Ive been trying to break in my new motor. Its a 383. I took it for a drive down the road then came back cause the temp was gettin high. I checked one of my plugs and it had a lil white on them. Im running 74 primary and 75 secondary. does anyone know how many jet sizes i should go up?

 

74 is probably close for the primaries, but why do you have the teeny jets in the secondaries? IIRC, the Proform recommendation is 72/84 as a starting point.

That wouldn't make any difference driving up & down the street during break-in, assuming you didn't get into the secondaries during that brief run. You may need to go up a step or two in the primaries, a step being 2 jet sizes at a time. Do the primaries until you're happy with them, then work on the secondaries.

For the record, the reason you have bigger jets in the secondaries is because the primaries have the power valve circuit to enrichen the mixture under power & WOT. The typical PV equivalent is ~6-8, but for some reason Proform says 12 larger in the secondaries - probably a matter of the air bleeds they use. Of course, all of this is a matter of tuning, I ended up with 8 larger in the secondaries.

By the way, if you have the large #73 air bleeds in the secondary idle circuits (the outer bleeds), you need small #36 ones unless you have 4 corner idle. That gave me fits until I figured out what was going on, and it could contribute to a low-throttle lean condition such as you're seeing.

 

Dang thats crazy how you know all this. I try to read book but i cant do it. So I think ill try to go up to 76 primary and then maybe try 82 for the secondary. Im only 19 and Ive been trying to learn as much info as I can. Thanks a lot i appreciate it. Ill let you know what happens after I up size the jets. Thanks again!

 

Well, you can be sure that when I was 19, I didn't. I've had 32 extra years to figure some of these things out.

Check those secondary air bleeds. Things won't be right until they are.

 

i just swapped out those air bleeds. they were the big ones. i havent tried out the car yet but i will let you know how it turns out.

 

Ah, I was wondering what happened to you!

Yes, let us know. I had to play with the secondary throttle opening set screw as well, discovered the Holley baseplate hadn't been machined very carefully in that area. After having it off/apart 3 or 4 times, finally got it to behave. Made a big difference in how it idled and ran under low throttle cruise conditions.

That's a great looking combination you've got going there.

 

Yea i was away for a little while, I was on a skate trip in Amsterdam. I played with the car today. I adjusted the A/F mixture and replaced those air bleeds. The car idles real good now. Do you know how long i should wait until I can launch the car for a 1/4 mile pass?

 

If it's a flat-tappet cam, after you've run the cam in and changed the oil & filter, readjusted the valves, and made sure everything is up to snuff.

If it's a roller lifter cam, after the initial half hour or so of running, changed the oil & filter, readjusted the valves, and made sure everything is up to snuff.

GM has a break-in procedure that was linked to their crate engines. I believe it is posted in the FAQ forum. If you want, you can go through that procedure for peace of mind.

 

What about seating the pistons? I have already taken the car for a couple cruises up and down the street. I would acellerate up to 5000rpm then let off and let coast to 2000rpm i did that about 5 times.

 

that's good, that's pretty much the procedure to seat the rings. They say the first 20-50 miles is what does that. You let it engine brake down right? I think that's better than just coasting down, IMHO.
But yea, giv'er torque now!

 

By engine break down, you mean just letting off the throottle right away right? Or applying the brake.

 

engine braking, letting the engine slow the car down. So if you go 3/4 throttle up to 65mph, and you're in overdrive, it'll kinda "coast down". So I meant you'd drop it into 3rd gear to let the motor slow it down. It's the same kind of force to the pistons as when you're accelerating, just "opposite" basically. My car is a stickshift, so when I let off the gas, i'm engine braking. Nifty.

 

Yea ive been doing that in 2nd gear. maybe ill try drive in 3rd then downshift to second.