Engine Tune Up

I recently bought this vette for a guy who has left it sit in a garage for 20 years.  I have put most of it back together and i'm looking for a tune up chart or spec sheet or book to tune up my vette.  I have a non matching numbers car.  It has the 68 427 / 435 IR code engine with mechanical lifters.  It does not the the tripower carbs though.  It has a 4150 750cfm carb, holley.  Dist is HEI with mechanical tach.

engine assm plant code, T 10 24 IR

engine code suffix, IR

Block 3916321

Intake 3885069

 

Thanks for any help, i need to tune this up.

Bill42738941.8694791667

[QUOTE=Bill427]

I recently bought this vette for a guy who has left it sit in a garage for 20 years.  I have put most of it back together and i'm looking for a tune up chart or spec sheet or book to tune up my vette.  I have a non matching numbers car.  It has the 68 427 / 435 IR code engine with mechanical lifters.  It does not the the tripower carbs though.  It has a 4150 750cfm carb, holley.  Dist is HEI with mechanical tach.

engine assm plant code, T 10 24 IR

engine code suffix, IR

Block 3916321

Intake 3885069

Thanks for any help, i need to tune this up.

[/QUOTE]

well a tune up means different things to different people.

what exactly are you looking for?

you wont be able to use L-71 specs to tune as you dont have tri carbs.

also alot of the specs such as timing can be very different with modern fuel and really depend on how you have it set up.

cthulhu38942.2929976852

I was looking to get total timing specs, general ball park, i want to take compression tests on the cylinders, and i wanted to check the lifter specs.  Thanks.

[QUOTE=Bill427]I was looking to get total timing specs, general ball park, i want to take compression tests on the cylinders, and i wanted to check the lifter specs.  Thanks.[/QUOTE]

 

i dont have the lifter specs handy as my shop and books are all packed up in boxes right now...  but timing..  the book value for timing isnt going to be right.

you need to determine what value for timing works for your engine through experimentation.  are you still running points?

cthulhu38942.5293518519

Ok.  I have been experimenting now.  I'm running HEI, no points.  The vacuum advance isn't working at the moment, the diaphram must be broken.  So i need to order a new diaphram.  Right now the car is running real rich, so i'm trying to lean it out.  If your around the car your eyes will burn and if you try to stomp on it, it spits and sputters at first then takes off.  The carb is a holley 4150 dumble pumper.  I'm also going to order a new ignition coil.  Maybe the one in there is to weak to burn all the fuel.  I did replace the power valve.

Thanks.

[QUOTE=Bill427]

Ok.  I have been experimenting now.  I'm running HEI, no points.  The vacuum advance isn't working at the moment, the diaphram must be broken.  So i need to order a new diaphram.  Right now the car is running real rich, so i'm trying to lean it out.  If your around the car your eyes will burn and if you try to stomp on it, it spits and sputters at first then takes off.  The carb is a holley 4150 dumble pumper.  I'm also going to order a new ignition coil.  Maybe the one in there is to weak to burn all the fuel.  I did replace the power valve.

Thanks.

[/QUOTE]

what jet sizes ?

sounds like your running really rich, you'll have to adjust the floats in the front and rear bowl, that should help a little. Are you familiar with the process? Your timing being off isn't helping any either. To adjust the floats, with the engine at an idle and the car level remove the sight hole plug. It is located on the passanger side of the bowls. The fuel should be up to the threads and not coming out. To adjust the fuel level, on the top of the bowls there is a screw with a nut under it, loosen the screw, to raise the fuel level turn the nut 1/6 of a turn at a time counterclockwise, to lower the fuel level which it sounds like you need to do, turn the nut clockwise, go slow, don't loosen the screw too much or gas will come out all over the place. Also after you turn the nut a little tighten the screw back up and let it run a little bit. Also put some rags under the hole to keep the fuel from going onto the manifold.  the way I do it is if I rock the car and the fuel comes out of the hole it's good. The timing is 4 degrees btdc on the L71 motor.

thanks.  I have set the float level, they are brass.  Thanks for the timing info, i'll start with there.  I ordered a adjustable vacuum advance, should be at the house on Wednesday.  As far as jet sizes, i think the size was .60.

thanks.

[QUOTE=Bill427]thanks.  I have set the float level, they are brass.  Thanks for the timing info, i'll start with there.  I ordered a adjustable vacuum advance, should be at the house on Wednesday.  As far as jet sizes, i think the size was .60.

thanks.
[/QUOTE]

4 may be factory baseline...  but if you cant get 10-12 out of it for initial timing then you arent trying very hard.

Also..  for jet sizes..  if you are running too rich take it down a notch or two.  Are your plugs sooty after driving?  if so.. then you are running too rich and should take the jets down a little.

cthulhu38943.2647800926

Thanks for the info.  I will be doing some work on it this weekend, hopefully and i'll let you know what happens.