3814 Carb Tuning Issue

[Mark P.]

I need some advice regarding tuning of a 3814 Holley. The car has the K-19 removed and is a powerglide car. Last winter I sent the carb to a rebuild shop as I had absolutely no experience in rebuilding carbs and this carb was profusely leaking fuel. Since the rebuild, I experience stalling after the car is up to operating temperature when I need to stop at a stop sign. This is not good, but I get to meet a lot of nice people.

I have been able to reduce the stalls by advancing the initial timing to 10 degrees at 800 rpm. Previously the inital timing was 4 degrees at 800 rpm. I adjusted the fuel mixture screws by monitoring inches of Hg on the intake manifold and I currently have about 19 inches. Currently one screw is out 3/4 turn and the other 1 1/4 turn.

I contacted the rebuilder of the carb and he stated that I should back out each idle mixture screw 1/2 turn. If I see improvement, I should back out another 1/2 turn on each side. I have talked to others who say I need to have the floats reset as they are too low.

I would appreciate any advice---Mark

[Clem Z.]

does you engine require a carb throttle

dashpot that is not there? this will slow down how quickly the carb returns to idle. most auto tranmission cars have these but i never worked on a PG corvette so i have no first hand experience

[John H.]

Re: does you engine require a carb throttle

No dashpot on a 3814 (or its sister 3810); sounds like it could be a float level issue.

[Clem Z.]

since that is the case drop the secondary float

one flat on the adjustment nut. if that helps but does not cure it drop it another flat.

[John H.]

Re: since that is the case drop the secondary floa

Float bowl has to come off - 3810/3814 had non-externally-adjustable floats; just had a plug in the hole.

[Mark P.]

Re: since that is the case drop the secondary floa

As I stated in my initial post, I do not have experience in carb adjustment, but am willing to learn. If the adjustment is extremely complex, I will do as the builder suggested, back out the mixture screws and try that and it it does not work sent it back (it took 6 weeks for him to rebuild).

If someone is willing to provide a little direction, I would like to try to make this adjustment myself. Pictures would be great, but step by step is OK.

Thanks--Mark

[Clem Z.]

that what i get for never working on non

SPH corvettes.

[Clem Z.]

if you have never removed a gas loaded

float bowl i would get some help from some one who had done this. i would never do this on the engine but i would remove the carb from the engine and do this on the bench. getting things back together correctly so there are no leaks is not a walk in the park for someone who has never done it JMHO

[Mark P.]

Re: if you have never removed a gas loaded

Thanks Clem

That the information that I was looking for.

Mark

[Gerard F.]

Re: if you have never removed a gas loaded

Mark,

If it is a high float level especially on the secondary, you will almost see gas dripping into the air horn at hot idle. At a stop light, the rpm's will start to fluctuate and then die out as over-rich. This could be the float level, warped metering plate or block, or blocked idle vents.

Is the engine running hot or cold? If hot it could be a vacuum leak, at the base gasket.

Pulling the bowls while on the car is not a big deal, make a little sheet metal pan to go under, and have plenty of rags available, there is not much gas in the fuel bowls. But do it with a cool engine. The float settings for a 3814/3810
with non-externally adjustible floats is done by bending a tab inside to a specified gage distance 5/32" primary, 5/16"secondary. You better get a carb kit instructions for the procedure and where the measurements are taken.

However, before you pull the bowls check the vacuum leak end, and the correct initial timing for your distributor. If you have your original distributor on, the automatics with AIR had a different advance, and with an initial setting of 4 degrees AFTER TDC. Duke Williams knows a lot more about this then me, and hopefully he will chime in.

The timing may be your problem.

Jerry Fuccillo
#42179

[Mark P.]

Re: if you have never removed a gas loaded

Jerry

The car runs right at 180 degrees when up to temperature. I initally had the timing set at 4 degree after TDC, but have increased to 10 degrees and found that the stalling reduces by 80%, but the car is not street relieable. When I do set the timing right at 4 degrees the engine starts easier and is smooth at idle, but is much more prone to stalls.

I have noticed at times that the secondaries do drip some gas when the car is up to temp, but the dripping is sporadic.

The rotor is indexed to #1 on the distributor.

Thanks for your comments Jerry----Mark

[Gerard F.]

The dripping sounds like your problem

and is related to the fuel level in the secondary bowl. I found on my 3810 after adjusting the level to spec, that it was still dripping once in a while from the secondary. I found that the float was hanging up on the secondary metering plate. The clearances are pretty close.

I took the bowl off and simply bent the float back to the back of the bowl a little (not so that it rubs against the back if the bowl). No more dripping.

This may or may not be your problem, but might be worth a try.

Also take a look at this post in the archives:

https://www.ncrs.org/forum/archive22.cgi?review=180455

If one or more of the little vents in the top of the air horn is blocked, you could be siphoning in gas from the bowl to the air horn giving you an over-rich mixture at idle.

I think your idle mixture adjustments are about right if you are not dripping gas into the air horn, mine are about 1 turn out from the bottom. From 1 turn out you would adjust to the highest steady vacuum at your idle speed.

If you have to get into the secondary plate and warpage, I think I'd send it back to the rebuilder. The dripping just shouldn't happen.

Jerry Fuccillo
#42179

[Mark P.]

I will adjust the float

And if that does not do the trick, I will send back to the rebuilder. I did have an incident two weeks ago when, upon startup, the engine failed in about 15 seconds and the secondaries were flooded with fuel. The problem was solved by tapping on the bowl. Perhaps this all ties together will the drippage, as at times the float is to close to the bowl and needs to be bent back. Worth a try.

Thanks for you assistance Jerry.

Mark

[Gerard F.]

Re: I will adjust the float

Mark,

I use those blue resilient gaskets, they are a lot more forgiving for leaks.
Also make sure the O ring on the transfer tube is in the right position when you put it back on. I've made that mistake.

Jerry Fuccillo

[Joe R.]

Re: 3814 Carb Tuning Issue

Mark:

I suggest that you make sure the timing is set up correctly before you dig into the carb. The K19 timing was very unusual (for example, initial timing was 4 degrees *after* TDC, and the mechanical advance curve was unique) and there may be differences in the vacuum advance. I'm not sure what the difference was in the K19 carb (ported vacuum?), but hopefully someone like Duke Williams can comment.

If you have removed the K19 system your best bet would be to convert fully to the non-K19 setup for both distributor and carb.