RustyRotary

iTrader: (2)

After years of sitting, thought to be lost, I've got my '83 driving around again! So now I'm back to a problem that stalled the project in 2008: the carb dumps gas out onto the engine. Not cool.

Nobody I can find has been able to troubleshoot it. 2 rebuilds and an ultrasonic cleaning haven't helped.

It's a surprise Mikuni 44 that came off of a roller I bought solely for replacement windows. $80 on ebay!. However, the goon who owned it before me had tightened the idle screws down so hard that one of the tips broke off inside the seat. I lived with it for a long time on my '83 GS since I couldn't get it out. When it was time to put the carb on my street port GSL I took it to a shop to take care of it. "Sure, we can get that out for ya!" They came back 3 minutes later having taken a center punch and a mallet to it, messing up the seat. Nice. So I figure that's where my gas has been leaking from the whole time.

Even if that isn't actually the problem, I'm tired of messing with a carb that is doing its best to light my car on fire. It was basically free, so no big loss.

SO. What to get as a replacement?

Threads I've read about fuel injection indicate it can be either expensive or difficult or both. Should I stick with a carb? Weber 48 looks nice? After dealing with a side draft a down draft like the one on RB sounds enticing. I've heard mixed things about the RB Holley.

Weber 48's don't have a choke, right? Hard to start?

Other question, what to do about the manifold? My current intake is ported to match the street port. The Weber 48 mani on RB, for instance, looks like it would be hard to port and still have enough material left over. Some terrible photos of the port circa ~2006:




It has stock ignition and a full RB exhaust. Would now be a good time to upgrade the ignition?

Other thoughts?

Jeff20B

iTrader: (13)

Don't port match the manifold. The manifold needs to have a slight mismatch. The step is for anti-reversion.

EFI can be super frustrating, time consuming and expensive. Just ask Iotus and PercentSevenC.

Your intermediate iron is set up for a carb. Looks like a Y casting. There are no injector bungs in it. It's already ported too. Stick with a carb.

As for which carb, I've gotten into modded/hogged out Nikkis lately. A wonderful carb to work with and they respond well to mods. I have some 74 ported Y and R5 13Bs and the carb is plenty big enough for these if you enlarge the primary venturis. The "74 port" is like a small streetport and the carb doesn't run out of breath. I saw 8k easily. RB long primary exhaust. It's an excellent alternative to the big V8 carbs and Italian racing carbs everyone always defaults to.

RustyRotary

iTrader: (2)

Jeff, thanks for the reply.

I have a Nikki sitting around somewhere. Years ago I thought of doing the Sterling thing (a guy I bought a car from had a Sterling carb he loved), but I got the Mikuni first. Looks like Sterling is done? All of the posts about Nikki vendors I see seem to be from 2011 or older

DriveFast7

iTrader: (1)

Living in Indiana, I'd get something with a cold start assist. Like a Nikki, Weber IDF or a Dellorto in good shape if there are any left. Cold Starting an IDA in anything below 70* ambient isn't fun, below freezing would be terrible.

RustyRotary

iTrader: (2)

Well, its a good-weather-only car, so freezing starts wouldn't be a problem.

My biggest issue right now is I have very little time for this stage of the project, so something like an IDA that I could order today and have on the car this time next week would be a huge plus.

As far as an IDF goes, would a 48mm be the size to go with? The 44s this vendor sells have chokes while the 48's don't... Anybody familiar with this Dellorto.co.uk?
Weber 44 IDF

RustyRotary

iTrader: (2)

Sorry to add another post, but I'm past the edit window for my last post.

I called up Racing Beat to ask if they thought a 44 or 48 IDF could easily be modified to fit their 48 IDA manifold (or vice versa). The tech I talked to thinks I could save myself a lot of trouble by just getting a 45 DCOE. Will that fit the intake manifold I already have? I wanted to go away from side draft because I seemed to go lean during hard corners, but that carb never really was properly tuned to begin with

Part of pulling parts off of an ebay roller is that you don't always know exactly what they are or where they came from

bumpstart

weber 48 choke = plastic shopping bag pulled down over air cleaner

in 5 C conditions it will start without much effort or choke if you get a feel for the carb and its starting position and prime it with a couple of pumps of the throttle before key on

at worst it will stall once or twice before settling on an idle

RustyRotary

iTrader: (2)

Thanks Bumpstart, firsthand knowledge is valuable to me.

I dug this old bastard out this morning. I had a couple at one point and I think I kept this one because it had the most stuff still on it.







Good thing I kept a rats nest. Worth millions, I'm sure!



So, I'm now wondering what kind of time, effort and money are required to make a Nikki a better solution than a "default" Italian carb. I've read through a couple of strip-down tutorials (including those in the rats nest FAQ and the well-put-together Vipernicus pdf. Very good, but I get the feeling a strip down alone won't be enough for my engine.

I probably should have made it more clear in the original post that time is very important on this build. It's not a matter of patience. I love getting my hands dirty and the satisfaction of doing a job myself, but in this case there are external factors and I simply don't have the time to learn how to mill throttle shafts and enlarge venturis.

vipernicus42

iTrader: (4)

If you have to get the car back on the road and driving, I'd say to strip down that stock Nikki, get it mounted and driving smoothly without any serious mods. Then get a second one to play with, so that you can spend the time on the bench figuring out how to press the venturis out to lathe them and that kind of thing.

You could also post a WTB for a Sterling or a Paul Yaw Nikki. They come up from time to time, and are well worth the money if you can find one (especially the Sterling, some of his mods for things like the throttle linkages and springs are just ingenius and will save a ton of time when taking off the top to change jets).

Good luck,

Jon