73 Corvette Stingray?

Question

Beautiful car we just bought, we have replaced alot. But the car seems to want to idle to high. We have bought timming gun and replaced distributor, carb, and it is still running really rough. It has a blue printed racing engine. Is there something we maybe over looking?

Answer 1

Well, DUH. If it's a racing engine it probably has so much cam lift it will never idle properly. I think that model Stingray was beautiful also. The engines were so laden with smog equipment and de-tuned that they woul barely produce 200 hp in the seventies. You may want to take the plunge and replace the big cam with a much milder one (unless you are going racing) and a bolt-on aftermarket fuel injection system. It's expensive but will work wonders on a iron-age Corvette, i.e; start every time you twist the key, fuel mileage will soar, the car will go from evil beast on the street to a purring lion.

Answer 2

Boy: if your truck has electronic ignition, which probably has, the next blah blah blah will partially true. But get to the bottom where I write on electronic ignition. However mad it may look, i suggest you to give this bible a read if you'd consider. A- The spark mechanism is quite simple. Upon turning the ignition key (and not starting the motor), the ignition coil should have +12 volts on one pin. Check qitha 12v lamp from this pin to chassis. It should light up. The other pin goes to a switch in the distributor. B- Loose the cable into this pin. Check the cap that has a cable that runs from the axis of the coil to the center of the distributor. Unplug this cable from the distributor. Now put the loose end of the cable to a mere 1 mm. to the chassis. There must be no fuel loose in the nearby. Then get a piece of cable and connect momentarily the loose end of the coil to ground and release. This should make the 1 mm gap spark. If it sparks, the coil is OK. C- If not, there´s a capacitor shunted with the coil that usually fails. Change it and try again. I've never seen a coil fail, but capacitors many. D- Now remember the cable you loosed from the coil? Put it once again where it belongs. Then, keeping the 1 mm. gap, make someone start the motor. The motor will turn but not start. The gap should produce sparks. If not, the switch inside the distributor or it's capacitor have failed. Replace both. If ok, then another test. E- Replace the cable from the cap of the coil into the cap of the distributor. Unplug a cable, any, from a spark plug. Do the 1 mm. gap to chassis. Then, keeping the 1 mm. gap, make someone start the motor. This time the motor MAY start. So keep an eye. If the gap sparks, replace the cable and check other cable. If cable sparks, check another until tested half of them. If gap does't spark, then the distributor cap (the plastic piece that holds the cables from the spark plugs) might have failed or is greasy. Replace. Once you have all the cables tested by gaping, the electicity problem is solved. Did you smell gasoline? if so, there´s the probability that the admission system is working and the fuel system is not to blame. So, where's the problem? The distribution must be sicronized to the cilyders. Note that the distributor roates over it's axis (a screw is holding it in it's place). Add some mark to the position of the distributor. Then, make someone start the motor. Now Turn the Distributor each time 5 degrees to the right, then to the left. The motor should start by itself. Fix this position. Then, it was misalignment. That's all about electricity and the motor, the basic method. The tuning of the distributor's axis is behind todays scope. If there was am electronic ignition, there's the possibility of it's failure. Quite possible, because its electronic and dusty and rather but gloriously old. The electronic circuitry replaces the switch inside the distributor. Run A, B, and C, and if C failed, it's the electronic ignition who's to blame. Replace by new one. Not serviceable. No need to run other tests. Pheww. Going to bed. Me tired. Good luck. Note: sory for my english. Spelling seems out of order.

Answer 3

Your idle will have to be set higher because of the lope caused by the lumpy cam in your engine.

Be sure when checking timing you have the vacuum advance vacuum line off the distributor and plugged. Else you will get a false reading on the timing.

Your timing could possible be advanced further than factory spec's depending on what they did when they re-build the engine. Did they give you a timing range to tune to, or a total advance value for your timing?

Getting the timing to what they designed the engine for, vs factory timing spec may also play a little into the lope you have at idle.

Answer 4

Please re-visit your question and tell us exactly what brand make and model or carbuerator it has. The standard 454 had a Rochester Quadrajet carbeurator. Someone may have replaced the intake manifold, added a Holley carbeurator and at the time of the print job changed the camshaft. If it's a Holley the identification numbers numbers will be stamped on the front of the air horn that supports the choke valve.

A Rochester has the acceletator pump rod sticking out of the left hand top side of the carb. It'll take time to what to look for. And for me to explain any possible fixes.

Answer 5

When you say rough do you mean the idle is rough? It could be it has a very high lift camshaft,this could give the symptoms you describe as you say it has a 'racing' engine
Do you have access to the engine build sheet? This should tell you what camshaft was installed.But I bet the engine pulls like a train at higher R.P.M.
Hope this point you in the right direction.
Good Luck with your new car!

Answer 6

its a character of racing engines the don't idle well all the power Don't want to be idle. i bet it goes like an animal. but the rough idle it because the cam is different and the engine is set up to rev to the limiter as often as it can

Answer 7

It's a pure guess but have the carb jets been replaced with free flowing ones to prevent fuel starvation on the race track ?

Answer 8

if it idles high, the first thing I would check is the idle screw and then maybe the air/fuel mix screws.

You know, performance cams sometimes make a car rough sounding. Someone please correct me without a ton of neg. if that is not the case.

Answer 9

Runs great when Idleing-Kick it down to shift and it wants to stall will turning the idling screw up help

Answer 10

It could be the jets in the carb or the carb is no good.