Hey guys. I put together a 355 from some of the parts I Had lying around. It seems to run good, but I am having a bit of trouble tuning it.

For timing I have 11 deg. initial, and two medium weights springs in there now.

Not sure what Jet size to go with and more importantly, what powervalve. Its a 625 Road Demon carburator. The motor is a 355 with ported TBI heads, Weiand Stealth single plane intake, headers, 10" converter, 3.27 gears, 26" tall tires, 3500 lbs, 3500 feet altitude, cam is 234/244 duration, .520/.543 lift and 114 lsa.

Car exibits a long bog when I go to full throttle in first gear, then it picks up quickly. Also, up top, just past 5300 RPM, the motor starts to "bark" (miss, pop, etc). Am I running too lean or too rich. I had 66/76 jets to start, went to 69/78s and the problem didnt' go away, only thing is, upper RPM miss there moved up a few houndred RPM. Help!

 

invest in a o2 gauge. do you have a vac. gauge? if not get one. what do your plugs look like? are they black and sooty (rich) or are they white (lean) or are they a tan (perfect). what is your fuel press set at? good site to go to is http://www.bob2000.com/carb.htm. are your rockers adjusted right. dont go by the book from gm. they tell you to turn them 1 full turn only 1/2 turn is good more starts to cause valve float at higher rpms.

 

Vacuum guage is really the way to go.

The tried and true method is taking it to a strip (or quiet neighborhood) and testing response at WOT. Just keep switching jets and retest. Once you get a good feeling combo, check the plugs after 500 miles. If they have carbon deposits, then run a little leaner.

There's a way using equations and an o2 sensor, but it's not even worth bothering with.