Under sized carb for initial start up/break in.

[Samsquanch]

Hey everybody hows it going? Happy Moparing to you.
My question is, can I use my 450 cfm four barrel for my enitial start up and break in? the 450 is way undersized for what I need after the fact and I'm trying to trade a 650 summit DP and this Edelbrock 450 AVS2 for about a 750 cfm DP over on the pages for trade section but just in case I cant find a trade and want to start this monster can I use this 450cfm? the 650 summit has been sitting for about 4 years is why im opting for the AVS2.

 

[TT5.9mag]

It’ll start and run with any carb you put on there as long as the tune is set up for it.

 

[AJ/FormS]

A/A and,
for run in, setting the tune, at or near a single throttle-opening and a very modest rpm range, this is real simple.
With the engine at or near 2000 rpm;
just crank the advance up by ear until the engine slows down, then back it up a lil to find the highest rpm, then return the idle-speed to ~2200, Then set the mixture screws for maximum rpm. Then richen them up hair. Look for leaks, keep the engine cool, and if you have a flat tappet cam, just wait for about 20 minutes.. , while monitoring for leaks, especially for fuel-leaks.
After the break-in, return the engine to idle, set your power-timing, and twiddle the mixture screws as may be required.
Then Roadtest!

 

[rumblefish360]

Your good!

 

[CFD244]

A/A and,
for run in, setting the tune, at or near a single throttle-opening and a very modest rpm range, this is real simple.
With the engine at or near 2000 rpm;
just crank the advance up by ear until the engine slows down, then back it up a lil to find the highest rpm, then return the idle-speed to ~2200, Then set the mixture screws for maximum rpm. Then richen them up hair. Look for leaks, keep the engine cool, and if you have a flat tappet cam, just wait for about 20 minutes.. , while monitoring for leaks, especially for fuel-leaks.
After the break-in, return the engine to idle, set your power-timing, and twiddle the mixture screws as may be required.
Then Roadtest!

Can you explain setting power timing please?

 

[rumblefish360]

For engine break in, just run it and figure out quickly if it’s too darn lean. If it’s rich, it won’t matter much. To lean causes to much heat.

Put a timing light in it ASAP and just set it so it’ll run on its own and not to advanced or retarded for the break in. If no timing light is available, twist the distributor to advance it until the engine doesn’t pick up anymore rpm and then twist it back to back down the timing and relieve it some.

You should have a vacuum gauge. When the vacuum reaches the highest point, leave it there.

That’s what AJ is saying.

Everything else above that AJ was saying is good info but not needed for engine break in.

After break in, carb tuning takes a little time and you can work through it easy enough. Sometimes, the carb is good OOTB with maybe just a jetting change at most. Super dialing it in is your call. Drive it and make the call. When you’re happy with it, you can stop or push it. Again, your call.

 

[AndyF]

If the carb is in good shape then it will work just fine. Your engine probably only need a few CFM at idle so 450 is more than enough. The important thing is that the carb is working properly. No leaks, no missing parts, etc.