i have 73 l-48 and have replaced the points with a crane xr 1 and a fireball coil. a friend of mine did the swap for me and took out the mechanical advance weights and set the timong to 35 degrees.using only the initial timing and the vacuum advance unit.also he switched to full vacuum instead of ported.i have read about this before.i guess its an old hot rod trick so that the advance is always there.we also set the idle down to correspond with the advance that is always there.my question is 1 is this kosher? 2 will it have long term damaging effects on my engine as it only has 53000 miles.also i have a edelbrock torker single plane intake with a holley 570 street avenger.i have been told by other people to go dual plane.please help

 

So, you let Bubba work on your car, THEN you ask for advise.

 

You need new friends. The one you have didn't help you at all. Running full advance all the time is a perfect way to get into detonation and burn a hole thru a piston. He got it backwards. Taking the vacuum out and just running mechanical advance is the proper way to get it.

 

I agree with both above replies ... your friend screwed your car up. Please do not drive it until you get someone (or learn it yourself) to fix it correctly. There's not a thing wrong with the OE points design so long as they're in decent shape & adjusted correctly ... seldom do points need anything more than a yearly checkup.

I suggest you need both vacuum & mech advance for a typical hi-po carbed chevy street car.

Merry Christmas y'all

-add- there's a sticky at top of this forum ... the one by BarryK that has lotsa tuning/timing info ... you're an ideal candidate for it ... please study it.

 

Hopefully you described how your friend timed your engine incorrectly, because 35* at idle (even with full vacuum advance in effect) is too high. Basically, you typically want 34 - 36* total mechanical advance (without vacuum advance) at about 2800 RPM. Your distributer probably has 10* (20* measured at the crank) so your initial timing s/b 14 - 16*. Get a timing tape or dial back timing light and measure. FYI, the mechanical and vacuum advance are different and come in at different rpm and load. Anyway, that's how I do it...

 

your friend is a moron and you should not let him touch your car ever again.

Proper and correct timing set up is important for a number of reasons and if it's done incorrectly the results can range from simply a poor running car to destroying your pistons.

Removing the weights, therefore removing the mechanical advance out of the distributor, is definitely an example of how to do it wrong!

Correct ignition timing, putting it in simplistic terms, is controlled by two elements for a correctly tuned and running motor to achieve good performance, throttle response, good operating temperature, and fuel economy. These two elements are the mechanical advance which controls spark timing based on engine RPM and vacuum advance which controls spark timing based on engine load.
Now, in certain applications people will disable and not use a vacuum advance system but typically this is on race motors since their intended usage and typical vacuum level under use makes the vacuum advance system ineffective anyway, but disabling the mechanical advance is simply nothing short of stupidity. The motor now has no means to change spark timing as needed based on motor RPM during normal driving.

Read thru my stick at the top of this page and more importantly read thru the reference articles in that sticky by John Hinckley and Lars Grimsrud to get a fuller understanding of ignition timing and the different aspects of it to understand just how much of an idiot your friend is.

As already mentioned, please do not drive your car as is until you get this repaired back to a correct operating system.

BTW, I hope he didn't throw away the stock weights out of the distributor when he removed them as you will need them to put back in. The aftermarket weights that come in the distributor rebuild/recurve kits suck and typically are good only to use as a fishing weight. If the stock weights were thrown out you are going to have to start looking for good original stock weights to replace them.
Also, I don't know what your reasoning was to replace the points with the aftermarket electronic conversion kit, but there is NOTHING wrong with a correctly set-up points system. Your expense of money on the Crane electronic conversion kit has gained you zero performance and actually reduced the overall reliability of the ignition system compared to using points.

 

First let me say you sure came to the right place for help on timeing, i must have read these instructions a dozen times. I still had to ask a couple questions, (i think most people do). It"s a long read, but once you learn it you"ll never forget it. Once it"s over you"ll get the satifaction of knowing your car is timed perfect, an it makes picking out idot mechanics a breeze!!!!!!!! Make darn sure you read this twice an then ask any questions you may have, these guys are more than willing to take the time to help you learn this. Do not make the mistake of asking questions without reading the instructions, they catch on pretty quick........

http://forums.corvetteforum.com/c3-t...long-post.html

 

to comment on your intake and carb question. the torker causes a loss at low rpms. it is also the only square bore intake that will fit under a BBC. since you have the small block you can go with a dual plane like the performer or the weiand and get that low end back.

as far as size of the carb. that is a matter that is so highly debated that it may never be solved. some people will tell you that bigger is better. there are forumlas out there take take into account engine size, max rpm, efficiency of the engine etc. that formula will tell you a smaller carb is necessary than people like.
for example.
a 350 at 6000 rpms will turn app 85% efficiency (according to the calculator sites)
for this application you need a 516cfm carb based on the formula 350*6000/3456 (a constant) *.85 so in that case the 570 should work just fine.

other people will tell you that that carb formula is out dated and wont work and that for a 350 a 1000cfm double pumper is the minimum necessary.(slight exagertation)

 

May I strongly suggest that you leave your "friend" out of this process?

 

At this point, you should follow Lars/Barry's papers EXACTLY (step by step) and it will run much better.