Hi C3ers...I usually hang out next door in the C4 rooms, but I need to pic your brains about carburation. I have a boat with a 305 and rochester carb (#17059298). I was told that this was a corvette motor. Can anyone confirm this? Actually, I am looking for anything I can find on setting up this particular carb. Thanks in advance!

 

Somebody is feeding you a line there never has been a 305 corvette engine. On your Q-Jet problems you need to go back into the archives and look for a guy by the name of Lars out of Denver. He is the resident expert. He has posted jetting and trouble shooting info. If you cannot find it send me an email and I'll dig my copy out and send you one.

 

, the only C3s with 305s were the california emmision vettes, and there were very few of them made, so the chances of it winding up in your boat is slim to none. Lars is the man when it comes to carbs, especially q-jets, check out the search and you'll find a ton of info.

 

There was a 305 in 1980(and '79?). All the California sold vette's in '80 had the 305 for smog laws reasons. These cars were also the first equiped with a computer controled carb.
-Dan

 

I think the 305 was not uncommon in the Caprice Classic. I've just bought a whole Caprice classic so that I can put the engine and gearbox into my Blazer...

As for your carb, do you have any specific questions? I quite like the old Quadrajet but am no expert. I do, however, have a Rochester book and would be happy to give you any info out of that or even scan the pages.

Lemme know....

 

Ok, here is the deal with the quad: Initial symptom is high idle, she doesn't wanna come off choke it seems. I took the elec. choke off and the recess was gunked up, so I cleaned it out and also cleaned the heater coil. Vac pull off works great.

Now she comes off choke after about 10 minutes, but stalls. Next I messed with the choke rotation until she would start again, but almost got arrested with polluting...she was a tad rich...and rpms came up to 3000 at idle. I backed off the throttle stop screw until idle was reasonable (1800).

I have since rotated the choke to a leaner setting, she will start and idle comfortably at 2000 without the smoke. If I turn down the throttle stop to approach 800 rpms she quits...in fact when she hits 1200 she isn't stable.

As you can imagine, all of the above is quite unsuitable when approaching a dock in 3000 lbs of floating fibreglass. I guess I need to get the carb back to basics and then start balancing choke and rich/lean settings. Any help or advice would be appreciated.

 

Try here for lots of info on Q-Jets (mostly by Lars) and more too:

http://www.corvettefaq.com/listing.asp?group=1&sub=8

Good Luck!

 

G'day redvette1986, I had a look at the stuff by Lars (recommended by ACECO) and it's all real good stuff. You should be able to sort your probs out by having a read there.

I'm not sure if you still want it or not, but I've scanned what I thought was the applicable part of the troubleshooting part of my book. If you want further info from the part below, lemme know and I'll scan and post that for you. Good luck...

Engine is hard to start when hot

· The choke valve is not opening completely
1 Check for a binding choke valve and/or linkage. Clean and free up or replace parts as necessary. Note: Do not oil the choke linkage - use carburetor spray cleaner only.
2 Check and adjust the choke thermostatic coil.
3 See if the choke thermostatic coil is binding in the well or housing.
4 On an integral choke system, check for a vacuum leak.
· The engine is flooded
Refer to the procedure under Engine cranks but won't start.

· There's no fuel in the carburetor
1 Check the fuel pump. Run a pressure and volume test.
2 See if the float needle is sticking to its seat, or if the float is binding or sunk.
· The float bowl is leaking
Fill the bowl with fuel and check for leaks.

· Fuel is percolating
Open the throttle all the way and crank the engine to relieve an over-rich condition.

The engine starts, then stalls

· The engine does not have a fast enough idle speed when cold.
Adjust the fast-idle speed.
· The choke vacuum diaphragm unit is not adjusted to specification or it's defective.
1 Adjust the vacuum break to specification.
2 If it's already correctly adjusted, check the vacuum opening for proper operation as follows. Note: Always check the fast idle cam adjustment before adjusting the vacuum unit.

· The choke coil rod is out of adjustment (models with a divorced choke)
Adjust the choke coil rod.
· The choke valve and/or the linkage is sticking or binding
1 Clean and align the choke valve and linkage. Replace it if necessary.
2 If you have to replace the linkage, be sure to readjust it.

· The idle speed setting is incorrect
Adjust the idle speed to specifications (refer to the VECI decal in the engine compartment).
· There's not enough fuel in the carburetor
1 Check the fuel pump pressure and volume.
2 Check for a partially plugged fuel inlet filter.
Replace the filter if it's dirty.
3 Check the float level and adjust, if necessary.
· The engine is flooded
Refer to the procedure under Engine cranks but won't start.

 

The choke is used only to enrich the mixture when the engine is dead cold. Once it's the least bit warm, the choke should be fully open and stay that way

It's not to be used to balance rich/lean conditions at normal operating conditions.

 

on corvettefaq.com you will want to download lars qjet timing paper.
I cant find my home copy. the carb # looks correct for that era but cant confirm.

The paper has been a great help with me tuning my qjet.

 

or try this.......>>> http://www.corvettefaq.com/c3/QJetTuningPaper.doc