1st Start stock 340 w/ New or Rebuilt Carb?

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Danny Boy

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Hello all,
Hope this is the correct forum for this question.
If not, please advise and I will repost.
Also, if there is already information on the, please point me in the right direction

Given that cam break in is so critical when initially starting the engine for the 1st time after a rebuild how can one assure the engine will start quickly on the first start assuming:

-Timing is set correctly
-New Carburetor or rebuilt Carburetor.(Don't know if adjusted correctly)

My concern being, using either of the above carburetors for the 1st time and not knowing if they've been setup or adjusted correctly.

I'd hate to be cranking endlessly because of an unknown/ improperly adjusted carburetor and possibly ruining a new cam.

Please advise and I hope this makes sense.
 
One thing you can definitely do (if running a mechanical fuel pump) is use a funnel to pre-fill the carb bowls prior to cranking, make sure you are getting accelerator pump shot. Electric fuel pumps are nice for the first cranking
 
X2. Just went through this on a dyno session. Like said above, you really want a known good carb. Break in is basically just a steady-state condition that beds everything in together. It’s important to get the engine started right away and get it up to operating temp before you do any tuning. If you’re futzing around trying to get the thing started you increase the chances of wiping out the cam if it’s a flat tappet.

On the dyno session I mentioned above, we used the operator’s dyno mule carb. It wasn’t the best match for our combo but it started up on the second try and ran fine @ 2,000 rpm. The rebuilt carb we brought with us to try was leaking like crazy and would barely run so it was the right choice not to use it on first startup.
 
Generally, adjustments are curb idle/low speed. You will be breaking in at 2K RPM - on the high speed circuit of carb. Have never had a carb so far off in it's high speed circuit that I couldn't break it in. More often there were idling issues afterward
 
Some excerpts from David Vizards book “How To Super Tune Holley Carbs” which applies to any carb for initial firing:

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What carb?
Timing on first start is usually a bigger problem for most people. Crank in a bunch of timing. Like 30-40 degrees at 2000 rpm for break in. If it’s a Holley start with box stock jetting, set the idle mixture screws at one turn out and the set the curb idle screw so the transfer slots are square or a little more open. If it’s got a choke, disable it for break in. If you have the bowls off flip them upside down and set the floats level. If it’s not a Holley get a Holley. The last comment should get some response from the carter/thermoquad guys.
 
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First of all, thanks much for all the comments.
I have a factory carter avs4933s still needs rebuilding. Purchased separately.
Not averse to purchasing another carb if this one doesn't work out.
May have to contact mopar friends to borrow known good carb for break in
 
Danny Boy said:
First of all, thanks much for all the comments.
I have a factory carter avs4933s still needs rebuilding. Purchased separately.
Not averse to purchasing another carb if this one doesn't work out.
May have to contact mopar friends to borrow known good carb for break in
Click to expand...

That's exactly what you want to do. The one you have may be fine but if it's not a big problem just borrow one.

JW
 
Borrowing a known good running carb from a friend is a great option if it’s an option.
 
If you don't have an electric fuel pump, go to a pharmacy and get a kids liquid medicine syringe. Fill the fuel bowls via vent tubes on a holley, pretty easy. Hit the squirter arms on both ends and make sure they are shooting fuel.

Yes on borrowing a good known set carb if available.

You don't want the engine cranking to pick up fuel via mechanical pump to fill the bowls and get fired.

JMO, set the initial timing in the 20* range, get it fired right away and up it to 35-40* at 2000-3000 rpm and watch oil pressure and water temps. DO NOT set it to your desired total number, it likely won't have enough timing and will get hot. No load on it, so a bunch of timing isn't going to hurt it.
 
I like Holley's as well if you're looking for a new carb. I've even gotten the refurbished ones (directly from Holley) and had good luck and they are cheaper. I've had good luck also with the Summit brand carbs. They are also set (ballpark) correctly for a first start up.
Good luck!
 
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