I`m in the process of tuning my chevelle up and need some help! The car is a 70 SS
with a L34 396-350HP,standard shift.
So-far i`ve installed new plugs(AC)set at .035,points and con.(Standard brand)set dwell at 30*,cap and rotor and new fuel filter.
I have two question-What is the proper way to adj. the carb.(Roch./Q jet)?
My second question is ....My book says to set the ignition timming on TDC with the vac. adv.unplugged and blocked.When i set the timming on 0* w/vac. adv. unplugged,the car would barely idle.What should i do?
The motor is pretty much stock,it does have
a (Erson)camshaft,not sure on the specs.

Try backing the mixture screws out 1 turn and see if you can set the timing to spec then. The cam sounds bigger than stock, and if it is, the spec is pretty much void.

I`m have no clue on the cam specs.Couldn`t be a very high lift,you really can`t hear the cam,when idling.I`m guessing somewhere around 500" lift? If so,should i advance the timing more or retard from factory specs?

Ignore the factory initial timing specs. It's doubtful the original distributor is on the motor, which was what those specs were meant for. Get an adjustable timing light set the advance to 34-38 degrees at 3500 rpm, with the vac adv unhooked and plugged.

Larry,thanks for the reply on my posting.
I`m positive it`s the origional distributor,
i bought the car from the origional owner
13 years ago,everything was stock/orig..
How would this be done with a non-adj. timing light,What should it read?

get a timing tape from summit to stick on the balancer, then you can use your light and the timing pointer, without an adjustable light.

Set the static ignition timing to at least 8/10 degrees BTDC, with the engine at curb hot idle, not with a raised idle speed (a raised idle speed can bring part of the mechanical curve into the idle timing setting, and this retards the timing when you lower the idle speed to the right setting).

If the engine pings, have the distributor curved to reduce the total amount of timing at full mechanical advance. Check the vacuum advance for proper operation and connection to the proper vacuum port.

Note: most stock early vacuum advance cannisters have way too much timing in them for today's fuels, a strong suggestion is to get the Crane adjustable vacuum advance package (make sure you get the full package, the one with the cannister AND the scroll piece that sets the total amount of degrees of vacuum advance, not the one with just the cannister). For point distributors, use Crane part 99601-1, sorry, don't have the number for an HEI kit.

NAPA has a set timing vacuum advance for point distributors I use a lot, seems to work well for earlier engines and point distributors, VC1807.

AFTER you get the timing set, go for the carb, but not before the timing is done. Set the proper curb idle speed with the stop screw, then start with a two turn per fuel screw setting, and adjust each screw for the best idle, going back and forth from mix to stop screws until the engine runs best and has the desired idle speed.

A good rule of thumb for seeing if the fuel screws are correct is to fully warm the engine, drive it, then shut it off for a few minutes. If the engine starts without needing a bit of throttle, the fuel mix screws are set correctly. If the engine wants just a little bit of throttle to start, the fuel mix screws are too rich, making the engine want more air for hot start.

If all else is correct, the engine should run correctly, now.

If you can't get it right for any reason, please e/mail me directly. Address is above.

Boy, IgintionMan, that's about the best explanation of the procedure I read. This should go in the Tech Archives.

------------------
Pat Kelley
66 El Camino, daily driver
67 El Camino, STRIP/street

If you don't want to put a timing tape on your balancer, and your balancer is 7" diameter, Make a mark on your balancer 2.2" clockwise from the 0 mark for 36 deg. total timing. Set the timing to this with the engine revved up to where the timing stops increasing (with vacuum advance disconnected). If you have an 8" dia balancer, it would be 2.5". von

When setting the mixture screws I always use a vacuum gauge,make sure you connect it to manifold vacuum at the carb or intake. Set it for highest vacuum but don't go over. Stock motors are usually between 16-18 .Gauges are about 12 bucks.

When setting the mixture screws I always use a vacuum gauge,make sure you connect it to manifold vacuum at the carb or intake. Set it for highest vacuum but don't go over. Stock motors are usually between 16-18 .Gauges are about 12 bucks.

Thanks, Pat.

My six most important tools for engine diagnosis and tuning are:
Diagnosis: Compression tester, leakdown tester.
Tuneup: Good timing light, car battery driven tach-dwell meter, vacuum guage.
Overall: Volt-Ohm meter.

I should have suggested the timing light, tach-dwell meter and vacuum guage for the timing, advance curve, curb idle and fuel mixture screw tuning. All are needed for a comprehensive diagnosis and tune-up.

There are lots of good suggestions on this BB, by some really good posters. Keep it up.