stock jetting???

[Anonymous]

hi guys
are you using stock jetting on the carbs for triple setups? or do you have to change jets sizes? is there a consensus on this for southern california? I have the center carb only currently with a 264 x 112 x .440 cam with dual headers. i have weakened my advance spring with a pertronix ignition. it idles nice with the extra vacuum advance. it is a 200/C4 in a 68 sedan. i plan to add a tach, vacuum and fuel pressure guage in the next couple days. and get some break-in miles on her before removing the block-off plates under the end carbs. it is setup with 1100's. but i also have the option of end 1909's. waiting for a third 1909 so I will have that option also shortly.
but i have read recently that some guys are happy with 3 x 1100. but have got no feedback on jetting. any help guys???

thanks frankie

 

[CZLN6]

Howdy Back Frankie:

I've been watching this post and giving it some thought. I think part of the reason for the lack of response it that few have been down this road and that adaptations and tuning to circumstances is son varied.

When you say "Stock Jetting" That implies that all 1100s have the same size main jet. they do not. If you're in Cal with a Cailfornia buitl carb, it will be different thatn the other 48 states. So- Let's start over. Is this a Calif/emmisions equipped engine? What is the jet rating in the center carb you are using? Since it is a '68 I'm guessing that you have centrifugal advance in the distributor. Is that true? What is causing the extra Vacuum advance? Is the vacuum line hooked to the ported source on the carb?

Please describe how it works once you drive it. The main jet it came with is a good place to start and likely won't be too far off. Tune the center carb 1st , then add to end two for acceleration and WOT.

Know that Autolite 1100 came in several sizes and versions. They all look very similiar. You will need to know exactly what you have. The bigest factors will be to find 1100s with NO SCV and same ventri size. Critical factors will be tight throttle shafts and blades.

Holley 1909s cam in two sizes, with either a manual or hot air auto choke.

That should get you started.

Adios, David

 

[Anonymous]

i remounted the original 1100 that was the stock carb. i believe it to be all stock since eberything had the original tags and the car is pretty much untampered with.( until now).
i do not think it is a calif car although i am not sure. it did not have the smog pump but the other system( Impco or such???) i think it had some sort of electronic advancing little black box when i got it. with a bunch of thermal and vacuum switches. i took all that off last year and have been just running pcv system.

the car ran good on this carb though. now with the new cam , mild porting and headers, and a 3 x 1 offy manifold with the end holes capped for now.

the car would not idle. then i added a longer idle speed screw and i got it to idle pretty fast. trying to wslow it down it would stumble. i do think it is way open to where the idle mixture screw isnt real effective .

i do have the dual advance distributor which i am using as a straight vacuum advance only. i softened up the spring and it does pull in the full advance at idle. it idles much better with the full vacuum advance. on top of 6 degrees initial.

i seems to idle well enough and when i drop it into drive it keeps running. buit i havent driven it yet. i just finished the dual exhaust and am working on the header wrap and finishing off the oil cooler/ extra filters installation. and have to rearrange the stable weather permitting.\
car still on jackstands for finishing the header wrap.

I am also installing a fan shroud.

i have an assortment of carbs for the ends. i have a couple of manual 1100's ( the current one has the heat stove choke but not hooked up.) it is set about 1/3 closed at room temp. it opens up full once the car warms.
i have several 1904's, a pair of 1908's, and several 1909's.

i started with the original 1100 since it was what i knew the best about.
but it seems like the end 1100's will be too tall. in order for the the 1100's to opem they need a 1-1/2 hole underneath like the stock support base.
the ceneter hole on the offy works ok but the end holes are too small. i suppoes i could hog-out the holes. even then the front air cleaner will be real tight.
also the 1908's , i think these are the ones with the choke at the very top, are about 3/4 taller than 1904's or 1909's. the front air cleaner interferes with inner hood bracing bigtime.

I know you talked about plug readings for adjusting the jetting. i havent got there yet. but some of the guys talk about how well their setups run esp one guy with the 1100's on a 200. I wonder if he had to do much rejetting?

i changeed the vacuum spring. i had several colors of srpings from ford but they were all pretty stiff. blue green pirple. i opted for one from ACE hardware which are pretty soft when doing a typical mouth test. seems about half of what was stock. i havent actuall hooked up the vacuum guage yet

frankie

 

[CZLN6]

Howdy back Frankie:

You are looking at several variables that will alter the way your stock, original carb works. They are the new cam, the header exhaust and your alteration of the vacuum advance spring.

The cam and headers typically call for a richer jet, but I's start with the stock number and assess from there.

The altered vacuum advance spring is an unknown. Typically the vacuum advance/retard cannisters are altered by adding or removing washers/shims to tune the preload on the stock spring. In changing the spring you have a whole new ball game. A lighter spring will cause vacuum advance to begin sooner/lower vacuum signal. Since this distributor was designed to work with a ported vacuum signal from the carb, it may not work as designed. IIWY, I'd change this back to as close to what it was when the engine last ran good and start tuning from there.

Also pull the top off the carb an check the current jet size. It is stamped on the jet, located in the bottom of the top cover. It is good to know this for reference and planning for future changes.

Typically, when tuning the spark advance curve for performance you will want less vacuum advance, a quicker centrifugal advance curve and more initial advance.

I believe it was Slade who got three 1100s working good. He also had a very slick Cobra style air cleaner that cleared the hood.

I do believe the holleys are a little shorter than the 1100s. I don't have one for comparison so that's just from memory.

Adios, David