Carbs and overheating Options

[billh1963]

My Zambezi Green 2.0 has dual Weber 34's ( the single barrels). The car has always run on the hot side. I have read many times that a lean condition (as well as many other factors such as timing, valve adjustments, etc) can cause an engine to run hot.

My question is, are Weber 34's enough carb for a 2.0 engine? Can they flow enough fuel at RPM to keep the engine from running lean?

[ThePaintedMan]

Bill,
The 34s are a tad small for a 2.0, but they should be adequate... you just may not get the full potential out of the motor as far as power is concerned. However, I think a few people have reported that the 34 ICTs are the mileage kings when it comes to fuel efficiency on these engines. Someone was getting darn near 40 mpg with ICTs on a 1.7 I think?

How much fuel the carbs deliver is essentially infinitely adjustable with jet sizes. So if the car is indeed running lean than you would want to step up to the next size... maybe two. These engines enjoy running a little rich anyway. But first, a few things:

1) When you say it runs hot, are we talking CHTs? Or oil temp, or both? And what numbers are you seeing?
2) If it's CHT, under what condition is the engine running hottest? At cruise on the highway? Or at wide open throttle?
3) Do you have an AFR gauge on the car? I would guess not.
4) Timing and valves set correctly first?

If it's running lean under partial throttle, like cruising at 60, you might try opening up the idle mixture on both sides a little first. See if that helps. If not, can you find out what size idle and main jets you have on the carbs?

[billh1963]

George,
Thank you for the reply.

The car was seeing oil temps of 240 measured with a calibrated dipstick thermometer. Way too high, of course. The oil cooler is clear and valves adjusted and ignition in time. Anyway, the engine recently dropped a valve seat (or worse) so I need to pull it.

I have a very nice 2.0 long block I can replace it with but am worried about the carbs...was that causing my issue? Maybe not. Really don't want to go through the trouble of changing the engine and have the same issue.

How is the Pink Panther engine running for you?

[DBCooper]

When carbs are "too small" that only shows up at highest RPM's, when they can't flow enough air. Small carbs work fine on larger but low RPM engines because at low RPM's the carbs don't know if they're on a big engine spinning slowly or a small engine spinning fast. So if you were running hot because of the carbs they were jetted way too lean. Check the spark plugs and see if they have light tan almost white electrodes. What's the provenance of the car/engine/carbs? A long time thing? Or was the combination just put together recently?

[billh1963]

The engine has been that way since I got it. It has always run on the hot side.

It was tuned by a well known Porsche shop (valve adjustment, timing, etc.). I haven't pulled the plugs yet.

[ThePaintedMan]

(IMG:style_emoticons/default/agree.gif) with DB. I'd pull the plugs first. If the carbs were running lean enough to cause the oil temps to be that high, you'd be super, super lean, but that would show up on CHTs long before it would in high oil temps. Oil temps can be influenced by really high CHTs, which are directly influenced by mixture, advance and overall load on the engine. That's why they're not really a good gauge of how lean or rich the engine is running. CHTs are better, but an AFR gauge is ideal, and reading the plugs is like an old-school AFR gauge (IMG:style_emoticons/default/smile.gif)

What is more likely is something isn't right with the cooling system. Did you see that thready that someone just posted about the mice nests on top of the oil cooler? Also, do you know what condition the flaps are in? I.e. are they working and hooked up correctly?

The engine from the Pink Panther runs great! Still have some issues with getting the carbs synched, but over 4K that engine really screams. We're trying to figure out if it's got some kind of cam in it. Joe O'Brien heard it at the Tropical Ramble and seemed to think so.

[r_towle]

Op, go for some webers 40 mm carbs for your 2.0 liter and sell the smaller ones to someone who really wants them.
Might be the easiest way to go forward.

George,
Get a dial indicator, and a timing wheel.
You can mark your fan to use as a degree wheel using the template on pelican part, just mark it all the way around.
Good Sunday football thing to do.
Just an idea...
Use a Dremel or ideally and engraver and score each degree in lines, then cover with paint and wipe off the reside....
Should look like a painted framing square y would get at he depot....easy to see.

Anyways, with the degree wheeled fan and a dial indicator on the pushrods side of the rocker, you can get an accurate profile of the camshaft fairly easily.

Motor out, just buy a degree wheel and bolt it on in place of the fan.....faster and simpler.
Remove the plugs, easier to turn minor adjustments so you can see the peak of the lobe

Rich

[billh1963]

The engine from the Pink Panther runs great! Still have some issues with getting the carbs synched, but over 4K that engine really screams. We're trying to figure out if it's got some kind of cam in it. Joe O'Brien heard it at the Tropical Ramble and seemed to think so.

Excellent....glad to hear it's running for you. Should have kept it for me (IMG:style_emoticons/default/biggrin.gif)

[ThePaintedMan]

Op, go for some webers 40 mm carbs for your 2.0 liter and sell the smaller ones to someone who really wants them.
Might be the easiest way to go forward.

George,
Get a dial indicator, and a timing wheel.
You can mark your fan to use as a degree wheel using the template on pelican part, just mark it all the way around.
Good Sunday football thing to do.
Just an idea...
Use a Dremel or ideally and engraver and score each degree in lines, then cover with paint and wipe off the reside....
Should look like a painted framing square y would get at he depot....easy to see.

Anyways, with the degree wheeled fan and a dial indicator on the pushrods side of the rocker, you can get an accurate profile of the camshaft fairly easily.

Motor out, just buy a degree wheel and bolt it on in place of the fan.....faster and simpler.
Remove the plugs, easier to turn minor adjustments so you can see the peak of the lobe

Rich

That is cool as hell Rich! Never would have thought of that. I always thought the degree wheels were basically just for timing, a la the back of every hot rodded Beetle I've ever seen.


Regarding the switch to the 40s, I agree with Rich too. At some point you may consider doing that swap Bill to get the most out of that motor. I have the 44s that came off of the Pink Panther motor that I'm rebuilding if you want to give them a shot. Might be a tad big for the 2.0, but they'll work.

For now though, I doubt that the carbs are what's causing your high oil temps. If you get one of those cheap Harbor Freight borescopes, you can check to see if the oil cooler is blocked somehow. And I can talk you through verifying that the flaps are in their maximum cooling position. Sometimes they can get buggered with and the oil cooler doesn't receive the cooling that it should.

[r_towle]

He dropped a valve seat on the motor that WAS overheating.
He is just checking to make sure he does not do it again with the 2.0 liter.

Go for bigger carbs, 40mm, and use a known setup that works for a 2.0 liter by many of the people here.

44mm will require you learn all about tuning carbs.
40mm will be bolt on if they are setup properly from the start.
Even new carbs will need to be checked because from what I have heard the float setting is not correct and does not match from one to the other.
Aside from that, you can buy new one and bolt them on after you set the floats.

Rich

[billh1963]

I've got a pair of Weber 40's and two pairs of Dellorto 36's. All need to be rebuilt. I guess if I put the 2.0L in I'll put on a pair of those carbs and see what happens (after double checking oil cooler, flaps, times, valve adjustment. blah, blah , blah...)!

[ThePaintedMan]

Sorry, I guess I misunderstood. Sounds like you've got a good plan Bill. (IMG:style_emoticons/default/beerchug.gif)

[jmill]

Stock cam? Might be a nice time to swap it out with the engine out of the car. Lose the FI cam and get something with more overlap.