

There's a great article on this website or the 914 club by Kjell somethingorotherswedish IIRC about troubleshooting the D-jet.

Wayne told me that there are lots of 1.7l engines out there in CA that are basically worthless. ($30 I think he said, he mentioned a particular wrecker) Have these all been stripped of the FI?

Haven't tangled with repairs to my 2.0FI yet but I paid less for a running 1.7 parts car than a set of carbs upgrade would cost. (sold the engine and FI already) Lots of hassle, but lots of expensive spares too. You could build the second engine at your leisure and hopefully scavenge enough of the FI to get the 'first' engine going. Just a thought.
Good luck!
Dave
BTW - If I can't find a six reasonably I intend to ruin my 2.0 to get 150 or so HP, either through carbs or aftermarket FI and a top-notch build from the cases and crank on up. BTW, This is starting to make the six look cheap.
BTW also - Tim makes a good point about carbs, cost, splitting cases and the cam. I was reading in Tom wilson's book that type 4 cams tend to wear, with as many as 30% of those submitted as cores being unusable. Might be worth checking on that before you decide to plunk down real cash on the stock FI on the basis of NOT having to split the cases.