for those who have read my posts, you know i've had an adventure with this car.
it's back, rebuilt 2056 and i ran it around some yesterday.

i've come to the conclusion that the single biggest issue, one that's caused the demise of at least one engine has been:
the PMO Weber 40 IDF that were put on because the guys i initially took the car to and asked to get tuned up were too disinterested in tuning the f.i., so they dropped a giant bill on me and didn't even bother saving the parts they took off.

now i'm not really calling anyone out here. i'm writing a letter to PMO about the carbs and i hope they will be receptive (they didn't resond to my e-mails before) and will at least help me figure out what's wrong... i'm not even going to bother with "the guys"... check with chappy if you want any more on them!

here's my logic: i have had these carbs feeding FOUR (4) different engines (2- 1.8 liter and now 2- 2056's). i (and no less than 4 other humans) have jetted, mixed, dialed, tuned and massaged them till the cows come home, but they JUST REFUSE RUN SMOOTHLY!

worse yet, now i get the same wonkey, popping (from both ends) that i have from each of the 4 tries. literally, the only constant between all of them has been the carbs!

whew! thanks for letting me vent.

if there's any kind soles who have a set to just let me borrow to get the engine dialed in, i would be entirely indebted. i'd pay for shipping both ways, and even escrow what ever value you think they are worth to prove i'm not going to run away with them i'd be more than happy to do that!

meanwhile, i'm composing myself enough to HOPEFULLY get PMO to help me out on this deal before i burn up another fortune in engine work.

wish me luck!

paul

p.s. total miles on 4 engines mentioned: 22,465

popping= lean.

lean= dead engine.

Invest in a wideband O2 system and stop guessing at enrichment.

Nice to hear you have her back on the road. Sorry to hear you still have the same issues. I have no good carbs. I wonder if you could sell the carbs an use the cash to build a mega squirt of SDS or something.

edit: or do what Jake say's..

yes jake, and you of all my friends know of my investment in this. and thank you.

my point is that there is something mechanically wrong with the carbs i have. some fuel is getting by, or the operation between the barrels is not consistent.

there are no funds available to to what's needed for these carbs, which would be to o2 each manifold.

hey buddy! this build has a carb cam in it, i can't go to an f.i. unfortunately.

Though they specialize in the 3 barrel carbs, you might get some help in reading the technical section on the website of Performance Oriented (performance oriented.com).

I would also agree that a oxygen sensor might certainly help,mbut you really would need bungs on each seperate exhaust pipe to really know what's going on in each cylinder.

Has anyone used the color tune system? It might also help you diagnose the problem.

I didn't think that PMO made any Carbs for a 4Cyl !

at what rpm does the snapping develop? all the time? when you are coming off of the idle circuit? what sort of gaskets are you using @ the intakes to the heads? have you investigated the amount of fuel actually being delivered to the carbs? have you ever inspected the strainer sock in the fuel tank? with the system clean from the tank to the carb fuel inlets you should have a strong, consistent stream.

having not returned any of the fi components, and they should have been given to you, the shop that the installed the carbs is prob using them to fix other 914s.

k

I have never known of PMO to make IDF style carbs either, my bet is they reboxed Webers and used the PMO 4 cal intakes.

You can have something wrong with the carbs, BUT you can't find it until you gather some behavioral stats about them and doing so is most effectively done using a wideband O2.

Just pull the carbs and call Art Thraen at Aircooled Engineering. Ship them to him and pay the bill. The carbs will come back better than new and you can bolt them on without any issues. Art hot runs every set of carbs and adjusts them before they ever leave the shop. We are hard as hell to please and Art has never failed to exceed our expectations. If I do any work with used carbs I require that they go to Art before our dyno work, else it just wastes our efforts and dyno time if we have to fool with the carbs mechanically before tuning begins.

thanks jake, i'll look him up.
PMO didn't make the carbs for sure. that was just "the guy's" source because they're a 6-cyl shop. gotta go fro now, thanks to all who chimed in... keep 'em coming, i'll read them later!

What linkage do you have? It's often overlooked and can cause issues similar to what you've described.

Alternatively, you can take a bunch of pictures and post a bunch of questions and go through the carbs yourself. I won't call it 'rebuilding' because that word and carbs is way overused and has lost its meaning. You would need to completely disassemble them, post pictures, check everything and do a bunch of reading to learn how and why the carbs work to figure out why they're not working.

The good news is that the learning curve on carbs is not as steep as SDS or MegaSquirt.

I shipped my Dellortos to Art Thrane a few years back. I told him the engine stats and he knew the area I lived in. (grew up a few blocks North). I got them back, pretty much bolted them up and that was that. I think McMark made some adjustments as well...

Well if you know that PMO didn't make the Carbs, Why are you calling them out? If I were them, I wouldn't return your eMails or letters either - they didn't make make them and any advise they might give would be a guess. They have a business to run, aren't a big company and are quite busy doing what they do.

pardon me, but paragraph 3 in my initial post might need a review, friend.
i've owned this car for 11+ years and have been chasing this for 10 of them, but i've always done everything i can to communicate clearly and with civility.
unfortunately, that's a trait i didn't completely sense in your message.
now this one's on me~

it's nice, bar style with really nice adjustable downlinks. not cheap/bugpack/off brand/china made whatever, but i don't remember the exact name offhand.

again, i've been from one end of the spectrum to another with the adjustments and in all the different engines, the results are similar. this effectively eliminates everything except the carbs themselves to me.

other than the "black magic" part of carb tuning, i've done all this.

Your Paragraph 3 might classify as a "review", but the fact is you called out my friends at PMO for no reason.

I try to be friends with most, including you. But you have ignored my PMs and responses to your Classified Ads.

T.C.

I hate to say this but there is no black magic in carb tuning. They are a mechanical device that works in a predictable way. Buy the Weber Tech manual. Read it several times. Mentally disect the idle, main and accelerator circuits. Use the pictures in the manual as a visual reference. There is a reason for every piece in that carb. Once you know what every piece does and how it does it troubleshooting and tuning are easy.

I know the hassle, I'm going through it right now on my 6 with some 40IDA3Cs. Couldn't get it right 6 months ago, kept popping out the exhaust. Pulled it out of storage this weekend to give it another try. Now it's even worse popping out every opening....grrr.

If these are new carbs, then it's more than likely an issue of the correct combination, or to quote Jake Raby's mantra "it's all in the combo".

If the carbs have the wrong jet/venturi package, they won't run right on any engine. You need to confirm the jetting and venturi size before you do anything else.

In addition if they have junk fuel, or contaminated fuel, or trash in the fuel, you'll have trouble.

What distributor are you using, and what is the timing set at?

From my own experience, and some of the other guys can probably back me up on this; at least 25% of carb problems are really ignition problems, and probably 5% are fuel delivery or contamination problems.

Also John is right, there's no "black magic" to tuning carbs. Having the correct venturi and jetting, is much more involved, but it can be simply a matter of getting a couple sets of venturis, jets, and maybe a jet reamer set.

Or just listen to Jake and send the carbs to an expert.

Sounds great initially. After that is he going to send them out everytime an idle jet gets plugged, the linkage gets out of adjustment, they swallow water, he gets a vacuum leak, or has any other carb related issue? Carbs are far from plug and play and you need to know your way around them to keep them working correctly.

that's a good point, jmill.
i do know enough to clean and inspect the jetting and all. (just for fun i did a search for "carbs"+"lotus_65" and found 2 pages of my participation/thread generation on the topic, and there's more on the club site)
reading and studying the weber bible as we speak. if/when i send them out, i'll be able to keep them in tune when they come back.

I agree with you, knowing how to work on them is a real bonus. But Paul said he's had this problem on 4 engines and he's sure it's the carbs. So send the carbs to a carbs expert who will make them perfect. Run them on the car and enjoy. Then if performance drops, call the carb guy and ask what to do. We cant be experts on everything but there are experts out there to utilize.

I realize gas has changed in the last 25 years but when I ran my car with webbers, it ran perfect for 5 years without a glitch. Summer, winter, driving in the mountains. Just got in and turned the key. They were not adjusted once the car was built. I bet Paul would like some of that for a while.

does "popping" = "pinging" ?
if not, what does pinging equal?
just looking to clariffy

Check the carb to manifold and manifold to head mating surfaces and gaskets. Warped or mismatched flanges can result in vacuum leaks. It's very hard to get carbs working properly with leaks.

A method of troubleshooting is to spray carb cleaner on the mating surfaces with the engine running and look for changes in running conditions.

Cheers,

Eddie

No. Pinging is similar to detonation. Popping is a backfire through the carbs or exhaust.