Jetting 34ICTs for 1776

[kangaboy]

I know nothing about jetting...cept that my carbs are most likely not jetted correctly for my combo.
1776 (c25, 34ICTs, 009 bleh, stock heads, 1 1/2" single quiet pack) compression is about 7.8:1.
I dont wanna just start ordering new jets at $8 a pop...so please set me in the right range so i can try a few that will most likely be correct.
It runs ok in the lower end...just ok though, and has no upper end. I need to buy a sync tool as well to figure out what is happening but jetting would be good to know about too.

[Marc]

It's been so long since I last messed with the jetting on my ICTs that I've forgotten what I left in there, will have to pull one apart to see....I think the mains were in the 130-135 ballpark.
Now the useful information. ICTs use the same main jets as the 32/36 Weber progressive carbs (DFEV, etc). Rarely will you find one with the same size primary & secondary, but if you can find someone who has a pile of them he may be able to fix you up with a pair of used jets.
If you get the linkage mechanically synchronized, so both carbs hit idle & WOT simultaneously, you really shouldn't need a Uni-Syn - they're pretty easy to balance at idle by ear.
With your combo things are pretty much done by ~4500RPM (it'll rev further, but the power's dropping off so you may as well shift) so don't expect too much.

[kangaboy]

Well the jetting from the factory in these is supposedly made for stock 1600, not a 1776. Im pretty happy with the linkage and pretty sure that is all good and sync'ed. Its just everyone talks about "jetting the carbs to fit ur combo" but i havnt had anyone tell me what the ball park would be for my combo. I have no clue...i do know that i cant time it correctly cause it wont run correctly cause it doesnt have the proper jets. I was reading that the idle jet accounts for 80% of drivabilty, which will prolly need to be bigger for my larger displacement. But that is all ive gotten.

Stock is (Im pretty sure):
130 Main
160 Air correction
F78 Emulsion tube
52 Idle jet
40 Pump Exhaust valve
50 Pump jet
175 Needle Valve

Could someone explain what each of these needles and jets do specifically so i can get a better understanding of what is going on here? I guess im just going to have to buy a bunch of jets and figure this out myself.

[kangaboy]

Im going to go,
170 Air,
145 Mains,
60 Idle
Any thoughts or comments?

[kangaboy]

I have run this jetting for about 5000 miles, and it it hot. It doesnt really pop out of the carbs, but it runs hot. My CHT reads about 360-400 while cruzing, which is fine, but i cant touch a single thing in the motor bay after it is run for a while. Dipstick is on fire if i try to touch it. Should i use larger/smaller jets? Which ones?

[Clonebug]

Your best bet is to order a set of these drills. They are cheap and will work to get it close. The great thing about them is you can use them to check the size you have.

http://www.widgetsupply.com/page/WS/PRO ... auge/BBL50

Just because it has a number on there does not mean that is the size.

You could find another set of jets as a backup and work with a spare.

Keep a log of what you do every change and only do one change at a time.

Check your plugs for color, they can tell you whether it is on the lean side or too rich.

Here is an article to read on plugs. It will get you started and is a great learning tool.

First hit on Yahoo.

http://www.4secondsflat.com/Spark_plug_reading.html


I would think that a 60 idle is plenty big but I don't know those carbs.

Get the drills, it is only $15.00 shipped and go real slow and careful. A 60 drill bit is pretty stinking small!!!

Those numbers mean millimeter sizes in that a 60 idle is a 0.60 mm drill bit.

[Breaker]

You could also make the whole process of jetting easier for yourself, and probably gain in all-around driveability, by stepping DOWN a bit in exhaust dia., you'd be happier with 1 3/8, I woudl imaegine. Others to chime in?

[Breaker]

As for jetting,I'd go for smaller idle, like 50, and a main in the 125-130 range. What are the venturi sizes on those? I'm guessing 26-28mm? You don't ABSOLUTELY need an air-fuel meter, but from the gist of your questioning, it could only help....

Start the car.

Does it Idle ? cold engine, no chokes? then too rich at idle, that's the screw which lets you increase/decrease gas flow at idle.

tune for fastest idle possible . Synch carbs, then tune for fastest idle again. this is not fine tuning, but for a starter, this will get you in the ballpark.

Carbs should now be synched, tuned for best idle, and idling at 8-900 rpm (again, starters, ballpark).

Now crack the throttles(with your adjusted and synched linkage).....What happens?

It stutters..... bigger idles, and need to re-tune for best idle... or

It stumbles and belches black soot and fumes...idles too big, change and...re-tune for best idle......or

It roars!!!!! success (for now) on the idles, move on to mains....

Take it for a spin. Car has to drive. The idle is ok, and the transition off-idle is ok, so now, when you take it SLOWLY above this range(2000-2500rpm or thereabouts, depends on engine)...What happens?

It stutters and pops out the intakes: if timing is ok, and we've assumed it is so far, then the mains are too small ....or

It runs ok, but not that great, and has a muffled sound, and there's smog in the rear-view, then ...you guessed it.. mains too big.

This is where reading plugs gets interesting.

For the main Air jets, it's all about how the jetting evolves from that baseline main jet choice.... but we're getting ahead of ourselves here, that should get you rolling for now, keep us posted, good luck.

[Stufenheck]

The F78 has a flat spot when tranisitioning from the progression circuit to the main circuit.
Recommend that you use F5 emulsion tube.

If you follow the instructions below it will take you to archive database of old/inactive website html pages that will explain differences between F78 and F5 emulsion tube in more detail.

1st copy the following text.

jimsvw.xenetech.com/Tech_How_To_s/Emulsion_Tubes/emulsion_tubes.html

The use the link: http://www.archive.org/

Then paste the text in the waybackmachine section of the page after http://

Press the take me back icon/button

On the next page click on the date of August 11, 2001 which will take you archive website.

You can arrow up thru date on the top of the page but I did not notice any changes on the particular html page.

[Mike71Karmann]

I ran ict's on a 1776 8:1 comp c35 cam cb044 35.5/40mm valves 1&1/2 header to single qp muffler years ago. I found 135 mains &45 idle the best overall @ 500ft above sea level, the carbs were great but nosedive in power after 5000 rpm. I too remember running warmer with larger main but i also bumped the timing a bit since i thought i was lean before. I dont recall the emulsion tube number but didn't have your symptom flat spot to chase down either.
I second that the unisyn didn't help a lot setting the carbs up as the ring bounces up and down some and not steady, I would disconnect the linkage open each butterfly the same small amout a few thou off their seats , place idle mix screws 3 turns out , then turn in the idle mix screws till smooth then stumble approaching lean and turn back mix screw back out 1/2 turn or so from stumble. If one carb seems to be "off" from where the other tunes with idle needle screws the float height may need a check or float needle not sealing under pump pressure.
Putting the linkage back on make sure both carbs reach full butterfly at the same time. Drive read plugs repeat...

[kangaboy]

OK, I just got done driving this bastard 1800 miles from St. Louis, Mo to Los Angeles. Me and my dad did it in 33hours straight. Bug did great, till we got to Barstow, which was about 1hr from home. Blew out my sand seal going up and down the mountains, due to to much crankcase pressure. Anyway, I had to get a few qts of oil and keep it topped off every 20 miles. Got home, and let her rest for a few days. Alternator was shot, with cooked bearings. I found out this is almost common when driving over 6hrs straight. Whatever, got a new/used bosch for $40. Dropped the motor, cleaned it up, took off the carbs, and fan shroud and cleaned the oil and all the other crap off.
Now it comes time to reassemble. I put everything back in place, mount the motor, put the carbs back together, remounted them, charged the battery, and fired her up. No go. I loosened the distributor for some reason and knocked it when i was cleaning everything. Fine, static time it to 7.5btdc, until i can get it running and use my timing gun. K, turn it over again, runs like dog poop, which is fine cause my carbs will need to be re-tuned, but it is idling. Go back and mess with the carbs, nothing happening. I adjusted them the way the weber link says to, starting with the idle adjustment screw 1 1/2 turns in after contact with the stop plate, and with the mixture screws 2 turns from the bottom. I turned the mixture screw in and out and had no change, still idles at about 500rpm. Messed with the idle adjustment screw and then she just said "enough" and died. Hex bar linkage is off, so i can set each carb by itself. I ran it for about 4 min to get the motor warmed up. Now when i try to get it to idle, it wont...not..at...all. How the hell am i supposed to tune the carbs if i cant get it to idle!?!?!? The jets are the exact same ones that were in it for my long ass voyage, so i know they "work." But now i cant even get it to idle to tune.
I guess im just going to take them off this weekend, take them all apart, reset the floats, and hope for the best, and also check for vac leaks. Any other ideas would be great, and i appreciate it if you read this whole thing and can offer some advice.
Also i have a balance tube (from the correct ports in the carbs) connecting the two, and then "T"ed to my svda dist.

[kangaboy]

One last thing. When i do get it started, and even though it doesn't idle, i can keep it reved at about 2-3000rpm, and it runs great. Constant idle. There is a slight rumble once in a while, like a backfire out of the exhaust, but not like a pop, more like a growl. It also doesnt like to go above 3500 without full throttle. So i didnt even bother messing with it anymore.
And yes when i got to Cali i adjusted the valves. All were pretty close to spot on, cept hot #3, it was about .003-.004. So had to loosen it up a bit.

[Stufenheck]

Check if the intakes have become loose at cylinder head.

[kangaboy]

I had them off to clean, and bolted them back on with proper torque.
I think ur on the right track though. I did take it for a drive after I got it back to Cali, and before i took it all apart, and it worked. Must have been something i did with the carbs, or a vac leak.

[craigvwdude]

I have run this jetting for about 5000 miles, and it it hot. It doesnt really pop out of the carbs, but it runs hot. My CHT reads about 360-400 while cruzing, which is fine, but i cant touch a single thing in the motor bay after it is run for a while. Dipstick is on fire if i try to touch it. Should i use larger/smaller jets? Which ones?

CHT like that is probably why you had to adjust the valves on #3.
I run 350 MAX on a long hill. Normal freeway is around 325.
You better figure out a way to cool that thing down.